// Local cover-art storage for stations.
//
// Files live under <repo>/data/images/stations/<id>.<ext> and are served by
// express.static at /media/stations/<id>.<ext>. The DB tracks just the
// relative path in stations.image_path (e.g. "stations/12.jpg"), while
// stations.image_url keeps the original remote URL for refetch/debugging.

import { mkdirSync, existsSync, writeFileSync, readdirSync, unlinkSync, statSync } from 'node:fs';
import { resolve, join, dirname } from 'node:path';
import { fileURLToPath } from 'node:url';
import { getDb } from '../db/index.js';

const __dirname = dirname(fileURLToPath(import.meta.url));
// Where cover art lives. Overridable via env so Electron (packaged) can point
// it at app.getPath('userData')/data/images instead of the read-only asar dir.
const ROOT = process.env.ORADIO_IMAGE_ROOT
    ? resolve(process.env.ORADIO_IMAGE_ROOT)
    : resolve(__dirname, '..', '..', 'data', 'images');
const STATIONS_DIR = join(ROOT, 'stations');
// A browser-like UA is required by Wikimedia and several CDNs; an opaque
// UA like "OnlineRadioExplorer/0.1" gets HTTP 400/403 from upload.wikimedia.org.
// Override via env if you want to publish a contact URL.
const UA = process.env.IMAGE_FETCH_UA
    || 'Mozilla/5.0 (compatible; OnlineRadioExplorer/0.1; +https://github.com/marcoheine/onlineRadioExplorer)';
const FETCH_TIMEOUT_MS = 10_000;
const MAX_BYTES = 4 * 1024 * 1024; // 4 MB per image

const MIME_EXT = {
    'image/jpeg': 'jpg',
    'image/jpg': 'jpg',
    'image/pjpeg': 'jpg',
    'image/png': 'png',
    'image/webp': 'webp',
    'image/gif': 'gif',
    'image/svg+xml': 'svg',
    'image/x-icon': 'ico',
    'image/vnd.microsoft.icon': 'ico'
};

export function ensureImageDirs() {
    mkdirSync(STATIONS_DIR, { recursive: true });
}

export function getImageRoot() { return ROOT; }

// Strip any existing file for this station id (with any extension).
function removeExistingStationFile(id) {
    if (!existsSync(STATIONS_DIR)) return;
    const prefix = `${id}.`;
    for (const f of readdirSync(STATIONS_DIR)) {
        if (f.startsWith(prefix)) {
            try { unlinkSync(join(STATIONS_DIR, f)); } catch { }
        }
    }
}

function extFromMime(mime) {
    if (!mime) return null;
    const base = mime.split(';')[0].trim().toLowerCase();
    return MIME_EXT[base] || null;
}

function extFromMagic(buf) {
    if (buf.length < 12) return null;
    // PNG
    if (buf[0] === 0x89 && buf[1] === 0x50 && buf[2] === 0x4E && buf[3] === 0x47) return 'png';
    // JPEG
    if (buf[0] === 0xFF && buf[1] === 0xD8 && buf[2] === 0xFF) return 'jpg';
    // GIF
    if (buf[0] === 0x47 && buf[1] === 0x49 && buf[2] === 0x46) return 'gif';
    // WEBP: "RIFF...WEBP"
    if (buf[0] === 0x52 && buf[1] === 0x49 && buf[2] === 0x46 && buf[3] === 0x46
        && buf[8] === 0x57 && buf[9] === 0x45 && buf[10] === 0x42 && buf[11] === 0x50) return 'webp';
    // SVG: starts with "<?xml" or "<svg"
    const head = buf.slice(0, 256).toString('utf8').trimStart().toLowerCase();
    if (head.startsWith('<?xml') || head.startsWith('<svg')) return 'svg';
    // ICO
    if (buf[0] === 0x00 && buf[1] === 0x00 && buf[2] === 0x01 && buf[3] === 0x00) return 'ico';
    return null;
}

async function downloadToBuffer(url) {
    const ctl = new AbortController();
    const t = setTimeout(() => ctl.abort(), FETCH_TIMEOUT_MS);
    try {
        const res = await fetch(url, {
            headers: { 'User-Agent': UA, 'Accept': 'image/*' },
            redirect: 'follow',
            signal: ctl.signal
        });
        if (!res.ok) throw new Error(`HTTP ${res.status}`);
        const ct = res.headers.get('content-type') || '';
        const reader = res.body?.getReader();
        if (!reader) throw new Error('no body');
        const chunks = [];
        let received = 0;
        while (true) {
            const { done, value } = await reader.read();
            if (done) break;
            received += value.length;
            if (received > MAX_BYTES) { try { await reader.cancel(); } catch { } throw new Error('too large'); }
            chunks.push(Buffer.from(value));
        }
        return { buffer: Buffer.concat(chunks), contentType: ct };
    } finally { clearTimeout(t); }
}

/**
 * Persist a buffer as the station's cover-art file and update the DB.
 * Returns the relative path (e.g. "stations/12.jpg").
 */
export function saveStationImageFromBuffer(stationId, buf, mime, { source = 'upload' } = {}) {
    ensureImageDirs();
    // Reject obvious HTML responses (404 pages, SPA index, login walls) even
    // when the upstream lies about the content-type.
    const head = buf.slice(0, 512).toString('utf8').trimStart().toLowerCase();
    if (head.startsWith('<!doctype html') || head.startsWith('<html')) {
        throw new Error('response is HTML, not an image');
    }
    const ext = extFromMime(mime) || extFromMagic(buf);
    if (!ext) throw new Error('unsupported image type');
    removeExistingStationFile(stationId);
    const fileName = `${stationId}.${ext}`;
    writeFileSync(join(STATIONS_DIR, fileName), buf);
    const rel = `stations/${fileName}`;
    getDb().prepare(
        "UPDATE stations SET image_path = ?, image_source = ?, updated_at = datetime('now') WHERE id = ?"
    ).run(rel, source, stationId);
    return rel;
}

/**
 * Download an image from a URL and store it locally for the station.
 * Returns the relative path or null on failure.
 */
export async function saveStationImageFromUrl(stationId, url, { source = 'remote' } = {}) {
    if (!url) return null;
    let dl;
    try {
        dl = await downloadToBuffer(url);
    } catch {
        return null;
    }
    try {
        return saveStationImageFromBuffer(stationId, dl.buffer, dl.contentType, { source });
    } catch {
        return null;
    }
}

export function deleteStationImage(stationId) {
    removeExistingStationFile(stationId);
    getDb().prepare(
        "UPDATE stations SET image_path = NULL, image_source = NULL, updated_at = datetime('now') WHERE id = ?"
    ).run(stationId);
}

/** Public URL the kiosk should use. Local if cached, else the remote URL, else null. */
export function publicImageUrl({ image_path, image_url } = {}) {
    if (image_path) return `/media/${image_path}`;
    return image_url || null;
}

/** Total bytes used by the station-image cache (best effort). */
export function imageCacheStats() {
    if (!existsSync(STATIONS_DIR)) return { files: 0, bytes: 0 };
    let files = 0, bytes = 0;
    for (const f of readdirSync(STATIONS_DIR)) {
        try { bytes += statSync(join(STATIONS_DIR, f)).size; files++; } catch { }
    }
    return { files, bytes };
}