import sharp from 'sharp';
import { resolve, basename, extname, join, dirname } from 'path';
import { existsSync, mkdirSync, readdirSync, statSync } from 'fs';
import { fileURLToPath } from 'url';

const PROJECT_ROOT = resolve(fileURLToPath(import.meta.url), '../../..');
const DEFAULT_INPUT = resolve(PROJECT_ROOT, 'assets/items');
const DEFAULT_OUTPUT = resolve(PROJECT_ROOT, 'assets/icons');
const GRID = 4;
const SUPPORTED_EXTENSIONS = /\.(jpe?g|png|webp|tiff?)$/i;

async function splitSpriteSheet(filePath, outputDir) {
  const name = basename(filePath, extname(filePath));

  const { width, height } = await sharp(filePath).metadata();
  const cellWidth = Math.floor(width / GRID);
  const cellHeight = Math.floor(height / GRID);

  const tasks = [];

  for (let row = 0; row < GRID; row++) {
    for (let col = 0; col < GRID; col++) {
      const left = col * cellWidth;
      const top = row * cellHeight;
      const outputPath = join(outputDir, `${name}-${row}-${col}.png`);

      tasks.push(
        sharp(filePath)
          .extract({ left, top, width: cellWidth, height: cellHeight })
          .png()
          .toFile(outputPath)
          .then(() => outputPath)
      );
    }
  }

  return Promise.all(tasks);
}

function collectFiles(input) {
  if (statSync(input).isFile()) {
    return [input];
  }
  return readdirSync(input)
    .filter(f => SUPPORTED_EXTENSIONS.test(f))
    .map(f => join(input, f));
}

async function main() {
  const input = resolve(process.argv[2] || DEFAULT_INPUT);
  const outputDir = resolve(process.argv[3] || DEFAULT_OUTPUT);

  if (!existsSync(input)) {
    console.error(`Not found: ${input}`);
    process.exit(1);
  }

  mkdirSync(outputDir, { recursive: true });

  const files = collectFiles(input);

  if (files.length === 0) {
    console.error(`No image files found in: ${input}`);
    process.exit(1);
  }

  console.log(`Processing ${files.length} sprite sheet(s)...`);

  const allResults = await Promise.all(
    files.map(async (filePath) => {
      const results = await splitSpriteSheet(filePath, outputDir);
      console.log(`  ${basename(filePath)} -> ${results.length} images`);
      return results;
    })
  );

  const totalImages = allResults.reduce((sum, r) => sum + r.length, 0);
  console.log(`Done. ${totalImages} images saved to ${outputDir}`);
}

main();