import fs from "fs";
import path from "path";
import { execFileSync } from "child_process";
import { createCanvas } from "canvas";
import { Grid, copyGrid, Color } from "@snk/types/grid";
import { Snake } from "@snk/types/snake";
import {
  Options as DrawOptions,
  drawLerpWorld,
  getCanvasWorldSize,
} from "@snk/draw/drawWorld";
import type { Point } from "@snk/types/point";
import { step } from "@snk/solver/step";
import tmp from "tmp";
import gifsicle from "gifsicle";
// @ts-ignore
import GIFEncoder from "gif-encoder-2";

const withTmpDir = async <T>(
  handler: (dir: string) => Promise<T>
): Promise<T> => {
  const { name: dir, removeCallback: cleanUp } = tmp.dirSync({
    unsafeCleanup: true,
  });

  try {
    return await handler(dir);
  } finally {
    cleanUp();
  }
};

export type AnimationOptions = { frameDuration: number; step: number };

export const createGif = async (
  grid0: Grid,
  cells: Point[] | null,
  chain: Snake[],
  drawOptions: DrawOptions,
  animationOptions: AnimationOptions
) =>
  withTmpDir(async (dir) => {
    const { width, height } = getCanvasWorldSize(grid0, drawOptions);

    const canvas = createCanvas(width, height);
    const ctx = canvas.getContext("2d")!;

    const grid = copyGrid(grid0);
    const stack: Color[] = [];

    const encoder = new GIFEncoder(width, height, "neuquant", true);
    encoder.setRepeat(0);
    encoder.setDelay(animationOptions.frameDuration);
    encoder.start();

    for (let i = 0; i < chain.length; i += 1) {
      const snake0 = chain[i];
      const snake1 = chain[Math.min(chain.length - 1, i + 1)];
      step(grid, stack, snake0);

      for (let k = 0; k < animationOptions.step; k++) {
        ctx.clearRect(0, 0, width, height);
        ctx.fillStyle = "#fff";
        ctx.fillRect(0, 0, width, height);
        drawLerpWorld(
          ctx,
          grid,
          cells,
          snake0,
          snake1,
          stack,
          k / animationOptions.step,
          drawOptions
        );

        encoder.addFrame(ctx);
      }
    }

    const outFileName = path.join(dir, "out.gif");
    const optimizedFileName = path.join(dir, "out.optimized.gif");

    encoder.finish();
    fs.writeFileSync(outFileName, encoder.out.getData());

    execFileSync(
      gifsicle,
      [
        //
        "--optimize=3",
        "--color-method=diversity",
        "--colors=18",
        outFileName,
        ["--output", optimizedFileName],
      ].flat()
    );

    return fs.readFileSync(optimizedFileName);
  });