"""Add app_settings table and expand perceptual_hash to 64 chars for 256-bit hashes

Revision ID: b26011901
Revises: a46e641430b8
Create Date: 2026-01-19

"""
from alembic import op
import sqlalchemy as sa


# revision identifiers, used by Alembic.
revision = 'b26011901'
down_revision = 'a46e641430b8'
branch_labels = None
depends_on = None


def upgrade():
    # Create app_settings table
    op.create_table(
        'app_settings',
        sa.Column('id', sa.Integer(), nullable=False),
        sa.Column('key', sa.String(length=64), nullable=False),
        sa.Column('value', sa.Text(), nullable=True),
        sa.Column('updated_at', sa.DateTime(), nullable=True),
        sa.PrimaryKeyConstraint('id'),
        sa.UniqueConstraint('key')
    )

    # Expand perceptual_hash column from 16 to 64 chars
    bind = op.get_bind()
    dialect = bind.dialect.name

    if dialect == "sqlite":
        # SQLite requires table recreation for column type changes.
        # IMPORTANT: When recreating image_record, we must also recreate
        # image_tags to preserve foreign key relationships.

        # Step 1: Backup image_tags data
        op.execute("CREATE TABLE image_tags_backup AS SELECT * FROM image_tags")

        # Step 2: Drop image_tags (it references image_record)
        op.drop_table("image_tags")

        # Step 3: Recreate image_record with new column size
        with op.batch_alter_table("image_record", recreate="always") as batch_op:
            batch_op.alter_column(
                'perceptual_hash',
                existing_type=sa.String(length=16),
                type_=sa.String(length=64),
                existing_nullable=True
            )

        # Step 4: Recreate image_tags with proper FK constraints
        op.create_table(
            "image_tags",
            sa.Column("image_id", sa.Integer(), nullable=False),
            sa.Column("tag_id", sa.Integer(), nullable=False),
            sa.PrimaryKeyConstraint("image_id", "tag_id"),
            sa.ForeignKeyConstraint(["image_id"], ["image_record.id"], ondelete="CASCADE"),
            sa.ForeignKeyConstraint(["tag_id"], ["tag.id"], ondelete="CASCADE"),
            sa.UniqueConstraint("image_id", "tag_id", name="uq_image_tag"),
        )

        # Step 5: Restore image_tags data
        op.execute("INSERT INTO image_tags (image_id, tag_id) SELECT image_id, tag_id FROM image_tags_backup")

        # Step 6: Drop backup table
        op.drop_table("image_tags_backup")
    else:
        # PostgreSQL and others can alter directly
        op.alter_column(
            'image_record',
            'perceptual_hash',
            existing_type=sa.String(length=16),
            type_=sa.String(length=64),
            existing_nullable=True
        )


def downgrade():
    bind = op.get_bind()
    dialect = bind.dialect.name

    # Shrink perceptual_hash back to 16 chars (will truncate data!)
    if dialect == "sqlite":
        # Same approach as upgrade: backup image_tags, recreate image_record,
        # then restore image_tags to preserve FK relationships

        # Step 1: Backup image_tags data
        op.execute("CREATE TABLE image_tags_backup AS SELECT * FROM image_tags")

        # Step 2: Drop image_tags (it references image_record)
        op.drop_table("image_tags")

        # Step 3: Recreate image_record with old column size
        with op.batch_alter_table("image_record", recreate="always") as batch_op:
            batch_op.alter_column(
                'perceptual_hash',
                existing_type=sa.String(length=64),
                type_=sa.String(length=16),
                existing_nullable=True
            )

        # Step 4: Recreate image_tags with proper FK constraints
        op.create_table(
            "image_tags",
            sa.Column("image_id", sa.Integer(), nullable=False),
            sa.Column("tag_id", sa.Integer(), nullable=False),
            sa.PrimaryKeyConstraint("image_id", "tag_id"),
            sa.ForeignKeyConstraint(["image_id"], ["image_record.id"], ondelete="CASCADE"),
            sa.ForeignKeyConstraint(["tag_id"], ["tag.id"], ondelete="CASCADE"),
            sa.UniqueConstraint("image_id", "tag_id", name="uq_image_tag"),
        )

        # Step 5: Restore image_tags data
        op.execute("INSERT INTO image_tags (image_id, tag_id) SELECT image_id, tag_id FROM image_tags_backup")

        # Step 6: Drop backup table
        op.drop_table("image_tags_backup")
    else:
        op.alter_column(
            'image_record',
            'perceptual_hash',
            existing_type=sa.String(length=64),
            type_=sa.String(length=16),
            existing_nullable=True
        )

    # Drop app_settings table
    op.drop_table('app_settings')