#!/usr/bin/env python3
"""Comment-triggered PR fix-ups, powered by Claude Code.

Runs when a maintainer comments `@claude <instruction>` on a pull request.
Checks out the PR head branch, hands the instruction to headless Claude Code
(subscription OAuth auth — no API billing), commits and pushes whatever it
changed (which re-runs the PR checks), and replies on the PR with a summary.

Uses only the Python standard library plus the `claude` CLI.

Required environment:
    CLAUDE_CODE_OAUTH_TOKEN  token from `claude setup-token`
    GITEA_TOKEN              run-scoped token (checkout auth handles the push)
    GITEA_SERVER_URL         e.g. https://privaterepo.sitaru.org
    GITEA_REPOSITORY         owner/repo
    PR_NUMBER                pull request index
    COMMENT_BODY             the triggering comment text
"""

import json
import os
import subprocess
import sys
import urllib.request

TRIGGER = "@claude"
CLAUDE_TIMEOUT_S = 2400  # 40 min ceiling for one fix-up session


def api(path: str, payload: dict | None = None) -> dict:
    server = os.environ["GITEA_SERVER_URL"].rstrip("/")
    repo = os.environ["GITEA_REPOSITORY"]
    req = urllib.request.Request(
        f"{server}/api/v1/repos/{repo}{path}",
        data=json.dumps(payload).encode() if payload is not None else None,
        headers={
            "Authorization": f"token {os.environ['GITEA_TOKEN']}",
            "Content-Type": "application/json",
        },
        method="POST" if payload is not None else "GET",
    )
    with urllib.request.urlopen(req, timeout=30) as resp:
        return json.loads(resp.read())


def run(*cmd: str, **kwargs) -> subprocess.CompletedProcess:
    return subprocess.run(cmd, check=True, capture_output=True, text=True, **kwargs)


def main() -> int:
    pr_number = os.environ["PR_NUMBER"]
    instruction = os.environ["COMMENT_BODY"].strip()
    if instruction.lower().startswith(TRIGGER):
        instruction = instruction[len(TRIGGER):].strip()
    if not instruction:
        print("Empty instruction after trigger word; nothing to do")
        return 0

    pr = api(f"/pulls/{pr_number}")
    head_ref = pr["head"]["ref"]
    base_ref = pr["base"]["ref"]

    run("git", "fetch", "origin", head_ref, base_ref)
    run("git", "checkout", head_ref)

    prompt = f"""You are working on pull request #{pr_number} ("{pr['title']}")
in the SchoolCompare repository. The PR branch is checked out; its base is
{base_ref}. A maintainer left this instruction on the PR:

{instruction}

Implement exactly what was asked, following the conventions in CLAUDE.md.
Run any relevant tests or typechecks you can. Do NOT commit or push — the
harness handles that. When done, summarise in a few sentences what you
changed and how you verified it."""

    proc = subprocess.run(
        ["claude", "-p", prompt, "--dangerously-skip-permissions", "--output-format", "json"],
        capture_output=True,
        text=True,
        timeout=CLAUDE_TIMEOUT_S,
    )
    if proc.returncode != 0:
        raise RuntimeError(f"claude CLI failed:\n{proc.stderr[-2000:]}")
    summary = json.loads(proc.stdout)["result"].strip()

    changed = run("git", "status", "--porcelain").stdout.strip()
    if changed:
        run("git", "config", "user.name", "Claude (CI)")
        run("git", "config", "user.email", "noreply@anthropic.com")
        run("git", "add", "-A")
        title = instruction.splitlines()[0][:60]
        run("git", "commit", "-m", f"ai: {title}\n\nRequested via PR comment; applied by Claude Code in CI.")
        run("git", "push", "origin", head_ref)
        sha = run("git", "rev-parse", "--short", "HEAD").stdout.strip()
        reply = f"## 🤖 Claude fix-up applied (`{sha}`)\n\n{summary}\n\n_PR checks re-run automatically on the new commit._"
    else:
        reply = f"## 🤖 Claude fix-up — no changes made\n\n{summary}"

    api(f"/issues/{pr_number}/comments", {"body": reply})
    print(reply)
    return 0


if __name__ == "__main__":
    sys.exit(main())