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

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

app.get("/api/sse-stream", (c) => {
  return streamSSE(c, async (stream) => {
    const result = await gateway.streamRequest({
      path: "/",
      body: {
        model: MODEL,
        stream: true,
        messages: [
          {
            role: "user",
            content: "What are AI agents and how do they work?",
          },
        ],
      },
    });

    let id = 0;
    for await (const chunk of readGatewayText(result.stream)) {
      await stream.writeSSE({
        event: "chunk",
        data: chunk,
        id: String(id++),
      });
    }

    const metadata = await result.metadata;
    const totalTokens =
      (metadata.cost?.promptTokens ?? 0) +
      (metadata.cost?.completionTokens ?? 0);

    await stream.writeSSE({
      event: "done",
      data: JSON.stringify({ totalTokens }),
      id: String(id),
    });
  });
});

// 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;