svelte

2025-08-10 14:32:15 -07:00 · 2025-08-10 14:32:15 -07:00 · 0b4b7db0be
commit 0b4b7db0be
parent 0f3eecceea
46 changed files with 3157 additions and 64 deletions
--- a/Cargo.lock
+++ b/Cargo.lock
@ -1228,11 +1228,11 @@ dependencies = [

 [[package]]
 name = "headers"
-version = "0.4.0"
+version = "0.4.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "322106e6bd0cba2d5ead589ddb8150a13d7c4217cf80d7c4f682ca994ccc6aa9"
+checksum = "b3314d5adb5d94bcdf56771f2e50dbbc80bb4bdf88967526706205ac9eff24eb"
 dependencies = [
- "base64 0.21.7",
+ "base64 0.22.1",
 "bytes",
 "headers-core",
 "http 1.3.1",
@ -1676,6 +1676,7 @@ dependencies = [
 "derive_builder",
 "dotenvy",
 "futures",
+ "headers",
 "interim-models",
 "interim-pgtypes",
 "oauth2",
--- a/dev-services/docker-compose.yaml
+++ b/dev-services/docker-compose.yaml
@ -0,0 +1,34 @@
+name: interim
+
+services:
+  pg:
+    image: postgres:17
+    restart: always
+    environment:
+      POSTGRES_USER: postgres
+      POSTGRES_PASSWORD: guest
+    ports:
+      - "127.0.0.1:5432:5432"
+    volumes:
+      - "./docker-entrypoint-initdb.d:/docker-entrypoint-initdb.d:ro"
+      - "./pgdata:/var/lib/postgresql/data"
+
+  keycloak:
+    depends_on: [pg]
+    restart: always
+    build:
+      context: .
+      dockerfile: keycloak.dockerfile
+    environment:
+      KC_DB: postgres
+      KC_DB_URL: jdbc:postgresql://pg:5432/keycloak
+      KC_DB_USERNAME: keycloak
+      KC_DB_PASSWORD: guest
+      KC_HOSTNAME: 0.0.0.0
+      KEYCLOAK_ADMIN: admin
+      KEYCLOAK_ADMIN_PASSWORD: guest
+    command: [start, --optimized]
+    ports:
+      - "127.0.0.1:9000:9000"
+      - "127.0.0.1:8443:8443"
+
--- a/dev-services/docker-entrypoint-initdb.d/init-app.sql
+++ b/dev-services/docker-entrypoint-initdb.d/init-app.sql
@ -0,0 +1,3 @@
+CREATE USER interim_app WITH ENCRYPTED PASSWORD 'guest';
+CREATE DATABASE interim_app;
+ALTER DATABASE interim_app OWNER TO interim_app;
--- a/dev-services/docker-entrypoint-initdb.d/init-keycloak.sql
+++ b/dev-services/docker-entrypoint-initdb.d/init-keycloak.sql
@ -0,0 +1,3 @@
+CREATE USER keycloak WITH ENCRYPTED PASSWORD 'guest';
+CREATE DATABASE keycloak;
+ALTER DATABASE keycloak OWNER TO keycloak;
--- a/dev-services/keycloak.dockerfile
+++ b/dev-services/keycloak.dockerfile
@ -0,0 +1,18 @@
+FROM quay.io/keycloak/keycloak:26.3.2 as builder
+
+# Enable health and metrics support
+ENV KC_HEALTH_ENABLED=true
+ENV KC_METRICS_ENABLED=true
+
+# Configure a database vendor
+ENV KC_DB=postgres
+
+WORKDIR /opt/keycloak
+# for demonstration purposes only, please make sure to use proper certificates in production instead
+RUN keytool -genkeypair -storepass password -storetype PKCS12 -keyalg RSA -keysize 2048 -dname "CN=server" -alias server -ext "SAN:c=DNS:localhost,IP:127.0.0.1" -keystore conf/server.keystore
+RUN /opt/keycloak/bin/kc.sh build
+
+FROM quay.io/keycloak/keycloak:26.3.2
+COPY --from=builder /opt/keycloak/ /opt/keycloak/
+
+ENTRYPOINT ["/opt/keycloak/bin/kc.sh"]
--- a/interim-models/src/field.rs
+++ b/interim-models/src/field.rs
@ -36,17 +36,21 @@ impl Field {

    pub fn webc_tag(&self) -> &str {
        match self.field_type.0 {
-            FieldType::Integer => "cell-integer",
-            FieldType::InterimUser => "cell-interim-user",
-            FieldType::Text => "cell-text",
+            FieldType::InterimUser {} => "cell-interim-user",
+            FieldType::Text {} => "cell-text",
            FieldType::Timestamp { .. } => "cell-timestamp",
-            FieldType::Uuid => "cell-uuid",
+            FieldType::Uuid { .. } => "cell-uuid",
            FieldType::Unknown => "cell-unknown",
        }
    }

    pub fn webc_custom_attrs(&self) -> Vec<(String, String)> {
-        vec![]
+        match self.field_type.clone() {
+            sqlx::types::Json(FieldType::Uuid {
+                default_with_version: Some(_),
+            }) => vec![("has_default".to_owned(), "true".to_owned())],
+            _ => vec![],
+        }
    }

    pub fn get_value_encodable(&self, row: &PgRow) -> Result<Encodable, ParseError> {
@ -56,9 +60,6 @@ impl Field {
        let type_info = value_ref.type_info();
        let ty = type_info.name();
        Ok(match ty {
-            "INT" | "INT4" => {
-                Encodable::Integer(<Option<i32> as Decode<Postgres>>::decode(value_ref).unwrap())
-            }
            "TEXT" | "VARCHAR" => {
                Encodable::Text(<Option<String> as Decode<Postgres>>::decode(value_ref).unwrap())
            }
@ -103,13 +104,14 @@ where lens_id = $1
 #[derive(Clone, Debug, Deserialize, Serialize)]
 #[serde(tag = "t", content = "c")]
 pub enum FieldType {
-    Integer,
-    InterimUser,
-    Text,
+    InterimUser {},
+    Text {},
    Timestamp {
        format: String,
    },
-    Uuid,
+    Uuid {
+        default_with_version: Option<String>,
+    },
    /// A special variant for when the field type is not specified and cannot be
    /// inferred. This isn't represented as an error, because we still want to
    /// be able to define display behavior via the .render() method.
@ -119,12 +121,13 @@ pub enum FieldType {
 impl FieldType {
    pub fn default_from_attr(attr: &PgAttribute) -> Self {
        match attr.regtype.as_str() {
-            "integer" => Self::Integer,
-            "text" => Self::Text,
+            "text" => Self::Text {},
            "timestamp" => Self::Timestamp {
                format: RFC_3339_S.to_owned(),
            },
-            "uuid" => Self::Uuid,
+            "uuid" => Self::Uuid {
+                default_with_version: None,
+            },
            _ => Self::Unknown,
        }
    }
@ -134,15 +137,28 @@ impl FieldType {
    /// None if the field type is Unknown.
    pub fn attr_data_type_fragment(&self) -> Option<&'static str> {
        match self {
-            Self::Integer => Some("integer"),
-            Self::InterimUser | Self::Text => Some("text"),
+            Self::InterimUser {} | Self::Text {} => Some("text"),
            Self::Timestamp { .. } => Some("timestamptz"),
-            Self::Uuid => Some("uuid"),
+            Self::Uuid { .. } => Some("uuid"),
            Self::Unknown => None,
        }
    }
+
+    pub fn default_for_insert(&self) -> Result<Encodable, FieldTypeUnknownError> {
+        match self {
+            Self::InterimUser {} => Ok(Encodable::Text(None)),
+            Self::Text {} => Ok(Encodable::Text(None)),
+            Self::Timestamp { .. } => Ok(Encodable::Timestamp(None)),
+            Self::Uuid { .. } => Ok(Encodable::Uuid(None)),
+            Self::Unknown => Err(FieldTypeUnknownError {}),
+        }
+    }
 }

+#[derive(Clone, Debug, Error)]
+#[error("field type is unknown")]
+pub struct FieldTypeUnknownError {}
+
 // -------- Insertable --------

 #[derive(Builder, Clone, Debug)]
@ -212,9 +228,8 @@ pub enum ParseError {
 #[derive(Clone, Debug, Deserialize, PartialEq, Serialize)]
 #[serde(tag = "t", content = "c")]
 pub enum Encodable {
-    Integer(Option<i32>),
    Text(Option<String>),
-    Timestamptz(Option<DateTime<Utc>>),
+    Timestamp(Option<DateTime<Utc>>),
    Uuid(Option<Uuid>),
 }

@ -224,9 +239,8 @@ impl Encodable {
        query: sqlx::query::Query<'a, Postgres, <sqlx::Postgres as sqlx::Database>::Arguments<'a>>,
    ) -> sqlx::query::Query<'a, Postgres, <sqlx::Postgres as sqlx::Database>::Arguments<'a>> {
        match self {
-            Self::Integer(value) => query.bind(value),
            Self::Text(value) => query.bind(value),
-            Self::Timestamptz(value) => query.bind(value),
+            Self::Timestamp(value) => query.bind(value),
            Self::Uuid(value) => query.bind(value),
        }
    }
--- a/interim-server/Cargo.toml
+++ b/interim-server/Cargo.toml
@ -15,6 +15,7 @@ config = "0.14.1"
 derive_builder = { workspace = true }
 dotenvy = "0.15.7"
 futures = { workspace = true }
+headers = "0.4.1"
 interim-models = { workspace = true }
 interim-pgtypes = { workspace = true }
 oauth2 = "4.4.2"
--- a/interim-server/src/auth.rs
+++ b/interim-server/src/auth.rs
@ -1,15 +1,15 @@
 use anyhow::{Context, Result};
 use async_session::{Session, SessionStore};
 use axum::{
+    Router,
    extract::{Query, State},
    response::{IntoResponse, Redirect},
    routing::get,
-    Router,
 };
 use axum_extra::extract::cookie::{Cookie, CookieJar, SameSite};
 use oauth2::{
-    basic::BasicClient, reqwest::async_http_client, AuthUrl, AuthorizationCode, ClientId,
-    ClientSecret, CsrfToken, RedirectUrl, RefreshToken, TokenResponse, TokenUrl,
+    AuthUrl, AuthorizationCode, ClientId, ClientSecret, CsrfToken, RedirectUrl, RefreshToken,
+    TokenResponse, TokenUrl, basic::BasicClient, reqwest::async_http_client,
 };
 use serde::{Deserialize, Serialize};

@ -74,7 +74,7 @@ async fn start_login(

    if session.get::<AuthInfo>(SESSION_KEY_AUTH_INFO).is_some() {
        tracing::debug!("already logged in, redirecting...");
-        return Ok(Redirect::to(&format!("{}/", root_path)).into_response());
+        return Ok(Redirect::to(&format!("{root_path}/")).into_response());
    }
    assert!(session.get_raw(SESSION_KEY_AUTH_REFRESH_TOKEN).is_none());

