#!/usr/bin/env python3
"""
Check commit messages against Penpot's commit guidelines.

Validates commit messages using the rules defined in:
  - .github/workflows/commit-checker.yml (regex pattern)
  - CONTRIBUTING.md (formatting rules, subject length, DCO)

By default, checks HEAD. Use --commit to specify a different commit.

Usage:
  ./scripts/check-commit
  ./scripts/check-commit --commit HEAD~1
  ./scripts/check-commit -c abc1234
"""

import argparse
import re
import subprocess
import sys

# ── Emoji list ───────────────────────────────────────────────────────────────
# Combined from commit-checker.yml AND CONTRIBUTING.md
VALID_EMOJIS = (
    "lipstick|globe_with_meridians|wrench|books|"
    "arrow_up|arrow_down|zap|ambulance|construction|"
    "boom|fire|whale|bug|sparkles|paperclip|tada|"
    "recycle|rewind|construction_worker|rocket"
)

# ── Regex from .github/workflows/commit-checker.yml ──────────────────────────
# Matches:
#   1) ":emoji: <Capitalized subject without trailing dot>"
#   2) "Merge|Revert|Reapply ... without trailing dot"
COMMIT_PATTERN = re.compile(
    r"^((:(" + VALID_EMOJIS + r"):\s[A-Z].*[^.]))$"
)

MERGE_PATTERN = re.compile(r"^(Merge|Revert|Reapply).+[^.]$")

# ═══════════════════════════════════════════════════════════════════════════════
# Helpers
# ═══════════════════════════════════════════════════════════════════════════════

def run_git(args):
    """Run a git command and return (returncode, stdout, stderr)."""
    try:
        result = subprocess.run(
            ["git"] + args,
            capture_output=True,
            text=True,
            check=False,
        )
        return result.returncode, result.stdout, result.stderr
    except FileNotFoundError:
        print("ERROR: git not found. Is it installed?", file=sys.stderr)
        sys.exit(1)


def get_commit_message(commit_ref):
    """Return the full commit message for *commit_ref*."""
    rc, out, err = run_git(["log", "--format=%B", "-n", "1", commit_ref])
    if rc != 0:
        print(f"ERROR: could not read commit {commit_ref}: {err.strip()}", file=sys.stderr)
        sys.exit(1)
    if not out.strip():
        print(f"ERROR: commit {commit_ref} has no message", file=sys.stderr)
        sys.exit(1)
    return out.rstrip("\n")


# ═══════════════════════════════════════════════════════════════════════════════
# Validators
# ═══════════════════════════════════════════════════════════════════════════════

def check_regex(message):
    """Check the commit message against the CI regex pattern."""
    # Normalise: strip trailing newlines for single-line matching
    first_line = message.split("\n")[0]

    if MERGE_PATTERN.match(first_line):
        return True, None

    if COMMIT_PATTERN.match(first_line):
        return True, None

    return False, (
        "Commit subject must match one of:\n"
        "  :emoji: <Capitalized subject without trailing dot>\n"
        "  Merge|Revert|Reapply <rest without trailing dot>\n"
        f"Got: {first_line!r}"
    )


def check_subject_length(message):
    """Subject line must be ≤ 90 characters."""
    first_line = message.split("\n")[0]
    if len(first_line) > 90:
        return False, (
            f"Subject line exceeds 90 characters ({len(first_line)} chars):\n"
            f"  {first_line}"
        )
    return True, None


def check_subject_no_trailing_dot(message):
    """Subject line must not end with a period ('.')."""
    first_line = message.split("\n")[0]
    if first_line.endswith("."):
        return False, (
            "Subject line must not end with a period:\n"
            f"  {first_line}"
        )
    return True, None


def check_subject_capitalized(message):
    """Subject must be capitalized, but only if it's a regular commit (not Merge/Revert/Reapply)."""
    first_line = message.split("\n")[0]

    # Skip check for Merge/Revert/Reapply commits
    if MERGE_PATTERN.match(first_line):
        return True, None

    # Strip emoji prefix before checking capitalization
    emoji_match = re.match(r"^:([a-z_]+):\s+(.*)", first_line)
    if emoji_match:
        rest = emoji_match.group(2)
    else:
        rest = first_line

    if rest and not rest[0].isupper():
        return False, (
            "Subject line must start with a capital letter "
            "(after the emoji prefix):\n"
            f"  {first_line}"
        )
    return True, None


def check_body_blank_line(message):
    """If a body exists, there must be a blank line between subject and body."""
    lines = message.split("\n")
    if len(lines) >= 3 and lines[1] != "":
        return False, (
            "A blank line must separate the subject from the body."
        )
    return True, None


def check_signed_off_by(message):
    """Check for the DCO Signed-off-by line (required for code changes)."""
    if "Signed-off-by:" not in message:
        return False, (
            "Missing 'Signed-off-by:' line in the commit footer.\n"
            "  Add it with 'git commit -s' or append it manually:\n"
            "    Signed-off-by: Your Real Name <your.email@example.com>"
        )
    return True, None


# ═══════════════════════════════════════════════════════════════════════════════

def main():
    parser = argparse.ArgumentParser(
        description="Check a commit message against Penpot commit guidelines."
    )
    parser.add_argument(
        "-c", "--commit",
        default="HEAD",
        help="Commit to check (default: HEAD)",
    )
    args = parser.parse_args()

    commit_ref = args.commit
    message = get_commit_message(commit_ref)

    print(f"Checking commit {commit_ref} ...\n")

    validators = [
        ("Regex pattern", check_regex),
        ("Subject ≤ 90 chars", check_subject_length),
        ("No trailing period in subject", check_subject_no_trailing_dot),
        ("Subject capitalized", check_subject_capitalized),
        ("Blank line after subject", check_body_blank_line),
    ]

    all_ok = True

    for name, validator in validators:
        ok, error_msg = validator(message)
        status = "✓" if ok else "✗"
        print(f"  [{status}] {name}")
        if not ok:
            all_ok = False
            print(f"         {error_msg}", file=sys.stderr)

    print()
    if all_ok:
        print("All checks passed.")
        sys.exit(0)
    else:
        print("Some checks FAILED. See messages above.", file=sys.stderr)
        sys.exit(1)


if __name__ == "__main__":
    main()