#!/usr/bin/env python3
"""
Migration script to convert flat task session files to directory structure.

This script migrates task sessions from the old flat file structure:
    .workflow/versions/v001/task_sessions/task_design.yml

To the new directory structure:
    .workflow/versions/v001/task_sessions/task_design/
        session.yml
        task.yml
        operations.log

Usage:
    python3 migrate_task_sessions.py [--dry-run]

Options:
    --dry-run    Show what would be done without making changes
"""

from __future__ import annotations

import sys
import argparse
from pathlib import Path
from datetime import datetime
from typing import Optional

# Add parent to path for imports
sys.path.insert(0, str(Path(__file__).parent))
from version_manager import load_yaml, save_yaml, get_workflow_dir


# ============================================================================
# Discovery Functions
# ============================================================================

def find_flat_task_sessions() -> list[tuple[Path, str]]:
    """
    Find all flat task session YAML files.

    Returns:
        List of tuples: (file_path, version_name)
    """
    workflow_dir = get_workflow_dir()
    versions_dir = workflow_dir / 'versions'

    flat_sessions = []
    if versions_dir.exists():
        for version_dir in versions_dir.iterdir():
            if version_dir.is_dir():
                task_sessions_dir = version_dir / 'task_sessions'
                if task_sessions_dir.exists():
                    for item in task_sessions_dir.iterdir():
                        # Check if it's a YAML file (not a directory)
                        if item.is_file() and item.suffix in ['.yml', '.yaml']:
                            flat_sessions.append((item, version_dir.name))

    return flat_sessions


# ============================================================================
# Migration Functions
# ============================================================================

def migrate_task_session(file_path: Path, version: str, dry_run: bool = False) -> dict:
    """
    Migrate a single flat task session to directory structure.

    Args:
        file_path: Path to the flat YAML file
        version: Version identifier (e.g., 'v001')
        dry_run: If True, only report what would be done

    Returns:
        Dictionary with migration results and actions taken
    """
    task_id = file_path.stem  # e.g., "task_design" from "task_design.yml"
    parent_dir = file_path.parent
    new_dir = parent_dir / task_id

    result = {
        'task_id': task_id,
        'version': version,
        'original_path': str(file_path),
        'new_path': str(new_dir),
        'success': False,
        'actions': []
    }

    if dry_run:
        result['actions'].append(f"Would create directory: {new_dir}")
        result['actions'].append(f"Would move {file_path.name} to {new_dir}/session.yml")
        result['actions'].append(f"Would create {new_dir}/task.yml (if source exists)")
        result['actions'].append(f"Would create {new_dir}/operations.log")
        result['success'] = True
        return result

    try:
        # Create directory
        new_dir.mkdir(exist_ok=True)
        result['actions'].append(f"Created directory: {new_dir}")

        # Move session file
        session_data = load_yaml(str(file_path))
        save_yaml(str(new_dir / 'session.yml'), session_data)
        file_path.unlink()  # Delete original
        result['actions'].append(f"Moved session data to: {new_dir}/session.yml")

        # Create task.yml snapshot (try to find original task)
        task_file = Path('tasks') / f'{task_id}.yml'
        if task_file.exists():
            task_data = load_yaml(str(task_file))
            task_data['snapshotted_at'] = datetime.now().isoformat()
            task_data['source_path'] = str(task_file)
            task_data['status_at_snapshot'] = task_data.get('status', 'migrated')
            task_data['migration_note'] = 'Created during migration from flat file structure'
            save_yaml(str(new_dir / 'task.yml'), task_data)
            result['actions'].append(f"Created task snapshot: {new_dir}/task.yml")
        else:
            # Create minimal task.yml from session data
            minimal_task = {
                'id': task_id,
                'type': session_data.get('task_type', 'unknown'),
                'agent': session_data.get('agent', 'unknown'),
                'snapshotted_at': datetime.now().isoformat(),
                'source_path': 'N/A - reconstructed from session',
                'status_at_snapshot': 'migrated',
                'migration_note': 'Task file not found - reconstructed from session data'
            }
            save_yaml(str(new_dir / 'task.yml'), minimal_task)
            result['actions'].append(f"Warning: Task file not found at {task_file}")
            result['actions'].append(f"Created minimal task snapshot: {new_dir}/task.yml")

