"""Create chat_sessions and messages tables.

Revision ID: 004
Revises: 003
Create Date: 2025-02-05 15:30:00.000000

"""
from typing import Sequence, Union

from alembic import op
import sqlalchemy as sa
from sqlalchemy.dialects import postgresql

# revision identifiers, used by Alembic.
revision: str = "004"
down_revision: Union[str, None] = "003"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    from sqlalchemy import inspect
    
    conn = op.get_bind()
    inspector = inspect(conn)
    tables = inspector.get_table_names()
    
    if "chat_sessions" not in tables:
        op.create_table(
            "chat_sessions",
            sa.Column("id", sa.Integer(), nullable=False, autoincrement=True),
            sa.Column("external_user_id", sa.String(128), nullable=False),
            sa.Column("external_name", sa.String(128), nullable=True),
            sa.Column("status", sa.String(32), nullable=False, server_default="open"),
            sa.Column("created_at", sa.DateTime(timezone=True), server_default=sa.func.now(), nullable=False),
            sa.Column("updated_at", sa.DateTime(timezone=True), server_default=sa.func.now(), nullable=False),
            sa.PrimaryKeyConstraint("id"),
        )
        op.create_index(op.f("ix_chat_sessions_external_user_id"), "chat_sessions", ["external_user_id"], unique=False)
    
    if "messages" not in tables:
        op.create_table(
            "messages",
            sa.Column("id", sa.Integer(), nullable=False, autoincrement=True),
            sa.Column("session_id", sa.Integer(), nullable=False),
            sa.Column("role", sa.String(16), nullable=False),
            sa.Column("content", sa.Text(), nullable=False),
            sa.Column("created_at", sa.DateTime(timezone=True), server_default=sa.func.now(), nullable=False),
            sa.ForeignKeyConstraint(["session_id"], ["chat_sessions.id"], ondelete="CASCADE"),
            sa.PrimaryKeyConstraint("id"),
        )
        op.create_index(op.f("ix_messages_session_id"), "messages", ["session_id"], unique=False)


def downgrade() -> None:
    op.drop_index(op.f("ix_messages_session_id"), table_name="messages")
    op.drop_table("messages")
    op.drop_index(op.f("ix_chat_sessions_external_user_id"), table_name="chat_sessions")
    op.drop_table("chat_sessions")