#!/usr/bin/env python3
import shlex
import subprocess
import sys
from typing import List


def exit(message: str) -> None:
    print("PROBLEM!")
    print(message)
    sys.exit(1)


def run(command: List[str]) -> None:
    print(f"\n>>> {shlex.join(command)}")
    subprocess.check_call(command)


def check_output(command: List[str]) -> str:
    return subprocess.check_output(command, text=True)


def get_git_branch() -> str:
    command = ["git", "rev-parse", "--abbrev-ref", "HEAD"]
    output = check_output(command)
    return output.strip()


def check_git_pristine() -> None:
    command = ["git", "status", "--porcelain"]
    output = check_output(command)
    if output.strip():
        exit("Git is not pristine:\n" + output)


def ensure_on_clean_main() -> None:
    branch = get_git_branch()
    if branch != "main":
        exit(f"You are still on a feature branch: {branch}")
    check_git_pristine()
    run(["git", "fetch", "upstream", "main"])
    run(["git", "rebase", "upstream/main"])


def create_pull_branch(pull_id: int) -> None:
    run(["git", "fetch", "upstream", f"pull/{pull_id}/head"])
    run(["git", "checkout", "-B", f"review-{pull_id}", "FETCH_HEAD"])
    run(["git", "rebase", "upstream/main"])
    run(["git", "log", "upstream/main..", "--oneline"])
    run(["git", "diff", "upstream/main..", "--name-status"])

    print()
    print(f"PR: {pull_id}")
    print(subprocess.check_output(["git", "log", "HEAD~..", "--pretty=format:Author: %an"]))


def review_pr() -> None:
    try:
        pull_id = int(sys.argv[1])
    except Exception:
        exit("please provide an integer pull request id")

    ensure_on_clean_main()
    create_pull_branch(pull_id)


if __name__ == "__main__":
    review_pr()