import {
  BufferDrawing,
  BufferSize,
  CharBuffer,
  Color,
  PaletteMap,
} from "./base.ts";
import { Display } from "./display.ts";

/**
 * Common abstraction for a textual UI
 */
export class TextUI {
  private screen = new CharBuffer({ w: 1, h: 1 });
  private palettemap: PaletteMap = [];

  constructor(private display: Display) {
  }

  get drawing(): BufferDrawing {
    return new BufferDrawing(this.screen, this.palettemap);
  }

  /**
   * Initializes the display
   */
  async init(palette: UIPalette): Promise<void> {
    var size = await this.display.getSize();
    this.screen = new CharBuffer(size);
    this.palettemap = await this.getPaletteMapping(palette);
    await this.display.clear();
  }

  /**
   * Get the current display size
   */
  getSize(): BufferSize {
    return this.screen.getSize();
  }

  /**
   * Flush the internal buffer to the display
   */
  async flush(): Promise<void> {
    // TODO only dirty chars
    const { w, h } = this.screen.getSize();
    for (let y = 0; y < h; y++) {
      for (let x = 0; x < w; x++) {
        await this.display.setChar({ x, y }, this.screen.get({ x, y }));
      }
    }
  }

  /**
   * Start the event loop, waiting for input
   */
  async loop(refresh = 1000): Promise<void> {
    while (true) {
      await this.flush();
      await new Promise((resolve) => setTimeout(resolve, refresh));
    }
  }

  private async getPaletteMapping(
    palette: UIPalette,
  ): Promise<PaletteMap> {
    // get the colors supported by display
    const allcolors = palette
      .map((c): Color[] => Array.isArray(c) ? c : [c])
      .reduce((acc, val) => acc.concat(val), []);
    const supported = await this.display.setupPalette(allcolors);

    // TODO find the best color mapping for each source color

    return palette.map((_, idx) => idx);
  }
}

/**
 * Color palette requirements.
 *
 * The array represents the "ideal" colors desired by the application.
 * When drawing things, *bg* and *fg* color information should be an index
 * in this palette.
 *
 * For each palette index, a single color can be requested, or an
 * array of accepted alternatives, with decreasing priority.
 */
export type UIPalette = ReadonlyArray<Color | ReadonlyArray<Color>>;