// Node entry point: serves the client and shared modules as static files and
// hosts the authoritative game over a WebSocket. Run with:
//
//     node server/server.js [--port 27015] [--bind 127.0.0.1]
//
// The browser client connects to ws(s)://<host>/ws on the same origin. The
// wiring is exposed through startServer() so the test suite can boot the same
// server on an ephemeral port.

import { createServer } from "node:http";
import { readFile, stat } from "node:fs/promises";
import { dirname, extname, join, normalize, sep } from "node:path";
import { fileURLToPath, pathToFileURL } from "node:url";
import { WebSocketServer } from "./websocket.js";
import { GameServer } from "./game_server.js";
import { SECONDS_PER_HOUR } from "../shared/game_clock.js";

const ROOT = normalize(join(dirname(fileURLToPath(import.meta.url)), ".."));

const MIME = {
  ".html": "text/html; charset=utf-8",
  ".js": "text/javascript; charset=utf-8",
  ".mjs": "text/javascript; charset=utf-8",
  ".css": "text/css; charset=utf-8",
  ".json": "application/json; charset=utf-8",
  ".png": "image/png",
  ".svg": "image/svg+xml",
  ".jpg": "image/jpeg",
  ".jpeg": "image/jpeg",
  ".gif": "image/gif",
  ".wav": "audio/wav",
  ".mp3": "audio/mpeg",
  ".ogg": "audio/ogg",
  ".flac": "audio/flac",
  ".ttf": "font/ttf",
  ".woff": "font/woff",
  ".woff2": "font/woff2",
  ".ico": "image/x-icon",
};

const TICK_MS = 50;
// Movement still simulates every tick, but snapshots are broadcast at most this
// often. A full snapshot is hundreds of KiB, and sending one per 50ms tick made
// every client parse, allocate and repaint at 20Hz; the browser dead-reckons
// movement between snapshots, so a lower rate is invisible in play.
const SNAPSHOT_INTERVAL_S = 0.1;

async function serveStatic(request, response) {
  try {
    const url = new URL(request.url, "http://localhost");
    const pathname = decodeURIComponent(url.pathname);
    if (pathname === "/") {
      response.writeHead(302, { Location: "/client/index.html" });
      response.end();
      return;
    }
    const safe = normalize(pathname).replace(/^(\.\.[/\\])+/, "");
    const filePath = join(ROOT, safe);
    if (!filePath.startsWith(ROOT + sep) && filePath !== ROOT) {
      response.writeHead(403).end("Forbidden");
      return;
    }
    const info = await stat(filePath).catch(() => null);
    if (!info || !info.isFile()) {
      response.writeHead(404, { "Content-Type": "text/plain" }).end("Not found");
      return;
    }
    const body = await readFile(filePath);
    response.writeHead(200, {
      "Content-Type": MIME[extname(filePath).toLowerCase()] || "application/octet-stream",
      "Cache-Control": "no-cache",
    });
    response.end(body);
  } catch {
    response.writeHead(500, { "Content-Type": "text/plain" }).end("Server error");
  }
}

// Whether a peer address is the local machine. Handles the IPv4-mapped IPv6
// form Node reports for a v4 socket ("::ffff:127.0.0.1") as well as plain v4/v6.
export function isLoopback(address) {
  if (!address) return false;
  const value = String(address).replace(/^::ffff:/, "");
  return value === "::1" || value === "localhost" || value.startsWith("127.");
}

// Whether a connection came from a page served on the local machine. The socket
// has to be loopback and the browser's Origin header (which page scripts cannot
// forge) has to name a loopback host, so a proxied remote client whose socket
// looks local is still treated as remote.
export function isLocalRequest(remoteAddress, origin) {
  if (!isLoopback(remoteAddress)) return false;
  let host;
  try {
    host = new URL(String(origin)).hostname;
  } catch {
    return false;
  }
  return isLoopback(host.replace(/^\[|\]$/g, ""));
}

// Builds the whole server without listening. `listen()` resolves once the port
// is bound and yields the bound address. A game is configured here, before any
// player connects: the server owns one persistent world and clients only join
// it (`seed`, `testing` and `civilisations` exist for tests and operators).
export function startServer({
  port = 27015,
  bind = "127.0.0.1",
  log = console.log,
  seed = 0,
  testing = false,
  civilisations = [],
  mapConfig = null,
  warmupDays = 0,
} = {}) {
  const httpServer = createServer(serveStatic);
  const wsServer = new WebSocketServer(httpServer, { path: "/ws" });
  const connections = new Map();

  const network = {
    getPeerIds() {
      return Array.from(connections.keys());
    },
    send(peerId, message) {
      const connection = connections.get(peerId);
      if (connection) connection.send(JSON.stringify(message));
    },
  };

