/**
 * Web server factory module.
 * Exports a function to create and start the web server.
 * This allows the server to be started in-process from the main application.
 */

import { serve, spawn, type Subprocess } from "bun";
import { join, resolve, dirname } from "path";

export interface WebServerConfig {
    port?: number;
    hostname?: string;
}

export interface WebServerInstance {
    server: ReturnType<typeof serve>;
    stop: () => Promise<void>;
    url: string;
}

/**
 * Creates and starts the web server.
 * 
 * Automatically handles building the frontend:
 * - In development: Spawns 'bun run build.ts --watch'
 * - In production: Assumes 'dist' is already built (or builds once)
 */
export async function createWebServer(config: WebServerConfig = {}): Promise<WebServerInstance> {
    const { port = 3000, hostname = "localhost" } = config;

    // Resolve directories
    // server.ts is in web/src/, so we go up one level to get web/
    const currentDir = dirname(new URL(import.meta.url).pathname);
    const webRoot = resolve(currentDir, "..");
    const distDir = join(webRoot, "dist");

    // Manage build process in development
    let buildProcess: Subprocess | undefined;
    const isDev = process.env.NODE_ENV !== "production";

    if (isDev) {
        console.log("🛠️  Starting Web Bundler in Watch Mode...");
        try {
            buildProcess = spawn(["bun", "run", "build.ts", "--watch"], {
                cwd: webRoot,
                stdout: "inherit",
                stderr: "inherit",
            });
        } catch (error) {
            console.error("Failed to start build process:", error);
        }
    }

    // Configuration constants
    const MAX_CONNECTIONS = 10;
    const MAX_PAYLOAD_BYTES = 16384; // 16KB
    const IDLE_TIMEOUT_SECONDS = 60;

    // Interval for broadcasting stats to all connected WS clients
    let statsBroadcastInterval: Timer | undefined;

    // Cache for activity stats (heavy aggregation)
    let activityPromise: Promise<import("@shared/modules/dashboard/dashboard.types").ActivityData[]> | null = null;
    let lastActivityFetch: number = 0;
    const ACTIVITY_CACHE_TTL = 5 * 60 * 1000; // 5 minutes

    const server = serve({
        port,
        hostname,
        async fetch(req, server) {
            const url = new URL(req.url);

            // Upgrade to WebSocket
            if (url.pathname === "/ws") {
                // Security Check: limit concurrent connections
                const currentConnections = server.pendingWebSockets;
                if (currentConnections >= MAX_CONNECTIONS) {
                    console.warn(`⚠️ [WS] Connection rejected: limit reached (${currentConnections}/${MAX_CONNECTIONS})`);
                    return new Response("Connection limit reached", { status: 429 });
                }

                const success = server.upgrade(req);
                if (success) return undefined;
                return new Response("WebSocket upgrade failed", { status: 400 });
            }

            // API routes
            if (url.pathname === "/api/health") {
                return Response.json({ status: "ok", timestamp: Date.now() });
            }

            if (url.pathname === "/api/stats") {
                try {
                    const stats = await getFullDashboardStats();
                    return Response.json(stats);
                } catch (error) {
                    console.error("Error fetching dashboard stats:", error);
                    return Response.json(
                        { error: "Failed to fetch dashboard statistics" },
                        { status: 500 }
                    );
                }
            }

            if (url.pathname === "/api/stats/activity") {
                try {
                    // Security Check: Token-based authentication
                    const { env } = await import("@shared/lib/env");
                    const authHeader = req.headers.get("Authorization");
                    if (authHeader !== `Bearer ${env.ADMIN_TOKEN}`) {
                        console.warn(`⚠️ [API] Unauthorized activity analytics access attempt from ${req.headers.get("x-forwarded-for") || "unknown"}`);
                        return new Response("Unauthorized", { status: 401 });
                    }

                    const now = Date.now();

                    // If we have a valid cache, return it
                    if (activityPromise && (now - lastActivityFetch < ACTIVITY_CACHE_TTL)) {
                        const data = await activityPromise;
                        return Response.json(data);
                    }

                    // Otherwise, trigger a new fetch (deduplicated by the promise)
                    if (!activityPromise || (now - lastActivityFetch >= ACTIVITY_CACHE_TTL)) {
                        activityPromise = (async () => {
                            const { dashboardService } = await import("@shared/modules/dashboard/dashboard.service");
                            return await dashboardService.getActivityAggregation();
                        })();
                        lastActivityFetch = now;
                    }

                    const activity = await activityPromise;
                    return Response.json(activity);
                } catch (error) {
                    console.error("Error fetching activity stats:", error);
                    return Response.json(
                        { error: "Failed to fetch activity statistics" },
                        { status: 500 }
                    );
                }
            }

