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

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

/**
 *  CONFIG
 */

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

const asmFilePaths = [
  "src/consts/arch.asm",
  "src/consts/game.asm",
  "src/consts/keyboard.asm",
  "src/consts/map.asm",
  "src/consts/scene.asm",
  "src/consts/screen.asm",
  "src/consts/sprites.asm",

  "src/init.asm",
  "src/main.asm",

  "src/lib/game.asm",
  "src/lib/drawing.asm",
  "src/lib/sprite_rotation.asm",
];
const reservedSpacePath = "src/reserved_space.asm";

const mapMatchingValues = {
  0x00_00_00: 0, // Empty
  0xFF_00_00: 1, // Wall
  0xFF_FF_00: 2, // Coin
};

const spritesMatchingValues = {
  0x00_00_00: 0, // 0b000_000_00
  0x00_00_FF: 3, // 0b000_000_11
  0x00_FF_00: 28, // 0b000_111_00
  0x99_50_00: 68, // 0b010_001_00
  0x77_77_77: 110, // 0b011_011_10
  0xB3_B3_B3: 146, // 0b100_100_10
  0xFF_00_00: 224, // 0b111_000_00
  0xFF_00_FF: 227, // 0b111_000_11
  0xFF_80_00: 240, // 0b111_100_00
  0xFF_FF_00: 248, // 0b111_110_00
  0xFF_FF_FF: 255, // 0b111_111_11
};

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 build(output: WritableStreamDefaultWriter<string>) {
  for (const path of asmFilePaths) {
    const file = await Deno.open(path);
    const readable = file.readable.pipeThrough(new TextDecoderStream())
      .pipeThrough(new TextLineStream());

    await output.write(`
;/*******************************
;* ${path}
;*******************************/
`);

    for await (const line of readable) {
      if (!line.startsWith("include ")) {
        await output.write(`${line}\n`);
      }
    }
  }

  const asmRawRepresentations = [];

  const mapBytes = await getDataFromPPM(mapPath);
  asmRawRepresentations.push(
    bytesToAsmConstU8("map", mapBytes, mapMatchingValues),
  );

  for (const [label, path] of Object.entries(spritesPath)) {
    const bytes = await getDataFromPPM(path);
    asmRawRepresentations.push(
      bytesToAsmConstU8(label, bytes, spritesMatchingValues),
    );
  }

  await output.write(asmRawRepresentations.join("\n\n"));

  await output.write(`
;
; RESERVED RAM SPACE
;
`);

  await output.write(await Deno.readTextFile(reservedSpacePath));
  await output.close();
}

/**
 * Return an ASM constant (U8) representation of the given data
 *
 * If needed, the representation will be padded to ensure the following code stays aligned on the instruction's length
 *
 * @param label The label to write before the first raw data
 * @param data An array of bytes to interprete as 24 bits values
 * @param matchingValues An associative array with a string representation for each possible 24 bit data value
 *
 * @returns The ASM representation of that raw data, pre- and post-fixed by the given label
 */
function bytesToAsmConstU8(
  label: string,
  data: Uint8Array,
  matchingValues: Record<number, number>,
): string {
  if (data.length % 3 !== 0) {
    console.error(
      "Length of data passed to bytesToAsmConstU8 are not a multiple of 3 (it needs to, as each resulting byte need a Red, a Green and a Blue value)",
    );
    Deno.exit(1);
  }

  const lines = [`${label}:`];
  for (let i = 0; i < data.length; i += 3) {
    const pixelValue = (data[i] << 16) + (data[i + 1] << 8) + (data[i + 2]);
    if (!Object.hasOwn(matchingValues, pixelValue)) {
      console.error(
        `No matching value defined for "${
          pixelValue.toString(2)
        }" (which is ${label}'s ${i} pixel)`,
      );
      Deno.exit(1);
    }

    lines.push(`U8 ${matchingValues[pixelValue]}`);
  }
  lines.push(`${label}_end:`);

  const bytesNb = data.length / 3;
  const unalignedBytesNb = bytesNb % instructionLength;

  for (let i = 0; i < instructionLength - unalignedBytesNb; i++) {
    lines.push(
      `U8 0 ; padding to preserve ${8 * instructionLength} bits alignment`,
    );
  }

  return lines.join("\n");
}

/**
 * Return the image pixels data (excluding all other fields) from a given PPM file
 *
 * The implementation differ from the format definition (https://netpbm.sourceforge.net/doc/ppm.html) but match the file created by GIMP.
 */
async function getDataFromPPM(path: string): Promise<Uint8Array> {
  const endOfComment = [
    0x0a,
    0x0d,
  ];
  const whitespaces = [
    0x09,
    0x0a,
    0x0b,
    0x0c,
    0x0d,
    0x20,
  ];
  const numbers = [
    0x30,
    0x31,
    0x32,
    0x33,
    0x34,
    0x35,
    0x36,
    0x37,
    0x38,
    0x39,
  ];

  const hashtag = 0x23;

  const content = await Deno.readFile(path);
  let offset = 0;

  // magic number
  while (!whitespaces.includes(content[offset])) {
    offset++;
  }

  offset++; // whitespace

  // potential comment
  if (content[offset] === hashtag) {
    while (!endOfComment.includes(content[offset])) {
      offset++;
    }

    offset++; // end of comment
  }

  // image width
  while (numbers.includes(content[offset])) {
    offset++;
  }

  offset++; // whitespace

  // image height
  while (numbers.includes(content[offset])) {
    offset++;
  }

  offset++; // whitespace

  // maximum color value
  while (numbers.includes(content[offset])) {
    offset++;
  }

  offset++; // whitespace

  return content.slice(offset, content.length);
}

function printUsage(into: (message: string) => void) {
  into(`Usage:
\tbuild.ts [--minify]
\t\tMerge the hardcoded files and output the result to stdout. The "--minify" option can be used to strip the result of all comments, leading/trailing double whitespaces, empty lines and use the more compact raw data representation.
\tbuild.ts --help
\t\tPrint this message`);
}

/**
 *  SCRIPT
 */

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

let minify = false;
if (Deno.args.length === 1) {
  switch (Deno.args[0]) {
    case "--help":
      printUsage(console.log);
      Deno.exit(0);
      break;
    case "--minify":
      minify = true;
      break;
    default:
      printUsage(console.error);
      Deno.exit(1);
      break;
  }
}

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

if (minify) {
  const minifier = new Minifier(stdoutWritable);
  await build(minifier.stream.writable.getWriter());
} else {
  await build(stdoutWritable.getWriter());
}