import { Color, PaletteMap } from "./base.ts";
import { UIPalette } from "./config.ts";
import { cmp } from "../deps.ts";
import { Display } from "./display.ts";

export async function getPaletteMapping(
  palette: UIPalette,
  display: Display,
): 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 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;
}

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),
  );
}