            // Administrative Actions
            if (url.pathname.startsWith("/api/actions/") && req.method === "POST") {
                try {
                    // Security Check: Token-based authentication
                    const { env } = await import("@shared/lib/env");
                    const authHeader = req.headers.get("Authorization");
                    if (authHeader !== `Bearer ${env.ADMIN_TOKEN}`) {
                        console.warn(`⚠️ [API] Unauthorized administrative action attempt from ${req.headers.get("x-forwarded-for") || "unknown"}`);
                        return new Response("Unauthorized", { status: 401 });
                    }

                    const { actionService } = await import("@shared/modules/admin/action.service");
                    const { MaintenanceModeSchema } = await import("@shared/modules/dashboard/dashboard.types");

                    if (url.pathname === "/api/actions/reload-commands") {
                        const result = await actionService.reloadCommands();
                        return Response.json(result);
                    }

                    if (url.pathname === "/api/actions/clear-cache") {
                        const result = await actionService.clearCache();
                        return Response.json(result);
                    }

                    if (url.pathname === "/api/actions/maintenance-mode") {
                        const rawBody = await req.json();
                        const parsed = MaintenanceModeSchema.safeParse(rawBody);

                        if (!parsed.success) {
                            return Response.json({ error: "Invalid payload", issues: parsed.error.issues }, { status: 400 });
                        }

                        const result = await actionService.toggleMaintenanceMode(parsed.data.enabled, parsed.data.reason);
                        return Response.json(result);
                    }
                } catch (error) {
                    console.error("Error executing administrative action:", error);
                    return Response.json(
                        { error: "Failed to execute administrative action" },
                        { status: 500 }
                    );
                }
            }

            // Static File Serving
            let pathName = url.pathname;
            if (pathName === "/") pathName = "/index.html";

            // Construct safe file path
            // Remove leading slash to join correctly
            const safePath = join(distDir, pathName.replace(/^\//, ""));

            // Security check: ensure path is within distDir
            if (!safePath.startsWith(distDir)) {
                return new Response("Forbidden", { status: 403 });
            }

            const fileRef = Bun.file(safePath);
            if (await fileRef.exists()) {
                // If serving index.html, inject env vars for frontend
                if (pathName === "/index.html") {
                    let html = await fileRef.text();
                    const { env } = await import("@shared/lib/env");
                    const envScript = `<script>window.AURORA_ENV = { ADMIN_TOKEN: "${env.ADMIN_TOKEN}" };</script>`;
                    html = html.replace("</head>", `${envScript}</head>`);
                    return new Response(html, { headers: { "Content-Type": "text/html" } });
                }
                return new Response(fileRef);
            }

            // SPA Fallback: Serve index.html for unknown non-file routes
            const parts = pathName.split("/");
            const lastPart = parts[parts.length - 1];

            // If it's a direct request for a missing file (has dot), return 404
            // EXCEPT for index.html which is our fallback entry point
            if (lastPart?.includes(".") && lastPart !== "index.html") {
                return new Response("Not Found", { status: 404 });
            }

            const indexFile = Bun.file(join(distDir, "index.html"));
            if (!(await indexFile.exists())) {
                if (isDev) {
                    return new Response("<html><body><h1>🛠️ Dashboard is building...</h1><p>Please refresh in a few seconds. The bundler is currently generating the static assets.</p><script>setTimeout(() => location.reload(), 2000);</script></body></html>", {
                        status: 503,
                        headers: { "Content-Type": "text/html" }
                    });
                }
                return new Response("Dashboard Not Found", { status: 404 });
            }

            let indexHtml = await indexFile.text();
            const { env: sharedEnv } = await import("@shared/lib/env");
            const script = `<script>window.AURORA_ENV = { ADMIN_TOKEN: "${sharedEnv.ADMIN_TOKEN}" };</script>`;
            indexHtml = indexHtml.replace("</head>", `${script}</head>`);
            return new Response(indexHtml, { headers: { "Content-Type": "text/html" } });
        },

        websocket: {
            open(ws) {
                ws.subscribe("dashboard");
                console.log(`🔌 [WS] Client connected. Total: ${server.pendingWebSockets}`);

                // Send initial stats
                getFullDashboardStats().then(stats => {
                    ws.send(JSON.stringify({ type: "STATS_UPDATE", data: stats }));
                });

