"""Minimal PR-review agent.

Runs the OpenAI Agents SDK with one tool that fetches a unified diff from
GitHub. Prints a short review to stdout.

Usage:
    uv sync
    uv run python pr_review.py <owner> <repo> <pr_number>

Auth: optional GITHUB_TOKEN env var. Anonymous calls also work for public
repos under standard rate limits.
"""

from __future__ import annotations

import os
import sys

import httpx
from agents import Agent, Runner, function_tool


@function_tool
def get_pr_diff(owner: str, repo: str, number: int) -> str:
    """Fetch the unified diff for a GitHub pull request."""
    url = f"https://api.github.com/repos/{owner}/{repo}/pulls/{number}"
    headers = {"Accept": "application/vnd.github.v3.diff"}
    if token := os.environ.get("GITHUB_TOKEN"):
        headers["Authorization"] = f"Bearer {token}"
    response = httpx.get(url, headers=headers, timeout=30.0)
    response.raise_for_status()
    return response.text


SYSTEM_PROMPT = """You are a senior code reviewer.

Given a unified diff, write a short review focused on:
- correctness issues
- missing or insufficient tests
- unclear or risky changes

Be concise. Use bullet points. Skip praise. If the diff is empty or
unreadable, say so."""


def main() -> int:
    if len(sys.argv) != 4:
        print("Usage: uv run python pr_review.py <owner> <repo> <pr_number>", file=sys.stderr)
        return 1
    owner, repo, number_str = sys.argv[1], sys.argv[2], sys.argv[3]
    try:
        number = int(number_str)
    except ValueError:
        print(f"pr_number must be an integer, got: {number_str!r}", file=sys.stderr)
        return 1

    agent = Agent(
        name="pr-reviewer",
        instructions=SYSTEM_PROMPT,
        tools=[get_pr_diff],
        model="gpt-5",
    )
    prompt = f"Review pull request {number} in {owner}/{repo}. Use the get_pr_diff tool."
    result = Runner.run_sync(agent, prompt)
    print(result.final_output)
    return 0


if __name__ == "__main__":
    raise SystemExit(main())