import express from "express";
import fetch, { Headers } from "node-fetch";
import crypto from "node:crypto";
import { setInterval as nodeSetInterval } from "node:timers";
import config from "./config.js";
import { get, set, del, initCache } from "./cache.js";
// pro-Key In-Flight Lock gegen Thundering Herd
const inflight = new Map();
const app = express();
app.disable("x-powered-by");
// Optional: schlankes CORS
if (config.allowCors) {
    app.use((req, res, next) => {
        res.setHeader("Access-Control-Allow-Origin", config.corsOrigin);
        res.setHeader("Access-Control-Allow-Methods", "GET,HEAD,OPTIONS");
        res.setHeader("Access-Control-Allow-Headers", "*");
        if (req.method === "OPTIONS")
            return res.sendStatus(204);
        next();
    });
}
// Optional: minimalistisches Rate-Limit (global)
if (config.rateLimitRps > 0) {
    let tokens = config.rateLimitRps;
    nodeSetInterval(() => {
        tokens = config.rateLimitRps;
    }, 1000).unref();
    app.use((req, res, next) => {
        if (req.method === "GET" || req.method === "HEAD") {
            if (tokens > 0) {
                tokens--;
                return next();
            }
            res.setHeader("Retry-After", "1");
            return res.status(429).send("Too Many Requests");
        }
        next();
    });
}
// Health
app.get("/_healthz", (_req, res) => {
    res.json({ ok: true, ts: new Date().toISOString() });
});
// Purge per URL (optional; mit Secret schützen)
app.post("/_purge", express.json(), async (req, res) => {
    const { secret, url } = req.query;
    if (secret !== process.env.PURGE_SECRET || !url)
        return res.sendStatus(403);
    const key = cacheKeyFromUrl(String(url));
    await del(key);
    res.json({ purged: true, key });
});
function cacheKeyFromUrl(fullUrl) {
    const vary = ""; // Purge-Variante: bewusst ohne Header-Vary
    return crypto.createHash("sha1").update(`GET|${fullUrl}|${vary}`).digest("hex");
}
function cacheKey(req) {
    const varyHeaders = ["accept"];
    const h = varyHeaders.map((hn) => `${hn}:${req.header(hn) ?? ""}`).join("|");
    const url = new URL(req.originalUrl, "http://x"); // Base egal, wir brauchen nur Pfad/Query
    return crypto
        .createHash("sha1")
        .update(`${req.method}|${url.pathname}|${url.searchParams.toString()}|${h}`)
        .digest("hex");
}
function pickTtl(pathname) {
    for (const r of config.routeTtls) {
        if (r.re.test(pathname))
            return r.seconds;
    }
    return config.ttlSeconds;
}
function isFresh(entry, ttl, now) {
    return now - entry.ts < ttl * 1000;
}
function isStaleOk(entry, ttl, stale, now) {
    return now - entry.ts < (ttl + stale) * 1000;
}
app.all("*", async (req, res) => {
    if (!["GET", "HEAD", "OPTIONS"].includes(req.method)) {
        return res.status(405).send("Method Not Allowed");
    }
    if (req.method === "OPTIONS")
        return res.sendStatus(204);
    const upstreamUrl = new URL(req.originalUrl, config.upstreamBase).toString();
    const key = cacheKey(req);
    const now = Date.now();
    const ttl = pickTtl(new URL(upstreamUrl).pathname);
    const entry = await get(key);
    if (entry && isFresh(entry, ttl, now)) {
        res.set("X-Cache-Status", "HIT");
        Object.entries(entry.headers).forEach(([k, v]) => res.set(k, v));
        return res.status(entry.status).send(entry.body);
    }
    if (entry && isStaleOk(entry, ttl, config.staleSeconds, now)) {
        res.set("X-Cache-Status", "STALE");
        Object.entries(entry.headers).forEach(([k, v]) => res.set(k, v));
        res.status(entry.status).send(entry.body);
        void backgroundRefresh(upstreamUrl, req, key, entry).catch(() => { });
        return;
    }
    try {
        const fresh = await getOrFetch(upstreamUrl, req, key, entry ?? undefined);
        res.set("X-Cache-Status", entry ? "MISS-EXPIRED" : "MISS");
        Object.entries(fresh.headers).forEach(([k, v]) => res.set(k, v));
        res.status(fresh.status).send(fresh.body);
    }
    catch {
        if (entry) {
            res.set("X-Cache-Status", "STALE-ERROR");
            Object.entries(entry.headers).forEach(([k, v]) => res.set(k, v));
            return res.status(entry.status).send(entry.body);
        }
        res.status(502).send("Bad Gateway");
    }
});
async function backgroundRefresh(upstreamUrl, req, key, prev) {
    try {
        await getOrFetch(upstreamUrl, req, key, prev);
    }
    catch { }
}
async function getOrFetch(upstreamUrl, req, key, prev) {
    if (inflight.has(key))
        return inflight.get(key);
    const p = (async () => {
        const headers = new Headers();
        ["accept", "user-agent"].forEach((hn) => {
            const v = req.header(hn);
            if (v)
                headers.set(hn, v);
        });
        if (prev?.etag)
            headers.set("if-none-match", prev.etag);
        if (prev?.lastModified)
            headers.set("if-modified-since", prev.lastModified);
        // Epirent Auth-Header (nur upstream)
        headers.set("X-EPI-NO-SESSION", config.epiNoSession);
        headers.set("X-EPI-ACC-TOK", config.epiAccessToken);
        const resp = await fetch(upstreamUrl, { method: "GET", headers });
        if (resp.status === 304 && prev) {
            const refreshed = { ...prev, ts: Date.now() };
            await set(key, refreshed);
            return refreshed;
        }
        const body = Buffer.from(await resp.arrayBuffer());
        const outHeaders = {};
        let etag;
        let lastMod;
        for (const [k, v] of resp.headers.entries()) {
            const kl = k.toLowerCase();
            if (["content-type", "etag", "last-modified", "cache-control", "date"].includes(kl)) {
                outHeaders[kl] = v;
            }
            if (kl === "etag")
                etag = v;
            if (kl === "last-modified")
                lastMod = v;
        }
        const stored = {
            status: resp.status,
            headers: outHeaders,
            body,
            ts: Date.now(),
            etag,
            lastModified: lastMod
        };
        await set(key, stored);
        return stored;
    })();
    inflight.set(key, p);
    try {
        return await p;
    }
    finally {
        inflight.delete(key);
    }
}
initCache().then(() => {
    app.listen(config.port, () => {
        console.log(`Epirent Read-Only Cache läuft auf :${config.port}`);
    });
});