--- a/interim-server/src/router.rs
+++ b/interim-server/src/router.rs
@ -65,6 +65,10 @@ pub fn new_router(state: AppState) -> Router<()> {
            "/d/{base_id}/r/{class_oid}/l/{lens_id}/",
            get(routes::lenses::lens_page),
        )
+        .route(
+            "/d/{base_id}/r/{class_oid}/l/{lens_id}/get-data",
+            get(routes::lenses::get_data_page_get),
+        )
        // .route(
        //     "/d/{base_id}/r/{class_oid}/l/{lens_id}/add-selection",
        //     post(routes::lenses::add_selection_page_post),
--- a/interim-server/src/routes/lenses.rs
+++ b/interim-server/src/routes/lenses.rs
@ -13,7 +13,7 @@ use interim_models::{
    lens::{Lens, LensDisplayType},
 };
 use interim_pgtypes::{escape_identifier, pg_attribute::PgAttribute, pg_class::PgClass};
-use serde::Deserialize;
+use serde::{Deserialize, Serialize};
 use serde_json::json;
 use sqlx::{
    postgres::{PgRow, types::Oid},
@ -205,7 +205,7 @@ pub async fn lens_page(
        .collect();

    #[derive(Template)]
-    #[template(path = "lens.html")]
+    #[template(path = "lens0_2.html")]
    struct ResponseTemplate {
        fields: Vec<Field>,
        all_columns: Vec<PgAttribute>,
@ -237,6 +237,94 @@ pub async fn lens_page(
    .into_response())
 }

+pub async fn get_data_page_get(
+    State(settings): State<Settings>,
+    State(mut base_pooler): State<BasePooler>,
+    AppDbConn(mut app_db): AppDbConn,
+    CurrentUser(current_user): CurrentUser,
+    Path(LensPagePath {
+        lens_id,
+        base_id,
+        class_oid,
+    }): Path<LensPagePath>,
+) -> Result<Response, AppError> {
+    // FIXME auth
+    let base = Base::with_id(base_id).fetch_one(&mut app_db).await?;
+    let lens = Lens::with_id(lens_id).fetch_one(&mut app_db).await?;
+
+    let mut base_client = base_pooler
+        .acquire_for(lens.base_id, RoleAssignment::User(current_user.id))
+        .await?;
+    let rel = PgClass::with_oid(lens.class_oid)
+        .fetch_one(&mut base_client)
+        .await?;
+
+    let attrs = PgAttribute::all_for_rel(lens.class_oid)
+        .fetch_all(&mut base_client)
+        .await?;
+    let fields = Field::belonging_to_lens(lens.id)
+        .fetch_all(&mut app_db)
+        .await?;
+    let pkey_attrs = PgAttribute::pkeys_for_rel(lens.class_oid)
+        .fetch_all(&mut base_client)
+        .await?;
+
+    const FRONTEND_ROW_LIMIT: i64 = 1000;
+    let rows: Vec<PgRow> = query(&format!(
+        "select {0} from {1}.{2} limit $1",
+        pkey_attrs
+            .iter()
+            .chain(attrs.iter())
+            .map(|attr| escape_identifier(&attr.attname))
+            .collect::<Vec<_>>()
+            .join(", "),
+        escape_identifier(&rel.regnamespace),
+        escape_identifier(&rel.relname),
+    ))
+    .bind(FRONTEND_ROW_LIMIT)
+    .fetch_all(base_client.get_conn())
+    .await?;
+
+    #[derive(Serialize)]
+    struct DataRow {
+        pkey: String,
+        data: Vec<Encodable>,
+    }
+
+    let mut data: Vec<DataRow> = vec![];
+    let mut pkeys: Vec<String> = vec![];
+    for row in rows.iter() {
+        let mut pkey_values: HashMap<String, Encodable> = HashMap::new();
+        for attr in pkey_attrs.clone() {
+            let field = Field::default_from_attr(&attr);
+            pkey_values.insert(field.name.clone(), field.get_value_encodable(row)?);
+        }
+        let pkey = serde_json::to_string(&pkey_values)?;
+        pkeys.push(pkey.clone());
+        let mut row_data: Vec<Encodable> = vec![];
+        for field in fields.iter() {
+            row_data.push(field.get_value_encodable(row)?);
+        }
+        data.push(DataRow {
+            pkey,
+            data: row_data,
+        });
+    }
+
+    #[derive(Serialize)]
+    struct ResponseBody {
+        pkeys: Vec<String>,
+        data: Vec<DataRow>,
+        fields: Vec<Field>,
+    }
+    Ok(Json(ResponseBody {
+        fields,
+        pkeys,
+        data,
+    })
+    .into_response())
+}
+
 #[derive(Debug, Deserialize)]
 pub struct AddColumnPageForm {
    name: String,
--- a/interim-server/templates/lens.html
+++ b/interim-server/templates/lens.html
@ -13,7 +13,7 @@
        <thead>
          <tr>
            {% for field in fields %}
-            <th class="viewer-table__column-header" width="{{ field.width_px }}">
+            <th class="viewer-table__column-header" width="{{ field.width_px }}" scope="col">
              {{ field.label.clone().unwrap_or(field.name.clone()) }}
            </th>
            {% endfor %}
@ -52,6 +52,23 @@
            {% endfor %}
          </tr>
          {% endfor %}
+          <tr class="viewer-table__insertable-row">
+            {% for (i, field) in fields.iter().enumerate() %}
+            <td class="viewer-table__td viewer-table__td--insertable">
+              <{{ field.webc_tag() | safe }}
+                {% for (k, v) in field.webc_custom_attrs() %}
+                {{ k }}="{{ v }}"
+                {% endfor %}
+                row="{{ pkeys.len() }}"
+                column="{{ i }}"
+                class="cell"
+                insertable="true"
+                value="{{ field.field_type.default_for_insert()? | json }}"
+              >
+              </{{ field.webc_tag() | safe }}
+            </td>
+            {% endfor %}
+          </tr>
        </tbody>
      </table>
      <viewer-hoverbar root-path="{{ settings.root_path }}"></viewer-hoverbar>
--- a/interim-server/templates/lens0_2.html
+++ b/interim-server/templates/lens0_2.html
@ -0,0 +1,16 @@
+{% extends "base.html" %}
+
+{% block main %}
+<link rel="stylesheet" href="{{ settings.root_path }}/css_dist/viewer.css">
+<div class="page-grid">
+  <div class="page-grid__toolbar"></div>
+  <div class="page-grid__sidebar">
+    {{ navbar | safe }}
+  </div>
+  <main class="page-grid__main">
+    <table-viewer root-path="{{ settings.root_path }}"></table-viewer>
+  </main>
+</div>
+<script src="{{ settings.root_path }}/js_dist/TableViewer.js"></script>
+{% endblock %}
+
--- a/mise.toml
+++ b/mise.toml
@ -8,15 +8,21 @@ rust = { version = "1.88.0", components = "rust-analyzer,clippy" }
 watchexec = "latest"
 "github:sass/dart-sass" = "1.89.2"

-[tasks.postgres]
-run = "docker run --rm -it -e POSTGRES_PASSWORD=guest -v './pgdata:/var/lib/postgresql/data' -p 127.0.0.1:5432:5432 postgres:17"
+[tasks.dev-services]
+run = "docker compose up"
+dir = "./dev-services"

 [tasks.server]
 run = "cargo run serve"
 description = "Run the server. For development: `mise watch --restart serve`."
 sources = ["**/*.rs", "**/*.html"]

-[tasks.build-js]
+[tasks.build-svelte]
+run = "deno run -A npm:vite build"
+dir = "./svelte"
+sources = ["svelte/src/**/*.ts", "svelte/src/**/*.svelte"]
+
+[tasks.build-gleam]
 run = "sh build.sh"
 dir = "./webc"
 sources = ["webc/src/**/*.gleam", "webc/src/**/*.mjs"]
--- a/sass/_globals.scss
+++ b/sass/_globals.scss
@ -59,6 +59,7 @@ $notice-color-info: #39d;
  font-family: inherit;
  font-size: inherit;
  font-weight: inherit;
+  outline: none;
 }

@mixin rounded-sm {
--- a/sass/main.scss
+++ b/sass/main.scss
@ -67,6 +67,7 @@ button, input[type="submit"] {

  &__main {
    grid-area: main;
+    overflow: hidden;
  }
 }

--- a/sass/viewer.scss
+++ b/sass/viewer.scss
@ -1,34 +1,135 @@
-.viewer-table {
-  border-collapse: collapse;
-  height: 1px; // css hack to make percentage based cell heights work
+@use 'globals';
+@use 'sass:color';

-  &__column-header {
-    border: solid 1px #ccc;
-    border-top: none;
-    font-family: "Funnel Sans";
-    background: #0001;
-    height: 100%; // css hack to make percentage based cell heights work
-    padding: 0.5rem;
-    text-align: left;
+$table-border-color: #ccc;

-    &:first-child {
-      border-left: none;
-    }
+.lens-grid {
+  display: grid;
+  grid-template:
+    'table' 1fr
+    'editor' max-content;
+  height: 100%;
+  width: 100%;
+}
+
+.lens-table {
+  display: grid;
+  grid-area: table;
+  grid-template:
+    'headers' max-content
+    'main' 1fr
+    'inserter' max-content;
+  height: 100%;
+  outline: none;
+  overflow: auto;
+  width: 100%;
+
+  &__headers {
+    display: flex;
+    grid-area: headers;
+    align-items: stretch;
  }

-  &__actions-header {
+  &__header {
+    display: flex;
+    flex: none;
+    align-items: center;
+    border: solid 1px #ccc;
+    border-top: none;
+    border-left: none;
+    font-family: "Funnel Sans";
+    background: #0001;
+    padding: 0.5rem;
+    text-align: left;
+  }
+
+  &__header-actions {
    border: none;
    background: none;
    padding: 0;
  }

-  &__td {
-    border: solid 1px #ccc;
-    height: 100%; // css hack to make percentage based cell heights work
+  &__main {
+    grid-area: main;
+    overflow-y: auto;
+  }
+
+  &__row {
+    align-items: stretch;
+    display: flex;
+  }
+
+  &__cell {
+    flex: none;
+    border: solid 1px $table-border-color;
+    border-left: none;
+    border-top: none;
    padding: 0;

