src/api/server.py

from fastapi import FastAPI, Request
from fastapi.responses import HTMLResponse, StreamingResponse
import asyncio
import os
import uvicorn
import logging

# Disable uvicorn access logs to prevent stdout pollution for OpenEnv
logging.getLogger("uvicorn.access").setLevel(logging.WARNING)

app = FastAPI(title="Dynamic Guardrail Env")


METRICS_FILE = "metrics.jsonl"

async def event_generator(request: Request):
    if not os.path.exists(METRICS_FILE):
        open(METRICS_FILE, "w").close()

    with open(METRICS_FILE, "r", encoding="utf-8") as f:
        last_pos = f.tell()
        while True:
            if await request.is_disconnected():
                break

            try:
                file_size = os.path.getsize(METRICS_FILE)
            except OSError:
                await asyncio.sleep(0.2)
                continue

            # Handle truncation or log rotation safely.
            if file_size < last_pos:
                f.seek(0)
                last_pos = 0

            f.seek(last_pos)
            new_lines = f.readlines()
            if not new_lines:
                await asyncio.sleep(0.1)
                continue

            last_pos = f.tell()
            for line in new_lines:
                payload = line.strip()
                if not payload:
                    continue
                yield f"data: {payload}\n\n"

@app.get("/stream")
async def stream(request: Request):
    return StreamingResponse(event_generator(request), media_type="text/event-stream")

@app.get("/")
async def get_index():
    ui_path = os.path.join(os.path.dirname(os.path.dirname(__file__)), "ui", "index.html")
    if os.path.exists(ui_path):
        with open(ui_path, "r", encoding="utf-8") as f:
            return HTMLResponse(content=f.read())
    return {"detail": "Frontend not found"}

if __name__ == "__main__":
    uvicorn.run("src.api.server:app", host="0.0.0.0", port=8000, log_level="warning")