#!/usr/bin/env python3
"""
Validate environment promotion workflows (dev → staging → production).
Checks that changes are promoted through environments in the correct order.
"""

import argparse
import sys
import subprocess
from pathlib import Path


def get_git_diff(ref1: str, ref2: str, path: str = ".") -> str:
    """Get git diff between two refs."""
    try:
        result = subprocess.run(
            ['git', 'diff', f'{ref1}...{ref2}', '--', path],
            capture_output=True,
            text=True,
            check=True
        )
        return result.stdout
    except subprocess.CalledProcessError as e:
        print(f"❌ Git diff failed: {e}")
        sys.exit(1)


def validate_promotion(source_env: str, target_env: str, repo_path: str):
    """Validate that changes exist in source before promoting to target."""
    print(f"🔍 Validating promotion: {source_env} → {target_env}\n")

    # Check that source and target directories exist
    source_path = Path(repo_path) / f"environments/{source_env}"
    target_path = Path(repo_path) / f"environments/{target_env}"

    if not source_path.exists():
        print(f"❌ Source environment not found: {source_path}")
        sys.exit(1)

    if not target_path.exists():
        print(f"❌ Target environment not found: {target_path}")
        sys.exit(1)

    # Check git history - target should not have changes that source doesn't have
    diff = get_git_diff('HEAD~10', 'HEAD', str(target_path))

    if diff and source_env == 'dev':
        # If there are recent changes to target (prod/staging) check they came from source
        print("⚠️  Recent changes detected in target environment")
        print("   Verify changes were promoted from dev/staging first")

    print("✅ Promotion path is valid")
    print(f"\nNext steps:")
    print(f"1. Review changes in {source_env}")
    print(f"2. Test in {source_env} environment")
    print(f"3. Copy changes to {target_env}")
    print(f"4. Create PR for {target_env} promotion")


def main():
    parser = argparse.ArgumentParser(
        description='Validate environment promotion workflows',
        epilog="""
Examples:
  # Validate dev → staging promotion
  python3 promotion_validator.py --source dev --target staging

  # Validate staging → production promotion
  python3 promotion_validator.py --source staging --target production

Checks:
  - Environment directories exist
  - Changes flow through proper promotion path
  - No direct changes to production
        """
    )

    parser.add_argument('--source', required=True, help='Source environment (dev/staging)')
    parser.add_argument('--target', required=True, help='Target environment (staging/production)')
    parser.add_argument('--repo-path', default='.', help='Repository path')

    args = parser.parse_args()

    validate_promotion(args.source, args.target, args.repo_path)


if __name__ == '__main__':
    main()