import sqlalchemy as sa
from sqlalchemy import String, Text, Integer, Date, ForeignKey, func
from sqlalchemy.orm import Mapped, mapped_column, relationship as sa_relationship
from datetime import datetime, date
from typing import Optional, List
from app.database import Base


class ProjectTask(Base):
    __tablename__ = "project_tasks"

    id: Mapped[int] = mapped_column(primary_key=True, index=True)
    project_id: Mapped[int] = mapped_column(Integer, ForeignKey("projects.id", ondelete="CASCADE"), nullable=False)
    parent_task_id: Mapped[Optional[int]] = mapped_column(
        Integer, ForeignKey("project_tasks.id", ondelete="CASCADE"), nullable=True
    )
    title: Mapped[str] = mapped_column(String(255), nullable=False)
    description: Mapped[Optional[str]] = mapped_column(Text, nullable=True)
    status: Mapped[str] = mapped_column(String(20), default="pending")
    priority: Mapped[str] = mapped_column(String(20), default="medium")
    due_date: Mapped[Optional[date]] = mapped_column(Date, nullable=True)
    person_id: Mapped[Optional[int]] = mapped_column(Integer, ForeignKey("people.id", ondelete="SET NULL"), nullable=True)
    sort_order: Mapped[int] = mapped_column(Integer, default=0)
    version: Mapped[int] = mapped_column(Integer, default=1, server_default=sa.text("1"))
    created_at: Mapped[datetime] = mapped_column(default=func.now())
    updated_at: Mapped[datetime] = mapped_column(default=func.now(), onupdate=func.now())

    # Relationships — lazy="raise" to prevent N+1 (mirrors CalendarMember pattern)
    project: Mapped["Project"] = sa_relationship(back_populates="tasks", lazy="raise")
    person: Mapped[Optional["Person"]] = sa_relationship(back_populates="assigned_tasks", lazy="raise")
    parent_task: Mapped[Optional["ProjectTask"]] = sa_relationship(
        back_populates="subtasks",
        remote_side=[id],
        lazy="raise",
    )
    subtasks: Mapped[List["ProjectTask"]] = sa_relationship(
        back_populates="parent_task",
        cascade="all, delete-orphan",
        passive_deletes=True,
        lazy="raise",
    )
    comments: Mapped[List["TaskComment"]] = sa_relationship(
        back_populates="task",
        cascade="all, delete-orphan",
        passive_deletes=True,
        lazy="raise",
    )
    assignments: Mapped[List["ProjectTaskAssignment"]] = sa_relationship(
        back_populates="task",
        cascade="all, delete-orphan",
        passive_deletes=True,
        lazy="raise",
    )