from __future__ import annotations

from datetime import datetime, timezone
from typing import List, Optional

import pytz
from flask_sqlalchemy import SQLAlchemy
from flask import current_app
from sqlalchemy import Boolean, Column, DateTime, String, TypeDecorator, ForeignKey, UniqueConstraint
from sqlalchemy.orm import Mapped, mapped_column, relationship
db : SQLAlchemy = SQLAlchemy()

deck_password = db.Table(
    "deck_password",
    Column("deck_id", db.Integer, db.ForeignKey("deck.id"), primary_key=True),
    Column("password_id", db.Integer, db.ForeignKey("password.id"), primary_key=True)
)

deck_token = db.Table(
    "deck_token",
    Column("deck_id", db.Integer, db.ForeignKey("deck.id"), primary_key=True),
    Column("token_id", db.Integer, db.ForeignKey("token.id"), primary_key=True)
)


class UTCDateTime(TypeDecorator):
    impl = DateTime

    def process_bind_param(self, value, dialect):
        # Ensure datetime is stored in naive UTC
        if value is not None and value.tzinfo is not None:
            value = value.astimezone(pytz.utc).replace(tzinfo=None)
        return value

    def process_result_value(self, value, dialect):
        # Re-attach UTC tzinfo when reading
        if value is not None:
            value = value.replace(tzinfo=pytz.utc)
        return value

class Password(db.Model):
    __tablename__ = "password"

    id : Mapped[int] = mapped_column(primary_key=True)
    value : Mapped[str] = mapped_column(String(60)) 
    expires_at: Mapped[Optional[datetime]] = mapped_column(UTCDateTime())  # Optional expiration

    decks : Mapped[List[Deck]] = relationship("Deck", secondary=deck_password, back_populates='passwords')

    def __init__(self, value: str, expires_at: datetime|None) -> None:
        self.value = value
        self.expires_at = expires_at

    def is_expired(self) -> bool:
        """Check if the password is expired"""
        return self.expires_at is not None and datetime.now(timezone.utc) > self.expires_at

    def __repr__(self) -> str:
        return f"<Password(value={self.value}, expires_at={self.expires_at})>"


class Deck(db.Model):
    __tablename__ = "deck"

    __table_args__ = (
        UniqueConstraint('course_id', 'deck', name='_course_deck_uc'),
    )

    id : Mapped[int] = mapped_column(primary_key=True) 
    name : Mapped[str] = mapped_column(String(60), unique=True, nullable=False)
    deck : Mapped[str] = mapped_column(String(60), nullable=False)
    description : Mapped[str] = mapped_column(String(60))
    index_file: Mapped[str] = mapped_column(String(40), nullable=False)

    passwords : Mapped[List[Password]] = relationship("Password", secondary=deck_password, back_populates='decks')
    tokens : Mapped[List[Token]] = relationship("Token", secondary=deck_token, back_populates='decks')
    course_id: Mapped[int] = mapped_column(ForeignKey("course.id"))
    course: Mapped['Course'] = relationship("Course", back_populates='decks')


    def __init__(self, name: str, deck: str, course: Course, description: str = "", index_file: str = "index.html") -> None:
        self.name = name
        self.deck = deck
        self.description = description
        self.course = course
        self.index_file = index_file

    def __repr__(self) -> str:
        return f"<Deck(name={self.name}, deck={self.deck}, course={self.course}, index={self.index_file})>"

class Token(db.Model):
    __tablename__ = "token"
    id : Mapped[int] = mapped_column(primary_key=True) 
    name: Mapped[str] = mapped_column(String(60), unique=True, nullable=False)
    active_course_id: Mapped[int] = mapped_column(ForeignKey("course.id"), nullable=True)
    active_course: Mapped[Course] = relationship("Course", foreign_keys=[active_course_id]) 
    decks : Mapped[List[Deck]]= relationship("Deck", secondary=deck_token, back_populates='tokens')

    def __init__(self, name: str) -> None:
        self.name = name
        self.active_course_id = current_app.config["DEFAULT_COURSE"]

    def __repr__(self) -> str:
        return f"<Token(id={self.id}, name={self.name}, active_course_id={self.active_course_id})>"

    def is_unlocked(self, deck: str) -> bool :
        return deck in [deck.deck for deck in self.decks]

class Course(db.Model):
    __tablename__ = "course"
    id : Mapped[int] = mapped_column(primary_key=True) 
    folder: Mapped[str] = mapped_column(String(20), unique=True, nullable=False)
    name: Mapped[str] = mapped_column(String(60), unique=True, nullable=False)
    decks: Mapped[List['Deck']] = relationship(back_populates='course') 

    def __init__(self, name: str, folder: str) -> None:
        self.name = name
        self.folder = folder

    def __repr__(self) -> str:
        return f"<Course(id={self.id}, name={self.name})>"


class InfoBanner(db.Model):
    __tablename__ = "info_banner"
    id : Mapped[int] = mapped_column(primary_key=True)
    content : Mapped[str] = mapped_column(String(280))
    is_active : Mapped[bool] = mapped_column(Boolean)

    def __init__(self, content : str) -> None:
        self.content = content
        self.is_active = False