import uuid
from sqlalchemy import Column, String, ForeignKey, Date, Integer, Numeric, DateTime, UniqueConstraint, Index
from sqlalchemy.sql import func
from sqlalchemy.orm import relationship
from app.core.database import Base


class WorkloadSnapshot(Base):
    """Stores historical workload snapshots for trend analysis."""
    __tablename__ = "pjctrl_workload_snapshots"

    id = Column(String(36), primary_key=True, default=lambda: str(uuid.uuid4()))
    user_id = Column(String(36), ForeignKey("pjctrl_users.id", ondelete="CASCADE"), nullable=False)
    week_start = Column(Date, nullable=False)
    allocated_hours = Column(Numeric(8, 2), nullable=False, default=0)
    capacity_hours = Column(Numeric(8, 2), nullable=False, default=40)
    load_percentage = Column(Numeric(5, 2), nullable=False, default=0)
    task_count = Column(Integer, nullable=False, default=0)
    created_at = Column(DateTime, server_default=func.now(), nullable=False)
    updated_at = Column(DateTime, server_default=func.now(), onupdate=func.now(), nullable=False)

    # Relationships
    user = relationship("User", backref="workload_snapshots")

    # Constraints
    __table_args__ = (
        UniqueConstraint('user_id', 'week_start', name='uk_user_week'),
        Index('idx_workload_week_start', 'week_start'),
    )