const express = require("express");
const OpenAI = require("openai");
const path = require("path");

const app = express();

const PORT = process.env.PORT || 3000;

app.use(express.json({ limit: "2mb" }));

// Serve frontend
app.use(express.static(path.join(__dirname, "public")));


/*
==================================================
CHAT ENDPOINT
==================================================
*/

app.post("/api/chat", async (req, res) => {

  try {

    const {
      apiKey,
      model,
      messages
    } = req.body;


    if (!apiKey) {

      return res.status(400).json({
        error: {
          message: "AgentRouter API key is required."
        }
      });

    }


    if (!Array.isArray(messages)) {

      return res.status(400).json({
        error: {
          message: "messages must be an array."
        }
      });

    }


    /*
    ==============================================
    AgentRouter through OpenAI Node SDK
    ==============================================
    */

    const client = new OpenAI({

      apiKey: apiKey,

      baseURL: "https://agentrouter.org/v1"

    });


    /*
    ==============================================
    STREAMING
    ==============================================
    */

    const stream =
      await client.chat.completions.create({

        model: model || "gpt-5.6-sol",

        messages: messages,

        stream: true

      });


    /*
    ==============================================
    SSE RESPONSE
    ==============================================
    */

    res.setHeader(
      "Content-Type",
      "text/event-stream"
    );

    res.setHeader(
      "Cache-Control",
      "no-cache"
    );

    res.setHeader(
      "Connection",
      "keep-alive"
    );

    res.flushHeaders();


    try {

      for await (const chunk of stream) {

        const content =
          chunk.choices?.[0]?.delta?.content;


        if (content) {

          res.write(
            `data: ${JSON.stringify({
              content: content
            })}\n\n`
          );

        }

      }


      res.write(
        "data: [DONE]\n\n"
      );


    } catch (streamError) {

      console.error(
        "Stream error:",
        streamError
      );


      res.write(
        `data: ${JSON.stringify({
          error: streamError.message
        })}\n\n`
      );

    }


    res.end();


  } catch (error) {

    console.error(
      "AgentRouter error:",
      error
    );


    if (res.headersSent) {

      res.end();

      return;

    }


    const status =
      error.status || 500;


    res.status(status).json({

      error: {

        message:
          error.message ||
          "AgentRouter request failed."

      }

    });

  }

});


/*
==================================================
START SERVER
==================================================
*/

app.listen(PORT, () => {

  console.log("");
  console.log("======================================");
  console.log(" AgentRouter Chat");
  console.log("======================================");
  console.log("");
  console.log(
    `Open http://localhost:${PORT}`
  );
  console.log("");

});