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 = "viewer-controller"

pub fn component() -> App(Nil, Model, Msg) {
  lustre.component(init, update, view, [
    component.on_attribute_change("root-path", fn(value) {
      ParentChangedRootPath(value) |> Ok
    }),
    component.on_attribute_change("pkeys", fn(value) {
      value
      |> json.parse(
        decode.list(decode.dict(decode.string, encodable.decoder())),
      )
      |> result.map(fn(lst) {
        list.zip(list.range(0, list.length(lst)), lst)
        |> dict.from_list()
        |> ParentChangedPkeys()
      })
      |> result.replace_error(Nil)
    }),
    component.on_attribute_change("fields", fn(value) {
      value
      |> json.parse(decode.list(field.decoder()))
      |> result.map(fn(lst) {
        list.zip(list.range(0, list.length(lst)), lst)
        |> dict.from_list()
        |> ParentChangedFields()
      })
      |> result.replace_error(Nil)
    }),
    component.on_attribute_change("root-path", fn(value) {
      ParentChangedRootPath(value) |> Ok
    }),
  ])
}

// -------- Model -------- //

pub type Model {
  Model(
    root_path: String,
    root_path_consumers: List(Dynamic),
    selections: List(#(Int, Int)),
    editing: Bool,
    pkeys: Dict(Int, Dict(String, Encodable)),
    fields: Dict(Int, Field),
    // 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),
  )
}

fn init(_) -> #(Model, Effect(Msg)) {
  #(
    Model(
      root_path: "",
      root_path_consumers: [],
      selections: [],
      editing: False,
      pkeys: dict.new(),
      fields: 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)
          "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 Msg {
  ParentChangedRootPath(String)
  ParentChangedPkeys(Dict(Int, Dict(String, Encodable)))
  ParentChangedFields(Dict(Int, Field))
  ChildEmittedEditStartEvent
  ChildEmittedEditUpdateEvent(original: Encodable, edited: Encodable)
  ChildEmittedEditEndEvent(original: Encodable, edited: Encodable)
  ChildRequestedRootPath(callback: Dynamic, subscribe: Bool)
  ServerUpdateValuePost(Result(Response(String), rsvp.Error))
  UserClickedCell(Int, Int)
  UserDoubleClickedCell(Int, Int)
  UserPressedDirectionalKey(String)
  UserPressedEnterKey
  UserPressedTypingKey(String)
  UserPressedModifierKey(String)
  UserReleasedModifierKey(String)
}

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),
      ),
    )
    ParentChangedPkeys(pkeys) -> #(Model(..model, pkeys:), effect.none())
    ParentChangedFields(fields) -> #(Model(..model, fields:), effect.none())
    ChildEmittedEditStartEvent -> #(
      Model(..model, editing: True),
      effect.none(),
    )
    ChildEmittedEditUpdateEvent(_original, edited) -> {
      case model.selections {
        [coords] -> #(model, set_cell_value(coords, edited))
        _ -> todo
      }
    }
    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 ->
          Model(..model, root_path_consumers: [
            callback,
            ..model.root_path_consumers
          ])
        False -> model
      },
      context.update_consumers([callback], dynamic.string(model.root_path)),
    )
    ServerUpdateValuePost(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())
        }
      }
    }
    UserClickedCell(row, column) -> assign_selection(model:, to: #(row, column))
    // TODO 
    UserDoubleClickedCell(_row, _column) -> #(model, case model.editing {
      True -> effect.none()
      False -> focus_hoverbar()
    })
    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([], [])],
  )
}