from contextlib import asynccontextmanager
from datetime import datetime
from typing import List

from fastapi import FastAPI, Depends, HTTPException, Response, status, Query
from fastapi.middleware.cors import CORSMiddleware
from pydantic import BaseModel
from sqlalchemy import select, func, desc
from sqlalchemy.ext.asyncio import AsyncSession

from database import engine, get_db, Base
from models import Counter, User, SumRecord, CounterRecord, Permission, Role
from auth import (
    ACCESS_TOKEN_EXPIRE_MINUTES,
    COOKIE_NAME,
    UserCreate,
    UserLogin,
    UserResponse,
    get_password_hash,
    get_user_by_email,
    authenticate_user,
    create_access_token,
    get_current_user,
    require_permission,
    build_user_response,
)


@asynccontextmanager
async def lifespan(app: FastAPI):
    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)
    yield


app = FastAPI(lifespan=lifespan)

app.add_middleware(
    CORSMiddleware,
    allow_origins=["http://localhost:3000"],
    allow_methods=["*"],
    allow_headers=["*"],
    allow_credentials=True,
)


def set_auth_cookie(response: Response, token: str) -> None:
    response.set_cookie(
        key=COOKIE_NAME,
        value=token,
        httponly=True,
        secure=False,  # Set to True in production with HTTPS
        samesite="lax",
        max_age=ACCESS_TOKEN_EXPIRE_MINUTES * 60,
    )


async def get_default_role(db: AsyncSession) -> Role | None:
    """Get the default 'regular' role for new users."""
    result = await db.execute(select(Role).where(Role.name == "regular"))
    return result.scalar_one_or_none()


# Auth endpoints
@app.post("/api/auth/register", response_model=UserResponse)
async def register(
    user_data: UserCreate,
    response: Response,
    db: AsyncSession = Depends(get_db),
):
    existing_user = await get_user_by_email(db, user_data.email)
    if existing_user:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Email already registered",
        )
    
    user = User(
        email=user_data.email,
        hashed_password=get_password_hash(user_data.password),
    )
    
    # Assign default role if it exists
    default_role = await get_default_role(db)
    if default_role:
        user.roles.append(default_role)
    
    db.add(user)
    await db.commit()
    await db.refresh(user)
    
    access_token = create_access_token(data={"sub": str(user.id)})
    set_auth_cookie(response, access_token)
    return await build_user_response(user, db)


@app.post("/api/auth/login", response_model=UserResponse)
async def login(
    user_data: UserLogin,
    response: Response,
    db: AsyncSession = Depends(get_db),
):
    user = await authenticate_user(db, user_data.email, user_data.password)
    if not user:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Incorrect email or password",
        )
    
    access_token = create_access_token(data={"sub": str(user.id)})
    set_auth_cookie(response, access_token)
    return await build_user_response(user, db)


@app.post("/api/auth/logout")
async def logout(response: Response):
    response.delete_cookie(key=COOKIE_NAME)
    return {"ok": True}


@app.get("/api/auth/me", response_model=UserResponse)
async def get_me(
    current_user: User = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    return await build_user_response(current_user, db)


# Counter endpoints
async def get_or_create_counter(db: AsyncSession) -> Counter:
    result = await db.execute(select(Counter).where(Counter.id == 1))
    counter = result.scalar_one_or_none()
    if not counter:
        counter = Counter(id=1, value=0)
        db.add(counter)
        await db.commit()
        await db.refresh(counter)
    return counter


@app.get("/api/counter")
async def get_counter(
    db: AsyncSession = Depends(get_db),
    _current_user: User = Depends(require_permission(Permission.VIEW_COUNTER)),
):
    counter = await get_or_create_counter(db)
    return {"value": counter.value}


@app.post("/api/counter/increment")
async def increment_counter(
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(require_permission(Permission.INCREMENT_COUNTER)),
):
    counter = await get_or_create_counter(db)
    value_before = counter.value
    counter.value += 1
    
    record = CounterRecord(
        user_id=current_user.id,
        value_before=value_before,
        value_after=counter.value,
    )
    db.add(record)
    await db.commit()
    return {"value": counter.value}


# Sum endpoints
class SumRequest(BaseModel):
    a: float
    b: float


class SumResponse(BaseModel):
    a: float
    b: float
    result: float


@app.post("/api/sum", response_model=SumResponse)
async def calculate_sum(
    data: SumRequest,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(require_permission(Permission.USE_SUM)),
):
    result = data.a + data.b
    record = SumRecord(
        user_id=current_user.id,
        a=data.a,
        b=data.b,
        result=result,
    )
    db.add(record)
    await db.commit()
    return SumResponse(a=data.a, b=data.b, result=result)


# Audit endpoints
class CounterRecordResponse(BaseModel):
    id: int
    user_email: str
    value_before: int
    value_after: int
    created_at: datetime


class SumRecordResponse(BaseModel):
    id: int
    user_email: str
    a: float
    b: float
    result: float
    created_at: datetime


class PaginatedCounterRecords(BaseModel):
    records: List[CounterRecordResponse]
    total: int
    page: int
    per_page: int
    total_pages: int


class PaginatedSumRecords(BaseModel):
    records: List[SumRecordResponse]
    total: int
    page: int
    per_page: int
    total_pages: int


@app.get("/api/audit/counter", response_model=PaginatedCounterRecords)
async def get_counter_records(
    page: int = Query(1, ge=1),
    per_page: int = Query(10, ge=1, le=100),
    db: AsyncSession = Depends(get_db),
    _current_user: User = Depends(require_permission(Permission.VIEW_AUDIT)),
):
    # Get total count
    count_result = await db.execute(select(func.count(CounterRecord.id)))
    total = count_result.scalar() or 0
    total_pages = (total + per_page - 1) // per_page if total > 0 else 1

    # Get paginated records with user email
    offset = (page - 1) * per_page
    query = (
        select(CounterRecord, User.email)
        .join(User, CounterRecord.user_id == User.id)
        .order_by(desc(CounterRecord.created_at))
        .offset(offset)
        .limit(per_page)
    )
    result = await db.execute(query)
    rows = result.all()

    records = [
        CounterRecordResponse(
            id=record.id,
            user_email=email,
            value_before=record.value_before,
            value_after=record.value_after,
            created_at=record.created_at,
        )
        for record, email in rows
    ]

    return PaginatedCounterRecords(
        records=records,
        total=total,
        page=page,
        per_page=per_page,
        total_pages=total_pages,
    )


@app.get("/api/audit/sum", response_model=PaginatedSumRecords)
async def get_sum_records(
    page: int = Query(1, ge=1),
    per_page: int = Query(10, ge=1, le=100),
    db: AsyncSession = Depends(get_db),
    _current_user: User = Depends(require_permission(Permission.VIEW_AUDIT)),
):
    # Get total count
    count_result = await db.execute(select(func.count(SumRecord.id)))
    total = count_result.scalar() or 0
    total_pages = (total + per_page - 1) // per_page if total > 0 else 1

    # Get paginated records with user email
    offset = (page - 1) * per_page
    query = (
        select(SumRecord, User.email)
        .join(User, SumRecord.user_id == User.id)
        .order_by(desc(SumRecord.created_at))
        .offset(offset)
        .limit(per_page)
    )
    result = await db.execute(query)
    rows = result.all()

    records = [
        SumRecordResponse(
            id=record.id,
            user_email=email,
            a=record.a,
            b=record.b,
            result=record.result,
            created_at=record.created_at,
        )
        for record, email in rows
    ]

    return PaginatedSumRecords(
        records=records,
        total=total,
        page=page,
        per_page=per_page,
        total_pages=total_pages,
    )