-    &:first-child {
+    &--insertable {
+      border-style: dashed;
+    }
+
+    &--selected {
+      .lens-table__cell-content {
+        outline: 3px solid #37f;
+        outline-offset: -2px;
+      }
+    }
+  }
+
+  &__cell-content {
+    font-family: globals.$font-family-data;
+
+    &--null {
+      color: color.scale(#000, $lightness: 50%, $space: hsl);
+      font-style: oblique;
+      text-align: center;
+      padding: 0.5rem;
+    }
+
+    &--text {
+      overflow: hidden;
+      text-overflow: ellipsis;
+      white-space: nowrap;
+      padding: 0.5rem;
+    }
+
+    &--uuid {
+      font-family: globals.$font-family-mono;
+      overflow: hidden;
+      text-overflow: ellipsis;
+      white-space: nowrap;
+      padding: 0.5rem;
+    }
+  }
+
+  &__inserter {
+    grid-area: inserter;
+    margin-bottom: 2rem;
+
+    .lens-table__cell {
+      border: dashed 1px $table-border-color;
      border-left: none;
+      border-top: none;
+    }
+
+    .lens-table__row:first-child .lens-table__cell {
+      border-top: dashed 1px $table-border-color;
    }
  }
 }
+
+.lens-editor {
+  align-items: stretch;
+  border-top: globals.$default-border;
+  display: flex;
+  grid-area: editor;
+
+  &__input {
+    @include globals.reset_input;
+    padding: 0.5rem;
+    font-family: globals.$font-family-data;
+    flex: 1;
+  }
+}
--- a/svelte/.gitignore
+++ b/svelte/.gitignore
@ -0,0 +1,24 @@
+# Logs
+logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+pnpm-debug.log*
+lerna-debug.log*
+
+node_modules
+dist
+dist-ssr
+*.local
+
+# Editor directories and files
+.vscode/*
+!.vscode/extensions.json
+.idea
+.DS_Store
+*.suo
+*.ntvs*
+*.njsproj
+*.sln
+*.sw?
--- a/svelte/.npmrc
+++ b/svelte/.npmrc
@ -0,0 +1 @@
+@jsr:registry=https://npm.jsr.io
--- a/svelte/README.md
+++ b/svelte/README.md
@ -0,0 +1,47 @@
+# Svelte + TS + Vite
+
+This template should help get you started developing with Svelte and TypeScript in Vite.
+
+## Recommended IDE Setup
+
+[VS Code](https://code.visualstudio.com/) + [Svelte](https://marketplace.visualstudio.com/items?itemName=svelte.svelte-vscode).
+
+## Need an official Svelte framework?
+
+Check out [SvelteKit](https://github.com/sveltejs/kit#readme), which is also powered by Vite. Deploy anywhere with its serverless-first approach and adapt to various platforms, with out of the box support for TypeScript, SCSS, and Less, and easily-added support for mdsvex, GraphQL, PostCSS, Tailwind CSS, and more.
+
+## Technical considerations
+
+**Why use this over SvelteKit?**
+
+- It brings its own routing solution which might not be preferable for some users.
+- It is first and foremost a framework that just happens to use Vite under the hood, not a Vite app.
+
+This template contains as little as possible to get started with Vite + TypeScript + Svelte, while taking into account the developer experience with regards to HMR and intellisense. It demonstrates capabilities on par with the other `create-vite` templates and is a good starting point for beginners dipping their toes into a Vite + Svelte project.
+
+Should you later need the extended capabilities and extensibility provided by SvelteKit, the template has been structured similarly to SvelteKit so that it is easy to migrate.
+
+**Why `global.d.ts` instead of `compilerOptions.types` inside `jsconfig.json` or `tsconfig.json`?**
+
+Setting `compilerOptions.types` shuts out all other types not explicitly listed in the configuration. Using triple-slash references keeps the default TypeScript setting of accepting type information from the entire workspace, while also adding `svelte` and `vite/client` type information.
+
+**Why include `.vscode/extensions.json`?**
+
+Other templates indirectly recommend extensions via the README, but this file allows VS Code to prompt the user to install the recommended extension upon opening the project.
+
+**Why enable `allowJs` in the TS template?**
+
+While `allowJs: false` would indeed prevent the use of `.js` files in the project, it does not prevent the use of JavaScript syntax in `.svelte` files. In addition, it would force `checkJs: false`, bringing the worst of both worlds: not being able to guarantee the entire codebase is TypeScript, and also having worse typechecking for the existing JavaScript. In addition, there are valid use cases in which a mixed codebase may be relevant.
+
+**Why is HMR not preserving my local component state?**
+
+HMR state preservation comes with a number of gotchas! It has been disabled by default in both `svelte-hmr` and `@sveltejs/vite-plugin-svelte` due to its often surprising behavior. You can read the details [here](https://github.com/rixo/svelte-hmr#svelte-hmr).
+
+If you have state that's important to retain within a component, consider creating an external store which would not be replaced by HMR.
+
+```ts
+// store.ts
+// An extremely simple external store
+import { writable } from 'svelte/store'
+export default writable(0)
+```
--- a/svelte/deno.json
+++ b/svelte/deno.json
@ -0,0 +1,11 @@
+{
+  "tasks": {
+    "dev": "deno run --watch main.ts"
+  },
+  "imports": {
+    "@std/assert": "jsr:@std/assert@1",
+    "@std/path": "jsr:@std/path@^1.1.1",
+    "@std/uuid": "jsr:@std/uuid@^1.0.9",
+  },
+  "unstable": ["fmt-component"]
+}
--- a/svelte/deno.lock
+++ b/svelte/deno.lock
--- a/svelte/index.html
+++ b/svelte/index.html
@ -0,0 +1,13 @@
+<!doctype html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <link rel="icon" type="image/svg+xml" href="/vite.svg" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <title>Vite + Svelte + TS</title>
+  </head>
+  <body>
+    <div id="app"></div>
+    <script type="module" src="/src/main.ts"></script>
+  </body>
+</html>
--- a/svelte/main.ts
+++ b/svelte/main.ts
@ -0,0 +1,8 @@
+export function add(a: number, b: number): number {
+  return a + b;
+}
+
+// Learn more at https://docs.deno.com/runtime/manual/examples/module_metadata#concepts
+if (import.meta.main) {
+  console.log("Add 2 + 3 =", add(2, 3));
+}
--- a/svelte/main_test.ts
+++ b/svelte/main_test.ts
@ -0,0 +1,6 @@
+import { assertEquals } from "@std/assert";
+import { add } from "./main.ts";
+
+Deno.test(function addTest() {
+  assertEquals(add(2, 3), 5);
+});
--- a/svelte/package.json
+++ b/svelte/package.json
@ -0,0 +1,27 @@
+{
+  "name": "vite-project",
+  "private": true,
+  "version": "0.0.0",
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "vite build",
+    "preview": "vite preview",
+    "check": "svelte-check --tsconfig ./tsconfig.app.json && tsc -p tsconfig.node.json"
+  },
+  "dependencies": {
+    "@deno/vite-plugin": "^1.0.5",
+    "@jsr/std__uuid": "^1.0.9",
+    "@sveltejs/vite-plugin-svelte": "^6.1.1",
+    "svelte-language-server": "^0.17.19",
+    "uuid": "^11.1.0",
+    "vite": "^7.1.1",
+    "zod": "^4.0.17"
+  },
+  "devDependencies": {
+    "@tsconfig/svelte": "^5.0.4",
+    "svelte": "^5.37.3",
+    "svelte-check": "^4.3.1",
+    "typescript": "~5.8.3"
+  }
+}
--- a/svelte/public/vite.svg
+++ b/svelte/public/vite.svg
@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" aria-hidden="true" role="img" class="iconify iconify--logos" width="31.88" height="32" preserveAspectRatio="xMidYMid meet" viewBox="0 0 256 257"><defs><linearGradient id="IconifyId1813088fe1fbc01fb466" x1="-.828%" x2="57.636%" y1="7.652%" y2="78.411%"><stop offset="0%" stop-color="#41D1FF"></stop><stop offset="100%" stop-color="#BD34FE"></stop></linearGradient><linearGradient id="IconifyId1813088fe1fbc01fb467" x1="43.376%" x2="50.316%" y1="2.242%" y2="89.03%"><stop offset="0%" stop-color="#FFEA83"></stop><stop offset="8.333%" stop-color="#FFDD35"></stop><stop offset="100%" stop-color="#FFA800"></stop></linearGradient></defs><path fill="url(#IconifyId1813088fe1fbc01fb466)" d="M255.153 37.938L134.897 252.976c-2.483 4.44-8.862 4.466-11.382.048L.875 37.958c-2.746-4.814 1.371-10.646 6.827-9.67l120.385 21.517a6.537 6.537 0 0 0 2.322-.004l117.867-21.483c5.438-.991 9.574 4.796 6.877 9.62Z"></path><path fill="url(#IconifyId1813088fe1fbc01fb467)" d="M185.432.063L96.44 17.501a3.268 3.268 0 0 0-2.634 3.014l-5.474 92.456a3.268 3.268 0 0 0 3.997 3.378l24.777-5.718c2.318-.535 4.413 1.507 3.936 3.838l-7.361 36.047c-.495 2.426 1.782 4.5 4.151 3.78l15.304-4.649c2.372-.72 4.652 1.36 4.15 3.788l-11.698 56.621c-.732 3.542 3.979 5.473 5.943 2.437l1.313-2.028l72.516-144.72c1.215-2.423-.88-5.186-3.54-4.672l-25.505 4.922c-2.396.462-4.435-1.77-3.759-4.114l16.646-57.705c.677-2.35-1.37-4.583-3.769-4.113Z"></path></svg>
--- a/svelte/src/App.svelte
+++ b/svelte/src/App.svelte
@ -0,0 +1,47 @@
+<script lang="ts">
+  import svelteLogo from './assets/svelte.svg'
+  import viteLogo from '/vite.svg'
+  import Counter from './lib/Counter.svelte'
+</script>
+
+<main>
+  <div>
+    <a href="https://vite.dev" target="_blank" rel="noreferrer">
+      <img src={viteLogo} class="logo" alt="Vite Logo" />
+    </a>
+    <a href="https://svelte.dev" target="_blank" rel="noreferrer">
+      <img src={svelteLogo} class="logo svelte" alt="Svelte Logo" />
+    </a>
+  </div>
+  <h1>Vite + Svelte</h1>
+
+  <div class="card">
+    <Counter />
+  </div>
+
+  <p>
+    Check out <a href="https://github.com/sveltejs/kit#readme" target="_blank" rel="noreferrer">SvelteKit</a>, the official Svelte app framework powered by Vite!
+  </p>
+
+  <p class="read-the-docs">
+    Click on the Vite and Svelte logos to learn more
+  </p>
+</main>
+
+<style>
+  .logo {
+    height: 6em;
+    padding: 1.5em;
+    will-change: filter;
+    transition: filter 300ms;
+  }
+  .logo:hover {
+    filter: drop-shadow(0 0 2em #646cffaa);
+  }
+  .logo.svelte:hover {
+    filter: drop-shadow(0 0 2em #ff3e00aa);
+  }
+  .read-the-docs {
+    color: #888;
+  }
+</style>
--- a/svelte/src/TableViewer.svelte
+++ b/svelte/src/TableViewer.svelte
@ -0,0 +1,533 @@
+<svelte:options customElement={{ tag: "table-viewer", shadow: "none" }} />
+
+<script lang="ts">
+  import * as uuid from "uuid";
+
+  import {
+    type Coords,
+    type Encodable,
+    type Field,
+    type Row,
+    type FieldType,
+    coords_eq,
+  } from "./field.svelte";
+
+  type CommittedChange = {
+    coords_initial: Coords;
+    // This will be identical to coords_initial, unless the change altered a
+    // primary key.
+    coords_updated: Coords;
+    value_initial: Encodable;
+    value_updated: Encodable;
+  };
+
+  type LazyData = {
+    rows: Row[];
+    fields: Field[];
+  };
+
+  type Selection = {
+    region: "main" | "inserter";
+    coords: Coords;
+    original_value: Encodable;
+  };
+
+  type ParsedPkey = Record<string, Encodable>;
+
+  let selections = $state<Selection[]>([]);
+  let editing = $state(false);
+  let editor_input_value = $state("");
+  let committed_changes = $state<CommittedChange[][]>([]);
+  let reverted_changes = $state<CommittedChange[][]>([]);
+  let editor_input_element = $state<HTMLInputElement | undefined>();
+  let table_element = $state<HTMLDivElement | undefined>();
+  let inserter_rows = $state<Row[]>([]);
