from datetime import datetime, timedelta, timezone

from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer
from sqlalchemy.ext.asyncio import AsyncSession

from app.auth import repository as auth_repository
from app.auth.schemas import (
    LoginRequest,
    RegisterRequest,
    RequestPasswordResetRequest,
    ResendVerificationRequest,
    ResetPasswordRequest,
    TokenResponse,
    VerifyEmailRequest,
)
from app.config.settings import settings
from app.database.session import get_db
from app.email.service import EmailService, get_email_service
from app.users.models import User
from app.users.repository import create_user, get_user_by_email, get_user_by_id, get_user_by_username
from app.utils.security import (
    create_access_token,
    create_refresh_token,
    decode_token,
    generate_random_token,
    hash_password,
    verify_password,
)

oauth2_scheme = OAuth2PasswordBearer(tokenUrl=f"{settings.api_v1_prefix}/auth/login")


async def register_user(
    db: AsyncSession,
    payload: RegisterRequest,
    email_service: EmailService,
) -> None:
    existing_email = await get_user_by_email(db, payload.email)
    if existing_email:
        raise HTTPException(status_code=status.HTTP_409_CONFLICT, detail="Email is already registered")

    existing_username = await get_user_by_username(db, payload.username)
    if existing_username:
        raise HTTPException(status_code=status.HTTP_409_CONFLICT, detail="Username is already taken")

    user = await create_user(
        db,
        email=payload.email,
        username=payload.username,
        password_hash=hash_password(payload.password),
    )

    verification_token = generate_random_token()
    expires_at = datetime.now(timezone.utc) + timedelta(hours=settings.email_verification_token_expire_hours)
    await auth_repository.delete_email_verification_tokens_for_user(db, user.id)
    await auth_repository.create_email_verification_token(db, user.id, verification_token, expires_at)
    await db.commit()

    await email_service.send_verification_email(payload.email, verification_token)


async def verify_email(db: AsyncSession, payload: VerifyEmailRequest) -> None:
    record = await auth_repository.get_email_verification_token(db, payload.token)
    if not record:
        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="Invalid verification token")

    now = datetime.now(timezone.utc)
    expires_at = record.expires_at if record.expires_at.tzinfo else record.expires_at.replace(tzinfo=timezone.utc)
    if expires_at < now:
        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="Verification token expired")

    user = await get_user_by_id(db, record.user_id)
    if not user:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="User not found")

    user.email_verified = True
    await auth_repository.delete_email_verification_tokens_for_user(db, user.id)
    await db.commit()


async def resend_verification_email(
    db: AsyncSession,
    payload: ResendVerificationRequest,
    email_service: EmailService,
) -> None:
    user = await get_user_by_email(db, payload.email)
    if not user or user.email_verified:
        return

    verification_token = generate_random_token()
    expires_at = datetime.now(timezone.utc) + timedelta(hours=settings.email_verification_token_expire_hours)
    await auth_repository.delete_email_verification_tokens_for_user(db, user.id)
    await auth_repository.create_email_verification_token(db, user.id, verification_token, expires_at)
    await db.commit()

    await email_service.send_verification_email(user.email, verification_token)


async def login_user(db: AsyncSession, payload: LoginRequest) -> TokenResponse:
    user = await get_user_by_email(db, payload.email)
    if not user or not verify_password(payload.password, user.password_hash):
        raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="Invalid credentials")

    if not user.email_verified:
        raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="Email not verified")

    return TokenResponse(
        access_token=create_access_token(str(user.id)),
        refresh_token=create_refresh_token(str(user.id)),
    )


async def request_password_reset(
    db: AsyncSession,
    payload: RequestPasswordResetRequest,
    email_service: EmailService,
) -> None:
    user = await get_user_by_email(db, payload.email)
    if not user:
        return

    reset_token = generate_random_token()
    expires_at = datetime.now(timezone.utc) + timedelta(hours=settings.password_reset_token_expire_hours)
    await auth_repository.delete_password_reset_tokens_for_user(db, user.id)
    await auth_repository.create_password_reset_token(db, user.id, reset_token, expires_at)
    await db.commit()

    await email_service.send_password_reset_email(user.email, reset_token)


async def reset_password(db: AsyncSession, payload: ResetPasswordRequest) -> None:
    record = await auth_repository.get_password_reset_token(db, payload.token)
    if not record:
        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="Invalid reset token")

    now = datetime.now(timezone.utc)
    expires_at = record.expires_at if record.expires_at.tzinfo else record.expires_at.replace(tzinfo=timezone.utc)
    if expires_at < now:
        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="Reset token expired")

    user = await get_user_by_id(db, record.user_id)
    if not user:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="User not found")

    user.password_hash = hash_password(payload.new_password)
    await auth_repository.delete_password_reset_tokens_for_user(db, user.id)
    await db.commit()


async def get_current_user(token: str = Depends(oauth2_scheme), db: AsyncSession = Depends(get_db)) -> User:
    credentials_error = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": "Bearer"},
    )
    try:
        payload = decode_token(token)
    except ValueError as exc:
        raise credentials_error from exc

    if payload.get("type") != "access":
        raise credentials_error

    user_id = payload.get("sub")
    if not user_id or not str(user_id).isdigit():
        raise credentials_error

    user = await get_user_by_id(db, int(user_id))
    if not user:
        raise credentials_error
    return user


async def get_current_user_for_ws(token: str, db: AsyncSession) -> User:
    try:
        payload = decode_token(token)
    except ValueError as exc:
        raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="Invalid token") from exc

    if payload.get("type") != "access":
        raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="Invalid token type")

    user_id = payload.get("sub")
    if not user_id or not str(user_id).isdigit():
        raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="Invalid token payload")

    user = await get_user_by_id(db, int(user_id))
    if not user:
        raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="User not found")
    return user


def get_email_sender() -> EmailService:
    return get_email_service()