/*
 * ======= • ======= • ======= • ======= • =======• =======
 * AniKotoAPI — server.js
 * Repository: https://github.com/Shineii86/AniKotoAPI
 *
 * @description
 *   Main entry point for the AniKotoAPI Express server.
 *   Configures CORS, middleware, static files, API routes,
 *   and 404 handling. Starts the server on the configured port.
 *
 * @exports
 *   None (side-effect: starts Express server)
 *
 * @author  Shinei Nouzen
 * @license MIT
 * ======= • ======= • ======= • ======= • =======• =======
 */

import dotenv from "dotenv";
import express from "express";
import compression from "compression";
import path from "path";
import fs from "fs";
import crypto from "crypto";
import { fileURLToPath } from "url";
import { dirname } from "path";
import { createApiRoutes } from "./src/routes/apiRoutes.js";
import { getCacheStats } from "./src/helper/cache.helper.js";
import { addCreatorInfo } from "./src/middleware/creatorInfo.js";

dotenv.config();

// ══════════════════════════════════════════════════════════════
// SERVER CONFIGURATION
// ══════════════════════════════════════════════════════════════

const app = express();
const PORT = process.env.PORT || 4444;
const __filename = fileURLToPath(import.meta.url);
const __dirname = dirname(__filename);
const publicDir = path.join(process.cwd(), "public");
const has404File = fs.existsSync(path.join(publicDir, "404.html"));
const allowedOrigins = process.env.ALLOWED_ORIGINS?.split(",");

// ---- FEATURE: Response compression ----
app.use(compression({
  filter: (req, res) => {
    if (req.headers["x-no-compression"]) return false;
    return compression.filter(req, res);
  },
  level: 6,
  threshold: 1024
}));

// ---- FEATURE: Request body size limits ----
app.use(express.json({ limit: "10kb" }));
app.use(express.urlencoded({ extended: false, limit: "10kb" }));

// ══════════════════════════════════════════════════════════════
// REQUEST ID TRACKING
// ══════════════════════════════════════════════════════════════

// ---- FEATURE: Unique request ID for debugging ----
app.use((req, res, next) => {
  req.id = crypto.randomUUID();
  res.setHeader("X-Request-Id", req.id);
  next();
});

// ══════════════════════════════════════════════════════════════
// CORS MIDDLEWARE
// ══════════════════════════════════════════════════════════════

// NOTE: Single unified CORS middleware — handles all origin validation
app.use((req, res, next) => {
  const origin = req.headers.origin;
  if (!allowedOrigins || allowedOrigins.includes("*") || (origin && allowedOrigins.includes(origin))) {
    res.setHeader("Access-Control-Allow-Origin", origin || "*");
  }
  res.setHeader("Access-Control-Allow-Methods", "GET, POST, OPTIONS");
  res.setHeader("Access-Control-Allow-Headers", "Content-Type, X-Requested-With");
  if (req.method === "OPTIONS") {
    return res.status(204).end();
  }
  next();
});

// ---- FEATURE: Security headers ----
app.use((req, res, next) => {
  res.setHeader("X-Frame-Options", "DENY");
  res.setHeader("X-Content-Type-Options", "nosniff");
  res.setHeader("X-XSS-Protection", "1; mode=block");
  res.setHeader("Referrer-Policy", "strict-origin-when-cross-origin");
  res.setHeader("Permissions-Policy", "camera=(), microphone=(), geolocation=()");
  res.setHeader("Content-Security-Policy", "default-src 'self'; script-src 'self' 'unsafe-inline'; style-src 'self' 'unsafe-inline'; img-src 'self' data: https:; font-src 'self' data:; connect-src 'self'");
  res.setHeader("Strict-Transport-Security", "max-age=31536000; includeSubDomains");
  res.setHeader("X-Permitted-Cross-Domain-Policies", "none");
  next();
});

// ══════════════════════════════════════════════════════════════
// STATIC FILES
// ══════════════════════════════════════════════════════════════

// NOTE: redirect: false prevents automatic redirects to index.html
app.use(express.static(publicDir, { redirect: false }));

// ══════════════════════════════════════════════════════════════
// CLEAN URL ROUTES
// ══════════════════════════════════════════════════════════════

// Serve HTML files without .html extension
app.get("/tos", (req, res) => {
  res.sendFile(path.join(publicDir, "tos.html"));
});

app.get("/privacy", (req, res) => {
  res.sendFile(path.join(publicDir, "privacy.html"));
});

// ══════════════════════════════════════════════════════════════
// RESPONSE HELPERS
// ══════════════════════════════════════════════════════════════

// ---- FEATURE: Standardized JSON response wrapper ----
/**
 * Wraps data in a standardized success JSON response.
 *
 * @param {object} res - Express response object
 * @param {*} data - The data to return in the response
 * @param {number} status - HTTP status code (default: 200)
 */
const jsonResponse = (res, data, status = 200) =>
  res.status(status).json({ success: true, results: data });

// ---- FEATURE: Standardized error response wrapper ----
/**
 * Returns a standardized error JSON response.
 *
 * @param {object} res - Express response object
 * @param {string} message - Error message to return (default: "Internal server error")
 * @param {number} status - HTTP status code (default: 500)
 */
const jsonError = (res, message = "Internal server error", status = 500) =>
  res.status(status).json({ success: false, message });

// ══════════════════════════════════════════════════════════════
// API ROUTES
// ══════════════════════════════════════════════════════════════

