from __future__ import annotations
from typing import Optional

import enum
import uuid
from datetime import datetime

from sqlalchemy import BigInteger, DateTime, Enum, ForeignKey, String, Text, UniqueConstraint, func
from sqlalchemy.dialects.postgresql import UUID
from sqlalchemy.orm import Mapped, mapped_column, relationship

from app.db.base_class import Base


class DocumentVersionStatus(str, enum.Enum):
    DRAFT = "DRAFT"
    SUBMITTED = "SUBMITTED"
    APPROVED = "APPROVED"
    EFFECTIVE = "EFFECTIVE"
    SUPERSEDED = "SUPERSEDED"
    ARCHIVED = "ARCHIVED"
    WITHDRAWN = "WITHDRAWN"


class DocumentVersion(Base):
    __tablename__ = "document_versions"
    __table_args__ = (UniqueConstraint("document_id", "version_no", name="uq_document_versions_doc_no"),)

    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"), nullable=False)
    version_no: Mapped[str] = mapped_column(String(50), nullable=False)
    parent_version_id: Mapped[Optional[uuid.UUID]] = mapped_column(
        UUID(as_uuid=True),
        ForeignKey("document_versions.id"),
        nullable=True,
    )
    derived_from_version_id: Mapped[Optional[uuid.UUID]] = mapped_column(
        UUID(as_uuid=True),
        ForeignKey("document_versions.id"),
        nullable=True,
    )
    status: Mapped[DocumentVersionStatus] = mapped_column(
        Enum(DocumentVersionStatus, name="document_version_status"),
        nullable=False,
        server_default=DocumentVersionStatus.DRAFT.value,
    )
    effective_at: Mapped[Optional[datetime]] = mapped_column(DateTime(timezone=True), nullable=True)
    superseded_at: Mapped[Optional[datetime]] = mapped_column(DateTime(timezone=True), nullable=True)
    file_uri: Mapped[str] = mapped_column(String(500), nullable=False)
    file_hash: Mapped[str] = mapped_column(String(128), nullable=False)
    file_size: Mapped[int] = mapped_column(BigInteger, nullable=False)
    mime_type: Mapped[Optional[str]] = mapped_column(String(100), nullable=True)
    change_summary: Mapped[Optional[str]] = mapped_column(Text, nullable=True)
    created_by: Mapped[Optional[uuid.UUID]] = mapped_column(UUID(as_uuid=True), ForeignKey("users.id"), nullable=True)
    submitted_at: Mapped[Optional[datetime]] = mapped_column(DateTime(timezone=True), nullable=True)
    approved_at: Mapped[Optional[datetime]] = mapped_column(DateTime(timezone=True), nullable=True)
    withdrawn_at: Mapped[Optional[datetime]] = mapped_column(DateTime(timezone=True), nullable=True)
    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), nullable=False, server_default=func.now())

    document = relationship("Document", back_populates="versions", foreign_keys=[document_id])
    parent_version = relationship("DocumentVersion", remote_side=[id], foreign_keys=[parent_version_id])
    derived_from_version = relationship("DocumentVersion", remote_side=[id], foreign_keys=[derived_from_version_id])
    distributions = relationship("Distribution", back_populates="version")