from fastapi import APIRouter, Depends, HTTPException, status
from typing import List
from models import SubjectCreate, SubjectUpdate, SubjectResponse, SubjectInDB, UserInDB
from database import get_database
from routes.auth_routes import get_current_user
from bson import ObjectId
from datetime import datetime

router = APIRouter(prefix="/subjects", tags=["subjects"])


@router.post("", response_model=SubjectResponse, status_code=status.HTTP_201_CREATED)
async def create_subject(
    subject: SubjectCreate,
    current_user: UserInDB = Depends(get_current_user)
):
    """Create a new subject"""
    db = get_database()
    
    subject_in_db = SubjectInDB(
        **subject.model_dump(),
        user_id=current_user.id
    )
    
    subject_dict = subject_in_db.model_dump(by_alias=True)
    subject_dict["_id"] = ObjectId(subject_dict["_id"])
    
    result = await db.subjects.insert_one(subject_dict)
    subject_dict["_id"] = str(result.inserted_id)
    
    return SubjectResponse(**subject_dict)


@router.get("", response_model=List[SubjectResponse])
async def get_subjects(current_user: UserInDB = Depends(get_current_user)):
    """Get all subjects for the current user"""
    db = get_database()
    
    cursor = db.subjects.find({"user_id": current_user.id})
    subjects = await cursor.to_list(length=None)
    
    for subject in subjects:
        subject["_id"] = str(subject["_id"])
    
    return [SubjectResponse(**subject) for subject in subjects]


@router.get("/{subject_id}", response_model=SubjectResponse)
async def get_subject(
    subject_id: str,
    current_user: UserInDB = Depends(get_current_user)
):
    """Get a specific subject"""
    db = get_database()
    
    if not ObjectId.is_valid(subject_id):
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Invalid subject ID"
        )
    
    subject = await db.subjects.find_one({
        "_id": ObjectId(subject_id),
        "user_id": current_user.id
    })
    
    if not subject:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Subject not found"
        )
    
    subject["_id"] = str(subject["_id"])
    return SubjectResponse(**subject)


@router.put("/{subject_id}", response_model=SubjectResponse)
async def update_subject(
    subject_id: str,
    subject_update: SubjectUpdate,
    current_user: UserInDB = Depends(get_current_user)
):
    """Update a subject"""
    db = get_database()
    
    if not ObjectId.is_valid(subject_id):
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Invalid subject ID"
        )
    
    # Check if subject exists and belongs to user
    existing_subject = await db.subjects.find_one({
        "_id": ObjectId(subject_id),
        "user_id": current_user.id
    })
    
    if not existing_subject:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Subject not found"
        )
    
    # Update only provided fields
    update_data = subject_update.model_dump(exclude_unset=True)
    if update_data:
        update_data["updated_at"] = datetime.utcnow()
        await db.subjects.update_one(
            {"_id": ObjectId(subject_id)},
            {"$set": update_data}
        )
    
    # Fetch updated subject
    updated_subject = await db.subjects.find_one({"_id": ObjectId(subject_id)})
    updated_subject["_id"] = str(updated_subject["_id"])
    
    return SubjectResponse(**updated_subject)


@router.delete("/{subject_id}", status_code=status.HTTP_204_NO_CONTENT)
async def delete_subject(
    subject_id: str,
    current_user: UserInDB = Depends(get_current_user)
):
    """Delete a subject and all associated grades"""
    db = get_database()
    
    if not ObjectId.is_valid(subject_id):
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Invalid subject ID"
        )
    
    # Check if subject exists and belongs to user
    subject = await db.subjects.find_one({
        "_id": ObjectId(subject_id),
        "user_id": current_user.id
    })
    
    if not subject:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Subject not found"
        )
    
    # Delete subject
    await db.subjects.delete_one({"_id": ObjectId(subject_id)})
    
    # Delete all grades for this subject
    await db.grades.delete_many({"subject_id": subject_id, "user_id": current_user.id})
    
    return None