const express = require('express');
const path = require('path');
const fs = require('fs');
const https = require('https');
const { formatStoryName, naturalSort } = require('./utils');
const { fetchHFData, forceRefreshHFData, startAutoRefresh, getHFStories, getHFCacheStatus, getHFAssetBase } = require('./hfService');

const app = express();
app.disable('x-powered-by'); // Hide "Express" header

const PORT = process.env.PORT || 3000;
const DATA_DIR = path.join(__dirname, 'data');

// Serve static files
app.use(express.static(path.join(__dirname, 'public')));
app.use('/data', express.static(DATA_DIR));

// ============================================
// Image Proxy Endpoint
// Proxy images from Hugging Face with proper URL encoding
// ============================================
app.get('/api/proxy/*', (req, res) => {
    const assetPath = req.params[0];

    if (!assetPath) {
        return res.status(400).json({ error: 'Missing asset path' });
    }

    const MAX_REDIRECTS = 5;
    const TIMEOUT_MS = 30000; // 30 seconds timeout

    // Build properly encoded URL
    const targetUrl = encodeURI(`${getHFAssetBase()}/${assetPath}`);

    const fetchWithRedirects = (url, redirectCount = 0) => {
        if (redirectCount > MAX_REDIRECTS) {
            console.error('[Proxy] Too many redirects');
            if (!res.headersSent) {
                return res.status(502).json({ error: 'Too many redirects' });
            }
            return;
        }

        const request = https.get(url, { timeout: TIMEOUT_MS }, (proxyRes) => {
            const { statusCode, headers } = proxyRes;

            // Handle redirects (301, 302, 303, 307, 308)
            if (statusCode >= 300 && statusCode < 400 && headers.location) {
                return fetchWithRedirects(headers.location, redirectCount + 1);
            }

            // Handle non-success status codes
            if (statusCode !== 200) {
                console.error(`[Proxy] Upstream error: ${statusCode} for ${url.substring(0, 80)}`);
                if (!res.headersSent) {
                    return res.status(statusCode).json({
                        error: 'Failed to fetch resource',
                        upstream_status: statusCode
                    });
                }
                return;
            }

            // Forward response headers
            if (headers['content-type']) {
                res.setHeader('Content-Type', headers['content-type']);
            }
            if (headers['content-length']) {
                res.setHeader('Content-Length', headers['content-length']);
            }

            // Set caching headers (1 hour for images)
            res.setHeader('Cache-Control', 'public, max-age=3600');
            res.setHeader('X-Proxy-Source', 'huggingface');

            // Stream response to client
            proxyRes.pipe(res);

            // Handle stream errors
            proxyRes.on('error', (err) => {
                console.error('[Proxy] Stream error:', err.message);
                if (!res.headersSent) {
                    res.status(500).json({ error: 'Stream error' });
                }
            });
        });

        // Handle request errors
        request.on('error', (err) => {
            console.error('[Proxy] Request error:', err.message);
            if (!res.headersSent) {
                res.status(502).json({ error: 'Failed to connect to upstream' });
            }
        });

        // Handle timeout
        request.on('timeout', () => {
            console.error('[Proxy] Request timeout');
            request.destroy();
            if (!res.headersSent) {
                res.status(504).json({ error: 'Upstream timeout' });
            }
        });
    };

    fetchWithRedirects(targetUrl);
});

// Helper: Get local stories
function getLocalStories() {
    try {
        if (!fs.existsSync(DATA_DIR)) return [];
        return fs.readdirSync(DATA_DIR, { withFileTypes: true })
            .filter(dirent => dirent.isDirectory())
            .map(dirent => {
                const storyPath = path.join(DATA_DIR, dirent.name);
                return { id: dirent.name, path: storyPath };
            });
    } catch (e) { return []; }
}

