import { existsSync, mkdirSync, writeFileSync } from 'fs';
import { basename, join, extname } from 'path';
import { upsertMediaFile } from '../db.js';

const UA = 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36';

export function parseUserUrl(url) {
  const parsed = new URL(url);
  const base = `${parsed.protocol}//${parsed.hostname}`;
  const m = parsed.pathname.match(/^\/([^/]+)\/user\/([^/?#]+)/);
  if (!m) throw new Error(`Can't parse URL. Expected: https://coomer.su/SERVICE/user/USER_ID`);
  return { base, service: m[1], userId: m[2] };
}

async function fetchApi(apiUrl, logFn, retries = 3) {
  for (let attempt = 0; attempt < retries; attempt++) {
    try {
      const resp = await fetch(apiUrl, {
        headers: { 'User-Agent': UA, 'Accept': 'application/json' },
        signal: AbortSignal.timeout(15000),
      });

      if (resp.ok) return await resp.json();
      if (resp.status === 404) return [];
      if (resp.status === 429) {
        const wait = 5 * (attempt + 1);
        logFn(`Rate limited, waiting ${wait}s...`);
        await sleep(wait * 1000);
        continue;
      }
      if (resp.status >= 500) {
        await sleep(2000);
        continue;
      }
      logFn(`API error ${resp.status}: ${apiUrl}`);
      return null;
    } catch (err) {
      if (attempt < retries - 1) {
        await sleep(2000);
      } else {
        throw err;
      }
    }
  }
  return null;
}

function sleep(ms) {
  return new Promise(r => setTimeout(r, ms));
}

export function collectFiles(posts, cdnBase) {
  const files = [];
  const seen = new Set();

  for (const post of posts) {
    const items = [];
    if (post.file && post.file.path) items.push(post.file);
    if (post.attachments) {
      for (const att of post.attachments) {
        if (att.path) items.push(att);
      }
    }
    for (const f of items) {
      const fileUrl = `${cdnBase}${f.path}`;
      if (seen.has(fileUrl)) continue;
      seen.add(fileUrl);
      const name = f.name || basename(f.path);
      files.push({ url: fileUrl, name });
    }
  }
  return files;
}

async function downloadFile(url, outputDir, name, logFn) {
  let filepath = join(outputDir, name);
  if (existsSync(filepath)) {
    // File already exists, skip
    return { skipped: true };
  }

  try {
    const resp = await fetch(url, {
      headers: { 'User-Agent': UA },
      signal: AbortSignal.timeout(60000),
    });
    if (!resp.ok) {
      logFn(`FAILED (${resp.status}): ${name}`);
      return { error: true };
    }

    const buf = Buffer.from(await resp.arrayBuffer());

    // Handle filename collision (different content)
    if (existsSync(filepath)) {
      const ext = extname(name);
      const base = name.slice(0, -ext.length);
      let i = 1;
      while (existsSync(filepath)) {
        filepath = join(outputDir, `${base}_${i}${ext}`);
        i++;
      }
    }

    writeFileSync(filepath, buf);
    const savedName = basename(filepath);
    const folderName = basename(outputDir);
    const ext = extname(savedName).toLowerCase();
    const fileType = ['.mp4', '.mov', '.avi', '.webm', '.mkv', '.m4v'].includes(ext) ? 'video' : 'image';
    try { upsertMediaFile(folderName, savedName, fileType, buf.length, Date.now(), null); } catch { /* ignore */ }
    const sizeKb = (buf.length / 1024).toFixed(1);
    return { filename: savedName, sizeKb };
  } catch (err) {
    logFn(`FAILED: ${name} - ${err.message}`);
    return { error: true };
  }
}

export async function fetchAllPosts(base, service, userId, maxPages, logFn, checkCancelled) {
  const allFiles = [];

  for (let page = 0; page < maxPages; page++) {
    if (checkCancelled()) break;

    const offset = page * 50;
    const apiUrl = `${base}/api/v1/${service}/user/${userId}/posts?o=${offset}`;

    let posts;
    try {
      posts = await fetchApi(apiUrl, logFn);
    } catch (err) {
      logFn(`API failed: ${err.message}`);
      break;
    }

    if (!posts || posts.length === 0) break;

    const parsed = new URL(base);
    const cdnHost = `n1.${parsed.hostname}`;
    const cdnBase = `${parsed.protocol}//${cdnHost}/data`;

    const files = collectFiles(posts, cdnBase);
    allFiles.push(...files);

    logFn(`Page ${page + 1}: ${posts.length} posts (${allFiles.length} files total)`);

    if (posts.length < 50) break;
  }

  return allFiles;
}

export async function downloadFiles(files, outputDir, concurrency, logFn, progressFn, checkCancelled) {
  mkdirSync(outputDir, { recursive: true });

  // Filter out already existing files
  const toDownload = [];
  let skipped = 0;
  for (const f of files) {
    if (existsSync(join(outputDir, f.name))) {
      skipped++;
    } else {
      toDownload.push(f);
    }
  }

  if (skipped > 0) logFn(`Skipping ${skipped} already downloaded files`);
  logFn(`Downloading ${toDownload.length} files with ${concurrency} workers...`);

  let completed = 0;
  let errors = 0;
  let active = 0;
  let index = 0;

  // Simple semaphore-based concurrency
  async function processNext() {
    while (index < toDownload.length) {
      if (checkCancelled()) return;

      const current = index++;
      const file = toDownload[current];

      const result = await downloadFile(file.url, outputDir, file.name, logFn);
      if (result.error) {
        errors++;
      } else if (!result.skipped) {
        completed++;
        logFn(`[${completed}/${toDownload.length}] ${result.filename} (${result.sizeKb} KB)`);
      }
      progressFn(completed + skipped, errors, files.length);
    }
  }

  const workers = [];
  for (let i = 0; i < Math.min(concurrency, toDownload.length); i++) {
    workers.push(processNext());
  }
  await Promise.all(workers);

  return { completed, errors, skipped, total: files.length };
}