const express = require('express');
const multer = require('multer');
const path = require('path');
const fs = require('fs');
const { v4: uuidv4 } = require('uuid');
const cors = require('cors');
const sharp = require('sharp');

const app = express();
const PORT = process.env.PORT || 3000;

// Max dimension for processed images (4K)
const MAX_DIM = 3840;

// Word list for random title generation
const WORDS = [
  'Ball', 'Help', 'Tree', 'Moon', 'River', 'Storm', 'Cloud', 'Fire',
  'Ocean', 'Stone', 'Flame', 'Frost', 'Shadow', 'Light', 'Spark',
  'Blaze', 'Drift', 'Hawk', 'Wolf', 'Bear', 'Lion', 'Eagle', 'Shark',
  'Coral', 'Moss', 'Fern', 'Pine', 'Oak', 'Ash', 'Elm', 'Yew',
  'Bloom', 'Thorn', 'Root', 'Leaf', 'Seed', 'Wave', 'Tide', 'Rain',
  'Snow', 'Hail', 'Dew', 'Mist', 'Fog', 'Gale', 'Wind', 'Dust',
  'Sand', 'Clay', 'Rock', 'Crag', 'Peak', 'Ridge', 'Dale', 'Glen',
  'Cove', 'Bay', 'Strait', 'Reef', 'Shore', 'Cliff', 'Dune', 'Cave',
  'Grot', 'Arch', 'Pill', 'Beam', 'Rune', 'Glyph', 'Mark', 'Sign',
  'Glyph', 'Echo', 'Bane', 'Ward', 'Veil', 'Haze', 'Glow', 'Shine'
];

function generateRandomTitle() {
  const pick = () => WORDS[Math.floor(Math.random() * WORDS.length)];
  let a, b, c;
  do { a = pick(); } while (false);
  do { b = pick(); } while (b === a);
  do { c = pick(); } while (c === a || c === b);
  return `${a}${b}${c}`;
}

function deriveTitle(filename) {
  if (!filename) return generateRandomTitle();
  // Strip extension, clean up
  let base = path.basename(filename, path.extname(filename));
  // Replace non-alpha with spaces, then title-case
  base = base.replace(/[^a-zA-Z0-9]+/g, ' ').trim();
  if (!base) return generateRandomTitle();
  // Title-case each word
  return base.split(/\s+/).map(w => w.charAt(0).toUpperCase() + w.slice(1).toLowerCase()).join(' ').slice(0, 80);
}

// Middleware
app.use(cors());
app.use(express.json());
app.use(express.static('public'));
app.use('/uploads', express.static(path.join(__dirname, 'public', 'uploads')));

// In-memory data store
let posts = [];
let comments = [];

// Multer: save raw upload to temp, we process with sharp after
const rawStorage = multer.diskStorage({
  destination: (req, file, cb) => {
    const tmpDir = path.join(__dirname, 'public', 'uploads', 'tmp');
    if (!fs.existsSync(tmpDir)) fs.mkdirSync(tmpDir, { recursive: true });
    cb(null, tmpDir);
  },
  filename: (req, file, cb) => {
    cb(null, `${uuidv4().slice(0, 8)}${path.extname(file.originalname)}`);
  }
});

const ALLOWED_TYPES = ['image/jpeg', 'image/png', 'image/gif', 'image/webp'];

const upload = multer({
  storage: rawStorage,
  limits: { fileSize: 20 * 1024 * 1024 },
  fileFilter: (req, file, cb) => {
    if (ALLOWED_TYPES.includes(file.mimetype)) {
      cb(null, true);
    } else {
      cb(new Error('Unsupported file type. Only JPEG, PNG, GIF, and WebP are allowed.'), false);
    }
  }
});

// Process image with sharp: resize to max 4K, output JPEG quality 92
async function processImage(inputPath) {
  const uploadDir = path.join(__dirname, 'public', 'uploads');
  const outFilename = `${uuidv4().slice(0, 8)}.jpg`;
  const outputPath = path.join(uploadDir, outFilename);

  await sharp(inputPath)
    .resize(MAX_DIM, MAX_DIM, {
      fit: 'inside',
      withoutEnlargement: true,
      withoutAspectRatio: false
    })
    .jpeg({
      quality: 92,
      mozjpeg: true,
      progressive: true,
      chromaSubsampling: '4:4:4'
    })
    .toFile(outputPath);

  // Remove temp file
  await fs.promises.unlink(inputPath).catch(() => {});

  return outFilename;
}

// Load seed data
function loadSeedData() {
  const seedPath = path.join(__dirname, 'seed', 'data.js');
  if (fs.existsSync(seedPath)) {
    const seed = require(seedPath);
    posts = seed.posts.map(p => ({ ...p, id: p.id, createdAt: new Date().toISOString() }));
    comments = seed.comments || [];
  }
}

