"""Persist dimension-checked vector snapshots with composite scope constraints."""

import sqlalchemy as sa
from alembic import op

revision = "0006_vectors"
down_revision = "0005_chunk_indexes"
branch_labels = None
depends_on = None


class ExtensionVector(sa.types.UserDefinedType):
    """Qualify extension type without adding public business tables to search_path."""

    def get_col_spec(self, **kw):
        return "public.vector"


def upgrade():
    schema = op.get_bind().scalar(
        sa.text("SELECT extnamespace::regnamespace::text FROM pg_extension WHERE extname='vector'")
    )
    if schema != "public":
        raise RuntimeError("vector 扩展须安装在 public；请由数据库管理员核对，迁移不会移动共享扩展")
    op.create_unique_constraint("uq_chunk_text_scope", "chunks", ["id", "index_version_id"])
    op.create_table(
        "embedding_spaces",
        sa.Column("id", sa.String(64), primary_key=True),
        sa.Column("dimension", sa.Integer(), nullable=False),
        sa.Column("spec", sa.JSON(), nullable=False),
        sa.UniqueConstraint("id", "dimension", name="uq_embedding_space_dimension"),
        sa.CheckConstraint("dimension BETWEEN 1 AND 2000", name="ck_embedding_space_dimension"),
    )
    op.create_table(
        "vector_versions",
        sa.Column("id", sa.String(36), primary_key=True),
        sa.Column(
            "text_index_version_id",
            sa.String(36),
            sa.ForeignKey("index_versions.id"),
            nullable=False,
        ),
        sa.Column("space_id", sa.String(64), nullable=False),
        sa.Column("dimension", sa.Integer(), nullable=False),
        sa.Column("chunk_count", sa.Integer(), nullable=False),
        sa.Column("status", sa.String(20), nullable=False),
        sa.Column("created_by", sa.Integer(), sa.ForeignKey("users.id"), nullable=False),
        sa.Column(
            "created_at", sa.DateTime(timezone=True), server_default=sa.func.now(), nullable=False
        ),
        sa.Column("published_at", sa.DateTime(timezone=True)),
        sa.ForeignKeyConstraint(
            ["space_id", "dimension"],
            ["embedding_spaces.id", "embedding_spaces.dimension"],
            name="fk_vector_version_space",
        ),
        sa.UniqueConstraint(
            "id", "text_index_version_id", "space_id", "dimension", name="uq_vector_version_scope"
        ),
        sa.CheckConstraint(
            "status IN ('ready', 'published', 'superseded')", name="ck_vector_version_status"
        ),
        sa.CheckConstraint("chunk_count BETWEEN 0 AND 2000", name="ck_vector_version_count"),
    )
    op.create_table(
        "chunk_vectors",
        sa.Column("version_id", sa.String(36), primary_key=True),
        sa.Column("chunk_id", sa.String(36), primary_key=True),
        sa.Column("text_index_version_id", sa.String(36), nullable=False),
        sa.Column("space_id", sa.String(64), nullable=False),
        sa.Column("dimension", sa.Integer(), nullable=False),
        sa.Column("embedding", ExtensionVector(), nullable=False),
        sa.ForeignKeyConstraint(
            ["version_id", "text_index_version_id", "space_id", "dimension"],
            [
                "vector_versions.id",
                "vector_versions.text_index_version_id",
                "vector_versions.space_id",
                "vector_versions.dimension",
            ],
            name="fk_chunk_vector_scope",
        ),
        sa.ForeignKeyConstraint(
            ["chunk_id", "text_index_version_id"],
            ["chunks.id", "chunks.index_version_id"],
            name="fk_chunk_vector_text",
        ),
        sa.CheckConstraint("public.vector_dims(embedding) = dimension", name="ck_vector_dimension"),
        sa.CheckConstraint(
            "public.vector_norm(embedding) BETWEEN 0.9999 AND 1.0001", name="ck_vector_unit_norm"
        ),
    )
    op.create_table(
        "vector_state",
        sa.Column("id", sa.Integer(), primary_key=True),
        sa.Column("active_version_id", sa.String(36), sa.ForeignKey("vector_versions.id")),
        sa.Column("generation", sa.Integer(), nullable=False),
        sa.CheckConstraint("id = 1", name="ck_vector_state_singleton"),
    )
    op.execute(sa.text("INSERT INTO vector_state (id, generation) VALUES (1, 0)"))
    op.create_table(
        "vector_publications",
        sa.Column("generation", sa.Integer(), primary_key=True),
        sa.Column("previous_version_id", sa.String(36), sa.ForeignKey("vector_versions.id")),
        sa.Column("version_id", sa.String(36), sa.ForeignKey("vector_versions.id"), nullable=False),
        sa.Column("actor_id", sa.Integer(), sa.ForeignKey("users.id"), nullable=False),
        sa.Column(
            "published_at", sa.DateTime(timezone=True), server_default=sa.func.now(), nullable=False
        ),
    )


def downgrade():
    for table in [
        "vector_publications",
        "vector_state",
        "chunk_vectors",
        "vector_versions",
        "embedding_spaces",
    ]:
        op.drop_table(table)
    op.drop_constraint("uq_chunk_text_scope", "chunks", type_="unique")