/**
 * The dialog behind "+ → Texture / Font / Sound": everything the server holds of one kind, with
 * what the project already calls it. Offering the server's files rather than the machine's is the
 * point – uploading the same file twice is wasteful, and nothing collects the files a project
 * stopped referencing. Uploading is still one button away.
 *
 * The list differs per kind (tiles for pictures, rows with a sample line for typefaces, rows with a
 * ▶ for sounds); the dialog around it does not.
 */
import { type Container, type FederatedPointerEvent, type Graphics, Text } from 'pixi.js';
import type { AssetType } from '../core/model/AssetTypes';
import type { Project } from '../core/model/Project';
import type { StoredFile } from '../core/store/FileStore';
import {
  Button,
  drawControlBox,
  formatBytes,
  HStack,
  Label,
  Popup,
  pressCount,
  ScrollContainer,
  Spacer,
  Theme,
  textStyle,
  Widget,
} from '../ui';

/** The dialog keeps this size whatever the list turns out to be, so it does not jump on opening. */
export const PICKER_WIDTH = 560;
export const PICKER_HEIGHT = 340;

/** One offered file, with the asset that already wears it (if any). */
export type PickerItem<S extends StoredFile = StoredFile> = S & { assetName: string | null };

/** Pairs what the server lists with what the project calls it – the asset name is the caption worth showing. */
export function withAssetNames<S extends StoredFile>(
  stored: S[],
  project: Project,
  type: AssetType,
): PickerItem<S>[] {
  const named = new Map<string, string>();
  for (const asset of project.assets) {
    if (asset.type === type && 'file' in asset) named.set(asset.file, asset.name);
  }
  return stored.map((item) => ({ ...item, assetName: named.get(item.file) ?? null }));
}

/** The line under the list for a picked file: its upload name and size, and who wears it. */
export function describeStored(item: PickerItem): string {
  const size = item.name ? `${item.name} – ${formatBytes(item.bytes)}` : formatBytes(item.bytes);
  return item.assetName ? `${size} – already in the project as "${item.assetName}"` : size;
}

export interface PickerRow {
  /** A Container holding the rest, not a Graphics with children: Pixi v8 only lets containers have them. */
  box: Container;
  background: Graphics;
  caption: Text;
}

/**
 * The selectable part of the dialog: one entry per file, one of them picked, a double press
 * confirms. How entries are built, placed and drawn is the subclass's.
 */
export abstract class PickerList<Item extends PickerItem, Row extends PickerRow> extends Widget {
  protected items: Item[] = [];
  protected rows: Row[] = [];
  private selectedFile: string | null = null;
  private readonly empty = new Text({ text: '', style: textStyle('muted') });
  private readonly unwatch: (() => void)[] = [];
  onPick?: (file: string) => void;
  onActivate?: (file: string) => void;
  emptyText = '';

  constructor() {
    super();
    this.addChild(this.empty);
    this.on('pointerdown', (e: FederatedPointerEvent) => this.onPress(e));
  }

  /** Redraws whenever a library reports an arrival, until the list is destroyed. */
  protected watch(library: { onChange(fn: () => void): () => void }, onArrive: () => void): void {
    this.unwatch.push(library.onChange(onArrive));
  }

  setItems(items: Item[]): void {
    this.items = items;
    for (const row of this.rows) row.box.destroy({ children: true });
    this.rows = items.map(() => {
      const row = this.buildRow();
      this.addChild(row.box);
      return row;
    });
    if (!items.some((item) => item.file === this.selectedFile)) this.selectedFile = null;
    this.layout();
    this.redraw();
  }

  get selected(): Item | null {
    return this.items.find((item) => item.file === this.selectedFile) ?? null;
  }

  get fileList(): string[] {
    return this.items.map((item) => item.file);
  }

  get usedFiles(): string[] {
    return this.items.filter((item) => item.assetName !== null).map((item) => item.file);
  }

