from typing import List, Optional
from sqlalchemy.orm import Session
from sqlalchemy import func

from app.models.tag import Tag
from app.models.todo import Todo
from app.schemas.tag import TagCreate, TagUpdate


def get_tag(db: Session, tag_id: int) -> Optional[Tag]:
    """Get a single tag by ID."""
    return db.query(Tag).filter(Tag.id == tag_id).first()


def get_tag_by_name(db: Session, name: str) -> Optional[Tag]:
    """Get a tag by name."""
    return db.query(Tag).filter(Tag.name == name).first()


def get_tags(db: Session, skip: int = 0, limit: int = 100) -> List[Tag]:
    """Get multiple tags with pagination."""
    return db.query(Tag).offset(skip).limit(limit).all()


def get_tags_count(db: Session) -> int:
    """Get total count of tags."""
    return db.query(func.count(Tag.id)).scalar()


def create_tag(db: Session, tag: TagCreate) -> Tag:
    """Create a new tag."""
    db_tag = Tag(name=tag.name, color=tag.color)
    db.add(db_tag)
    db.commit()
    db.refresh(db_tag)
    return db_tag


def update_tag(db: Session, tag_id: int, tag: TagUpdate) -> Optional[Tag]:
    """Update an existing tag."""
    db_tag = db.query(Tag).filter(Tag.id == tag_id).first()
    if db_tag:
        update_data = tag.model_dump(exclude_unset=True)
        for field, value in update_data.items():
            setattr(db_tag, field, value)
        db.commit()
        db.refresh(db_tag)
    return db_tag


def delete_tag(db: Session, tag_id: int) -> bool:
    """Delete a tag."""
    db_tag = db.query(Tag).filter(Tag.id == tag_id).first()
    if db_tag:
        db.delete(db_tag)
        db.commit()
        return True
    return False


def add_tag_to_todo(db: Session, todo_id: int, tag_id: int) -> bool:
    """Add a tag to a todo."""
    todo = db.query(Todo).filter(Todo.id == todo_id).first()
    tag = db.query(Tag).filter(Tag.id == tag_id).first()

    if todo and tag and tag not in todo.tags:
        todo.tags.append(tag)
        db.commit()
        return True
    return False


def remove_tag_from_todo(db: Session, todo_id: int, tag_id: int) -> bool:
    """Remove a tag from a todo."""
    todo = db.query(Todo).filter(Todo.id == todo_id).first()
    tag = db.query(Tag).filter(Tag.id == tag_id).first()

    if todo and tag and tag in todo.tags:
        todo.tags.remove(tag)
        db.commit()
        return True
    return False


def get_todos_by_tag(
    db: Session, tag_id: int, skip: int = 0, limit: int = 100
) -> List[Todo]:
    """Get all todos that have a specific tag."""
    tag = db.query(Tag).filter(Tag.id == tag_id).first()
    if tag:
        return tag.todos[skip : skip + limit]
    return []