"""add_order_item_exceptions

Revision ID: d2e3f4a5b6c7
Revises: c1d2e3f4a5b6
Create Date: 2025-12-20

This migration adds the Order Item Exception system:
- Adds needs_product_match column to order_items table
- Creates order_item_exceptions table for tracking unmatched products

The exception system allows marketplace orders to be imported even when
products are not found by GTIN. Items are linked to a placeholder product
and exceptions are tracked for QC resolution.
"""
from typing import Sequence, Union

from alembic import op
import sqlalchemy as sa
from sqlalchemy import inspect


# revision identifiers, used by Alembic.
revision: str = 'd2e3f4a5b6c7'
down_revision: Union[str, None] = 'c1d2e3f4a5b6'
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def column_exists(table_name: str, column_name: str) -> bool:
    """Check if a column exists in a table."""
    bind = op.get_bind()
    inspector = inspect(bind)
    columns = [col['name'] for col in inspector.get_columns(table_name)]
    return column_name in columns


def table_exists(table_name: str) -> bool:
    """Check if a table exists in the database."""
    bind = op.get_bind()
    inspector = inspect(bind)
    return table_name in inspector.get_table_names()


def index_exists(index_name: str, table_name: str) -> bool:
    """Check if an index exists on a table."""
    bind = op.get_bind()
    inspector = inspect(bind)
    try:
        indexes = inspector.get_indexes(table_name)
        return any(idx['name'] == index_name for idx in indexes)
    except Exception:
        return False


def upgrade() -> None:
    # =========================================================================
    # Step 1: Add needs_product_match column to order_items
    # =========================================================================
    if not column_exists('order_items', 'needs_product_match'):
        op.add_column(
            'order_items',
            sa.Column(
                'needs_product_match',
                sa.Boolean(),
                server_default='0',
                nullable=False
            )
        )

    if not index_exists('ix_order_items_needs_product_match', 'order_items'):
        op.create_index(
            'ix_order_items_needs_product_match',
            'order_items',
            ['needs_product_match']
        )

    # =========================================================================
    # Step 2: Create order_item_exceptions table
    # =========================================================================
    if not table_exists('order_item_exceptions'):
        op.create_table(
            'order_item_exceptions',
            sa.Column('id', sa.Integer(), nullable=False),
            sa.Column('order_item_id', sa.Integer(), nullable=False),
            sa.Column('vendor_id', sa.Integer(), nullable=False),
            sa.Column('original_gtin', sa.String(length=50), nullable=True),
            sa.Column('original_product_name', sa.String(length=500), nullable=True),
            sa.Column('original_sku', sa.String(length=100), nullable=True),
            sa.Column(
                'exception_type',
                sa.String(length=50),
                nullable=False,
                server_default='product_not_found'
            ),
            sa.Column(
                'status',
                sa.String(length=50),
                nullable=False,
                server_default='pending'
            ),
            sa.Column('resolved_product_id', sa.Integer(), nullable=True),
            sa.Column('resolved_at', sa.DateTime(timezone=True), nullable=True),
            sa.Column('resolved_by', sa.Integer(), nullable=True),
            sa.Column('resolution_notes', sa.Text(), nullable=True),
            sa.Column(
                'created_at',
                sa.DateTime(timezone=True),
                server_default=sa.text('(CURRENT_TIMESTAMP)'),
                nullable=False
            ),
            sa.Column(
                'updated_at',
                sa.DateTime(timezone=True),
                server_default=sa.text('(CURRENT_TIMESTAMP)'),
                nullable=False
            ),
            sa.ForeignKeyConstraint(
                ['order_item_id'],
                ['order_items.id'],
                ondelete='CASCADE'
            ),
            sa.ForeignKeyConstraint(['vendor_id'], ['vendors.id']),
            sa.ForeignKeyConstraint(['resolved_product_id'], ['products.id']),
            sa.ForeignKeyConstraint(['resolved_by'], ['users.id']),
            sa.PrimaryKeyConstraint('id')
        )

        # Create indexes
        op.create_index(
            'ix_order_item_exceptions_id',
            'order_item_exceptions',
            ['id']
        )
        op.create_index(
            'ix_order_item_exceptions_vendor_id',
            'order_item_exceptions',
            ['vendor_id']
        )
        op.create_index(
            'ix_order_item_exceptions_status',
            'order_item_exceptions',
            ['status']
        )
        op.create_index(
            'idx_exception_vendor_status',
            'order_item_exceptions',
            ['vendor_id', 'status']
        )
        op.create_index(
            'idx_exception_gtin',
            'order_item_exceptions',
            ['vendor_id', 'original_gtin']
        )

        # Unique constraint on order_item_id (one exception per item)
        op.create_index(
            'uq_order_item_exception',
            'order_item_exceptions',
            ['order_item_id'],
            unique=True
        )


def downgrade() -> None:
    # Drop order_item_exceptions table
    if table_exists('order_item_exceptions'):
        op.drop_index('uq_order_item_exception', table_name='order_item_exceptions')
        op.drop_index('idx_exception_gtin', table_name='order_item_exceptions')
        op.drop_index('idx_exception_vendor_status', table_name='order_item_exceptions')
        op.drop_index('ix_order_item_exceptions_status', table_name='order_item_exceptions')
        op.drop_index('ix_order_item_exceptions_vendor_id', table_name='order_item_exceptions')
        op.drop_index('ix_order_item_exceptions_id', table_name='order_item_exceptions')
        op.drop_table('order_item_exceptions')

    # Remove needs_product_match column from order_items
    if column_exists('order_items', 'needs_product_match'):
        if index_exists('ix_order_items_needs_product_match', 'order_items'):
            op.drop_index('ix_order_items_needs_product_match', table_name='order_items')
        op.drop_column('order_items', 'needs_product_match')