const fs = require('fs');
const path = require('path');
const https = require('https');

class DownloadAssetsPlugin {
  constructor(assets) {
    this.assets = assets;
    this.hasRun = false;
    this.createdDirs = new Set();
  }

  safeUnlink(filePath) {
    try {
      fs.unlinkSync(filePath);
    } catch (err) {
      // Ignore cleanup errors
    }
  }

  apply(compiler) {
    compiler.hooks.beforeCompile.tapAsync('DownloadAssetsPlugin', (params, callback) => {
      // Only run once per webpack process
      if (this.hasRun) {
        callback();
        return;
      }

      console.log('📦 Checking and downloading required assets...');

      const downloadPromises = this.assets.map(asset => this.downloadFile(asset));

      Promise.allSettled(downloadPromises)
        .then((results) => {
          const failed = results.filter(r => r.status === 'rejected');
          if (failed.length > 0) {
            console.warn(`⚠️  ${failed.length} asset(s) failed to download, continuing anyway...`);
          }
          console.log('✅ Asset check complete!');
          this.hasRun = true;
          callback();
        });
    });
  }

  downloadFile({ url, output }) {
    return new Promise((resolve, reject) => {
      // Ensure directory exists (only once per unique path)
      if (!this.createdDirs.has(output)) {
        fs.mkdirSync(output, { recursive: true });
        this.createdDirs.add(output);
      }

      const filename = path.basename(url);
      const filePath = path.join(output, filename);

      // Skip if file already exists
      if (fs.existsSync(filePath)) {
        resolve();
        return;
      }

      console.log(`  Downloading ${filename}...`);

      const file = fs.createWriteStream(filePath);

      const downloadFromUrl = (downloadUrl) => {
        https.get(downloadUrl, (response) => {
          // Handle redirects
          if (response.statusCode === 302 || response.statusCode === 301) {
            file.close();
            this.safeUnlink(filePath);
            downloadFromUrl(response.headers.location);
            return;
          }

          if (response.statusCode !== 200) {
            file.close();
            this.safeUnlink(filePath);
            reject(new Error(`Failed to download ${filename}: HTTP ${response.statusCode}`));
            return;
          }

          response.pipe(file);

          file.on('finish', () => {
            file.close();
            console.log(`  ✓ Downloaded ${filename}`);
            resolve();
          });

          file.on('error', (err) => {
            this.safeUnlink(filePath);
            reject(err);
          });
        }).on('error', (err) => {
          if (fs.existsSync(filePath)) {
            this.safeUnlink(filePath);
          }
          reject(err);
        });
      };

      downloadFromUrl(url);
    });
  }
}

module.exports = DownloadAssetsPlugin;