import { Router } from 'express';
import { readdirSync, statSync, existsSync, mkdirSync, unlinkSync, createReadStream } from 'fs';
import { join, extname } from 'path';
import { execFile } from 'child_process';
import { promisify } from 'util';
import { createHash } from 'crypto';
import {
  getPostDateByFilename, getSetting,
  upsertMediaFileBatch, removeMediaFile, removeStaleFiles,
  getMediaFolders, getMediaFiles, getMediaFileCount, getAllIndexedFolders,
} from './db.js';

const execFileAsync = promisify(execFile);
const router = Router();
const MEDIA_PATH = process.env.MEDIA_PATH || './data/media';
const THUMB_DIR = '.thumbs';

// In-flight thumb generation promises (dedup concurrent requests for same file)
const thumbInFlight = new Map();

const IMAGE_EXTS = new Set(['.jpg', '.jpeg', '.png', '.gif', '.webp', '.bmp']);
const VIDEO_EXTS = new Set(['.mp4', '.mov', '.avi', '.webm', '.mkv', '.m4v']);

function getMediaType(filename) {
  const ext = extname(filename).toLowerCase();
  if (IMAGE_EXTS.has(ext)) return 'image';
  if (VIDEO_EXTS.has(ext)) return 'video';
  return null;
}

// --- Background filesystem scanner ---

export function scanMediaFiles() {
  const startTime = Date.now();
  console.log('[gallery] Starting media index scan...');

  if (!existsSync(MEDIA_PATH)) {
    console.log('[gallery] Media path does not exist, skipping scan');
    return;
  }

  let entries;
  try {
    entries = readdirSync(MEDIA_PATH, { withFileTypes: true });
  } catch (err) {
    console.error('[gallery] Failed to read media path:', err.message);
    return;
  }

  const scannedFolders = new Set();
  let totalFiles = 0;

  for (const entry of entries) {
    if (!entry.isDirectory() || entry.name.startsWith('.') || entry.name.startsWith('_')) continue;
    const folderName = entry.name;
    scannedFolders.add(folderName);
    const dirPath = join(MEDIA_PATH, folderName);

    let files;
    try {
      files = readdirSync(dirPath);
    } catch { continue; }

    const batch = [];
    const validFilenames = [];

    for (const file of files) {
      if (file.startsWith('.')) continue;
      const mediaType = getMediaType(file);
      if (!mediaType) continue;

      validFilenames.push(file);
      const filePath = join(dirPath, file);
      try {
        const stat = statSync(filePath);
        const postedAt = getPostDateByFilename(file);
        batch.push({
          folder: folderName,
          filename: file,
          type: mediaType,
          size: stat.size,
          modified: stat.mtimeMs,
          postedAt: postedAt || null,
        });
      } catch { continue; }
    }

    if (batch.length > 0) {
      upsertMediaFileBatch(batch);
      totalFiles += batch.length;
    }

    // Remove DB rows for files that no longer exist in this folder
    removeStaleFiles(folderName, validFilenames);
  }

  // Remove DB rows for folders that no longer exist on disk
  const indexedFolders = getAllIndexedFolders();
  for (const f of indexedFolders) {
    if (!scannedFolders.has(f)) {
      removeStaleFiles(f, []);
    }
  }

  const elapsed = ((Date.now() - startTime) / 1000).toFixed(2);
  const dbCount = getMediaFileCount();
  console.log(`[gallery] Index scan complete: ${totalFiles} files in ${scannedFolders.size} folders (${elapsed}s). DB total: ${dbCount}`);
}

// GET /api/gallery/folders — list all folders with file counts (from DB index)
router.get('/api/gallery/folders', (req, res, next) => {
  try {
    const folders = getMediaFolders();
    res.json(folders);
  } catch (err) {
    next(err);
  }
});

