"""Sync database with current model state

Revision ID: 003
Revises: 002
Create Date: 2024-01-01 00:00:02.000000

"""
from typing import Sequence, Union

from alembic import op
import sqlalchemy as sa
from sqlalchemy.engine.reflection import Inspector

# revision identifiers, used by Alembic.
revision: str = '003'
down_revision: Union[str, None] = '002'
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def table_exists(table_name):
    """Check if a table exists"""
    bind = op.get_bind()
    inspector = Inspector.from_engine(bind)
    return table_name in inspector.get_table_names()


def column_exists(table_name, column_name):
    """Check if a column exists in a table"""
    if not table_exists(table_name):
        return False
    bind = op.get_bind()
    inspector = Inspector.from_engine(bind)
    columns = [c['name'] for c in inspector.get_columns(table_name)]
    return column_name in columns


def upgrade() -> None:
    """
    This migration ensures the database is in sync with the current model state.
    It safely handles the case where tables/columns may already exist.
    """
    
    # Check if users table exists, if not create it with all fields
    if not table_exists('users'):
        op.create_table('users',
            sa.Column('id', sa.Integer(), nullable=False),
            sa.Column('email', sa.String(), nullable=False),
            sa.Column('password_hash', sa.String(), nullable=False),
            sa.Column('first_name', sa.String(), nullable=True),
            sa.Column('last_name', sa.String(), nullable=True),
            sa.Column('phone', sa.String(), nullable=True),
            sa.Column('bio', sa.String(), nullable=True),
            sa.Column('preferred_language', sa.String(), nullable=True),
            sa.Column('timezone', sa.String(), nullable=True),
            sa.Column('created_at', sa.DateTime(timezone=True), server_default=sa.text('(CURRENT_TIMESTAMP)'), nullable=True),
            sa.Column('updated_at', sa.DateTime(timezone=True), server_default=sa.text('(CURRENT_TIMESTAMP)'), nullable=True),
            sa.PrimaryKeyConstraint('id')
        )
        op.create_index(op.f('ix_users_email'), 'users', ['email'], unique=True)
        op.create_index(op.f('ix_users_id'), 'users', ['id'], unique=False)
    else:
        # Table exists, check for missing profile columns and add them
        profile_columns = [
            ('first_name', sa.Column('first_name', sa.String(), nullable=True)),
            ('last_name', sa.Column('last_name', sa.String(), nullable=True)),
            ('phone', sa.Column('phone', sa.String(), nullable=True)),
            ('bio', sa.Column('bio', sa.String(), nullable=True)),
            ('preferred_language', sa.Column('preferred_language', sa.String(), nullable=True)),
            ('timezone', sa.Column('timezone', sa.String(), nullable=True)),
            ('updated_at', sa.Column('updated_at', sa.DateTime(timezone=True), server_default=sa.text('(CURRENT_TIMESTAMP)'), nullable=True))
        ]
        
        for column_name, column_def in profile_columns:
            if not column_exists('users', column_name):
                op.add_column('users', column_def)
    
    # Set default values for profile fields
    if column_exists('users', 'preferred_language'):
        op.execute("UPDATE users SET preferred_language = 'en' WHERE preferred_language IS NULL")
    if column_exists('users', 'timezone'):
        op.execute("UPDATE users SET timezone = 'UTC' WHERE timezone IS NULL")


def downgrade() -> None:
    """
    Downgrade removes the profile fields added in this migration
    """
    if table_exists('users'):
        profile_columns = [
            'updated_at',
            'timezone',
            'preferred_language', 
            'bio',
            'phone',
            'last_name',
            'first_name'
        ]
        
        for column_name in profile_columns:
            if column_exists('users', column_name):
                op.drop_column('users', column_name)