// --- API Routes ---

// GET /api/posts
app.get('/api/posts', (req, res) => {
  const { sort = 'new' } = req.query;
  let sorted = [...posts];

  switch (sort) {
    case 'viral':
      sorted.sort((a, b) => (b.upvotes || 0) - (a.upvotes || 0));
      break;
    case 'top':
      const today = new Date();
      today.setHours(0, 0, 0, 0);
      const todayPosts = posts.filter(p => new Date(p.createdAt) >= today);
      sorted = todayPosts.sort((a, b) => (b.upvotes || 0) - (a.upvotes || 0));
      break;
    case 'user':
      sorted.sort((a, b) => new Date(b.createdAt) - new Date(a.createdAt));
      break;
    default:
      sorted.sort((a, b) => new Date(b.createdAt) - new Date(a.createdAt));
  }

  sorted = sorted.map(p => ({
    ...p,
    commentCount: comments.filter(c => c.postId === p.id).length
  }));

  res.json(sorted);
});

// GET /api/posts/:id
app.get('/api/posts/:id', (req, res) => {
  const post = posts.find(p => p.id === req.params.id);
  if (!post) return res.status(404).json({ error: 'Post not found' });
  const commentCount = comments.filter(c => c.postId === post.id).length;
  res.json({ ...post, commentCount });
});

// POST /api/posts - Create post with image
app.post('/api/posts', upload.single('image'), async (req, res) => {
  if (!req.file) {
    return res.status(400).json({ error: 'No image file provided' });
  }

  try {
    const processedFilename = await processImage(req.file.path);
    const title = req.body.title?.trim() || deriveTitle(req.file.originalname);

    const post = {
      id: uuidv4().slice(0, 8),
      title,
      url: `/uploads/${processedFilename}`,
      upvotes: 1,
      views: 0,
      tags: req.body.tags ? req.body.tags.split(',').map(t => t.trim()).filter(Boolean) : [],
      createdAt: new Date().toISOString(),
      author: req.body.author || 'Anonymous'
    };

    posts.unshift(post);
    res.status(201).json(post);
  } catch (err) {
    await fs.promises.unlink(req.file.path).catch(() => {});
    console.error('Image processing error:', err);
    res.status(500).json({ error: 'Failed to process image' });
  }
});

// POST /api/posts/:id/vote
app.post('/api/posts/:id/vote', (req, res) => {
  const post = posts.find(p => p.id === req.params.id);
  if (!post) return res.status(404).json({ error: 'Post not found' });

  const { direction } = req.body;
  if (direction === 'up') {
    post.upvotes = (post.upvotes || 0) + 1;
  } else if (direction === 'down') {
    post.upvotes = Math.max(0, (post.upvotes || 0) - 1);
  }

  post.views = (post.views || 0) + 1;
  res.json({ upvotes: post.upvotes, views: post.views });
});

// GET /api/comments/:postId
app.get('/api/comments/:postId', (req, res) => {
  const postComments = comments.filter(c => c.postId === req.params.postId);
  res.json(postComments);
});

// POST /api/comments
app.post('/api/comments', (req, res) => {
  const { postId, text, author, parentId } = req.body;

  if (!postId || !text) {
    return res.status(400).json({ error: 'postId and text are required' });
  }

  const comment = {
    id: uuidv4().slice(0, 8),
    postId,
    text,
    author: author || 'Anonymous',
    parentId: parentId || null,
    timestamp: new Date().toISOString()
  };

  comments.push(comment);
  res.status(201).json(comment);
});

// POST /api/upload - Main upload endpoint
app.post('/api/upload', upload.single('image'), async (req, res) => {
  if (!req.file) {
    return res.status(400).json({ error: 'No file uploaded' });
  }

  try {
    const processedFilename = await processImage(req.file.path);
    const title = req.body.title?.trim() || deriveTitle(req.file.originalname);

    const post = {
      id: uuidv4().slice(0, 8),
      title,
      url: `/uploads/${processedFilename}`,
      upvotes: 1,
      views: 0,
      tags: req.body.tags ? req.body.tags.split(',').map(t => t.trim()).filter(Boolean) : [],
      createdAt: new Date().toISOString(),
      author: req.body.author || 'You'
    };

    posts.unshift(post);
    res.status(201).json(post);
  } catch (err) {
    await fs.promises.unlink(req.file.path).catch(() => {});
    console.error('Image processing error:', err);
    res.status(500).json({ error: 'Failed to process image' });
  }
});

// Health check
app.get('/api/health', (req, res) => {
  res.json({ status: 'ok', posts: posts.length, comments: comments.length, uptime: process.uptime() });
});

// Initialize and start
loadSeedData();
console.log(`🚀 Imgur Clone running on port ${PORT}`);
console.log(`📦 ${posts.length} seed posts loaded`);

const server = app.listen(PORT, () => {
  console.log(`✅ Server listening on http://0.0.0.0:${PORT}`);
  console.log(`✅ Server listening on http://[::]:${PORT}`);
});