"""add context memory lifecycle status fields

Revision ID: 20260520_context_memory_status_gate
Revises: 20260519_add_pmflow_ai_context_memories
Create Date: 2026-05-20
"""

from __future__ import annotations

from alembic import op
import sqlalchemy as sa


revision = "20260520_context_memory_status_gate"
down_revision = "20260519_add_pmflow_ai_context_memories"
branch_labels = None
depends_on = None


def _table_exists(table_name: str) -> bool:
    return sa.inspect(op.get_bind()).has_table(table_name)


def _column_exists(table_name: str, column_name: str) -> bool:
    if not _table_exists(table_name):
        return False
    inspector = sa.inspect(op.get_bind())
    return any(item.get("name") == column_name for item in inspector.get_columns(table_name))


def _index_exists(table_name: str, index_name: str) -> bool:
    if not _table_exists(table_name):
        return False
    inspector = sa.inspect(op.get_bind())
    return any(item.get("name") == index_name for item in inspector.get_indexes(table_name))


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


def upgrade() -> None:
    if not _table_exists("pmflow_ai_context_memories"):
        return
    if not _column_exists("pmflow_ai_context_memories", "status"):
        op.add_column("pmflow_ai_context_memories", sa.Column("status", sa.String(length=32), nullable=False, server_default="active"))
    if not _column_exists("pmflow_ai_context_memories", "confidence_score"):
        op.add_column("pmflow_ai_context_memories", sa.Column("confidence_score", sa.Float(), nullable=False, server_default="0.6"))
    if not _column_exists("pmflow_ai_context_memories", "supersedes_memory_id"):
        op.add_column("pmflow_ai_context_memories", sa.Column("supersedes_memory_id", sa.BigInteger(), nullable=True))
        op.create_foreign_key(
            "fk_pmflow_ai_context_memories_supersedes",
            "pmflow_ai_context_memories",
            "pmflow_ai_context_memories",
            ["supersedes_memory_id"],
            ["id"],
            ondelete="SET NULL",
        )
    if not _column_exists("pmflow_ai_context_memories", "invalidation_reason"):
        op.add_column("pmflow_ai_context_memories", sa.Column("invalidation_reason", sa.Text(), nullable=True))
    if not _column_exists("pmflow_ai_context_memories", "last_validated_at"):
        op.add_column("pmflow_ai_context_memories", sa.Column("last_validated_at", sa.TIMESTAMP(), nullable=True))

    _create_index_once("ix_pmflow_ai_context_memories_status", "pmflow_ai_context_memories", ["status"])
    _create_index_once("ix_pmflow_ai_context_memories_confidence_score", "pmflow_ai_context_memories", ["confidence_score"])
    _create_index_once("ix_pmflow_ai_context_memories_supersedes_memory_id", "pmflow_ai_context_memories", ["supersedes_memory_id"])
    _create_index_once("ix_pmflow_ai_context_memories_last_validated_at", "pmflow_ai_context_memories", ["last_validated_at"])


def downgrade() -> None:
    if not _table_exists("pmflow_ai_context_memories"):
        return
    for index_name in (
        "ix_pmflow_ai_context_memories_last_validated_at",
        "ix_pmflow_ai_context_memories_supersedes_memory_id",
        "ix_pmflow_ai_context_memories_confidence_score",
        "ix_pmflow_ai_context_memories_status",
    ):
        if _index_exists("pmflow_ai_context_memories", index_name):
            op.drop_index(index_name, table_name="pmflow_ai_context_memories")
    for column_name in ("last_validated_at", "invalidation_reason", "supersedes_memory_id", "confidence_score", "status"):
        if _column_exists("pmflow_ai_context_memories", column_name):
            op.drop_column("pmflow_ai_context_memories", column_name)