// API: Get all stories (Merged)
app.get('/api/stories', (req, res) => {
    try {
        // 1. Get Local Stories
        const localStories = getLocalStories().map(s => {
            const storyPath = s.path;
            const chapters = fs.readdirSync(storyPath, { withFileTypes: true })
                .filter(d => d.isDirectory());

            // Cover logic
            let cover = null;
            const thumbFiles = fs.readdirSync(storyPath)
                .filter(f => /^thum\.(jpg|jpeg|png|webp|gif)$/i.test(f));
            if (thumbFiles.length > 0) {
                cover = `/data/${s.id}/${thumbFiles[0]}`;
            } else if (chapters.length > 0) {
                try {
                    const firstChapterPath = path.join(storyPath, chapters[0].name);
                    const images = fs.readdirSync(firstChapterPath)
                        .filter(f => /\.(png|jpg|jpeg|webp|gif)$/i.test(f)).sort();
                    if (images.length > 0) cover = `/data/${s.id}/${chapters[0].name}/${images[0]}`;
                } catch (e) { }
            }

            return {
                id: s.id,
                name: formatStoryName(s.id),
                chapterCount: chapters.length,
                cover: cover,
                source: 'local'
            };
        });

        // 2. Merge with HF Stories
        const mergedMap = new Map();
        const hfStories = getHFStories();

        // Add local first
        localStories.forEach(s => mergedMap.set(s.id, s));

        // Merge HF
        Object.values(hfStories).forEach(hfStory => {
            // Construct proxy URL for cover
            const proxyCover = hfStory.cover ? `/api/proxy/${hfStory.cover}` : null;

            if (mergedMap.has(hfStory.id)) {
                const local = mergedMap.get(hfStory.id);
                if (!local.cover && proxyCover) local.cover = proxyCover;
            } else {
                mergedMap.set(hfStory.id, {
                    id: hfStory.id,
                    name: formatStoryName(hfStory.id),
                    chapterCount: Object.keys(hfStory.chapters).length,
                    cover: proxyCover,
                    source: 'remote'
                });
            }
        });

        res.json(Array.from(mergedMap.values()));
    } catch (error) {
        console.error(error);
        res.status(500).json({ error: 'Failed to load stories' });
    }
});

// API: Get chapters of a story
app.get('/api/stories/:story/chapters', (req, res) => {
    try {
        const storyId = req.params.story;
        const localPath = path.join(DATA_DIR, storyId);

        let chapters = [];
        const seenChapters = new Set();

        // 1. Local Chapters
        if (fs.existsSync(localPath)) {
            const localDirs = fs.readdirSync(localPath, { withFileTypes: true })
                .filter(dirent => dirent.isDirectory())
                .map(d => d.name)
                .sort(naturalSort); // Use natural sort

            chapters = localDirs.map(chapterName => {
                seenChapters.add(chapterName);
                const chapterPath = path.join(localPath, chapterName);
                const images = fs.readdirSync(chapterPath).filter(f => /\.(png|jpg|jpeg|webp|gif)$/i.test(f));

                let thumb = null;
                if (images.length > 0) thumb = `/data/${storyId}/${chapterName}/${images[0]}`;

                return {
                    id: chapterName,
                    name: `Chapter ${chapterName}`,
                    imageCount: images.length,
                    thumbnail: thumb,
                    source: 'local'
                };
            });
        }

        // 2. HF Chapters
        const hfStories = getHFStories();
        const hfStory = hfStories[storyId];
        if (hfStory) {
            const hfChapterIds = Object.keys(hfStory.chapters).sort(naturalSort); // Use natural sort

            hfChapterIds.forEach(chId => {
                if (!seenChapters.has(chId)) {
                    const imgs = hfStory.chapters[chId];
                    const thumb = imgs.length > 0 ? `/api/proxy/${imgs[0].path}` : null;

                    chapters.push({
                        id: chId,
                        name: `Chapter ${chId}`,
                        imageCount: imgs.length,
                        thumbnail: thumb,
                        source: 'remote'
                    });
                }
            });
        }

