/**
 * 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);
        }
    }

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

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

            // Upgrade to WebSocket
            if (url.pathname === "/ws") {
                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 }
                    );
                }
            }

            // 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()) {
                return new Response(fileRef);
            }

            // SPA Fallback: Serve index.html for unknown non-file routes
            // If the path looks like a file (has extension), return 404
            // Otherwise serve index.html
            const parts = pathName.split("/");
            const lastPart = parts[parts.length - 1];
            if (lastPart?.includes(".")) {
                return new Response("Not Found", { status: 404 });
            }

            return new Response(Bun.file(join(distDir, "index.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);
                }
            },
            message(ws, message) {
                // Handle messages if needed (e.g. heartbeat)
                try {
                    const data = JSON.parse(message.toString());
                    if (data.type === "PING") ws.send(JSON.stringify({ type: "PONG" }));
                } catch (e) { }
            },
            close(ws) {
                ws.unsubscribe("dashboard");
                console.log(`🔌 [WS] Client disconnected.`);

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

        development: isDev,
    });

    /**
     * Helper to fetch full dashboard stats object
     */
    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.toISOString(),
            })),
            uptime: clientStats.uptime,
            lastCommandTimestamp: clientStats.lastCommandTimestamp,
        };
    }

    // 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);
}