import { defineConfig, loadEnv, type Plugin } from "vite";
import react from "@vitejs/plugin-react";
import path from "node:path";

function apiChatPlugin(): Plugin {
  return {
    name: "api-chat-middleware",
    configureServer(server) {
      server.middlewares.use("/api/chat", async (req, res, next) => {
        if (req.method !== "POST") return next();
        try {
          const mod = await server.ssrLoadModule("/api/chat.ts");
          const handler = (mod as { POST: (req: Request) => Promise<Response> })
            .POST;

          const chunks: Buffer[] = [];
          for await (const c of req) chunks.push(c as Buffer);
          const body = chunks.length ? Buffer.concat(chunks) : undefined;

          const headers = new Headers();
          for (const [k, v] of Object.entries(req.headers)) {
            if (Array.isArray(v)) headers.set(k, v.join(", "));
            else if (typeof v === "string") headers.set(k, v);
          }

          const fetchReq = new Request(
            `http://localhost${req.url ?? "/api/chat"}`,
            { method: "POST", headers, body },
          );
          const response = await handler(fetchReq);

          res.statusCode = response.status;
          response.headers.forEach((value, key) => res.setHeader(key, value));

          if (response.body) {
            const reader = response.body.getReader();
            while (true) {
              const { done, value } = await reader.read();
              if (done) break;
              res.write(Buffer.from(value));
            }
          }
          res.end();
        } catch (err) {
          console.error("/api/chat error", err);
          res.statusCode = 500;
          res.end(err instanceof Error ? err.message : "internal error");
        }
      });
    },
  };
}

export default defineConfig(({ mode }) => {
  const env = loadEnv(mode, process.cwd(), "");
  for (const k of Object.keys(env)) {
    if (process.env[k] === undefined) process.env[k] = env[k];
  }

  return {
    plugins: [react(), apiChatPlugin()],
    resolve: {
      alias: {
        "@": path.resolve(__dirname, "."),
        "~": path.resolve(__dirname, "."),
      },
    },
    server: {
      port: 3001,
    },
  };
});