from core_db import AuditMixin, Base, EntityMixin
from core_shared import JSONValue
from sqlalchemy import Integer, String, Text, cast
from sqlalchemy import JSON
from sqlalchemy.orm import Mapped, mapped_column
from sqlalchemy.sql.expression import ColumnElement
from sqlalchemy.types import UserDefinedType

EMBEDDING_DIMENSIONS = 1536


class PgVector(UserDefinedType[str]):
    cache_ok = True

    def __init__(self, dimensions: int) -> None:
        self.dimensions = dimensions

    def get_col_spec(self, **kw: object) -> str:
        return f"public.vector({self.dimensions})"

    def bind_expression(self, bindvalue: ColumnElement[str]) -> ColumnElement[str]:
        return cast(bindvalue, self)


class KnowledgeChunk(EntityMixin, AuditMixin, Base):
    __tablename__ = "knowledge_chunk"

    knowledge_base_id: Mapped[str] = mapped_column(String(36), index=True)
    document_id: Mapped[str] = mapped_column(String(36), index=True)
    chunk_index: Mapped[int] = mapped_column(Integer)
    content_text: Mapped[str] = mapped_column(Text)
    token_count: Mapped[int] = mapped_column(Integer, default=0)
    embedding_model: Mapped[str | None] = mapped_column(String(64), nullable=True, index=True)
    embedding_json: Mapped[list[float] | None] = mapped_column(JSON, nullable=True)
    embedding_vector: Mapped[str | None] = mapped_column(PgVector(EMBEDDING_DIMENSIONS), nullable=True)
    metadata_json: Mapped[dict[str, JSONValue] | None] = mapped_column(JSON, nullable=True)