import express from "express";
import fs from "fs/promises";
import path from "path";
import Docker from "dockerode";
import { fileURLToPath } from "url";

const __dirname = path.dirname(fileURLToPath(import.meta.url));

const PORT = process.env.PORT || 8080;
const SQUID_CONTAINER = process.env.SQUID_CONTAINER || "squid";
const STATE_FILE = "/data/state.json";
const SQUID_CONFIG_DIR = "/squid-config";
const WPAD_DIR = "/wpad";

const docker = new Docker({ socketPath: "/var/run/docker.sock" });
const app = express();

app.use(express.json({ limit: "100kb" }));
app.use(express.static(path.join(__dirname, "public")));

const DEFAULTS = {
  networks: ["192.168.0.0/24", "192.168.1.0/24", "192.168.2.0/24"],
  domains: ["*.netflix.com", "*.spotify.com"],
  upstreamHost: "gluetun",
  upstreamPort: "8888",
  proxyHost: "cerberus.lan",
  proxyPort: "3128",
};

// ---------- State persistence ----------

async function loadState() {
  try {
    const raw = await fs.readFile(STATE_FILE, "utf-8");
    return { ...DEFAULTS, ...JSON.parse(raw) };
  } catch {
    return { ...DEFAULTS };
  }
}

async function writeAtomic(filePath, content) {
  const tmp = filePath + ".tmp";
  await fs.writeFile(tmp, content, { mode: 0o644 });
  await fs.rename(tmp, filePath);
}

async function saveState(state) {
  await writeAtomic(STATE_FILE, JSON.stringify(state, null, 2));
}

// ---------- Validation ----------

const CIDR_RE = /^\d{1,3}(\.\d{1,3}){3}\/\d{1,2}$/;
const HOST_RE = /^[a-zA-Z0-9.\-*_]+$/;
const PORT_RE = /^\d{1,5}$/;

function validate(state) {
  if (!state || typeof state !== "object") throw new Error("invalid payload");
  if (!Array.isArray(state.networks)) throw new Error("networks must be array");
  if (!Array.isArray(state.domains)) throw new Error("domains must be array");
  for (const n of state.networks) {
    if (!CIDR_RE.test(n)) throw new Error(`invalid network: ${n}`);
  }
  for (const d of state.domains) {
    if (!HOST_RE.test(d)) throw new Error(`invalid domain: ${d}`);
  }
  for (const f of ["upstreamHost", "proxyHost"]) {
    if (typeof state[f] !== "string" || !HOST_RE.test(state[f])) {
      throw new Error(`invalid ${f}`);
    }
  }
  for (const f of ["upstreamPort", "proxyPort"]) {
    if (!PORT_RE.test(String(state[f])) || +state[f] < 1 || +state[f] > 65535) {
      throw new Error(`invalid ${f}`);
    }
  }
}

// ---------- Generators ----------

function generateSquidConf(s) {
  return `http_port 3128

# Erlaubte Subnetze
${s.networks.map((n) => `acl localnet src ${n}`).join("\n")}

http_access allow localnet
http_access deny all

# Domain-Whitelist
acl vpn_domains dstdomain "/squid-config/vpn_domains.txt"

# Upstream zu Gluetun
cache_peer ${s.upstreamHost} parent ${s.upstreamPort} 0 no-query default name=gluetun
never_direct allow vpn_domains
cache_peer_access gluetun allow vpn_domains
cache_peer_access gluetun deny all

never_direct deny all
forwarded_for delete

access_log /var/log/squid/access.log
cache_log /var/log/squid/cache.log
`;
}

function generateVpnDomains(s) {
  return (
    s.domains
      .map((d) => (d.startsWith("*.") ? "." + d.slice(2) : d))
      .join("\n") + "\n"
  );
}

function generateWpadDat(s) {
  return `function FindProxyForURL(url, host) {
    var vpn_domains = [
${s.domains.map((d) => `        "${d}"`).join(",\n")}
    ];

    for (var i = 0; i < vpn_domains.length; i++) {
        if (shExpMatch(host, vpn_domains[i])) {
            return "PROXY ${s.proxyHost}:${s.proxyPort}";
        }
    }

    return "DIRECT";
}
`;
}

async function applyConfig(state) {
  await writeAtomic(
    path.join(SQUID_CONFIG_DIR, "squid.conf"),
    generateSquidConf(state)
  );
  await writeAtomic(
    path.join(SQUID_CONFIG_DIR, "vpn_domains.txt"),
    generateVpnDomains(state)
  );
  await writeAtomic(path.join(WPAD_DIR, "wpad.dat"), generateWpadDat(state));
}

// ---------- Squid reload ----------

async function reloadSquid() {
  const container = docker.getContainer(SQUID_CONTAINER);
  const exec = await container.exec({
    Cmd: ["squid", "-k", "reconfigure"],
    AttachStdout: true,
    AttachStderr: true,
  });
  const stream = await exec.start({ hijack: true, stdin: false });
  return new Promise((resolve, reject) => {
    let out = "";
    stream.on("data", (chunk) => (out += chunk.toString()));
    stream.on("end", async () => {
      const info = await exec.inspect();
      if (info.ExitCode === 0) resolve(out);
      else reject(new Error(`squid -k reconfigure exit ${info.ExitCode}: ${out}`));
    });
    stream.on("error", reject);
  });
}

// ---------- API ----------

app.get("/api/config", async (req, res) => {
  try {
    res.json(await loadState());
  } catch (e) {
    res.status(500).json({ error: e.message });
  }
});

app.post("/api/config", async (req, res) => {
  try {
    validate(req.body);
    await saveState(req.body);
    await applyConfig(req.body);
    let reloaded = false;
    let reloadError = null;
    try {
      await reloadSquid();
      reloaded = true;
    } catch (e) {
      reloadError = e.message;
      console.error("[reload]", e.message);
    }
    res.json({ ok: true, reloaded, reloadError });
  } catch (e) {
    res.status(400).json({ error: e.message });
  }
});

app.post("/api/reload", async (req, res) => {
  try {
    const out = await reloadSquid();
    res.json({ ok: true, output: out });
  } catch (e) {
    res.status(500).json({ error: e.message });
  }
});

app.get("/api/health", (req, res) => res.json({ ok: true }));

// Initial bootstrap: ensure files exist on first start
(async () => {
  const state = await loadState();
  await applyConfig(state).catch((e) =>
    console.error("[bootstrap] could not write configs:", e.message)
  );
  app.listen(PORT, () =>
    console.log(`squid-configurator listening on :${PORT}`)
  );
})();