// GET /api/gallery/files?folder=&type=&sort=&offset=&limit= (from DB index)
router.get('/api/gallery/files', (req, res, next) => {
  try {
    const { folder, type, sort, offset, limit } = req.query;
    const foldersParam = req.query.folders;
    const foldersArr = foldersParam
      ? foldersParam.split(',').map((f) => f.trim()).filter(Boolean)
      : undefined;

    const offsetNum = parseInt(offset || '0', 10);
    const limitNum = parseInt(limit || '50', 10);
    const hlsEnabled = (getSetting('hls_enabled') || process.env.HLS_ENABLED) === 'true';

    const { total, rows } = getMediaFiles({
      folder: folder || undefined,
      folders: foldersArr,
      type: type || 'all',
      sort: sort || 'latest',
      offset: offsetNum,
      limit: limitNum,
    });

    const files = rows.map((r) => {
      const fileObj = {
        folder: r.folder,
        filename: r.filename,
        type: r.type,
        size: r.size,
        modified: r.modified,
        postedAt: r.posted_at || null,
        url: `/api/gallery/media/${encodeURIComponent(r.folder)}/${encodeURIComponent(r.filename)}`,
      };
      if (hlsEnabled && r.type === 'video') {
        fileObj.hlsUrl = `/api/hls/${encodeURIComponent(r.folder)}/${encodeURIComponent(r.filename)}/master.m3u8`;
      }
      return fileObj;
    });

    res.json({ total, offset: offsetNum, limit: limitNum, files });
  } catch (err) {
    next(err);
  }
});

// POST /api/gallery/rescan — trigger a media index rescan
let rescanState = { running: false, lastRun: null, fileCount: 0, elapsed: null };

router.post('/api/gallery/rescan', (req, res) => {
  if (rescanState.running) {
    return res.json({ status: 'already_running', ...rescanState });
  }
  rescanState = { running: true, lastRun: null, fileCount: 0, elapsed: null };
  res.json({ status: 'started' });

  setImmediate(() => {
    try {
      scanMediaFiles();
      rescanState.fileCount = getMediaFileCount();
    } catch (err) {
      console.error('[gallery] Rescan failed:', err.message);
    } finally {
      rescanState.running = false;
      rescanState.lastRun = new Date().toISOString();
    }
  });
});

router.get('/api/gallery/rescan/status', (req, res) => {
  res.json({ ...rescanState, fileCount: rescanState.running ? rescanState.fileCount : getMediaFileCount() });
});

// GET /api/gallery/media/:folder/:filename — serve actual file
router.get('/api/gallery/media/:folder/:filename', (req, res) => {
  const { folder, filename } = req.params;

  // Prevent path traversal
  if (folder.includes('..') || filename.includes('..')) {
    return res.status(400).json({ error: 'Invalid path' });
  }

  const filePath = join(MEDIA_PATH, folder, filename);
  res.sendFile(filePath, { root: '/' }, (err) => {
    if (err && !res.headersSent) {
      res.status(404).json({ error: 'File not found' });
    }
  });
});

// --- Video Thumbnails ---

function getThumbPath(folder, filename) {
  const thumbDir = join(MEDIA_PATH, folder, THUMB_DIR);
  const thumbName = filename.replace(/\.[^.]+$/, '.jpg');
  return { thumbDir, thumbPath: join(thumbDir, thumbName) };
}

async function generateThumb(folder, filename) {
  const videoPath = join(MEDIA_PATH, folder, filename);
  const { thumbDir, thumbPath } = getThumbPath(folder, filename);

  if (existsSync(thumbPath)) return thumbPath;

  // Dedup concurrent requests
  const key = `${folder}/${filename}`;
  if (thumbInFlight.has(key)) return thumbInFlight.get(key);

  const promise = (async () => {
    try {
      if (!existsSync(thumbDir)) mkdirSync(thumbDir, { recursive: true });
      await execFileAsync('ffmpeg', [
        '-ss', '1',
        '-i', videoPath,
        '-frames:v', '1',
        '-vf', 'scale=320:-1',
        '-q:v', '6',
        '-y',
        thumbPath,
      ], { timeout: 10000 });
      return thumbPath;
    } catch (err) {
      console.error(`[gallery] thumb failed for ${key}:`, err.message);
      return null;
    } finally {
      thumbInFlight.delete(key);
    }
  })();

  thumbInFlight.set(key, promise);
  return promise;
}

// GET /api/gallery/thumb/:folder/:filename — serve or generate a video thumbnail
router.get('/api/gallery/thumb/:folder/:filename', async (req, res) => {
  const { folder, filename } = req.params;
  if (folder.includes('..') || filename.includes('..')) {
    return res.status(400).json({ error: 'Invalid path' });
  }

  const { thumbPath } = getThumbPath(folder, filename);