        // Re-sort all chapters
        chapters.sort((a, b) => naturalSort(a.id, b.id)); // Use natural sort

        res.json({
            story: {
                id: storyId,
                name: formatStoryName(storyId)
            },
            chapters: chapters
        });
    } catch (error) {
        console.error(error);
        res.status(500).json({ error: 'Failed to load chapters' });
    }
});

// API: Get images of a chapter
app.get('/api/stories/:story/chapters/:chapter/images', (req, res) => {
    try {
        const storyId = req.params.story;
        const chapterId = req.params.chapter;
        const hfStories = getHFStories();

        let images = [];
        let source = 'unknown';

        // 1. Try Local first
        const chapterPath = path.join(DATA_DIR, storyId, chapterId);
        if (fs.existsSync(chapterPath)) {
            images = fs.readdirSync(chapterPath)
                .filter(f => /\.(png|jpg|jpeg|webp|gif)$/i.test(f))
                .sort(naturalSort) // Optional: Sort images naturally too if they are numbered
                .map(f => `/data/${storyId}/${chapterId}/${f}`);
            source = 'local';
        }
        // 2. If not local, try HF
        if (images.length === 0 && hfStories[storyId]?.chapters[chapterId]) {
            images = hfStories[storyId].chapters[chapterId].map(img => `/api/proxy/${img.path}`);
            source = 'remote';
        }

        if (images.length === 0) {
            return res.status(404).json({ error: 'Chapter not found' });
        }

        // Navigation Logic
        let allChapterIds = new Set();

        // Local IDs
        if (fs.existsSync(path.join(DATA_DIR, storyId))) {
            fs.readdirSync(path.join(DATA_DIR, storyId), { withFileTypes: true })
                .filter(d => d.isDirectory())
                .forEach(d => allChapterIds.add(d.name));
        }
        // HF IDs
        if (hfStories[storyId]) {
            Object.keys(hfStories[storyId].chapters).forEach(id => allChapterIds.add(id));
        }

        // Sort using natural sort
        const sortedChapters = Array.from(allChapterIds).sort(naturalSort);
        const currentIndex = sortedChapters.indexOf(chapterId);

        res.json({
            story: { id: storyId, name: formatStoryName(storyId) },
            chapter: { id: chapterId, name: `Chapter ${chapterId}` },
            images: images,
            source: source,
            navigation: {
                prevChapter: currentIndex > 0 ? sortedChapters[currentIndex - 1] : null,
                nextChapter: currentIndex < sortedChapters.length - 1 ? sortedChapters[currentIndex + 1] : null,
                totalChapters: sortedChapters.length,
                currentIndex: currentIndex + 1
            }
        });
    } catch (error) {
        console.error(error);
        res.status(500).json({ error: 'Failed to load images' });
    }
});

// API: Get cache status and manual refresh
app.get('/api/hf-status', (req, res) => {
    res.json(getHFCacheStatus());
});

// Refresh HF data - supports both GET and POST
app.get('/api/refresh', async (req, res) => {
    try {
        const result = await forceRefreshHFData();
        res.json({ success: true, ...result });
    } catch (error) {
        res.status(500).json({ success: false, error: 'Failed to refresh' });
    }
});

app.post('/api/refresh', async (req, res) => {
    try {
        const result = await forceRefreshHFData();
        res.json({ success: true, ...result });
    } catch (error) {
        res.status(500).json({ success: false, error: 'Failed to refresh' });
    }
});

// Fallback to index.html for SPA routes - MUST BE LAST
app.get('*', (req, res) => {
    res.sendFile(path.join(__dirname, 'public', 'index.html'));
});

// Start server and fetch data
app.listen(PORT, async () => {
    console.log(`🚀 Web Truyện is running at http://localhost:${PORT}`);
    await fetchHFData();
    startAutoRefresh(); // Enable auto-refresh every 15 minutes
});