from sqlalchemy import (
    CheckConstraint, DateTime, Integer, ForeignKey, Index,
    String, UniqueConstraint, func,
)
from sqlalchemy.orm import Mapped, mapped_column, relationship
from datetime import datetime
from typing import Optional
from app.database import Base


class ProjectMember(Base):
    __tablename__ = "project_members"
    __table_args__ = (
        UniqueConstraint("project_id", "user_id", name="uq_project_members_proj_user"),
        CheckConstraint(
            "permission IN ('read_only', 'create_modify')",
            name="ck_project_members_permission",
        ),
        CheckConstraint(
            "status IN ('pending', 'accepted', 'rejected')",
            name="ck_project_members_status",
        ),
        CheckConstraint(
            "source IN ('invited', 'auto_assigned')",
            name="ck_project_members_source",
        ),
        Index("ix_project_members_user_id", "user_id"),
        Index("ix_project_members_project_id", "project_id"),
        Index("ix_project_members_status", "status"),
    )

    id: Mapped[int] = mapped_column(primary_key=True, index=True)
    project_id: Mapped[int] = mapped_column(
        Integer, ForeignKey("projects.id", ondelete="CASCADE"), nullable=False
    )
    user_id: Mapped[int] = mapped_column(
        Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False
    )
    invited_by: Mapped[int] = mapped_column(
        Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False
    )
    permission: Mapped[str] = mapped_column(String(20), nullable=False)
    status: Mapped[str] = mapped_column(String(20), nullable=False, default="pending")
    source: Mapped[str] = mapped_column(String(20), nullable=False, default="invited")
    created_at: Mapped[datetime] = mapped_column(
        DateTime, default=func.now(), server_default=func.now()
    )
    updated_at: Mapped[datetime] = mapped_column(
        DateTime, default=func.now(), server_default=func.now(), onupdate=func.now()
    )
    accepted_at: Mapped[Optional[datetime]] = mapped_column(DateTime, nullable=True)

    # Relationships — lazy="raise" to prevent N+1 (mirrors CalendarMember)
    project: Mapped["Project"] = relationship(back_populates="members", lazy="raise")
    user: Mapped["User"] = relationship(foreign_keys=[user_id], lazy="raise")
    inviter: Mapped[Optional["User"]] = relationship(
        foreign_keys=[invited_by], lazy="raise"
    )