  // Serve cached thumb immediately
  if (existsSync(thumbPath)) {
    return res.sendFile(thumbPath, { root: '/' }, (err) => {
      if (err && !res.headersSent) res.status(404).json({ error: 'Not found' });
    });
  }

  // Generate on-demand
  const result = await generateThumb(folder, filename);
  if (result && existsSync(result)) {
    res.sendFile(result, { root: '/' }, (err) => {
      if (err && !res.headersSent) res.status(500).json({ error: 'Failed to serve thumbnail' });
    });
  } else {
    res.status(500).json({ error: 'Thumbnail generation failed' });
  }
});

// Bulk thumbnail generation state
let thumbGenState = { running: false, total: 0, done: 0, errors: 0 };

// POST /api/gallery/generate-thumbs — bulk generate all video thumbnails
router.post('/api/gallery/generate-thumbs', (req, res) => {
  if (thumbGenState.running) {
    return res.json({ status: 'already_running', ...thumbGenState });
  }

  // Collect all videos
  const videos = [];
  const dirs = readdirSync(MEDIA_PATH, { withFileTypes: true })
    .filter((e) => e.isDirectory() && !e.name.startsWith('.') && !e.name.startsWith('_'));

  for (const dir of dirs) {
    const dirPath = join(MEDIA_PATH, dir.name);
    try {
      const files = readdirSync(dirPath);
      for (const file of files) {
        if (file.startsWith('.')) continue;
        const ext = extname(file).toLowerCase();
        if (VIDEO_EXTS.has(ext)) {
          const { thumbPath } = getThumbPath(dir.name, file);
          if (!existsSync(thumbPath)) {
            videos.push({ folder: dir.name, filename: file });
          }
        }
      }
    } catch { continue; }
  }

  if (videos.length === 0) {
    return res.json({ status: 'done', total: 0, done: 0, errors: 0, message: 'All thumbnails already exist' });
  }

  thumbGenState = { running: true, total: videos.length, done: 0, errors: 0 };
  res.json({ status: 'started', total: videos.length });

  // Run in background with concurrency limit
  (async () => {
    const CONCURRENCY = 3;
    let i = 0;
    const next = async () => {
      while (i < videos.length) {
        const { folder, filename } = videos[i++];
        const result = await generateThumb(folder, filename);
        if (result) thumbGenState.done++;
        else thumbGenState.errors++;
      }
    };
    await Promise.all(Array.from({ length: Math.min(CONCURRENCY, videos.length) }, () => next()));
    thumbGenState.running = false;
  })();
});

// GET /api/gallery/generate-thumbs/status — check bulk generation progress
router.get('/api/gallery/generate-thumbs/status', (req, res) => {
  res.json(thumbGenState);
});

// --- Duplicate File Scanning ---

let duplicateScanState = { running: false, total: 0, done: 0, groups: 0 };
let duplicateGroups = [];

function hashFilePartial(filePath, bytes = 65536) {
  return new Promise((resolve, reject) => {
    const hash = createHash('md5');
    const stream = createReadStream(filePath, { start: 0, end: bytes - 1 });
    stream.on('data', (chunk) => hash.update(chunk));
    stream.on('end', () => resolve(hash.digest('hex')));
    stream.on('error', reject);
  });
}

// POST /api/gallery/scan-duplicates — start background duplicate scan
router.post('/api/gallery/scan-duplicates', (req, res) => {
  if (duplicateScanState.running) {
    return res.json({ status: 'already_running', ...duplicateScanState });
  }

  // Phase 1: group all files by size
  const bySize = new Map();
  const dirs = readdirSync(MEDIA_PATH, { withFileTypes: true })
    .filter((e) => e.isDirectory() && !e.name.startsWith('.') && !e.name.startsWith('_'));

  for (const dir of dirs) {
    const dirPath = join(MEDIA_PATH, dir.name);
    let files;
    try { files = readdirSync(dirPath); } catch { continue; }
    for (const file of files) {
      if (file.startsWith('.')) continue;
      const mediaType = getMediaType(file);
      if (!mediaType) continue;
      const filePath = join(dirPath, file);
      try {
        const stat = statSync(filePath);
        const key = stat.size;
        if (!bySize.has(key)) bySize.set(key, []);
        bySize.get(key).push({ folder: dir.name, filename: file, type: mediaType, size: stat.size, modified: stat.mtimeMs, filePath });
      } catch { continue; }
    }
  }