        # Create operations.log
        log_content = f"# Operations Log for {task_id}\n"
        log_content += f"# Migrated: {datetime.now().isoformat()}\n"
        log_content += "# Format: [timestamp] OPERATION target_type: target_id (path)\n"
        log_content += "=" * 70 + "\n\n"
        log_content += f"[{datetime.now().isoformat()}] MIGRATION: Converted from flat file structure\n"

        # If session has operations, add them to the log
        if 'operations' in session_data and session_data['operations']:
            log_content += f"\n# Historical operations from session data:\n"
            for op in session_data['operations']:
                timestamp = op.get('performed_at', 'unknown')
                op_type = op.get('type', 'UNKNOWN')
                target_type = op.get('target_type', 'unknown')
                target_id = op.get('target_id', 'unknown')
                target_path = op.get('target_path', '')

                entry = f"[{timestamp}] {op_type} {target_type}: {target_id}"
                if target_path:
                    entry += f" ({target_path})"

                diff_summary = op.get('changes', {}).get('diff_summary', '')
                if diff_summary:
                    entry += f"\n    Summary: {diff_summary}"

                log_content += entry + "\n"

        (new_dir / 'operations.log').write_text(log_content)
        result['actions'].append(f"Created operations log: {new_dir}/operations.log")

        result['success'] = True

    except Exception as e:
        result['error'] = str(e)
        result['actions'].append(f"Error: {e}")

    return result


# ============================================================================
# Main Entry Point
# ============================================================================

def main():
    """Main migration script entry point."""
    parser = argparse.ArgumentParser(
        description='Migrate task session files from flat structure to directories',
        formatter_class=argparse.RawDescriptionHelpFormatter,
        epilog=__doc__
    )
    parser.add_argument(
        '--dry-run',
        action='store_true',
        help='Show what would be done without making changes'
    )

    args = parser.parse_args()
    dry_run = args.dry_run

    # Header
    print("=" * 70)
    print("Task Session Migration Script".center(70))
    print(f"Mode: {'DRY RUN' if dry_run else 'LIVE MIGRATION'}".center(70))
    print("=" * 70)
    print()

    # Find flat sessions
    flat_sessions = find_flat_task_sessions()

    if not flat_sessions:
        print("No flat task session files found. Nothing to migrate.")
        print()
        print("This could mean:")
        print("  1. All task sessions are already migrated")
        print("  2. No task sessions exist yet")
        print("  3. .workflow directory doesn't exist")
        return

    print(f"Found {len(flat_sessions)} flat task session file(s) to migrate:")
    print()

    # Process each file
    results = []
    for file_path, version in flat_sessions:
        print(f"Processing: {version}/{file_path.name}")
        print("-" * 70)

        result = migrate_task_session(file_path, version, dry_run)
        results.append(result)

        for action in result['actions']:
            print(f"  {action}")

        if not result['success'] and 'error' in result:
            print(f"  ERROR: {result['error']}")

        print()

    # Summary
    successful = sum(1 for r in results if r['success'])
    failed = len(results) - successful

    print("=" * 70)
    print("Migration Summary".center(70))
    print("=" * 70)
    print(f"Total files processed: {len(results)}")
    print(f"Successful migrations: {successful}")
    print(f"Failed migrations: {failed}")
    print()

    if dry_run:
        print("This was a DRY RUN. No files were modified.")
        print("Run without --dry-run to perform the migration.")
    else:
        if successful > 0:
            print("Migration completed successfully!")
            print()
            print("Next steps:")
            print("  1. Verify migrated files in .workflow/versions/*/task_sessions/")
            print("  2. Check that each task has session.yml, task.yml, and operations.log")
            print("  3. Test the system to ensure compatibility")

        if failed > 0:
            print()
            print(f"WARNING: {failed} migration(s) failed. Review the errors above.")

    print()


if __name__ == '__main__':
    main()