                // Start broadcast interval if this is the first client
                if (!statsBroadcastInterval) {
                    statsBroadcastInterval = setInterval(async () => {
                        try {
                            const stats = await getFullDashboardStats();
                            server.publish("dashboard", JSON.stringify({ type: "STATS_UPDATE", data: stats }));
                        } catch (error) {
                            console.error("Error in stats broadcast:", error);
                        }
                    }, 5000);
                }
            },
            async message(ws, message) {
                try {
                    const messageStr = message.toString();

                    // Defense-in-depth: redundant length check before parsing
                    if (messageStr.length > MAX_PAYLOAD_BYTES) {
                        console.error("❌ [WS] Payload exceeded maximum limit");
                        return;
                    }

                    const rawData = JSON.parse(messageStr);
                    const { WsMessageSchema } = await import("@shared/modules/dashboard/dashboard.types");
                    const parsed = WsMessageSchema.safeParse(rawData);

                    if (!parsed.success) {
                        console.error("❌ [WS] Invalid message format:", parsed.error.issues);
                        return;
                    }

                    if (parsed.data.type === "PING") {
                        ws.send(JSON.stringify({ type: "PONG" }));
                    }
                } catch (e) {
                    console.error("❌ [WS] Failed to handle message:", e instanceof Error ? e.message : "Malformed JSON");
                }
            },
            close(ws) {
                ws.unsubscribe("dashboard");
                console.log(`🔌 [WS] Client disconnected. Total remaining: ${server.pendingWebSockets}`);

                // Stop broadcast interval if no clients left
                if (server.pendingWebSockets === 0 && statsBroadcastInterval) {
                    clearInterval(statsBroadcastInterval);
                    statsBroadcastInterval = undefined;
                }
            },
            maxPayloadLength: MAX_PAYLOAD_BYTES,
            idleTimeout: IDLE_TIMEOUT_SECONDS,
        },

        development: isDev,
    });

    /**
     * Helper to fetch full dashboard stats object.
     * Unified for both HTTP API and WebSocket broadcasts.
     */
    async function getFullDashboardStats() {
        // Import services (dynamic to avoid circular deps)
        const { dashboardService } = await import("@shared/modules/dashboard/dashboard.service");
        const { getClientStats } = await import("../../bot/lib/clientStats");

        // Fetch all data in parallel
        const [clientStats, activeUsers, totalUsers, economyStats, recentEvents] = await Promise.all([
            Promise.resolve(getClientStats()),
            dashboardService.getActiveUserCount(),
            dashboardService.getTotalUserCount(),
            dashboardService.getEconomyStats(),
            dashboardService.getRecentEvents(10),
        ]);

        return {
            bot: clientStats.bot,
            guilds: { count: clientStats.guilds },
            users: { active: activeUsers, total: totalUsers },
            commands: { total: clientStats.commandsRegistered },
            ping: { avg: clientStats.ping },
            economy: {
                totalWealth: economyStats.totalWealth.toString(),
                avgLevel: economyStats.avgLevel,
                topStreak: economyStats.topStreak,
            },
            recentEvents: recentEvents.map(event => ({
                ...event,
                timestamp: event.timestamp instanceof Date ? event.timestamp.toISOString() : event.timestamp,
            })),
            uptime: clientStats.uptime,
            lastCommandTimestamp: clientStats.lastCommandTimestamp,
            maintenanceMode: (await import("../../bot/lib/BotClient")).AuroraClient.maintenanceMode,
        };
    }

    // Listen for real-time events from the system bus
    const { systemEvents, EVENTS } = await import("@shared/lib/events");
    systemEvents.on(EVENTS.DASHBOARD.NEW_EVENT, (event) => {
        server.publish("dashboard", JSON.stringify({ type: "NEW_EVENT", data: event }));
    });

    const url = `http://${hostname}:${port}`;

    return {
        server,
        url,
        stop: async () => {
            if (buildProcess) {
                buildProcess.kill();
            }
            if (statsBroadcastInterval) {
                clearInterval(statsBroadcastInterval);
            }
            server.stop(true);
        },
    };
}

/**
 * Starts the web server from the main application root.
 * Kept for backward compatibility, but assumes webProjectPath is handled internally or ignored
 * in favor of relative path resolution from this file.
 */
export async function startWebServerFromRoot(
    webProjectPath: string,
    config: WebServerConfig = {}
): Promise<WebServerInstance> {
    // Current implementation doesn't need CWD switching thanks to absolute path resolution
    return createWebServer(config);
}