import enum

from sqlalchemy import Column, Integer, String, TIMESTAMP, Text, ForeignKey, Enum, UniqueConstraint, Float, func
from sqlalchemy.orm import relationship

from .base import Base
from .book import Book
from .member import Member
from .librarian import Librarian


class LoanStatusEnum(enum.Enum):
    borrowed = 'borrowed'
    returned = 'returned'
    overdue  = 'overdue'
    reserved = 'reserved'


class Loan(Base):
    __tablename__  = 'loan'
    __table_args__ = (UniqueConstraint('id'),)

    id           = Column(Integer, primary_key=True, autoincrement=True)
    book_id      = Column(Integer, ForeignKey('book.id'), nullable=False)
    member_id    = Column(Integer, ForeignKey('member.id'), nullable=False)
    librarian_id = Column(Integer, ForeignKey('librarian.id'), nullable=False)
    loan_date    = Column(TIMESTAMP, nullable=False, server_default=func.now())
    due_date     = Column(TIMESTAMP, nullable=False)
    return_date  = Column(TIMESTAMP, nullable=True)
    status       = Column(Enum(LoanStatusEnum), nullable=False, default=LoanStatusEnum.borrowed)
    overdue_fee  = Column(Float, nullable=True)
    last_updated = Column(TIMESTAMP, nullable=False, server_default=func.now())

    book      = relationship('Book', backref='loans')
    member    = relationship('Member', backref='loans')
    librarian = relationship('Librarian', backref='loans')


__all__ = ["Loan", "LoanStatusEnum"]