+  let lazy_data = $state<LazyData | undefined>();
+
+  // -------- Helper Functions -------- //
+
+  function arrow_key_direction(
+    key: string,
+  ): "Down" | "Left" | "Right" | "Up" | undefined {
+    if (key === "ArrowDown") {
+      return "Down";
+    } else if (key === "ArrowLeft") {
+      return "Left";
+    } else if (key === "ArrowRight") {
+      return "Right";
+    } else if (key === "ArrowUp") {
+      return "Up";
+    } else {
+      return undefined;
+    }
+  }
+
+  function try_parse_editor_value(
+    field_type: FieldType,
+  ): Encodable | undefined {
+    if (field_type.t === "Text") {
+      return {
+        t: "Text",
+        c: editor_input_value,
+      };
+    }
+    if (field_type.t === "Uuid") {
+      try {
+        return {
+          t: "Uuid",
+          c: uuid.stringify(uuid.parse(editor_input_value)),
+        };
+      } catch {
+        // uuid.parse() throws a TypeError if unsuccessful.
+        return undefined;
+      }
+    }
+    throw new Error("Unknown field type");
+  }
+
+  // -------- Updates and Effects -------- //
+
+  function set_selections(arr: Omit<Selection, "original_value">[]) {
+    selections = arr.map((sel) => {
+      let cell_data: Encodable | undefined;
+      if (sel.region === "main") {
+        cell_data = lazy_data?.rows[sel.coords[0]].data[sel.coords[1]];
+      } else if (sel.region === "inserter") {
+        cell_data = inserter_rows[sel.coords[0]].data[sel.coords[1]];
+      } else {
+        throw new Error("invalid region");
+      }
+      return {
+        ...sel,
+        original_value: cell_data!,
+      };
+    });
+    if (arr.length === 1) {
+      const [sel] = arr;
+      let cell_data: Encodable | undefined;
+      if (sel.region === "main") {
+        cell_data = lazy_data?.rows[sel.coords[0]].data[sel.coords[1]];
+      } else if (sel.region === "inserter") {
+        cell_data = inserter_rows[sel.coords[0]].data[sel.coords[1]];
+      }
+      if (cell_data?.t === "Text" || cell_data?.t === "Uuid") {
+        editor_input_value = cell_data.c ?? "";
+      } else {
+        editor_input_value = "";
+      }
+    } else {
+      editor_input_value = "";
+    }
+  }
+
+  function try_move_selection(direction: "Down" | "Left" | "Right" | "Up") {
+    if (lazy_data && !editing && selections.length > 0) {
+      const last_selection = selections[selections.length - 1];
+      if (
+        direction === "Right" &&
+        last_selection.coords[1] < lazy_data.fields.length - 1
+      ) {
+        set_selections([
+          {
+            region: last_selection.region,
+            coords: [last_selection.coords[0], last_selection.coords[1] + 1],
+          },
+        ]);
+      } else if (direction === "Left" && last_selection.coords[1] > 0) {
+        set_selections([
+          {
+            region: last_selection.region,
+            coords: [last_selection.coords[0], last_selection.coords[1] - 1],
+          },
+        ]);
+      } else if (direction === "Down") {
+        if (last_selection.region === "main") {
+          if (last_selection.coords[0] < lazy_data.rows.length - 1) {
+            set_selections([
+              {
+                region: "main",
+                coords: [
+                  last_selection.coords[0] + 1,
+                  last_selection.coords[1],
+                ],
+              },
+            ]);
+          } else {
+            // At bottom of main table.
+            set_selections([
+              {
+                region: "inserter",
+                coords: [0, last_selection.coords[1]],
+              },
+            ]);
+          }
+        } else if (last_selection.region === "inserter") {
+          if (last_selection.coords[0] < inserter_rows.length - 1) {
+            set_selections([
+              {
+                region: "inserter",
+                coords: [
+                  last_selection.coords[0] + 1,
+                  last_selection.coords[1],
+                ],
+              },
+            ]);
+          }
+        }
+      } else if (direction === "Up") {
+        if (last_selection.region === "main") {
+          if (last_selection.coords[0] > 0) {
+            set_selections([
+              {
+                region: "main",
+                coords: [
+                  last_selection.coords[0] - 1,
+                  last_selection.coords[1],
+                ],
+              },
+            ]);
+          }
+        } else if (last_selection.region === "inserter") {
+          if (last_selection.coords[0] > 0) {
+            set_selections([
+              {
+                region: "inserter",
+                coords: [
+                  last_selection.coords[0] - 1,
+                  last_selection.coords[1],
+                ],
+              },
+            ]);
+          } else {
+            // At top of inserter table.
+            set_selections([
+              {
+                region: "main",
+                coords: [lazy_data.rows.length - 1, last_selection.coords[1]],
+              },
+            ]);
+          }
+        }
+      }
+    }
+  }
+
+  function try_sync_edit_to_cells() {
+    if (lazy_data && editing && selections.length === 1) {
+      const [sel] = selections;
+      const parsed = try_parse_editor_value(
+        lazy_data.fields[sel.coords[1]].field_type,
+      );
+      if (parsed !== undefined) {
+        if (sel.region === "main") {
+          lazy_data.rows[sel.coords[0]].data[sel.coords[1]] = parsed;
+        } else if (sel.region === "inserter") {
+          inserter_rows[sel.coords[0]].data[sel.coords[1]] = parsed;
+        } else {
+          throw new Error("Unknown region");
+        }
+      }
+    }
+  }
+
+  function try_start_edit() {
+    if (!editing) {
+      editing = true;
+      editor_input_element?.focus();
+    }
+  }
+
+  function try_commit_edit() {
+    (async function () {
+      if (lazy_data && editing && selections.length === 1) {
+        const [sel] = selections;
+        const field = lazy_data.fields[sel.coords[1]];
+        const parsed = try_parse_editor_value(field.field_type);
+        if (parsed !== undefined) {
+          if (sel.region === "main") {
+            const pkey = JSON.parse(
+              lazy_data.rows[sel.coords[0]].key as string,
+            ) as ParsedPkey;
+            const resp = await fetch("update-value", {
+              method: "post",
+              headers: { "Content-Type": "application/json" },
+              body: JSON.stringify({
+                column: field.name,
+                pkeys: pkey,
+                value: parsed,
+              }),
+            });
+            if (resp.status >= 200 && resp.status < 300) {
+              committed_changes.push([
+                {
+                  coords_initial: sel.coords,
+                  coords_updated: sel.coords, // TODO: this assumes no inserted/deleted rows
+                  value_initial: sel.original_value,
+                  value_updated: parsed,
+                },
+              ]);
+              editing = false;
+              selections = [{ ...sel, original_value: parsed }];
+              table_element?.focus();
+            } else {
+              // TODO display feedback to user
+              console.error(resp);
+              console.error(await resp.text());
+            }
+          } else if (sel.region === "inserter") {
+            table_element?.focus();
+            editing = false;
+            selections = [{ ...sel, original_value: parsed }];
+          } else {
+            throw new Error("Unknown region");
+          }
+        } else {
+          // TODO
+        }
+      }
+    })().catch(console.error);
+  }
+
+  function cancel_edit() {
+    selections.forEach(({ coords, original_value, region }) => {
+      if (region === "main") {
+        if (lazy_data) {
+          lazy_data.rows[coords[0]].data[coords[1]] = original_value;
+        }
+      } else if (region === "inserter") {
+        inserter_rows[coords[0]].data[coords[1]] = original_value;
+      } else {
+        throw new Error("Unknown region");
+      }
+    });
+    // Reset editor input value
+    set_selections(selections);
+    editing = false;
+    table_element?.focus();
+  }
+
+  // -------- Event Handlers: Both Tables -------- //
+
+  function handle_table_keydown(ev: KeyboardEvent) {
+    const arrow_direction = arrow_key_direction(ev.key);
+    if (arrow_direction) {
+      try_move_selection(arrow_direction);
+      ev.preventDefault();
+    }
+    if (ev.key === "Enter") {
+      try_start_edit();
+    }
+  }
+
+  function handle_table_cell_dblclick(_: Coords) {
+    try_start_edit();
+  }
+
+  function handle_table_focus() {
+    if (selections.length === 0 && (lazy_data?.rows[0]?.data.length ?? 0) > 0) {
+      set_selections([{ region: "main", coords: [0, 0] }]);
+    }
+  }
+
+  // -------- Event Handlers: Main Table -------- //
+
+  function handle_main_cell_click(ev: MouseEvent, coords: Coords) {
+    if (!editing) {
+      if (ev.metaKey || ev.ctrlKey) {
+        // TODO
+        // selections = [...selections.filter((prev) => !coords_eq(prev, coords)), coords];
+        // editor_input_value = "";
+      } else {
+        set_selections([{ region: "main", coords }]);
+      }
+    }
+  }
+
+  // -------- Event Handlers: Inserter Table -------- //
+
+  function handle_inserter_cell_click(ev: MouseEvent, coords: Coords) {
+    if (!editing) {
+      if (ev.metaKey || ev.ctrlKey) {
+        // TODO
+        // selections = [...selections.filter((prev) => !coords_eq(prev, coords)), coords];
+        // editor_input_value = "";
+      } else {
+        set_selections([{ region: "inserter", coords }]);
+      }
+    }
+  }
+
+  // -------- Event Handlers: Editor -------- //
+
+  function handle_editor_blur() {
+    try_commit_edit();
+  }
+
+  function handle_editor_focus() {
+    try_start_edit();
+  }
+
+  function handle_editor_input() {
+    try_sync_edit_to_cells();
+  }
+
+  function handle_editor_keydown(ev: KeyboardEvent) {
+    if (ev.key === "Enter") {
+      try_commit_edit();
+    } else if (ev.key === "Escape") {
+      cancel_edit();
+    }
+  }
+
+  // -------- Initial API Fetch -------- //
+
+  (async function () {
+    interface GetDataResponse {
+      data: {
+        pkey: string;
+        data: Encodable[];
+      }[];
+      fields: Field[];
+    }
+    const resp = await fetch("get-data");
+    const body: GetDataResponse = await resp.json();
+    lazy_data = {
+      fields: body.fields,
+      rows: body.data.map(({ data, pkey }) => ({ data, key: pkey })),
+    };
+    inserter_rows = [
+      {
+        key: 0,
+        data: body.fields.map(() => ({ t: "Text", c: undefined })),
+      },
+    ];
+  })().catch(console.error);
+</script>
+
+{#snippet table_region({
+  region_name,
+  rows,
+  on_cell_click,
+}: {
+  region_name: string;
+  rows: Row[];
