#!/usr/bin/env python3
"""
git-claim-authorship.py

Rewrites git history so that any commit where you appear as a co-author
instead lists you as the sole author (removing the Co-authored-by line).

Usage:
    python git-claim-authorship.py --name "Your Name" --email "you@example.com"

Run from inside the repository you want to rewrite.
WARNING: This rewrites history. Force-push required afterwards.
"""

import subprocess
import re
import argparse
import sys


def run(cmd, capture=True, check=True):
    result = subprocess.run(
        cmd, shell=True, capture_output=capture, text=True, check=check
    )
    return result.stdout.strip() if capture else None


def get_all_commits():
    output = run("git log --format='%H' --all")
    return output.splitlines() if output else []


def get_commit_info(sha):
    msg = run(f"git log -1 --format=%B {sha}")
    author_name = run(f"git log -1 --format=%an {sha}")
    author_email = run(f"git log -1 --format=%ae {sha}")
    author_date = run(f"git log -1 --format=%aI {sha}")
    committer_name = run(f"git log -1 --format=%cn {sha}")
    committer_email = run(f"git log -1 --format=%ce {sha}")
    committer_date = run(f"git log -1 --format=%cI {sha}")
    return {
        "sha": sha,
        "message": msg,
        "author_name": author_name,
        "author_email": author_email,
        "author_date": author_date,
        "committer_name": committer_name,
        "committer_email": committer_email,
        "committer_date": committer_date,
    }


def find_coauthor_line(message, name, email):
    """Return True if a Co-authored-by line matches the given name or email."""
    pattern = re.compile(
        r"^Co-authored-by:.*?" + re.escape(name) + r".*$|"
        r"^Co-authored-by:.*?" + re.escape(email) + r".*$",
        re.IGNORECASE | re.MULTILINE,
    )
    return bool(pattern.search(message))


def remove_coauthor_line(message, name, email):
    """Strip matching Co-authored-by lines from the commit message."""
    pattern = re.compile(
        r"^Co-authored-by:.*?" + re.escape(name) + r".*\n?|"
        r"^Co-authored-by:.*?" + re.escape(email) + r".*\n?",
        re.IGNORECASE | re.MULTILINE,
    )
    cleaned = pattern.sub("", message)
    cleaned = re.sub(r"\n{3,}", "\n\n", cleaned).rstrip() + "\n"
    return cleaned


def main():
    parser = argparse.ArgumentParser(
        description="Claim authorship of co-authored commits."
    )
    parser.add_argument("--name", required=True, help="Your full name (as in git)")
    parser.add_argument("--email", required=True, help="Your email (as in git)")
    parser.add_argument(
        "--dry-run",
        action="store_true",
        help="Show what would change without modifying anything",
    )
    args = parser.parse_args()

    # Make sure we're in a git repo
    try:
        run("git rev-parse --is-inside-work-tree")
    except subprocess.CalledProcessError:
        print("Error: not inside a git repository.", file=sys.stderr)
        sys.exit(1)

    print(f"Scanning commits for co-authorship by: {args.name} <{args.email}>")
    commits = get_all_commits()
    print(f"Total commits found: {len(commits)}")

    matches = []
    for sha in commits:
        info = get_commit_info(sha)
        if find_coauthor_line(info["message"], args.name, args.email):
            matches.append(info)

    if not matches:
        print("No commits found with your Co-authored-by line. Nothing to do.")
        return

    print(f"\nFound {len(matches)} commit(s) to rewrite:\n")
    for info in matches:
        first_line = info["message"].split("\n")[0]
        print(f"  {info['sha'][:10]}  {first_line}")

    if args.dry_run:
        print("\n[Dry run] No changes made.")
        return

    confirm = input(
        "\n⚠️  This will rewrite history. Proceed? (yes/no): "
    ).strip().lower()
    if confirm != "yes":
        print("Aborted.")
        return

    # Build a filter-branch env filter script
    sha_set = {info["sha"] for info in matches}

    case_entries = []
    for info in matches:
        case_entries.append(
            f"  {info['sha']})\n"
            f"    export GIT_AUTHOR_NAME='{args.name}'\n"
            f"    export GIT_AUTHOR_EMAIL='{args.email}'\n"
            f"    ;;"
        )

    case_block = "\n".join(case_entries)

    env_filter = f"""
case $GIT_COMMIT in
{case_block}
esac
"""

    msg_case_entries = []
    for info in matches:
        new_msg = remove_coauthor_line(info["message"], args.name, args.email)
        escaped_msg = new_msg.replace("'", "'\\''").replace("`", "\\`").replace("$", "\\$")
        msg_case_entries.append(
            f"  {info['sha']})\n"
            f"    printf '%s' '{escaped_msg}'\n"
            f"    ;;"
        )

    msg_case_block = "\n".join(msg_case_entries)

    msg_filter = f"""
case $GIT_COMMIT in
{msg_case_block}
  *)
    cat
    ;;
esac
"""

    with open("/tmp/_msg_filter.sh", "w") as f:
        f.write(msg_filter)

    print("\nRewriting history with git filter-branch...")
    try:
        result = subprocess.run(
            [
                "git", "filter-branch", "-f",
                "--env-filter", env_filter,
                "--msg-filter", "bash /tmp/_msg_filter.sh",
                "--tag-name-filter", "cat",
                "--", "--all"
            ],
            capture_output=False,
            text=True,
        )
        if result.returncode != 0:
            print("filter-branch failed.", file=sys.stderr)
            sys.exit(1)
    except Exception as e:
        print(f"Error: {e}", file=sys.stderr)
        sys.exit(1)

    print("\n✅ Done! History rewritten.")
    print("\nTo publish the changes, force-push all branches:")
    print("  git push --force --all")
    print("  git push --force --tags")
    print("\nNote: Anyone else with a clone of this repo will need to re-clone or rebase.")


if __name__ == "__main__":
    main()