from fastapi import APIRouter, Depends, HTTPException, status, Query
from typing import List, Optional
from models import GradeCreate, GradeUpdate, GradeResponse, GradeInDB, 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="/grades", tags=["grades"])


@router.post("", response_model=GradeResponse, status_code=status.HTTP_201_CREATED)
async def create_grade(
    grade: GradeCreate,
    current_user: UserInDB = Depends(get_current_user)
):
    """Create a new grade/test entry"""
    db = get_database()
    
    # Verify subject exists and belongs to user
    if not ObjectId.is_valid(grade.subject_id):
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Invalid subject ID"
        )
    
    subject = await db.subjects.find_one({
        "_id": ObjectId(grade.subject_id),
        "user_id": current_user.id
    })
    
    if not subject:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Subject not found"
        )
    
    # Verify category exists in subject
    category_names = [cat["name"] for cat in subject.get("grading_categories", [])]
    if grade.category_name not in category_names:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail=f"Category '{grade.category_name}' not found in subject. Available: {', '.join(category_names)}"
        )
    
    grade_in_db = GradeInDB(
        **grade.model_dump(),
        user_id=current_user.id
    )
    
    grade_dict = grade_in_db.model_dump(by_alias=True)
    grade_dict["_id"] = ObjectId(grade_dict["_id"])
    
    result = await db.grades.insert_one(grade_dict)
    grade_dict["_id"] = str(result.inserted_id)
    
    return GradeResponse(**grade_dict)


@router.get("", response_model=List[GradeResponse])
async def get_grades(
    subject_id: Optional[str] = Query(None),
    current_user: UserInDB = Depends(get_current_user)
):
    """Get all grades for the current user, optionally filtered by subject"""
    db = get_database()
    
    query = {"user_id": current_user.id}
    if subject_id:
        if not ObjectId.is_valid(subject_id):
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Invalid subject ID"
            )
        query["subject_id"] = subject_id
    
    cursor = db.grades.find(query).sort("date", -1)  # Most recent first
    grades = await cursor.to_list(length=None)
    
    for grade in grades:
        grade["_id"] = str(grade["_id"])
    
    return [GradeResponse(**grade) for grade in grades]


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


@router.put("/{grade_id}", response_model=GradeResponse)
async def update_grade(
    grade_id: str,
    grade_update: GradeUpdate,
    current_user: UserInDB = Depends(get_current_user)
):
    """Update a grade"""
    db = get_database()
    
    if not ObjectId.is_valid(grade_id):
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Invalid grade ID"
        )
    
    # Check if grade exists and belongs to user
    existing_grade = await db.grades.find_one({
        "_id": ObjectId(grade_id),
        "user_id": current_user.id
    })
    
    if not existing_grade:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Grade not found"
        )
    
    # If updating category, verify it exists in subject
    if grade_update.category_name:
        subject = await db.subjects.find_one({
            "_id": ObjectId(existing_grade["subject_id"]),
            "user_id": current_user.id
        })
        
        if subject:
            category_names = [cat["name"] for cat in subject.get("grading_categories", [])]
            if grade_update.category_name not in category_names:
                raise HTTPException(
                    status_code=status.HTTP_400_BAD_REQUEST,
                    detail=f"Category '{grade_update.category_name}' not found in subject"
                )
    
    # Update only provided fields
    update_data = grade_update.model_dump(exclude_unset=True)
    if update_data:
        update_data["updated_at"] = datetime.utcnow()
        await db.grades.update_one(
            {"_id": ObjectId(grade_id)},
            {"$set": update_data}
        )
    
    # Fetch updated grade
    updated_grade = await db.grades.find_one({"_id": ObjectId(grade_id)})
    updated_grade["_id"] = str(updated_grade["_id"])
    
    return GradeResponse(**updated_grade)


@router.delete("/{grade_id}", status_code=status.HTTP_204_NO_CONTENT)
async def delete_grade(
    grade_id: str,
    current_user: UserInDB = Depends(get_current_user)
):
    """Delete a grade"""
    db = get_database()
    
    if not ObjectId.is_valid(grade_id):
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Invalid grade ID"
        )
    
    # Check if grade exists and belongs to user
    grade = await db.grades.find_one({
        "_id": ObjectId(grade_id),
        "user_id": current_user.id
    })
    
    if not grade:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Grade not found"
        )
    
    # Delete grade
    await db.grades.delete_one({"_id": ObjectId(grade_id)})
    
    return None