+  on_cell_click(ev: MouseEvent, coords: Coords): void;
+})}
+  {#if lazy_data}
+    {#each rows as row, row_index}
+      <div class="lens-table__row" role="row">
+        {#each lazy_data.fields as field, field_index}
+          {@const cell_data = row.data[field_index]}
+          {@const cell_coords: Coords = [row_index, field_index]}
+          {@const cell_selected = selections.some(
+            (sel) =>
+              sel.region === region_name && coords_eq(sel.coords, cell_coords),
+          )}
+          <!-- svelte-ignore a11y_click_events_have_key_events -->
+          <div
+            aria-colindex={field_index}
+            aria-rowindex={row_index}
+            aria-selected={cell_selected}
+            class={[
+              "lens-table__cell",
+              cell_selected && "lens-table__cell--selected",
+            ]}
+            onmousedown={(ev) => on_cell_click(ev, cell_coords)}
+            ondblclick={() => handle_table_cell_dblclick(cell_coords)}
+            role="gridcell"
+            style:width={`${field.width_px}px`}
+            tabindex="-1"
+          >
+            {#if cell_data.t === "Text"}
+              <div
+                class={[
+                  "lens-table__cell-content",
+                  "lens-table__cell-content--text",
+                  (cell_data.c ?? undefined) === undefined &&
+                    "lens-table__cell-content--null",
+                ]}
+              >
+                {cell_data.c ?? "Null"}
+              </div>
+            {:else if cell_data.t === "Uuid"}
+              <div
+                class={[
+                  "lens-table__cell-content",
+                  "lens-table__cell-content--uuid",
+                  (cell_data.c ?? undefined) === undefined &&
+                    "lens-table__cell-content--null",
+                ]}
+              >
+                {cell_data.c ?? "Null"}
+              </div>
+            {:else}
+              <div
+                class={[
+                  "lens-table__cell-content",
+                  "lens-table__cell-content--unknown",
+                ]}
+              >
+                UNKNOWN
+              </div>
+            {/if}
+          </div>
+        {/each}
+      </div>
+    {/each}
+  {/if}
+{/snippet}
+
+<div class="lens-grid">
+  {#if lazy_data}
+    <div
+      bind:this={table_element}
+      class="lens-table"
+      onfocus={handle_table_focus}
+      onkeydown={handle_table_keydown}
+      role="grid"
+      tabindex="0"
+    >
+      <div class={["lens-table__headers"]}>
+        {#each lazy_data.fields as field, field_index}
+          <div
+            aria-colindex={field_index}
+            class="lens-table__header"
+            role="columnheader"
+            style:width={`${field.width_px}px`}
+          >
+            <div>{field.label ?? field.name}</div>
+          </div>
+        {/each}
+        <div class="lens-table__header-actions">TODO</div>
+      </div>
+      <div class="lens-table__main">
+        {@render table_region({
+          region_name: "main",
+          rows: lazy_data.rows,
+          on_cell_click: handle_main_cell_click,
+        })}
+      </div>
+      <div class="lens-table__inserter">
+        {@render table_region({
+          region_name: "inserter",
+          rows: inserter_rows,
+          on_cell_click: handle_inserter_cell_click,
+        })}
+      </div>
+    </div>
+    <div class="lens-editor">
+      <input
+        bind:this={editor_input_element}
+        bind:value={editor_input_value}
+        class={[
+          "lens-editor__input",
+          selections.length !== 1 && "lens-editor__input--hidden",
+        ]}
+        onblur={handle_editor_blur}
+        onfocus={handle_editor_focus}
+        oninput={handle_editor_input}
+        onkeydown={handle_editor_keydown}
+      />
+    </div>
+  {/if}
+</div>
--- a/svelte/src/app.css
+++ b/svelte/src/app.css
@ -0,0 +1,79 @@
+:root {
+  font-family: system-ui, Avenir, Helvetica, Arial, sans-serif;
+  line-height: 1.5;
+  font-weight: 400;
+
+  color-scheme: light dark;
+  color: rgba(255, 255, 255, 0.87);
+  background-color: #242424;
+
+  font-synthesis: none;
+  text-rendering: optimizeLegibility;
+  -webkit-font-smoothing: antialiased;
+  -moz-osx-font-smoothing: grayscale;
+}
+
+a {
+  font-weight: 500;
+  color: #646cff;
+  text-decoration: inherit;
+}
+a:hover {
+  color: #535bf2;
+}
+
+body {
+  margin: 0;
+  display: flex;
+  place-items: center;
+  min-width: 320px;
+  min-height: 100vh;
+}
+
+h1 {
+  font-size: 3.2em;
+  line-height: 1.1;
+}
+
+.card {
+  padding: 2em;
+}
+
+#app {
+  max-width: 1280px;
+  margin: 0 auto;
+  padding: 2rem;
+  text-align: center;
+}
+
+button {
+  border-radius: 8px;
+  border: 1px solid transparent;
+  padding: 0.6em 1.2em;
+  font-size: 1em;
+  font-weight: 500;
+  font-family: inherit;
+  background-color: #1a1a1a;
+  cursor: pointer;
+  transition: border-color 0.25s;
+}
+button:hover {
+  border-color: #646cff;
+}
+button:focus,
+button:focus-visible {
+  outline: 4px auto -webkit-focus-ring-color;
+}
+
+@media (prefers-color-scheme: light) {
+  :root {
+    color: #213547;
+    background-color: #ffffff;
+  }
+  a:hover {
+    color: #747bff;
+  }
+  button {
+    background-color: #f9f9f9;
+  }
+}
--- a/svelte/src/assets/svelte.svg
+++ b/svelte/src/assets/svelte.svg
@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" aria-hidden="true" role="img" class="iconify iconify--logos" width="26.6" height="32" preserveAspectRatio="xMidYMid meet" viewBox="0 0 256 308"><path fill="#FF3E00" d="M239.682 40.707C211.113-.182 154.69-12.301 113.895 13.69L42.247 59.356a82.198 82.198 0 0 0-37.135 55.056a86.566 86.566 0 0 0 8.536 55.576a82.425 82.425 0 0 0-12.296 30.719a87.596 87.596 0 0 0 14.964 66.244c28.574 40.893 84.997 53.007 125.787 27.016l71.648-45.664a82.182 82.182 0 0 0 37.135-55.057a86.601 86.601 0 0 0-8.53-55.577a82.409 82.409 0 0 0 12.29-30.718a87.573 87.573 0 0 0-14.963-66.244"></path><path fill="#FFF" d="M106.889 270.841c-23.102 6.007-47.497-3.036-61.103-22.648a52.685 52.685 0 0 1-9.003-39.85a49.978 49.978 0 0 1 1.713-6.693l1.35-4.115l3.671 2.697a92.447 92.447 0 0 0 28.036 14.007l2.663.808l-.245 2.659a16.067 16.067 0 0 0 2.89 10.656a17.143 17.143 0 0 0 18.397 6.828a15.786 15.786 0 0 0 4.403-1.935l71.67-45.672a14.922 14.922 0 0 0 6.734-9.977a15.923 15.923 0 0 0-2.713-12.011a17.156 17.156 0 0 0-18.404-6.832a15.78 15.78 0 0 0-4.396 1.933l-27.35 17.434a52.298 52.298 0 0 1-14.553 6.391c-23.101 6.007-47.497-3.036-61.101-22.649a52.681 52.681 0 0 1-9.004-39.849a49.428 49.428 0 0 1 22.34-33.114l71.664-45.677a52.218 52.218 0 0 1 14.563-6.398c23.101-6.007 47.497 3.036 61.101 22.648a52.685 52.685 0 0 1 9.004 39.85a50.559 50.559 0 0 1-1.713 6.692l-1.35 4.116l-3.67-2.693a92.373 92.373 0 0 0-28.037-14.013l-2.664-.809l.246-2.658a16.099 16.099 0 0 0-2.89-10.656a17.143 17.143 0 0 0-18.398-6.828a15.786 15.786 0 0 0-4.402 1.935l-71.67 45.674a14.898 14.898 0 0 0-6.73 9.975a15.9 15.9 0 0 0 2.709 12.012a17.156 17.156 0 0 0 18.404 6.832a15.841 15.841 0 0 0 4.402-1.935l27.345-17.427a52.147 52.147 0 0 1 14.552-6.397c23.101-6.006 47.497 3.037 61.102 22.65a52.681 52.681 0 0 1 9.003 39.848a49.453 49.453 0 0 1-22.34 33.12l-71.664 45.673a52.218 52.218 0 0 1-14.563 6.398"></path></svg>
--- a/svelte/src/field.svelte.ts
+++ b/svelte/src/field.svelte.ts
@ -0,0 +1,75 @@
+import { z } from "zod";
+
+// -------- Encodable -------- //
+
+const encodable_text_schema = z.object({
+  t: z.literal("Text"),
+  c: z.string().nullish().transform((x) => x ?? undefined),
+});
+
+const encodable_timestamp_schema = z.object({
+  t: z.literal("Timestamp"),
+  c: z.coerce.date().nullish().transform((x) => x ?? undefined),
+});
+
+const encodable_uuid_schema = z.object({
+  t: z.literal("Uuid"),
+  c: z.string().nullish().transform((x) => x ?? undefined),
+});
+
+const encodable_schema = z.union([
+  encodable_text_schema,
+  encodable_timestamp_schema,
+  encodable_uuid_schema,
+]);
+
+export type Encodable = z.infer<typeof encodable_schema>;
+
+// -------- FieldType -------- //
+
+const integer_field_type_schema = z.object({
+  t: z.literal("Integer"),
+  c: z.unknown(),
+});
+
+const text_field_type_schema = z.object({
+  t: "Text",
+  c: z.unknown(),
+});
+
+const uuid_field_type_schema = z.object({
+  t: "Uuid",
+  c: z.unknown(),
+});
+
+export const field_type_schema = z.union([
+  integer_field_type_schema,
+  text_field_type_schema,
+  uuid_field_type_schema,
+]);
+
+export type FieldType = z.infer<typeof field_type_schema>;
+
+// -------- Field -------- //
+
+export type Field = {
+  id: string;
+  name: string;
+  label?: string;
+  field_type: FieldType;
+  width_px: number;
+};
+
+// -------- Table Utils -------- //
+// TODO move this to its own module
+
+export type Coords = [number, number];
+
+export type Row = {
+  key: string | number;
+  data: Encodable[];
+};
+
+export function coords_eq(a: Coords, b: Coords): boolean {
+  return a[0] === b[0] && a[1] === b[1];
+}
--- a/svelte/src/interactive-table.svelte
+++ b/svelte/src/interactive-table.svelte
@ -0,0 +1,122 @@
+<script lang="ts">
+  import {
+    type Coords,
+    type Field,
+    type Row,
+    coords_eq,
+  } from "./field.svelte";
+  
+  type Props = {
+    fields: Field[];
+    header_classes?: (string | boolean | undefined)[];
+    on_cell_click?(ev: MouseEvent, coords: Coords): void;
+    on_cell_dblclick?(coords: Coords): void;
+    on_focus?(): void;
+    on_keydown?(ev: KeyboardEvent): void;
+    rows: Row[];
+    root_element?: HTMLDivElement;
+    selections: Coords[];
+    show_headers?: boolean;
+    tab_index?: number;
+  };
+
+  let {
+    fields,
+    header_classes = [],
+    on_cell_click,
+    on_cell_dblclick,
+    on_focus,
+    on_keydown,
+    root_element = $bindable(),
+    rows,
+    selections,
+    show_headers = true,
+    tab_index = 0,
+  }: Props = $props();
+</script>
+
+<div
+  bind:this={root_element}
+  class="viewer-table"
+  onfocus={on_focus}
+  onkeydown={on_keydown}
+  role="grid"
+  tabindex={tab_index}
+>
+  {#if show_headers}
+    <div class={["viewer-table__headers", ...header_classes]}>
+      {#each fields as field, field_index}
+        <div
+          aria-colindex={field_index}
+          class="viewer-header"
+          role="columnheader"
+          style:width={`${field.width_px}px`}
+        >
+          <div>{field.label ?? field.name}</div>
+        </div>
+      {/each}
+      <div class="viewer-header-actions">
+        TODO
+      </div>
+    </div>
+  {/if}
+  <div class="viewer-table__body">
+    {#each rows as row, row_index}
+      <div aria-rowindex={row_index} class="viewer-row" role="row">
+        {#each fields as field, field_index}
+          {@const cell_data = row.data[field_index]}
+          {@const cell_coords: Coords = [row_index, field_index]}
+          {@const cell_selected = selections.some(
+            (sel_coords) => coords_eq(sel_coords, cell_coords),
+          )}
