"""add qa sessions and session fields

Revision ID: add_qa_sessions_and_turns
Revises: add_adaptive_rag_tables
Create Date: 2026-03-02
"""

from __future__ import annotations

from alembic import op
import sqlalchemy as sa

# revision identifiers, used by Alembic.
revision = "add_qa_sessions_and_turns"
down_revision = "add_adaptive_rag_tables"
branch_labels = None
depends_on = None


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 _column_exists(bind, table_name: str, column_name: str) -> bool:
    inspector = sa.inspect(bind)
    try:
        columns = inspector.get_columns(table_name)
    except Exception:
        return False
    return any(str(col.get("name")) == column_name for col in columns)


def _fk_exists(bind, table_name: str, constrained_columns: list[str]) -> bool:
    inspector = sa.inspect(bind)
    try:
        fks = inspector.get_foreign_keys(table_name)
    except Exception:
        return False
    expected = tuple(constrained_columns)
    for fk in fks:
        cols = tuple(fk.get("constrained_columns") or [])
        if cols == expected:
            return True
    return False


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()
    dialect_name = str(bind.dialect.name or "").lower()

    if not _table_exists(bind, "qa_sessions"):
        op.create_table(
            "qa_sessions",
            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("user_id", sa.BigInteger(), nullable=True),
            sa.Column("title", sa.String(length=120), nullable=False, server_default="新会话"),
            sa.Column("project_id", sa.BigInteger(), nullable=True),
            sa.Column("started_at", sa.TIMESTAMP(), nullable=True),
            sa.Column("last_message_at", sa.TIMESTAMP(), nullable=True),
            sa.Column("message_count", sa.Integer(), nullable=False, server_default="0"),
        )

    _create_index_if_not_exists(bind, "ix_qa_sessions_tenant_id", "qa_sessions", ["tenant_id"])
    _create_index_if_not_exists(bind, "ix_qa_sessions_created_at", "qa_sessions", ["created_at"])
    _create_index_if_not_exists(bind, "ix_qa_sessions_user_id", "qa_sessions", ["user_id"])
    _create_index_if_not_exists(bind, "ix_qa_sessions_project_id", "qa_sessions", ["project_id"])
    _create_index_if_not_exists(bind, "ix_qa_sessions_started_at", "qa_sessions", ["started_at"])
    _create_index_if_not_exists(bind, "ix_qa_sessions_last_message_at", "qa_sessions", ["last_message_at"])

    if _table_exists(bind, "qa_records"):
        if not _column_exists(bind, "qa_records", "session_id"):
            op.add_column("qa_records", sa.Column("session_id", sa.Integer(), nullable=True))
        if not _column_exists(bind, "qa_records", "turn_index"):
            op.add_column(
                "qa_records",
                sa.Column("turn_index", sa.Integer(), nullable=False, server_default="1"),
            )
        _create_index_if_not_exists(bind, "ix_qa_records_session_id", "qa_records", ["session_id"])
        _create_index_if_not_exists(bind, "ix_qa_records_turn_index", "qa_records", ["turn_index"])

        if (
            dialect_name != "sqlite"
            and _table_exists(bind, "qa_sessions")
            and not _fk_exists(bind, "qa_records", ["session_id"])
        ):
            op.create_foreign_key(
                "fk_qa_records_session_id",
                "qa_records",
                "qa_sessions",
                ["session_id"],
                ["id"],
                ondelete="SET NULL",
            )


def downgrade() -> None:
    bind = op.get_bind()
    dialect_name = str(bind.dialect.name or "").lower()

    if _table_exists(bind, "qa_records"):
        if dialect_name != "sqlite" and _fk_exists(bind, "qa_records", ["session_id"]):
            op.drop_constraint("fk_qa_records_session_id", "qa_records", type_="foreignkey")
        _drop_index_if_exists(bind, "ix_qa_records_turn_index", "qa_records")
        _drop_index_if_exists(bind, "ix_qa_records_session_id", "qa_records")
        if _column_exists(bind, "qa_records", "turn_index") or _column_exists(bind, "qa_records", "session_id"):
            with op.batch_alter_table("qa_records") as batch_op:
                if _column_exists(bind, "qa_records", "turn_index"):
                    batch_op.drop_column("turn_index")
                if _column_exists(bind, "qa_records", "session_id"):
                    batch_op.drop_column("session_id")

    if _table_exists(bind, "qa_sessions"):
        _drop_index_if_exists(bind, "ix_qa_sessions_last_message_at", "qa_sessions")
        _drop_index_if_exists(bind, "ix_qa_sessions_started_at", "qa_sessions")
        _drop_index_if_exists(bind, "ix_qa_sessions_project_id", "qa_sessions")
        _drop_index_if_exists(bind, "ix_qa_sessions_user_id", "qa_sessions")
        _drop_index_if_exists(bind, "ix_qa_sessions_created_at", "qa_sessions")
        _drop_index_if_exists(bind, "ix_qa_sessions_tenant_id", "qa_sessions")
        op.drop_table("qa_sessions")