  /** The captions as drawn, read off the rows themselves rather than recomputed (test hook). */
  get captions(): string[] {
    return this.rows.map((row) => row.caption.text);
  }

  select(file: string | null): void {
    if (file === this.selectedFile) return;
    this.selectedFile = file;
    this.redraw();
    if (file) this.onPick?.(file);
  }

  /** The row of a file, with its index; null when the file is not offered. */
  protected rowOf(file: string): { row: Row; index: number } | null {
    const index = this.items.findIndex((item) => item.file === file);
    const row = this.rows[index];
    return row ? { row, index } : null;
  }

  override redraw(): void {
    this.empty.text = this.items.length === 0 ? this.emptyText : '';
    this.empty.position.set(0, 0);
    this.rows.forEach((row, index) => {
      const item = this.items[index];
      if (item) this.redrawRow(row, item, item.file === this.selectedFile);
    });
  }

  override destroy(): void {
    for (const stop of this.unwatch) stop();
    super.destroy({ children: true });
  }

  protected drawBox(row: Row, w: number, h: number, selected: boolean): void {
    row.background.clear();
    drawControlBox(row.background, w, h, {
      fill: selected ? Theme.colors.selection : Theme.colors.control,
      border: selected ? Theme.colors.accent : Theme.colors.border,
    });
  }

  protected onPress(e: FederatedPointerEvent): void {
    const local = this.toLocal(e.global);
    const item = this.items[this.indexAt(local.x, local.y)];
    if (!item) return;
    this.select(item.file);
    if (pressCount(e, item.file) === 2) this.onActivate?.(item.file);
  }

  protected abstract buildRow(): Row;
  /** Which entry a local point is on; any index without an item means none. */
  protected abstract indexAt(x: number, y: number): number;
  protected abstract redrawRow(row: Row, item: Item, selected: boolean): void;
}

/** A list of equally tall rows, one under the other. */
export abstract class RowList<Item extends PickerItem, Row extends PickerRow> extends PickerList<Item, Row> {
  protected abstract readonly rowHeight: number;
  protected readonly rowGap = 4;

  /** Global centre of a row (test hook); `fromX` keeps clear of a column that does something else. */
  rowGlobal(file: string, fromX = 0): { x: number; y: number } | null {
    const found = this.rowOf(file);
    if (!found) return null;
    const p = found.row.box.getGlobalPosition();
    return { x: p.x + fromX + (this.w - fromX) / 2, y: p.y + this.rowHeight / 2 };
  }

  heightFor(count: number): number {
    return count === 0 ? 0 : count * this.rowHeight + (count - 1) * this.rowGap;
  }

  override measure(): { w: number; h: number } {
    return { w: this.minWidth, h: Math.max(this.minHeight, this.heightFor(this.items.length)) };
  }

  override layout(): void {
    this.rows.forEach((row, index) => row.box.position.set(0, index * (this.rowHeight + this.rowGap)));
  }

  protected override indexAt(x: number, y: number): number {
    return x >= 0 && x <= this.w ? Math.floor(y / (this.rowHeight + this.rowGap)) : -1;
  }
}

export interface PickerWords {
  title: string;
  loading: string;
  /** Under the list while nothing is picked; a hint for what the rows can do. */
  idle?: string;
  empty: string;
  use: string;
  /** "image", "font", "sound" – for "3 fonts on the server". */
  noun: string;
}

let current: FilePicker<PickerItem> | null = null;

/**
 * Opens the dialog centred, closing whichever picker was open before it, and starts the listing.
 * The listing starts here and not in the constructor: it asks the subclass, and a subclass's own
 * fields are not assigned until its constructor has run past `super()`.
 */
export function openPicker<P extends FilePicker<PickerItem>>(picker: P): P {
  current?.close();
  current = picker;
  picker.openCentered();
  void picker.load();
  return picker;
}