  const gameServer = new GameServer(network);
  if (warmupDays > 0) log(`settling the world for ${warmupDays} days...`);
  gameServer.configureGame({ seed, player_civ: 0, civilisations, testing, mapConfig, warmupDays });
  if (warmupDays > 0) log(`world settled at day ${warmupDays}`);

  function broadcastPlayers() {
    const players = {};
    for (const [peerId, connection] of connections) {
      if (!connection.name) continue;
      players[peerId] = {
        id: peerId,
        name: connection.name,
        admin: connection.name === gameServer.adminName,
      };
    }
    const message = JSON.stringify({ t: "players", players });
    for (const connection of connections.values()) connection.send(message);
  }

  function handleMessage(connection, message) {
    switch (message.t) {
      case "request_games":
        connection.send(JSON.stringify({ t: "game_list", games: gameServer.gameList() }));
        break;
      case "login": {
        const result = gameServer.authenticate(connection.id, message.name, message.password);
        if (!result.ok) {
          connection.send(JSON.stringify({ t: "login_rejected", reason: result.reason }));
          connection.close(1000);
          return;
        }
        connection.name = result.name;
        connection.send(JSON.stringify({
          t: "assigned",
          playerId: connection.id,
          admin: result.admin,
          name: result.name,
        }));
        broadcastPlayers();
        gameServer.onPeerJoined(connection.id, result.name);
        break;
      }
      case "claim_civ":
        gameServer.claimCiv(connection.id, message.civ);
        break;
      case "order": {
        const order = message.order || {};
        // The free shortcut is only honoured for a page on the local machine,
        // whatever the game's testing flag says.
        if (order.free && !isLocalRequest(connection.remoteAddress, connection.origin)) {
          order.free = false;
        }
        gameServer.enqueueOrder(connection.id, order);
        break;
      }
      default:
        break;
    }
  }

  wsServer.on("connection", (connection) => {
    connections.set(connection.id, connection);
    connection.name = "";
    gameServer.setPeerLocal(
      connection.id,
      isLocalRequest(connection.remoteAddress, connection.origin)
    );
    connection.on("message", (raw) => {
      let message;
      try {
        message = JSON.parse(raw);
      } catch {
        return;
      }
      handleMessage(connection, message);
    });
    connection.on("close", () => {
      connections.delete(connection.id);
      gameServer.onPeerLeft(connection.id);
      broadcastPlayers();
    });
  });

  // Fixed-step loop: movement advances every tick and the clock strikes an hour
  // every SECONDS_PER_HOUR real seconds. The state is only broadcast once per
  // SNAPSHOT_INTERVAL_S however often it changed, so a game with moving units
  // does not flood clients with full snapshots. Exposed as `step` so tests can
  // drive the clock deterministically.
  let hourAccumulator = 0;
  let snapshotAccumulator = 0;
  function step(seconds) {
    // Drain queued player orders first, under a small time budget, so a burst
    // from several players never runs every path search in one tick.
    gameServer.processOrders();
    gameServer.advanceMovement(seconds / SECONDS_PER_HOUR);
    hourAccumulator += seconds;
    while (hourAccumulator >= SECONDS_PER_HOUR) {
      hourAccumulator -= SECONDS_PER_HOUR;
      gameServer.tickHour();
    }
    snapshotAccumulator += seconds;
    if (snapshotAccumulator >= SNAPSHOT_INTERVAL_S) {
      snapshotAccumulator = 0;
      gameServer.flushIfDirty();
    }
  }
  const timer = setInterval(() => step(TICK_MS / 1000), TICK_MS);

  const listen = new Promise((resolve, reject) => {
    httpServer.once("error", reject);
    httpServer.listen(port, bind, () => {
      const address = httpServer.address();
      log(`Battle for 'Tismo listening on http://${bind}:${address.port}/ (ws://${bind}:${address.port}/ws)`);
      resolve(address);
    });
  });

  function close() {
    clearInterval(timer);
    for (const connection of connections.values()) connection.close(1001);
    connections.clear();
    httpServer.close();
  }

  return { httpServer, wsServer, gameServer, network, connections, listen, step, close };
}

function argValue(name, fallback) {
  const index = process.argv.indexOf(name);
  if (index >= 0 && index + 1 < process.argv.length) return process.argv[index + 1];
  return fallback;
}

if (process.argv[1] && import.meta.url === pathToFileURL(process.argv[1]).href) {
  startServer({
    port: Number(argValue("--port", process.env.PORT || 27015)),
    bind: argValue("--bind", process.env.BIND || "127.0.0.1"),
    seed: Number(argValue("--seed", process.env.SEED || 0)) | 0,
    // Free, instant orders for local play; remote peers still have their `free`
    // flag stripped in the order handler.
    testing: process.argv.includes("--testing"),
    // Settle the world this many days before serving, so the game opens with
    // its economy established. `--warmup 0` skips it.
    warmupDays: Number(argValue("--warmup", process.env.WARMUP || 150)) | 0,
  });
}