use anyhow::{Context as _, Result};
use askama::Template;
use axum::{
    extract::{Path, State},
    http::{header::CACHE_CONTROL, HeaderValue},
    response::{Html, IntoResponse as _, Response},
    routing::get,
    Router,
};
use deadpool_postgres::{tokio_postgres::Row, GenericClient};
use diesel::prelude::*;
use mdengine::{
    class_privileges_for_grantees,
    pg_attribute::{attributes_for_rel, PgAttribute},
    pg_class::{self, PgClass},
};
use serde::Deserialize;
use tower::ServiceBuilder;
use tower_http::{
    services::{ServeDir, ServeFile},
    set_header::SetResponseHeaderLayer,
};

use crate::{
    abstract_::{diesel_set_user_id, escape_identifier},
    app_error::AppError,
    app_state::{AppState, DieselConn, PgConn},
    auth,
    data_layer::{Field, FieldOptionsBuilder, ToHtmlString as _, Value},
    settings::Settings,
    users::CurrentUser,
};

const FRONTEND_ROW_LIMIT: i64 = 1000;

pub fn new_router(state: AppState) -> Router<()> {
    let base_path = state.settings.base_path.clone();
    let app = Router::new()
        .route("/", get(landing_page))
        .route("/c/{oid}/viewer", get(viewer_page))
        .nest("/auth", auth::new_router())
        .layer(SetResponseHeaderLayer::if_not_present(
            CACHE_CONTROL,
            HeaderValue::from_static("no-cache"),
        ))
        .fallback_service(
            ServiceBuilder::new()
                .layer(SetResponseHeaderLayer::if_not_present(
                    CACHE_CONTROL,
                    HeaderValue::from_static("max-age=21600, stale-while-revalidate=86400"),
                ))
                .service(
                    ServeDir::new("static").not_found_service(
                        ServiceBuilder::new()
                            .layer(SetResponseHeaderLayer::if_not_present(
                                CACHE_CONTROL,
                                HeaderValue::from_static("no-cache"),
                            ))
                            .service(ServeFile::new("static/_404.html")),
                    ),
                ),
        )
        .with_state(state);
    if base_path.is_empty() {
        app
    } else {
        Router::new().nest(&base_path, app).fallback_service(
            ServeDir::new("static").not_found_service(ServeFile::new("static/_404.html")),
        )
    }
}

async fn landing_page(
    State(Settings {
        base_path,
        pg_user_role_prefix,
        ..
    }): State<Settings>,
    DieselConn(db_conn): DieselConn,
    CurrentUser(current_user): CurrentUser,
) -> Result<Response, AppError> {
    let grantees = vec![format!(
        "{}{}",
        pg_user_role_prefix,
        current_user.id.simple()
    )];
    let visible_tables = db_conn
        .interact(move |conn| -> Result<Vec<_>> {
            diesel_set_user_id(&pg_user_role_prefix, current_user.id, conn)?;
            let privileges = class_privileges_for_grantees(grantees)
                .load(conn)
                .context("error reading classes")?;
            Ok(privileges.into_iter().map(|value| value.class).collect())
        })
        .await
        .unwrap()?;
    #[derive(Template)]
    #[template(path = "tmp.html")]
    struct ResponseTemplate {
        base_path: String,
        relations: Vec<PgClass>,
    }
    Ok(Html(
        ResponseTemplate {
            base_path,
            relations: visible_tables,
        }
        .render()?,
    )
    .into_response())
}

#[derive(Deserialize)]
struct ViewerPagePath {
    oid: u32,
}

async fn viewer_page(
    State(Settings {
        base_path,
        pg_user_role_prefix,
        ..
    }): State<Settings>,
    DieselConn(diesel_conn): DieselConn,
    PgConn(pg_client): PgConn,
    CurrentUser(current_user): CurrentUser,
    Path(params): Path<ViewerPagePath>,
) -> Result<Response, AppError> {
    pg_client
        .query(
            &format!(
                "SET ROLE {};",
                escape_identifier(&format!(
                    "{}{}",
                    pg_user_role_prefix,
                    current_user.id.simple()
                )),
            ),
            &[],
        )
        .await?;

    // FIXME: Ensure user has access to relation

    // One-off helper struct to hold Diesel results
    struct RelMeta {
        class: PgClass,
        attrs: Vec<PgAttribute>,
    }
    let RelMeta { class, attrs } = diesel_conn
        .interact(move |conn| -> Result<_> {
            Ok(RelMeta {
                class: pg_class::table
                    .filter(pg_class::dsl::oid.eq(params.oid))
                    .select(PgClass::as_select())
                    .first(conn)?,
                attrs: attributes_for_rel(params.oid).load(conn)?,
            })
        })
        .await
        .unwrap()?;
    let query = [
        "SELECT",
        &attrs
            .iter()
            .map(|attr| attr.attname.clone())
            .collect::<Vec<_>>()
            .join(", "),
        "FROM",
        &escape_identifier(&class.relname),
        "LIMIT",
        &FRONTEND_ROW_LIMIT.to_string(),
        ";",
    ]
    .join(" ");
    let rows = pg_client.query(&query, &[]).await?;
    #[derive(Template)]
    #[template(path = "class-viewer.html")]
    struct ResponseTemplate {
        base_path: String,
        fields: Vec<Field>,
        rows: Vec<Row>,
    }
    Ok(Html(
        ResponseTemplate {
            base_path,
            fields: attrs
                .into_iter()
                .map(|attr| Field {
                    options: FieldOptionsBuilder::default().build().unwrap(),
                    name: attr.attname,
                })
                .collect(),
            rows,
        }
        .render()?,
    )
    .into_response())
}