/** The open dialog if it is one of `kind`, for the test hooks. */
export function currentPicker<P extends FilePicker<PickerItem>>(
  kind: abstract new (...args: never[]) => P,
): P | null {
  return current instanceof kind ? current : null;
}

export abstract class FilePicker<Item extends PickerItem> extends Popup {
  protected readonly scroll = new ScrollContainer();
  private readonly status: Label;
  private readonly detail: Label;
  private readonly use: Button;

  constructor(
    protected readonly list: PickerList<Item, PickerRow>,
    private readonly words: PickerWords,
    upload: () => void,
  ) {
    super({ modal: true, padding: Theme.padding * 2, gap: Theme.gap });
    this.content.add(new Label(words.title, { style: 'bodyBold' }));
    this.status = new Label(words.loading, { style: 'muted' });
    this.content.add(this.status);

    list.minWidth = PICKER_WIDTH;
    list.emptyText = words.empty;
    list.onPick = () => this.refreshSelection();
    list.onActivate = () => this.confirm();
    this.scroll.minWidth = PICKER_WIDTH;
    this.scroll.minHeight = PICKER_HEIGHT;
    this.scroll.setContent(list);
    this.content.add(this.scroll);

    this.detail = new Label(words.idle ?? '', { style: 'muted' });
    this.content.add(this.detail);

    const buttons = new HStack({ gap: Theme.gap, align: 'center' });
    const uploadButton = new Button('Upload…');
    uploadButton.onClick = this.closeThen(upload);
    buttons.add(uploadButton);
    buttons.add(new Spacer(), 1);
    const cancel = new Button('Cancel');
    cancel.onClick = this.closeThen();
    buttons.add(cancel);
    this.use = new Button(words.use, { variant: 'primary' });
    this.use.onClick = () => this.confirm();
    this.use.setEnabled(false);
    buttons.add(this.use);
    this.content.add(buttons);
  }

  /** What the dialog offers, which of it the project already wears, and what is picked (test hook). */
  debugInfo(): { files: string[]; used: string[]; captions: string[]; selected: string | null } {
    return {
      files: this.list.fileList,
      used: this.list.usedFiles,
      captions: this.list.captions,
      selected: this.list.selected?.file ?? null,
    };
  }

  override close(): void {
    super.close();
    if (current === this) current = null;
    // Escape, Cancel and a confirmed pick all land here, and `Popup.close` tolerates a second
    // call; the list's listeners must be dropped exactly once.
    if (!this.list.destroyed) this.list.destroy();
  }

  async load(): Promise<void> {
    try {
      const items = await this.fetchItems();
      this.list.setItems(items);
      // Only as tall as the entries need, up to the cap: a handful of files should not leave half
      // a dialog of empty box under them.
      const { unit, total } = this.contentHeight(items.length);
      this.scroll.minHeight = Math.min(this.roomFor(this.scroll, unit), Math.max(unit, total));
      const { noun } = this.words;
      this.status.setText(
        items.length === 1 ? `1 ${noun} on the server` : `${items.length} ${noun}s on the server`,
      );
    } catch (error) {
      this.status.setText(
        `Could not list the ${this.words.noun}s: ${error instanceof Error ? error.message : String(error)}`,
      );
    }
    this.refreshSelection();
  }

  private refreshSelection(): void {
    const item = this.list.selected;
    this.use.setEnabled(item !== null && this.canUse(item));
    this.detail.setText(item ? this.describe(item) : (this.words.idle ?? ''));
    this.refreshLayout();
  }

  private confirm(): void {
    const item = this.list.selected;
    if (!item || !this.canUse(item)) return;
    this.close();
    this.adopt(item);
  }

  /** The server's list, paired with the project's names (`withAssetNames`). */
  protected abstract fetchItems(): Promise<Item[]>;
  /** How tall the list is for `count` entries, and the height of one – the least the scroll shows. */
  protected abstract contentHeight(count: number): { unit: number; total: number };
  protected abstract adopt(item: Item): void;

  protected canUse(_item: Item): boolean {
    return true;
  }

  protected describe(item: Item): string {
    return describeStored(item);
  }
}