  // Filter to only sizes with multiple files (potential dupes)
  const candidates = [];
  for (const [, files] of bySize) {
    if (files.length > 1) candidates.push(files);
  }

  const totalFiles = candidates.reduce((sum, g) => sum + g.length, 0);
  duplicateScanState = { running: true, total: totalFiles, done: 0, groups: 0 };
  duplicateGroups = [];
  res.json({ status: 'started', total: totalFiles, sizeGroups: candidates.length });

  // Phase 2: hash candidates in background
  (async () => {
    for (const sizeGroup of candidates) {
      const byHash = new Map();
      for (const file of sizeGroup) {
        try {
          const hash = await hashFilePartial(file.filePath);
          if (!byHash.has(hash)) byHash.set(hash, []);
          byHash.get(hash).push(file);
        } catch { /* skip unreadable */ }
        duplicateScanState.done++;
      }
      for (const [, files] of byHash) {
        if (files.length > 1) {
          duplicateGroups.push(files.map(({ filePath, ...rest }) => ({
            ...rest,
            path: filePath,
            url: `/api/gallery/media/${encodeURIComponent(rest.folder)}/${encodeURIComponent(rest.filename)}`,
            thumbUrl: rest.type === 'video'
              ? `/api/gallery/thumb/${encodeURIComponent(rest.folder)}/${encodeURIComponent(rest.filename)}`
              : undefined,
          })));
          duplicateScanState.groups = duplicateGroups.length;
        }
      }
    }
    duplicateScanState.running = false;
  })();
});

// GET /api/gallery/scan-duplicates/status
router.get('/api/gallery/scan-duplicates/status', (req, res) => {
  res.json(duplicateScanState);
});

// GET /api/gallery/duplicates — return found duplicate groups (paginated)
router.get('/api/gallery/duplicates', (req, res) => {
  const offset = parseInt(req.query.offset || '0', 10);
  const limit = parseInt(req.query.limit || '20', 10);
  const page = duplicateGroups.slice(offset, offset + limit);
  res.json({ total: duplicateGroups.length, offset, limit, groups: page });
});

// DELETE /api/gallery/media/:folder/:filename — delete a media file
router.delete('/api/gallery/media/:folder/:filename', (req, res) => {
  const { folder, filename } = req.params;
  if (folder.includes('..') || filename.includes('..')) {
    return res.status(400).json({ error: 'Invalid path' });
  }

  const filePath = join(MEDIA_PATH, folder, filename);
  if (!existsSync(filePath)) {
    return res.status(404).json({ error: 'File not found' });
  }

  try {
    unlinkSync(filePath);
    removeMediaFile(folder, filename);

    // Also delete cached thumbnail if it exists
    const { thumbPath } = getThumbPath(folder, filename);
    if (existsSync(thumbPath)) {
      try { unlinkSync(thumbPath); } catch { /* ignore */ }
    }

    // Remove from in-memory duplicate groups
    for (const group of duplicateGroups) {
      const idx = group.findIndex((f) => f.folder === folder && f.filename === filename);
      if (idx !== -1) { group.splice(idx, 1); break; }
    }
    // Remove empty or single-item groups
    duplicateGroups = duplicateGroups.filter((g) => g.length > 1);
    duplicateScanState.groups = duplicateGroups.length;

    res.json({ ok: true });
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
});

// POST /api/gallery/duplicates/clean — delete all duplicates, keeping one copy per group
router.post('/api/gallery/duplicates/clean', (req, res) => {
  let deleted = 0;
  let freed = 0;
  let errors = 0;

  for (const group of duplicateGroups) {
    // Keep the first file, delete the rest
    const toDelete = group.slice(1);
    for (const file of toDelete) {
      const filePath = join(MEDIA_PATH, file.folder, file.filename);
      try {
        if (existsSync(filePath)) {
          unlinkSync(filePath);
          freed += file.size;
          deleted++;
        }
        const { thumbPath } = getThumbPath(file.folder, file.filename);
        if (existsSync(thumbPath)) {
          try { unlinkSync(thumbPath); } catch { /* ignore */ }
        }
      } catch {
        errors++;
      }
    }
  }

  // Clear all groups since each now has at most 1 file
  duplicateGroups = [];
  duplicateScanState.groups = 0;

  res.json({ ok: true, deleted, freed, errors });
});

export default router;