from __future__ import annotations

import enum
import uuid
from datetime import datetime

from sqlalchemy import (
    DateTime,
    Enum,
    ForeignKey,
    Integer,
    String,
    UniqueConstraint,
    func,
)
from sqlalchemy.dialects.postgresql import UUID
from sqlalchemy.orm import Mapped, mapped_column, relationship

from app.database.database import Base

from typing import TYPE_CHECKING

if TYPE_CHECKING:
    from app.models.document_chunk import DocumentChunk

class DocumentVersionStatus(str, enum.Enum):
    UPLOADED = "UPLOADED"
    PROCESSING = "PROCESSING"
    PROCESSED = "PROCESSED"
    FAILED = "FAILED"


class DocumentVersion(Base):
    """
    Represents a specific uploaded version of a document.

    Each upload creates a new DocumentVersion while preserving
    the logical Document identity.
    """

    __tablename__ = "document_versions"

    __table_args__ = (
        UniqueConstraint(
            "document_id",
            "version_number",
            name="uq_document_version",
        ),
    )

    id: Mapped[uuid.UUID] = mapped_column(
        UUID(as_uuid=True),
        primary_key=True,
        default=uuid.uuid4,
    )

    document_id: Mapped[uuid.UUID] = mapped_column(
        UUID(as_uuid=True),
        ForeignKey("documents.id", ondelete="CASCADE"),
        nullable=False,
        index=True,
    )

    version_number: Mapped[int] = mapped_column(
        Integer,
        nullable=False,
        index=True,
    )

    filename: Mapped[str] = mapped_column(
        String(255),
        nullable=False,
    )

    file_type: Mapped[str] = mapped_column(
        String(20),
        nullable=False,
    )

    checksum: Mapped[str] = mapped_column(
        String(128),
        nullable=False,
        index=True,
    )

    storage_path: Mapped[str] = mapped_column(
        String(1000),
        nullable=False,
    )

    status: Mapped[DocumentVersionStatus] = mapped_column(
        Enum(DocumentVersionStatus, name="document_version_status"),
        nullable=False,
        default=DocumentVersionStatus.UPLOADED,
        server_default=DocumentVersionStatus.UPLOADED.value,
        index=True,
    )

    uploaded_by: Mapped[uuid.UUID] = mapped_column(
        UUID(as_uuid=True),
        ForeignKey("users.id"),
        nullable=False,
    )

    uploaded_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True),
        nullable=False,
        server_default=func.now(),
    )

    processed_at: Mapped[datetime | None] = mapped_column(
        DateTime(timezone=True),
        nullable=True,
    )

    # ------------------------------------------------------------------
    # Relationships
    # ------------------------------------------------------------------

    document: Mapped["Document"] = relationship(
        back_populates="versions",
    )

    uploader: Mapped["User"] = relationship()

    knowledge_items: Mapped[list["KnowledgeItem"]] = relationship(
        back_populates="document_version",
        cascade="all, delete-orphan",
        passive_deletes=True,
    )

    evidence: Mapped[list["KnowledgeEvidence"]] = relationship(
        back_populates="document_version",
        cascade="all, delete-orphan",
        passive_deletes=True,
    )

    chunks: Mapped[list["DocumentChunk"]] = relationship(
        back_populates="document_version",
        cascade="all, delete-orphan",
        passive_deletes=True,
    )

    workflow_runs: Mapped[list["WorkflowRun"]] = relationship(
        back_populates="document_version",
        cascade="all, delete-orphan",
        passive_deletes=True,
    )

    def __repr__(self) -> str:
        return (
            f"<DocumentVersion("
            f"document={self.document_id}, "
            f"version={self.version_number}, "
            f"status='{self.status.value}')>"
        )