+          <!-- svelte-ignore a11y_click_events_have_key_events -->
+          <div
+            aria-colindex={field_index}
+            aria-rowindex={row_index}
+            aria-selected={cell_selected}
+            class={[
+              "viewer-cell",
+              cell_selected && "viewer-cell--selected",
+            ]}
+            onclick={(ev) => on_cell_click?.(ev, cell_coords)}
+            ondblclick={() => on_cell_dblclick?.(cell_coords)}
+            role="gridcell"
+            style:width={`${field.width_px}px`}
+            tabindex="-1"
+          >
+            {#if cell_data.t === "Text"}
+              <div
+                class={[
+                  "viewer-cell__content",
+                  "viewer-cell__content--text",
+                  cell_data.c === null && "viewer-cell__content--null",
+                ]}
+              >
+                {cell_data.c}
+              </div>
+            {:else if cell_data.t === "Uuid"}
+              <div
+                class={[
+                  "viewer-cell__content",
+                  "viewer-cell__content--uuid",
+                  cell_data.c === null && "viewer-cell__content--null",
+                ]}
+              >
+                {cell_data.c}
+              </div>
+            {:else}
+              <div
+                class={[
+                  "viewer-cell__content",
+                  "viewer-cell__content--unknown",
+                ]}
+              >
+                UNKNOWN
+              </div>
+            {/if}
+          </div>
+        {/each}
+      </div>
+    {/each}
+  </div>
+</div>
--- a/svelte/src/lib/Counter.svelte
+++ b/svelte/src/lib/Counter.svelte
@ -0,0 +1,10 @@
+<script lang="ts">
+  let count: number = $state(0)
+  const increment = () => {
+    count += 1
+  }
+</script>
+
+<button onclick={increment}>
+  count is {count}
+</button>
--- a/svelte/src/main.ts
+++ b/svelte/src/main.ts
@ -0,0 +1,9 @@
+import { mount } from 'svelte'
+import './app.css'
+import App from './App.svelte'
+
+const app = mount(App, {
+  target: document.getElementById('app')!,
+})
+
+export default app
--- a/svelte/src/table-viewer/loaded.svelte
+++ b/svelte/src/table-viewer/loaded.svelte
@ -0,0 +1,168 @@
+<svelte:options customElement={{ tag: "table-viewer", shadow: "none" }} />
+
+<script lang="ts">
+  import { type Encodable, type Field } from "./field.svelte";
+
+  type Coords = [string, string];
+  interface CommittedChange {
+    coords_initial: Coords;
+    // This will be identical to coords_initial, unless the change altered a
+    // primary key.
+    coords_updated: Coords;
+    value_initial: Encodable;
+    value_updated: Encodable;
+  }
+
+  let selections = $state<Coords[]>([]);
+  let table_focused = $state(false);
+  let editing = $state(false);
+  let editor_input_value = $state("");
+  let committed_changes = $state<CommittedChange[][]>([]);
+  let reverted_changes = $state<CommittedChange[][]>([]);
+  let editor_input_element = $state<HTMLInputElement | undefined>();
+  
+  interface GetDataResult {
+    pkeys: string[];
+    data: Record<string, Record<string, Encodable>>;
+    fields: Record<string, Field>;
+    field_names: string[];
+  }
+
+  function coords_eq(a: Coords, b: Coords): boolean {
+    return a[0] === b[0] && a[1] === b[1];
+  }
+
+  function handle_click(ev: MouseEvent, coords: Coords, cell_data: Encodable) {
+    if (!editing) {
+      if (ev.metaKey || ev.ctrlKey) {
+        // TODO
+        // selections = [...selections.filter((prev) => !coords_eq(prev, coords)), coords];
+        // editor_input_value = "";
+      } else {
+        selections = [coords];
+        if (cell_data.t === "Text" || cell_data.t === "Uuid") {
+          editor_input_value = cell_data.c;
+        }
+      }
+    }
+  }
+
+  function handle_dblclick(_coords: Coords) {
+    if (!editing) {
+      editing = true;
+      editor_input_element?.focus();
+    }
+  }
+
+  function handle_table_focusin() {
+    table_focused = true;
+  }
+
+  function handle_table_focusout() {
+    table_focused = false;
+  }
+
+  function handle_keydown(ev: KeyboardEvent) {
+    if (table_focused && ev.key === "ArrowDown") {
+      
+    }
+  }
+
+  $effect(() => {
+    document.addEventListener("keydown", handle_keydown);
+    return () => document.removeEventListener("keydown", handle_keydown);
+  });
+
+  const data_promise: Promise<GetDataResult> = fetch("get-data")
+    .then((resp) => resp.json())
+    .then((body) => ({
+      ...body,
+      data: Object.fromEntries(body.data.map(({ pkey, data }) => [
+        pkey,
+        Object.fromEntries(body.fields.map(({ name }, i) => [name, data[i]])),
+      ])),
+      field_names: body.fields.map(({ name }) => name),
+      fields: Object.fromEntries(body.fields.map((field) => [field.name, field])),
+    }));
+</script>
+
+{#await data_promise}
+  <div class="loading-indicator">Loading...</div>
+{:then data}
+  <div
+    class="viewer-table"
+    onfocusin={handle_table_focusin}
+    onfocusout={handle_table_focusout}
+    role="grid"
+    tabindex="0"
+  >
+    <div class="viewer-table__headers">
+      {#each data.field_names as field_name, field_index}
+        <div
+          aria-colindex={field_index}
+          class="viewer-header"
+          role="columnheader"
+          style:width={`${data.fields[field_name].width_px}px`}
+        >
+          <div>{data.fields[field_name].label ?? field_name}</div>
+        </div>
+      {/each}
+      <div class="viewer-header-actions">
+        TODO
+      </div>
+    </div>
+    <div class="viewer-table__body">
+      {#each data.pkeys as pkey, row_index}
+        <div aria-rowindex={row_index} class="viewer-row" role="row">
+          {#each data.field_names as field_name, field_index}
+            {@const cell_data = data.data[pkey][field_name]}
+            {@const selected = selections.some(
+              ([sel_pkey, sel_field]) => sel_pkey === pkey && sel_field === field_name,
+            )}
+            <!-- svelte-ignore a11y_click_events_have_key_events -->
+            <div
+              aria-colindex={field_index}
+              aria-rowindex={row_index}
+              aria-selected={selected}
+              class="viewer-cell"
+              onclick={(ev) => handle_click(ev, [pkey, field_name], cell_data)}
+              ondblclick={() => handle_dblclick([pkey, field_name])}
+              role="gridcell"
+              style:width={`${data.fields[field_name].width_px}px`}
+              tabindex="-1"
+            >
+              {#if cell_data.t === "Text"}
+                <div
+                  class={[
+                    "viewer-cell__content",
+                    "viewer-cell__content--text",
+                    selections.some((coords) => coords_eq(coords, [pkey, field_name])) && "viewer-cell__content--selected",
+                  ]}
+                >
+                  {cell_data.c}
+                </div>
+              {:else if cell_data.t === "Uuid"}
+                <div class="viewer-cell__content viewer-cell__content--uuid">{cell_data.c}</div>
+              {:else}
+                <div class="viewer-cell__content viewer-cell__content--unknown">Unknown type</div>
+              {/if}
+            </div>
+          {/each}
+        </div>
+      {/each}
+    </div>
+  </div>
+  <div class="editor">
+    <input
+      class={["editor__input", selections.length !== 1 && "editor__input--hidden"]}
+      onfocus={() => {
+        editing = true;
+      }}
+      role="combobox"
+      bind:this={editor_input_element}
+      bind:value={editor_input_value}
+    />
+  </div>
+{:catch err}
+  Error {err}
+{/await}
--- a/svelte/src/vite-env.d.ts
+++ b/svelte/src/vite-env.d.ts
@ -0,0 +1,2 @@
+/// <reference types="svelte" />
+/// <reference types="vite/client" />
--- a/svelte/svelte.config.js
+++ b/svelte/svelte.config.js
@ -0,0 +1,8 @@
+import { vitePreprocess } from "@sveltejs/vite-plugin-svelte";
+
+export default {
+  compilerOptions: { customElement: true },
+  // Consult https://svelte.dev/docs#compile-time-svelte-preprocess
+  // for more information about preprocessors
+  preprocess: vitePreprocess(),
+};
--- a/svelte/tsconfig.app.json
+++ b/svelte/tsconfig.app.json
@ -0,0 +1,20 @@
+{
+  "extends": "@tsconfig/svelte/tsconfig.json",
+  "compilerOptions": {
+    "target": "ES2022",
+    "useDefineForClassFields": true,
+    "module": "ESNext",
+    "resolveJsonModule": true,
+    /**
+     * Typecheck JS in `.svelte` and `.js` files by default.
+     * Disable checkJs if you'd like to use dynamic types in JS.
+     * Note that setting allowJs false does not prevent the use
+     * of JS in `.svelte` files.
+     */
+    "allowJs": true,
+    "checkJs": true,
+    "isolatedModules": true,
+    "moduleDetection": "force"
+  },
+  "include": ["src/**/*.ts", "src/**/*.js", "src/**/*.svelte"]
+}
--- a/svelte/tsconfig.json
+++ b/svelte/tsconfig.json
@ -0,0 +1,7 @@
+{
+  "files": [],
+  "references": [
+    { "path": "./tsconfig.app.json" },
+    { "path": "./tsconfig.node.json" }
+  ]
+}
--- a/svelte/tsconfig.node.json
+++ b/svelte/tsconfig.node.json
@ -0,0 +1,25 @@
+{
+  "compilerOptions": {
+    "tsBuildInfoFile": "./node_modules/.tmp/tsconfig.node.tsbuildinfo",
+    "target": "ES2023",
+    "lib": ["ES2023"],
+    "module": "ESNext",
+    "skipLibCheck": true,
+
+    /* Bundler mode */
+    "moduleResolution": "bundler",
+    "allowImportingTsExtensions": true,
+    "verbatimModuleSyntax": true,
+    "moduleDetection": "force",
+    "noEmit": true,
+
+    /* Linting */
+    "strict": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "erasableSyntaxOnly": true,
+    "noFallthroughCasesInSwitch": true,
+    "noUncheckedSideEffectImports": true
+  },
+  "include": ["vite.config.ts"]
+}
--- a/svelte/vite.config.ts
+++ b/svelte/vite.config.ts
@ -0,0 +1,21 @@
+import { defineConfig } from "vite";
+import * as path from "@std/path";
+import { svelte } from "@sveltejs/vite-plugin-svelte";
+
+// https://vite.dev/config/
+export default defineConfig({
+  plugins: [svelte()],
+  build: {
+    rollupOptions: {
+      input: path.fromFileUrl(
+        new URL("./src/TableViewer.svelte", import.meta.url),
+      ),
+      output: {
+        dir: path.fromFileUrl(new URL("../js_dist", import.meta.url)),
+        entryFileNames: "[name].js",
+        chunkFileNames: "[name].js",
+        assetFileNames: "[name].[ext]",
+      },
+    },
+  },
+});
--- a/webc/src/cell_common.gleam
+++ b/webc/src/cell_common.gleam
@ -27,11 +27,23 @@ pub fn options_common(
    component.on_attribute_change("selected", fn(value) {
      ParentChangedSelected(value != "") |> CommonMsg |> map_msg |> Ok
    }),
+    component.on_attribute_change("insertable", fn(value) {
+      ParentChangedInsertable(value != "") |> CommonMsg |> map_msg |> Ok
+    }),
+    component.on_attribute_change("has-default", fn(value) {
+      ParentChangedInsertable(value != "") |> CommonMsg |> map_msg |> Ok
+    }),
  ]
 }

