"""
Align database schema to the unified design spec.

Changes:
- users: id INT, set defaults, drop extra columns not in design
- user_teams/exams: user_id INT
- teams: drop created_by/updated_by
- training_*: fix defaults; set created_by/updated_by to BIGINT where required
- training_reports: add unique(session_id)
- create or replace view v_user_course_progress
"""

from alembic import op
import sqlalchemy as sa


# revision identifiers, used by Alembic.
revision = "20250921_align_schema_to_design"
down_revision = "9245f8845fe1"
branch_labels = None
depends_on = None


def upgrade():
    connection = op.get_bind()

    # users: enforce INT PK, defaults, and drop extra columns
    op.execute("""
        ALTER TABLE `users`
            MODIFY COLUMN `id` INT AUTO_INCREMENT,
            MODIFY COLUMN `username` VARCHAR(50) NOT NULL,
            MODIFY COLUMN `email` VARCHAR(100) NOT NULL,
            MODIFY COLUMN `password_hash` VARCHAR(200) NOT NULL,
            MODIFY COLUMN `role` VARCHAR(20) DEFAULT 'trainee',
            MODIFY COLUMN `is_active` TINYINT(1) DEFAULT 1,
            MODIFY COLUMN `is_verified` TINYINT(1) DEFAULT 0,
            MODIFY COLUMN `created_at` DATETIME DEFAULT CURRENT_TIMESTAMP,
            MODIFY COLUMN `updated_at` DATETIME DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
    """)

    # Drop extra columns that are not in the design (ignore errors if absent)
    for col in [
        "is_superuser",
        "department",
        "position",
        "last_login",
        "login_count",
        "failed_login_count",
        "locked_until",
        "created_by",
        "updated_by",
        "is_deleted",
        "deleted_at",
    ]:
        try:
            op.execute(f"ALTER TABLE `users` DROP COLUMN `{col}`")
        except Exception:
            pass

    # user_teams: user_id INT
    op.execute("""
        ALTER TABLE `user_teams`
            MODIFY COLUMN `user_id` INT NOT NULL
    """)

    # exams: user_id INT
    op.execute("""
        ALTER TABLE `exams`
            MODIFY COLUMN `user_id` INT NOT NULL
    """)

    # teams: drop created_by/updated_by to match design
    for col in ["created_by", "updated_by"]:
        try:
            op.execute(f"ALTER TABLE `teams` DROP COLUMN `{col}`")
        except Exception:
            pass

    # training_scenes: set defaults and BIGINT audit fields
    op.execute("""
        ALTER TABLE `training_scenes`
            MODIFY COLUMN `status` ENUM('DRAFT','ACTIVE','INACTIVE') NOT NULL DEFAULT 'DRAFT',
            MODIFY COLUMN `is_public` TINYINT(1) NOT NULL DEFAULT 1,
            MODIFY COLUMN `created_at` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
            MODIFY COLUMN `updated_at` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
            MODIFY COLUMN `created_by` BIGINT NULL,
            MODIFY COLUMN `updated_by` BIGINT NULL
    """)

    # training_sessions: defaults and BIGINT audit fields
    op.execute("""
        ALTER TABLE `training_sessions`
            MODIFY COLUMN `start_time` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
            MODIFY COLUMN `status` ENUM('CREATED','IN_PROGRESS','COMPLETED','CANCELLED','ERROR') NOT NULL DEFAULT 'CREATED',
            MODIFY COLUMN `created_at` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
            MODIFY COLUMN `updated_at` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
            MODIFY COLUMN `created_by` BIGINT NULL,
            MODIFY COLUMN `updated_by` BIGINT NULL
    """)

    # training_messages: timestamps defaults
    op.execute("""
        ALTER TABLE `training_messages`
            MODIFY COLUMN `created_at` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
            MODIFY COLUMN `updated_at` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
    """)

    # training_reports: timestamps defaults and BIGINT audit fields
    op.execute("""
        ALTER TABLE `training_reports`
            MODIFY COLUMN `created_at` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
            MODIFY COLUMN `updated_at` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
            MODIFY COLUMN `created_by` BIGINT NULL,
            MODIFY COLUMN `updated_by` BIGINT NULL
    """)

    # Add unique constraint for training_reports.session_id per design
    try:
        op.create_unique_constraint(
            "uq_training_reports_session_id", "training_reports", ["session_id"]
        )
    except Exception:
        pass

    # Create or replace view v_user_course_progress
    op.execute("""
        CREATE OR REPLACE VIEW v_user_course_progress AS
        SELECT 
            u.id AS user_id,
            u.username,
            c.id AS course_id,
            c.name AS course_name,
            COUNT(DISTINCT e.id) AS exam_count,
            AVG(e.score) AS avg_score,
            MAX(e.score) AS best_score
        FROM users u
        CROSS JOIN courses c
        LEFT JOIN exams e 
            ON e.user_id = u.id 
           AND e.course_id = c.id 
           AND e.status = 'submitted'
        GROUP BY u.id, c.id
    """)


def downgrade():
    # Drop the view to rollback
    try:
        op.execute("DROP VIEW IF EXISTS v_user_course_progress")
    except Exception:
        pass

    # Note: Full downgrade to previous heterogeneous state is not implemented to avoid data loss.
    # Keep this as a no-op for column-level reversions.
    pass