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    SUPERSEDED = "SUPERSEDED"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    WITHDRAWN = "WITHDRAWN"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[uuid.UUID | None] = mapped_column(
        UUID(as_uuid=True),
        ForeignKey("document_versions.id"),
        nullable=True,
    )
    derived_from_version_id: Mapped[uuid.UUID | None] = 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[datetime | None] = mapped_column(DateTime(timezone=True), nullable=True)
    superseded_at: Mapped[datetime | None] = 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[str | None] = mapped_column(String(100), nullable=True)
    change_summary: Mapped[str | None] = mapped_column(Text, nullable=True)
    created_by: Mapped[uuid.UUID | None] = mapped_column(UUID(as_uuid=True), ForeignKey("users.id"), nullable=True)
    submitted_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True), nullable=True)
    approved_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True), nullable=True)
    withdrawn_at: Mapped[datetime | None] = 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")