"""add qa session state table

Revision ID: add_qa_session_state_table
Revises: add_project_knowledge_graph_tables
Create Date: 2026-03-02
"""

from __future__ import annotations

from alembic import op
import sqlalchemy as sa

try:
    from sqlalchemy.dialects.postgresql import JSONB
except Exception:  # pragma: no cover
    JSONB = sa.JSON


# revision identifiers, used by Alembic.
revision = "add_qa_session_state_table"
down_revision = "add_project_knowledge_graph_tables"
branch_labels = None
depends_on = None


def _json_type(bind):
    return JSONB() if bind.dialect.name == "postgresql" else sa.JSON()


def _table_exists(bind, table_name: str) -> bool:
    inspector = sa.inspect(bind)
    return inspector.has_table(table_name)


def _index_exists(bind, table_name: str, index_name: str) -> bool:
    inspector = sa.inspect(bind)
    indexes = inspector.get_indexes(table_name)
    return any(idx.get("name") == index_name for idx in indexes)


def _create_index_if_not_exists(bind, index_name: str, table_name: str, columns: list[str]) -> None:
    if not _index_exists(bind, table_name, index_name):
        op.create_index(index_name, table_name, columns)


def _drop_index_if_exists(bind, index_name: str, table_name: str) -> None:
    if _index_exists(bind, table_name, index_name):
        op.drop_index(index_name, table_name=table_name)


def upgrade() -> None:
    bind = op.get_bind()

    if not _table_exists(bind, "qa_session_states"):
        op.create_table(
            "qa_session_states",
            sa.Column("id", sa.Integer(), primary_key=True, autoincrement=True),
            sa.Column("tenant_id", sa.BigInteger(), nullable=False, server_default="1"),
            sa.Column("created_at", sa.TIMESTAMP(), nullable=False, server_default=sa.func.now()),
            sa.Column("updated_at", sa.TIMESTAMP(), nullable=False, server_default=sa.func.now(), onupdate=sa.func.now()),
            sa.Column("session_id", sa.Integer(), sa.ForeignKey("qa_sessions.id", ondelete="CASCADE"), nullable=False, unique=True),
            sa.Column("last_subject", sa.String(length=255), nullable=True),
            sa.Column("last_entity_ids", _json_type(bind), nullable=True),
            sa.Column("last_intent", sa.String(length=20), nullable=True),
            sa.Column("ambiguity", sa.String(length=20), nullable=True),
            sa.Column("rewrite_history", _json_type(bind), nullable=True),
        )

    _create_index_if_not_exists(bind, "ix_qa_session_states_tenant_id", "qa_session_states", ["tenant_id"])
    _create_index_if_not_exists(bind, "ix_qa_session_states_created_at", "qa_session_states", ["created_at"])
    _create_index_if_not_exists(bind, "ix_qa_session_states_session_id", "qa_session_states", ["session_id"])
    _create_index_if_not_exists(bind, "ix_qa_session_states_last_subject", "qa_session_states", ["last_subject"])
    _create_index_if_not_exists(bind, "ix_qa_session_states_last_intent", "qa_session_states", ["last_intent"])
    _create_index_if_not_exists(bind, "ix_qa_session_states_ambiguity", "qa_session_states", ["ambiguity"])


def downgrade() -> None:
    bind = op.get_bind()
    if not _table_exists(bind, "qa_session_states"):
        return

    _drop_index_if_exists(bind, "ix_qa_session_states_ambiguity", "qa_session_states")
    _drop_index_if_exists(bind, "ix_qa_session_states_last_intent", "qa_session_states")
    _drop_index_if_exists(bind, "ix_qa_session_states_last_subject", "qa_session_states")
    _drop_index_if_exists(bind, "ix_qa_session_states_session_id", "qa_session_states")
    _drop_index_if_exists(bind, "ix_qa_session_states_created_at", "qa_session_states")
    _drop_index_if_exists(bind, "ix_qa_session_states_tenant_id", "qa_session_states")
    op.drop_table("qa_session_states")