import { Hono } from "hono";
import { AIGatewayClient } from "@agentuity/aigateway";
import { getAIGatewayStreamDeltaText } from "@agentuity/aigateway";

const app = new Hono();
const gateway = new AIGatewayClient();
const encoder = new TextEncoder();
// Default model in the live demo; any gateway model id works here.
const MODEL = "anthropic/claude-opus-4-8";

app.post("/api/stream", async (c) => {
  const body: unknown = await c.req.json();
  const prompt =
    typeof body === "object" && body !== null && "prompt" in body
      ? String(body.prompt)
      : "Write a short note about AI agents.";

  const result = await gateway.streamRequest({
    path: "/",
    body: {
      model: MODEL,
      stream: true,
      messages: [{ role: "user", content: prompt }],
    },
  });

  const textStream = new ReadableStream<Uint8Array>({
    async start(controller) {
      for await (const chunk of readGatewayText(result.stream)) {
        controller.enqueue(encoder.encode(chunk));
      }
      controller.close();
    },
  });

  return new Response(textStream, {
    headers: { "content-type": "text/plain; charset=utf-8" },
  });
});

// For named SSE events and an explicit "done" frame, see the SSE Stream demo.

// streamRequest() returns the provider's raw SSE bytes. Split frames on
// blank lines; the SDK decodes each provider's delta shape to plain text.
async function* readGatewayText(stream: ReadableStream<Uint8Array>) {
  const reader = stream.getReader();
  const decoder = new TextDecoder();
  let buffer = "";

  try {
    for (;;) {
      const { value, done } = await reader.read();
      if (done) break;

      buffer += decoder.decode(value, { stream: true });
      const frames = buffer.split(/\r?\n\r?\n/);
      buffer = frames.pop() ?? "";

      for (const frame of frames) {
        const text = frameText(frame);
        if (text) yield text;
      }
    }

    buffer += decoder.decode();
    const text = frameText(buffer);
    if (text) yield text;
  } finally {
    reader.releaseLock();
  }
}

function frameText(frame: string): string {
  const data = frame
    .split(/\r?\n/)
    .filter((line) => line.startsWith("data:"))
    .map((line) => line.slice(5).trimStart())
    .join("\n")
    .trim();

  if (!data || data === "[DONE]") return "";

  try {
    return getAIGatewayStreamDeltaText(JSON.parse(data));
  } catch {
    return "";
  }
}

export default app;