import "dotenv/config";
import express from "express";
import { createServer } from "http";
import net from "net";
import { createExpressMiddleware } from "@trpc/server/adapters/express";
import { registerOAuthRoutes } from "./oauth";
import { appRouter } from "../routers";
import { createContext } from "./context";
import { serveStatic, setupVite } from "./vite";
import { seedDefaults } from "../seed";

const GATEWAY_BASE_URL = process.env.GATEWAY_URL ?? "http://localhost:18789";

function isPortAvailable(port: number): Promise<boolean> {
  return new Promise(resolve => {
    const server = net.createServer();
    server.listen(port, () => {
      server.close(() => resolve(true));
    });
    server.on("error", () => resolve(false));
  });
}

async function findAvailablePort(startPort: number = 3000): Promise<number> {
  for (let port = startPort; port < startPort + 20; port++) {
    if (await isPortAvailable(port)) {
      return port;
    }
  }
  throw new Error(`No available port found starting from ${startPort}`);
}

async function startServer() {
  const app = express();
  const server = createServer(app);
  // Configure body parser with larger size limit for file uploads
  app.use(express.json({ limit: "50mb" }));
  app.use(express.urlencoded({ limit: "50mb", extended: true }));
  // OAuth callback under /api/oauth/callback
  registerOAuthRoutes(app);

  // ── SSE proxy: POST /api/orchestrator/stream → Go Gateway SSE ──────────────
  // This proxies the SSE stream from the Go Gateway to the browser.
  // We need to do it at the Express level because tRPC doesn't support SSE yet.
  app.post("/api/orchestrator/stream", async (req, res) => {
    try {
      const gwRes = await fetch(`${GATEWAY_BASE_URL}/api/orchestrator/stream`, {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify(req.body),
      });

      if (!gwRes.ok || !gwRes.body) {
        res.status(gwRes.status).json({ error: "Gateway stream error" });
        return;
      }

      // Set SSE headers
      res.setHeader("Content-Type", "text/event-stream; charset=utf-8");
      res.setHeader("Cache-Control", "no-cache");
      res.setHeader("Connection", "keep-alive");
      res.setHeader("Access-Control-Allow-Origin", "*");
      res.flushHeaders();

      // Pipe the response body — use a single TextDecoder with stream:true
      // so multi-byte UTF-8 sequences (Cyrillic, CJK, etc.) are never split
      const reader = gwRes.body.getReader();
      const decoder = new TextDecoder("utf-8");

      const pump = async () => {
        try {
          while (true) {
            const { done, value } = await reader.read();
            if (done) break;
            res.write(decoder.decode(value, { stream: true }));
            // @ts-ignore
            if (res.flush) (res as any).flush();
          }
        } catch {
          // Client disconnected
        } finally {
          res.end();
        }
      };

      // Abort if client disconnects
      req.on("close", () => reader.cancel());
      await pump();
    } catch (err: any) {
      if (!res.headersSent) {
        res.status(502).json({ error: `Gateway unreachable: ${err.message}` });
      }
    }
  });

  // tRPC API
  app.use(
    "/api/trpc",
    createExpressMiddleware({
      router: appRouter,
      createContext,
    })
  );
  // development mode uses Vite, production mode uses static files
  if (process.env.NODE_ENV === "development") {
    await setupVite(app, server);
  } else {
    serveStatic(app);
  }

  const preferredPort = parseInt(process.env.PORT || "3000");
  const port = await findAvailablePort(preferredPort);

  if (port !== preferredPort) {
    console.log(`Port ${preferredPort} is busy, using port ${port} instead`);
  }

  // Run idempotent seed on every startup (no-op if data already exists)
  await seedDefaults();

  server.listen(port, () => {
    console.log(`Server running on http://localhost:${port}/`);
  });
}

startServer().catch(console.error);