 pub type ModelCommon {
-  ModelCommon(root_path: String, row: Int, column: Int, selected: Bool)
+  ModelCommon(
+    root_path: String,
+    row: Int,
+    column: Int,
+    selected: Bool,
+    insertable: Bool,
+  )
 }

 pub type Msg {
@ -39,13 +51,20 @@ pub type Msg {
  ParentChangedRow(Int)
  ParentChangedColumn(Int)
  ParentChangedSelected(Bool)
+  ParentChangedInsertable(Bool)
  UserClickedCell
  UserDoubleClickedCell
 }

 pub fn init(_) -> #(ModelCommon, Effect(CommonMsg)) {
  #(
-    ModelCommon(root_path: "", selected: False, row: -1, column: -1),
+    ModelCommon(
+      root_path: "",
+      selected: False,
+      row: -1,
+      column: -1,
+      insertable: False,
+    ),
    context.request_context(
      context: dynamic.string("root_path"),
      subscribe: False,
@ -79,6 +98,10 @@ pub fn update(
      ModelCommon(..model, selected:),
      effect.none(),
    )
+    ParentChangedInsertable(insertable) -> #(
+      ModelCommon(..model, insertable:),
+      effect.none(),
+    )
    UserClickedCell -> #(
      model,
      event.emit(
--- a/webc/src/cell_uuid_component.gleam
+++ b/webc/src/cell_uuid_component.gleam
@ -34,13 +34,13 @@ pub fn component() -> App(Nil, Model, Msg) {
 }