// ---- FEATURE: Rate limiting (configurable, default 100 requests per minute per IP) ----
const requestCounts = new Map();
const RATE_LIMIT = parseInt(process.env.RATE_LIMIT) || 100;
const RATE_WINDOW = parseInt(process.env.RATE_WINDOW) || 60000;

// ---- FEATURE: Rate limiter cleanup interval (every 5 minutes) ----
const RATE_CLEANUP_INTERVAL = 300000;
setInterval(() => {
  const now = Date.now();
  for (const [ip, timestamps] of requestCounts.entries()) {
    const validTimestamps = timestamps.filter(t => now - t < RATE_WINDOW);
    if (validTimestamps.length === 0) {
      requestCounts.delete(ip);
    } else {
      requestCounts.set(ip, validTimestamps);
    }
  }
}, RATE_CLEANUP_INTERVAL);

app.use((req, res, next) => {
  const ip = req.ip || req.connection.remoteAddress;
  const now = Date.now();
  if (!requestCounts.has(ip)) {
    requestCounts.set(ip, []);
  }
  const timestamps = requestCounts.get(ip).filter(t => now - t < RATE_WINDOW);
  requestCounts.set(ip, timestamps);
  if (timestamps.length >= RATE_LIMIT) {
    return res.status(429).json({
      success: false,
      message: "Rate limit exceeded. Try again later.",
      retryAfter: Math.ceil((timestamps[0] + RATE_WINDOW - now) / 1000)
    });
  }
  timestamps.push(now);
  res.setHeader("X-RateLimit-Limit", RATE_LIMIT);
  res.setHeader("X-RateLimit-Remaining", RATE_LIMIT - timestamps.length);
  next();
});

// ---- FEATURE: Cache stats endpoint ----
app.get("/api/cache/stats", (req, res) => {
  res.json({ success: true, results: getCacheStats() });
});

// ---- FEATURE: Creator info middleware (injects attribution into all responses) ----
app.use(addCreatorInfo);

// ---- FEATURE: Request timeout middleware (30 seconds) ----
app.use((req, res, next) => {
  const timeout = parseInt(process.env.REQUEST_TIMEOUT) || 30000;
  req.setTimeout(timeout, () => {
    if (!res.headersSent) {
      res.status(408).json({ success: false, message: "Request timeout" });
    }
  });
  next();
});

createApiRoutes(app, jsonResponse, jsonError);

// ══════════════════════════════════════════════════════════════
// 404 HANDLER
// ══════════════════════════════════════════════════════════════

// ---- FEATURE: Global error handler ----
app.use((err, req, res, next) => {
  console.error(`[ERROR] ${req.id} ${err.message}`, err.stack);
  if (err.type === 'entity.too.large') {
    return res.status(413).json({ success: false, message: "Request entity too large" });
  }
  res.status(err.status || 500).json({
    success: false,
    message: process.env.NODE_ENV === 'production' ? "Internal server error" : err.message
  });
});

// ---- FEATURE: Catch-all 404 handler for undefined routes ----
app.use((req, res) => {
  const filePath = path.join(publicDir, "404.html");
  if (fs.existsSync(filePath)) {
    res.status(404).sendFile(filePath);
  } else {
    res.status(404).json({
      success: false,
      message: "Endpoint not found",
      availableEndpoints: [
        "/", "/search", "/search/suggest", "/info", "/watch",
        "/episodes/:id", "/episodes-ajax/:id", "/stream", "/servers",
        "/mapper-servers", "/download", "/stream/resolve",
        "/stream/qualities", "/stream/proxy", "/stream/ts-proxy",
        "/spotlight", "/trending", "/top-ten", "/suggestions",
        "/random", "/most-popular", "/upcoming", "/top-rankings",
        "/recently-updated", "/completed", "/new-release",
        "/newly-added", "/latest-updated", "/trending-sidebar",
        "/seasons/:id", "/watch-order/:id", "/az-list/:letter",
        "/filter", "/genre/:genre", "/type/:type", "/status/:status",
        "/schedule", "/health", "/stats", "/cache/stats",
        "/mirrors", "/openapi"
      ]
    });
  }
});

// ══════════════════════════════════════════════════════════════
// SERVER START
// ══════════════════════════════════════════════════════════════

const server = app.listen(PORT, () => {
  console.info(`AniKotoAPI listening at ${PORT}`);
});

// ══════════════════════════════════════════════════════════════
// GRACEFUL SHUTDOWN
// ══════════════════════════════════════════════════════════════

// ---- FEATURE: Graceful shutdown handling ----
const gracefulShutdown = (signal) => {
  console.info(`\n[SHUTDOWN] Received ${signal}. Starting graceful shutdown...`);
  server.close(() => {
    console.info("[SHUTDOWN] Server closed. Goodbye.");
    process.exit(0);
  });
  setTimeout(() => {
    console.error("[SHUTDOWN] Forced shutdown after timeout.");
    process.exit(1);
  }, 10000);
};

process.on("SIGTERM", () => gracefulShutdown("SIGTERM"));
process.on("SIGINT", () => gracefulShutdown("SIGINT"));

process.on("unhandledRejection", (reason, promise) => {
  console.error("[UNHANDLED] Unhandled Rejection:", reason);
});

process.on("uncaughtException", (error) => {
  console.error("[UNCAUGHT] Uncaught Exception:", error);
  gracefulShutdown("uncaughtException");
});

// ══════════════════════════════════════════════════════════════ END: server.js