import {
  BufferDrawing,
  BufferSize,
  CharBuffer,
  Color,
  PaletteMap,
} from "./base.ts";
import { cmp } from "./deps.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 app_colors = palette.map((c): Color[] => Array.isArray(c) ? c : [c]);
    const all_colors = app_colors.reduce((acc, val) => acc.concat(val), []);
    const display_colors = await this.display.setupPalette(all_colors);

    // rank all supported colors by proximity to each app color
    let ranked: {
      color: Color;
      idx: number;
      penalty: number;
      matches: { color: Color; idx: number; distance: number }[];
    }[] = [];
    app_colors.forEach((colors, idx) => {
      colors.forEach((color, alt) => {
        ranked.push({
          color,
          idx,
          penalty: alt + 1,
          matches: display_colors.map((display_color, didx) => {
            return {
              color: display_color,
              idx: didx,
              distance: colorDistance(color, display_color),
            };
          }).sort(cmp({ key: (info) => info.distance })),
        });
      });
    });

    // TODO negatively score colors too much near previously chosen ones

    // find the best color mapping for each source color
    const result = palette.map(() => -1);
    while (ranked.length > 0) {
      ranked.sort(
        cmp({ key: (info) => info.matches[0].distance * info.penalty }),
      );

      const best = ranked[0];
      const app_idx = best.idx;
      const display_idx = best.matches[0].idx;
      result[app_idx] = display_idx;

      for (const color of ranked) {
        color.matches = color.matches.filter((match) =>
          match.idx !== display_idx
        );
      }
      ranked = ranked.filter((color) =>
        color.idx !== app_idx && color.matches.length > 0
      );
    }
    return result;
  }
}

/**
 * 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>>;

function colorDistance(e1: Color, e2: Color): number {
  /*return (e2.r - e1.r) * (e2.r - e1.r) +
    (e2.g - e1.g) * (e2.g - e1.g) +
    (e2.b - e1.b) * (e2.b - e1.b);*/
  const c = (x: number) => Math.round(x * 255);
  const rmean = (c(e1.r) + c(e2.r)) / 2;
  const r = c(e1.r) - c(e2.r);
  const g = c(e1.g) - c(e2.g);
  const b = c(e1.b) - c(e2.b);
  return Math.sqrt(
    (((512 + rmean) * r * r) >> 8) + 4 * g * g + (((767 - rmean) * b * b) >> 8),
  );
}