 pub type Model {
-  Model(common: ModelCommon, value: Option(String))
+  Model(common: ModelCommon, value: Option(String), has_default: Bool)
 }

 fn init(_) -> #(Model, Effect(Msg)) {
  let #(model_common, effect_common) = cell_common.init(Nil)
  #(
-    Model(common: model_common, value: option.None),
+    Model(common: model_common, value: None, has_default: False),
    effect_common
      |> effect.map(fn(effect_common) { Common(effect_common) }),
  )
@ -71,7 +71,17 @@ fn view(model: Model) -> Element(Msg) {
          False -> attr.class("cell__content--uuid")
        },
      ],
-      [html.text(model.value |> option.unwrap("Null"))],
+      [
+        html.text(
+          model.value
+          |> option.unwrap(
+            case model.common.insertable && model.common.has_default {
+              True -> "Default"
+              False -> "Null"
+            },
+          ),
+        ),
+      ],
    )
  })
 }
--- a/webc/src/history.gleam
+++ b/webc/src/history.gleam
@ -0,0 +1 @@
+
--- a/webc/src/table_viewer_component.gleam
+++ b/webc/src/table_viewer_component.gleam
@ -0,0 +1,465 @@
+import gleam/dict.{type Dict}
+import gleam/dynamic.{type Dynamic}
+import gleam/dynamic/decode
+import gleam/http/response.{type Response}
+import gleam/io
+import gleam/json
+import gleam/list
+import gleam/option.{None, Some}
+import gleam/pair
+import gleam/regexp
+import gleam/result
+import gleam/set.{type Set}
+import lustre.{type App}
+import lustre/component
+import lustre/effect.{type Effect}
+import lustre/element.{type Element}
+import lustre/element/html
+import lustre/event
+import plinth/browser/document
+import plinth/browser/event as plinth_event
+import rsvp
+
+import context
+import encodable.{type Encodable}
+import field.{type Field}
+import field_type.{type FieldType}
+
+pub const name: String = "table-viewer"
+
+pub fn component() -> App(Nil, Model, Msg) {
+  lustre.component(init, update, view, [
+    component.on_attribute_change("root-path", fn(value) {
+      ParentChangedRootPath(value) |> Ok
+    }),
+  ])
+}
+
+// -------- Model -------- //
+
+type Coord {
+  Coord(pkey: String, field: String)
+}
+
+type Cell {
+  Cell(value_committed: Encodable, value_current: Encodable)
+}
+
+pub type Model {
+  Model(
+    root_path: String,
+    selections: List(Coord),
+    editing: Bool,
+    fields: Dict(String, Field),
+    field_names: List(String),
+    history: List(HistoryEvent),
+    pkeys: List(String),
+    data: Dict(Coord, Encodable),
+    // Whether OS, ctrl, or alt keys are being held. If so, simultaneously
+    // pressing a typing key should not trigger an overwrite.
+    modifiers_held: Set(String),
+  )
+}
+
+pub type HistoryEvent {
+  CommitCellValue(from: Encodable, to: Encodable)
+}
+
+pub fn apply_history(ev: HistoryEvent) -> Effect(Msg) {
+  case ev {
+    CommitCellValue -> {
+      todo
+    }
+  }
+}
+
+fn init(_) -> #(Model, Effect(Msg)) {
+  #(
+    Model(
+      root_path: "",
+      selections: [],
+      editing: False,
+      fields: dict.new(),
+      field_names: [],
+      pkeys: [],
+      values: dict.new(),
+      modifiers_held: set.new(),
+    ),
+    effect.before_paint(fn(dispatch, _) -> Nil {
+      document.add_event_listener("keydown", fn(ev) -> Nil {
+        let key = plinth_event.key(ev)
+        case key {
+          "ArrowLeft" | "ArrowRight" | "ArrowUp" | "ArrowDown" ->
+            dispatch(UserPressedDirectionalKey(key))
+          "Enter" -> dispatch(UserPressedEnterKey)
+          "Shift", "Meta" | "Alt" | "Control" ->
+            dispatch(UserPressedModifierKey(key))
+          _ ->
+            case is_typing_key(key) {
+              True -> dispatch(UserPressedTypingKey(key))
+              False -> Nil
+            }
+        }
+      })
+      document.add_event_listener("keyup", fn(ev) -> Nil {
+        let key = plinth_event.key(ev)
+        case key {
+          "Meta" | "Alt" | "Control" -> dispatch(UserReleasedModifierKey(key))
+          _ -> Nil
+        }
+      })
+    }),
+  )
+}
+
+fn is_typing_key(key: String) -> Bool {
+  let assert Ok(re) =
+    regexp.from_string("^[a-zA-Z0-9!@#$%^&*._/?<>{}[\\]'\"~`-]$")
+  regexp.check(key, with: re)
+}
+
+// -------- Update -------- //
+
+pub type EditorMsg {
+  EditStarted
+  EditStateChanged(EditState)
+  EditFinished(Encodable)
+}
+
+pub type ApiMsg {
+  CellValueCommitted(Coord)
+  RowInserted
+}
+
+pub type MouseMsg {
+  UserClickedCell(Coord)
+  UserDoubleClickedCell(Coord)
+}
+
+pub type KeyboardMsg {
+  UserPressedDirectionalKey(String)
+  UserPressedEnterKey
+  UserPressedTypingKey(String)
+  UserPressedModifierKey(String)
+  UserReleasedModifierKey(String)
+}
+
+pub type Msg {
+  ParentChangedRootPath(String)
+  EditorMessage(EditorMsg)
+  ApiMessage(ApiMsg)
+  MouseMessage(MouseMsg)
+  KeyboardMessage(KeyboardMsg)
+}
+
+fn update(model: Model, msg: Msg) -> #(Model, Effect(Msg)) {
+  case msg {
+    ParentChangedRootPath(root_path) -> #(
+      Model(..model, root_path:),
+      context.update_consumers(
+        model.root_path_consumers,
+        dynamic.string(root_path),
+      ),
+    )
+    EditorMessage(sub_msg) -> editor_update(model, sub_msg)
+    MouseEvent(sub_msg) -> mouse_update(model, sub_msg)
+    KeyboardMessage(sub_msg) -> keyboard_update(model, sub_msg)
+  }
+}
+
+fn editor_update(model: Model, msg: EditorMsg) -> #(Model, Effect(Msg)) {
+  case msg {
+    EditStarted -> #(Model(..model, editing: True), effect.none())
+    EditStateChanged(_) -> todo
+    EditFinished -> todo
+  }
+}
+
+fn api_update(model: Model, msg: ApiMsg) -> #(Model, Effect(Msg)) {
+  case msg {
+    CellValueCommitted(response) -> {
+      case response {
+        Ok(_) -> #(Model(..model, editing: False), blur_hoverbar())
+        Error(rsvp.HttpError(response)) -> {
+          io.println_error("HTTP error while updating value: " <> response.body)
+          #(model, effect.none())
+        }
+        Error(err) -> {
+          echo err
+          #(model, effect.none())
+        }
+      }
+    }
+  }
+}
+
+fn mouse_update(model: Model, msg: ApiMsg) -> #(Model, Effect(Msg)) {
+  case msg {
+    UserClickedCell(row, column) -> assign_selection(model:, to: #(row, column))
+    // TODO 
+    UserDoubleClickedCell(_row, _column) -> #(model, case model.editing {
+      True -> effect.none()
+      False -> focus_hoverbar()
+    })
+  }
+}
+
+fn keyboard_update(model: Model, msg: KeyboardMsg) -> #(Model, Effect(Msg)) {
+  case msg {
+    UserPressedDirectionalKey(key) -> {
+      case model.editing, model.selections {
+        False, [#(selected_row, selected_col)] -> {
+          let first_row_selected = selected_row == 0
+          // No need to subtract 1 from pkeys size, because there's another
+          // row for "insert".
+          let last_row_selected = selected_row == dict.size(model.pkeys)
+          let first_col_selected = selected_col == 0
+          let last_col_selected = selected_col == dict.size(model.fields) - 1
+          case
+            key,
+            first_row_selected,
+            last_row_selected,
+            first_col_selected,
+            last_col_selected
+          {
+            "ArrowLeft", _, _, False, _ ->
+              assign_selection(model:, to: #(selected_row, selected_col - 1))
+            "ArrowRight", _, _, _, False ->
+              assign_selection(model:, to: #(selected_row, selected_col + 1))
+            "ArrowUp", False, _, _, _ ->
+              assign_selection(model:, to: #(selected_row - 1, selected_col))
+            "ArrowDown", _, False, _, _ ->
+              assign_selection(model:, to: #(selected_row + 1, selected_col))
+            _, _, _, _, _ -> #(model, effect.none())
+          }
+        }
+        False, [] ->
+          case dict.size(model.pkeys) > 0 && dict.size(model.fields) > 0 {
+            True -> assign_selection(model:, to: #(0, 0))
+            False -> #(model, effect.none())
+          }
+        _, _ -> #(model, effect.none())
+      }
+    }
+    UserPressedEnterKey -> #(model, case model.editing {
+      True -> effect.none()
+      False -> focus_hoverbar()
+    })
+    UserPressedTypingKey(key) ->
+      case model.editing, model.selections, set.is_empty(model.modifiers_held) {
+        False, [_], True -> #(model, overwrite_in_hoverbar(value: key))
+        _, _, _ -> #(model, effect.none())
+      }
+    UserPressedModifierKey(key) -> #(
+      Model(..model, modifiers_held: model.modifiers_held |> set.insert(key)),
+      effect.none(),
+    )
+    UserReleasedModifierKey(key) -> #(
+      Model(..model, modifiers_held: model.modifiers_held |> set.delete(key)),
+      effect.none(),
+    )
+  }
+}
+
+fn overwrite_in_hoverbar(value value: String) -> Effect(Msg) {
+  use _, _ <- effect.before_paint()
+  do_overwrite_in_hoverbar(value)
+}
+
+@external(javascript, "./viewer_controller_component.ffi.mjs", "overwriteInHoverbar")
+fn do_overwrite_in_hoverbar(value _value: String) -> Nil {
+  Nil
+}
+
+fn commit_change(model model: Model, value value: Encodable) -> Effect(Msg) {
+  case model.selections {
+    [#(row, col)] ->
+      rsvp.post(
+        "./update-value",
+        json.object([
+          #(
+            "column",
+            model.fields
+              |> dict.get(col)
+              |> result.map(fn(field) { field.name })
+              |> result.unwrap("")
+              |> json.string(),
+          ),
+          #(
+            "pkeys",
+            model.pkeys
+              |> dict.get(row)
+              |> result.unwrap(dict.new())
+              |> json.dict(fn(x) { x }, encodable.to_json),
+          ),
+          #("value", encodable.to_json(value)),
+        ]),
+        rsvp.expect_ok_response(ServerUpdateValuePost),
+      )
+    _ -> todo
+  }
+}
+
+/// Updater for when selection is being assigned to a single cell.
+fn assign_selection(
+  model model: Model,
+  to coords: #(Int, Int),
+) -> #(Model, Effect(Msg)) {
+  // Multiple sets of conditions fall back to the "selection actually changed"
+  // scenario, so this is a little awkward to write without a return keyword.
+  let early_return = case model.selections {
+    [prev_coords] ->
+      case prev_coords == coords {
+        True -> Some(#(model, effect.none()))
+        False -> None
+      }
+    _ -> None
+  }
+  case early_return {
+    Some(value) -> value
+    None -> #(
+      Model(..model, selections: [coords]),
+      effect.batch([
+        sync_cell_value_to_hoverbar(
+          coords,
+          model.fields
+            |> dict.get(pair.second(coords))
+            |> result.map(fn(f) { f.field_type })
+            |> result.unwrap(field_type.Unknown),
+        ),
+        change_selected_attrs([coords]),
+      ]),
+    )
+  }
+}
+
+// -------- Effects -------- //
+
+fn focus_hoverbar() -> Effect(Msg) {
+  use _dispatch, _root <- effect.before_paint()
+  do_focus_hoverbar()
+}
+
+@external(javascript, "./viewer_controller_component.ffi.mjs", "focusHoverbar")
+fn do_focus_hoverbar() -> Nil {
+  Nil
+}
+
+fn blur_hoverbar() -> Effect(Msg) {
+  use _dispatch, _root <- effect.before_paint()
+  do_blur_hoverbar()
+}
+
+@external(javascript, "./viewer_controller_component.ffi.mjs", "blurHoverbar")
+fn do_blur_hoverbar() -> Nil {
+  Nil
+}
+
+/// Effect that changes [selected=] attributes on assigned children. Should only
+/// be called when the new selection is different than the previous one (that
+/// is, not when selection is "moving" from a cell to the same cell).
+fn change_selected_attrs(to_coords coords: List(#(Int, Int))) -> Effect(msg) {
+  use _, _ <- effect.before_paint()
+  do_clear_selected_attrs()
+  coords
+  |> list.map(fn(coords) {
+    let #(row, column) = coords
+    do_set_cell_attr(row:, column:, key: "selected", value: "true")
+  })
+  Nil
+}
+
+fn set_cell_value(coords coords: #(Int, Int), value value: Encodable) {
+  use _, _ <- effect.before_paint()
+  let #(row, col) = coords
+  do_set_cell_attr(
+    row,
+    col,
+    "value",
+    value |> encodable.to_json() |> json.to_string(),
+  )
+}
+
+@external(javascript, "./viewer_controller_component.ffi.mjs", "clearSelectedAttrs")
+fn do_clear_selected_attrs() -> Nil {
+  Nil
+}
+
+@external(javascript, "./viewer_controller_component.ffi.mjs", "setCellAttr")
+fn do_set_cell_attr(
+  row _row: Int,
+  column _column: Int,
+  key _key: String,
+  value _value: String,
+) -> Nil {
+  Nil
+}
+
+fn sync_cell_value_to_hoverbar(
+  coords coords: #(Int, Int),
+  field_type f_type: FieldType,
+) -> Effect(Msg) {
+  use _, _root <- effect.before_paint()
+  let #(row, column) = coords
+  do_sync_cell_value_to_hoverbar(
+    row:,
+    column:,
+    field_type: f_type |> field_type.to_json() |> json.to_string(),
+  )
+}
+
+@external(javascript, "./viewer_controller_component.ffi.mjs", "syncCellValueToHoverbar")
+fn do_sync_cell_value_to_hoverbar(
+  row _row: Int,
+  column _column: Int,
+  field_type _field_type: String,
+) -> Nil {
+  Nil
+}
+
+// -------- View -------- //
+
+fn view(_: Model) -> Element(Msg) {
+  html.div(
+    [
+      context.on_context_request(
+        dynamic.string("root_path"),
+        ChildRequestedRootPath,
+      ),
+      event.on("cell-click", {
+        use msg <- decode.field("detail", {
+          use row <- decode.field("row", decode.int)
+          use column <- decode.field("column", decode.int)
+          decode.success(UserClickedCell(row, column))
+        })
+        decode.success(msg)
+      }),
+      event.on("cell-dblclick", {
+        use msg <- decode.field("detail", {
+          use row <- decode.field("row", decode.int)
+          use column <- decode.field("column", decode.int)
+          decode.success(UserDoubleClickedCell(row, column))
+        })
+        decode.success(msg)
+      }),
+      event.on("edit-start", decode.success(ChildEmittedEditStartEvent)),
+      event.on("edit-update", {
+        use original <- decode.subfield(
+          ["detail", "original"],
+          encodable.decoder(),
+        )
+        use edited <- decode.subfield(["detail", "edited"], encodable.decoder())
+        decode.success(ChildEmittedEditUpdateEvent(original:, edited:))
+      }),
+      event.on("edit-end", {
+        use original <- decode.subfield(
+          ["detail", "original"],
+          encodable.decoder(),
+        )
+        use edited <- decode.subfield(["detail", "edited"], encodable.decoder())
+        decode.success(ChildEmittedEditEndEvent(original:, edited:))
+      }),
+    ],
+    [component.default_slot([], [])],
+  )
+}
--- a/webc/src/viewer_controller_component.gleam
+++ b/webc/src/viewer_controller_component.gleam
@ -160,10 +160,17 @@ fn update(model: Model, msg: Msg) -> #(Model, Effect(Msg)) {
        _ -> todo
      }
    }
-    ChildEmittedEditEndEvent(_original, edited) -> #(
-      model,
-      commit_change(model:, value: edited),
-    )
+    ChildEmittedEditEndEvent(_original, edited) ->
+      case model.selections {
+        [#(selected_row, _)] ->
+          case selected_row == dict.size(model.pkeys) {
+            // Cell under edit is in "insert" row
+            True -> #(Model(..model, editing: False), effect.none())
+            False -> #(model, commit_change(model:, value: edited))
+          }
+        _ -> todo
+      }
+
    ChildRequestedRootPath(callback, subscribe) -> #(
      case subscribe {
        True ->
@ -198,7 +205,9 @@ fn update(model: Model, msg: Msg) -> #(Model, Effect(Msg)) {
      case model.editing, model.selections {
        False, [#(selected_row, selected_col)] -> {
          let first_row_selected = selected_row == 0
-          let last_row_selected = selected_row == dict.size(model.pkeys) - 1
+          // No need to subtract 1 from pkeys size, because there's another
+          // row for "insert".
+          let last_row_selected = selected_row == dict.size(model.pkeys)
          let first_col_selected = selected_col == 0
          let last_col_selected = selected_col == dict.size(model.fields) - 1
          case
				`@ -0,0 +1 @@`
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