#!/usr/bin/env -S deno run --allow-read --allow-write --allow-run

import { TextLineStream } from "jsr:@std/streams@1.1.0";

/**
 *  CONFIG
 */

const instructionLength = 4; // in bytes
const rawDataInstructionLengthPrefix = "U32";

const ppmToAsmScriptPath = "./ppmToAsm.ts";

const mapPath = "assets/map.ppm";
const spritesPath = {
  "sprite_empty": "assets/sprites/empty.ppm",
  "sprite_unimplemented": "assets/sprites/placeholder.ppm",
  "sprite_wall_end": "assets/sprites/wall_end.ppm",
  "sprite_wall_straight": "assets/sprites/wall_straight.ppm",
  "sprite_wall_corner": "assets/sprites/wall_corner.ppm",
  "sprite_robot": "assets/sprites/robot.ppm",
  "sprite_ghost": "assets/sprites/ghost.ppm",
  "sprite_coin": "assets/sprites/coin.ppm",
};

/**
 *  END OF CONFIG
 */

class Minifier {
  private buffer = "";
  private lines: Array<string> = [];
  stream;

  constructor(writableStream: WritableStream) {
    this.stream = new TransformStream<string>({
      transform: (chunk, controller) => {
        this.buffer += chunk;
        controller.enqueue(this.processChunk());
      },

      flush: (controller) => {
        this.buffer += "\n";
        controller.enqueue(this.processChunk());
        controller.enqueue(this.lines.join("\n") + "\n");
        this.lines = [];
      },
    });

    this.stream.readable.pipeTo(writableStream);
  }

  private processChunk(): string {
    const newLines = this.buffer.split("\n");
    this.buffer = newLines.pop() as string; // keep the last (potentially incomplete) line

    const removeComment = (line: string) => line.replace(/\s*;.*/, "");
    const removeLeadingWhitespaces = (line: string) => line.replace(/^\s+/, "");
    const removeTrailingWhitespaces = (line: string) =>
      line.replace(/\s+$/, "");
    const removeDoubleSpaces = (line: string) => line.replaceAll(/ +/g, " ");
    const isNotEmpty = (line: string) => line.length !== 0;

    const newLinesStripped = newLines
      .map(removeComment)
      .map(removeLeadingWhitespaces)
      .map(removeTrailingWhitespaces)
      .map(removeDoubleSpaces)
      .filter(isNotEmpty);

    this.lines.push(...newLinesStripped);

    return this.processLines();
  }

  private processLines() {
    const processedLines: Array<string> = [];
    while (this.lines.length >= instructionLength) {
      const mergeableLines = this.lines.slice(0, instructionLength);
      if (!mergeableLines.every((line) => line.startsWith("U8"))) {
        processedLines.push(this.lines.shift() as string);
        continue;
      }

      const bytesToMerge = mergeableLines.map((line) =>
        parseInt((line.match(/U8\s(\d+)/) as RegExpMatchArray)[1])
      );
      let mergedBytes = 0;
      for (let i = 0; i < bytesToMerge.length; i++) {
        mergedBytes += bytesToMerge[i] << (instructionLength - 1 - i) * 8;
      }
      processedLines.push(
        `${rawDataInstructionLengthPrefix} ${mergedBytes >>> 0}`,
      );
      this.lines.splice(0, instructionLength);
    }

    return processedLines.length === 0 ? "" : `${processedLines.join("\n")}\n`;
  }
}

async function ppmToAsm(
  mode: "map" | "sprite",
  label: string,
  path: string,
): Promise<string> {
  const command = new Deno.Command(ppmToAsmScriptPath, {
    args: [
      instructionLength.toString(),
      mode,
      label,
      path,
    ],
  });

  const { code, stdout, stderr } = await command.output();

  const decoder = new TextDecoder();

  if (code !== 0) {
    console.error(`ppmToAsm script returned non-zero value: ${code}`);
    console.error(`STDERR: \n${decoder.decode(stderr)}`);
    Deno.exit(1);
  }

  return decoder.decode(stdout);
}

async function build(
  pwd: string,
  path: string,
  output: WritableStreamDefaultWriter<string>,
) {
  const includeExpressionRegex = /^\s*include\s+([^\s;]+)/;

  const file = await Deno.open(`${pwd}/${path}`);
  const readable = file.readable.pipeThrough(new TextDecoderStream())
    .pipeThrough(new TextLineStream());

  for await (const line of readable) {
    const match = line.match(includeExpressionRegex);
    if (match === null) {
      await output.write(`${line}\n`);
      continue;
    }

    await build(pwd, `${match[1]}.asm`, output);
  }
}

function printUsage(into: (message: string) => void) {
  into(`Usage:
\tbuild.ts [options...] {file}
\t\tRead the given file and recursively include other '.asm' files to produce a single output.
\tbuild.ts --help
\t\tPrint this message

Options:
\t--minify\tWhen used, the result will be stripped of all comments, leading/trailing double whitespaces, empty lines and use the more compact raw data representation.
\t--ppm   \tWhen used, the hardcoded ppm files will be translated to their matching Symfony assembly reprensentation into src/dist.`);
}

/**
 *  SCRIPT
 */

if (Deno.args.length < 1) {
  printUsage(console.error);
  Deno.exit(1);
}

let minify = false;
let convertPPM = false;
let path: string | undefined = undefined;

Deno.args.forEach((arg, index) => {
  switch (arg) {
    case "--help":
      printUsage(console.log);
      Deno.exit(0);
      break;
    case "--minify":
      minify = true;
      break;
    case "--ppm":
      convertPPM = true;
      break;

    default:
      if (index !== Deno.args.length - 1) {
        printUsage(console.error);
        Deno.exit(1);
      }
      path = arg;
      break;
  }
});

if (path === undefined) {
  printUsage(console.error);
  Deno.exit(1);
}

if (convertPPM) {
  await Deno.mkdir(`${Deno.cwd()}/src/dist`, { recursive: true });
  const mapPromise = async () => {
    const assembly = await ppmToAsm("map", "map", mapPath);
    await Deno.writeTextFile(`${Deno.cwd()}/src/dist/map.asm`, assembly);
  };

  const spritePromises = Object.entries(spritesPath).map(async ([label, path]) => {
    const assembly = await ppmToAsm("sprite", label, path);
    const filename = path.split("/").pop()?.split('.')[0];
    await Deno.writeTextFile(`${Deno.cwd()}/src/dist/${filename}.asm`, assembly);
  });

  await Promise.all([
    mapPromise(),
    ...spritePromises,
  ]);
}

const encoder = new TextEncoder();
const stdoutWritable = new WritableStream<string>({
  async write(chunk) {
    await Deno.stdout.write(encoder.encode(chunk));
  },
});

const writer = minify
  ? (new Minifier(stdoutWritable)).stream.writable.getWriter()
  : stdoutWritable.getWriter();

await build(`${Deno.cwd()}/src`, path, writer);
await writer.close();