"""Migration: Create tryout_coaches association table and migrate existing data.

Run this script to create the many-to-many relationship between tryouts and coaches.
Usage: python migrations/add_tryout_coaches.py
"""

import sys
import os
sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))

from app.app import create_app
from app.extensions import db
from sqlalchemy import text

app = create_app()

with app.app_context():
    # Check if table already exists
    result = db.session.execute(text(
        "SELECT COUNT(*) FROM information_schema.tables "
        "WHERE table_name = 'tryout_coaches'"
    ))
    exists = result.scalar() > 0

    if exists:
        print("Table 'tryout_coaches' already exists. Skipping creation.")
    else:
        db.session.execute(text("""
            CREATE TABLE tryout_coaches (
                tryout_id INTEGER NOT NULL,
                coach_id INTEGER NOT NULL,
                PRIMARY KEY (tryout_id, coach_id),
                FOREIGN KEY (tryout_id) REFERENCES tryouts (id) ON DELETE CASCADE,
                FOREIGN KEY (coach_id) REFERENCES users (id) ON DELETE CASCADE
            )
        """))
        db.session.commit()
        print("Created 'tryout_coaches' association table.")

    # Migrate existing coach_id data into the new table
    result = db.session.execute(text(
        "SELECT COUNT(*) FROM tryouts WHERE coach_id IS NOT NULL"
    ))
    count = result.scalar()

    if count > 0:
        # Check how many already migrated
        migrated = db.session.execute(text(
            "SELECT COUNT(*) FROM tryout_coaches"
        )).scalar()

        if migrated == 0:
            db.session.execute(text("""
                INSERT INTO tryout_coaches (tryout_id, coach_id)
                SELECT id, coach_id FROM tryouts WHERE coach_id IS NOT NULL
            """))
            db.session.commit()
            print(f"Migrated {count} existing coach assignments to tryout_coaches.")
        else:
            print(f"Skipping data migration — {migrated} rows already exist in tryout_coaches.")
    else:
        print("No existing coach assignments to migrate.")

    print("Migration complete.")