import os
from datetime import timedelta
from typing import Tuple

from fastapi import APIRouter, Depends, HTTPException, status
from sqlalchemy.orm import Session

from app.api.dependencies import get_db
from app.core.security import (
    create_access_token,
    generate_verification_code,
    hash_password,
    hash_verification_code,
    verify_password,
    verify_verification_code,
)
from app.models.models import AppUser, EmailVerificationCode, VerificationPurpose, utcnow
from app.schemas.auth_schema import (
    AuthTokenResponse,
    LoginCodeSendRequest,
    LoginRequest,
    LoginWithCodeRequest,
    MessageResponse,
    RegisterCodeSendRequest,
    RegisterRequest,
    UserProfileResponse,
)
from app.utils.email_utils import send_html_email


router = APIRouter()

REGISTER_CODE_EXPIRE_MINUTES = int(os.getenv("REGISTER_CODE_EXPIRE_MINUTES", "10"))
LOGIN_CODE_EXPIRE_MINUTES = int(os.getenv("LOGIN_CODE_EXPIRE_MINUTES", "10"))


def _normalize_email(email: str) -> str:
    return email.strip().lower()


def _build_verification_email(code: str, purpose_text: str, expire_minutes: int) -> str:
    return f"""
    <div style="font-family: Arial, sans-serif; line-height: 1.6; color: #222;">
        <h2 style="margin-bottom: 12px;">InsightRadar Email Verification</h2>
        <p>Your {purpose_text} verification code is:</p>
        <p style="font-size: 28px; font-weight: bold; letter-spacing: 4px; color: #0b57d0;">{code}</p>
        <p>The code is valid for {expire_minutes} minutes. Do not share it with others.</p>
    </div>
    """


def _invalidate_unused_codes(db: Session, email: str, purpose: VerificationPurpose) -> None:
    db.query(EmailVerificationCode).filter(
        EmailVerificationCode.email == email,
        EmailVerificationCode.purpose == purpose,
        EmailVerificationCode.is_used.is_(False),
    ).update({EmailVerificationCode.is_used: True}, synchronize_session=False)
    db.commit()


def _create_code_record(
    db: Session,
    *,
    email: str,
    purpose: VerificationPurpose,
    expire_minutes: int,
) -> Tuple[EmailVerificationCode, str]:
    code = generate_verification_code()
    now = utcnow()
    code_record = EmailVerificationCode(
        email=email,
        purpose=purpose,
        code_hash=hash_verification_code(code),
        expires_at=now + timedelta(minutes=expire_minutes),
    )
    db.add(code_record)
    db.commit()
    return code_record, code


def _build_auth_response(user: AppUser) -> AuthTokenResponse:
    token, expires_in = create_access_token(user_id=user.id, email=user.email)
    return AuthTokenResponse(
        access_token=token,
        expires_in=expires_in,
        user=UserProfileResponse.model_validate(user),
    )


@router.post("/register/send-code", response_model=MessageResponse)
async def send_register_code(payload: RegisterCodeSendRequest, db: Session = Depends(get_db)):
    email = _normalize_email(payload.email)

    existing_user = db.query(AppUser).filter(AppUser.email == email).first()
    if existing_user:
        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="Email is already registered")

    _invalidate_unused_codes(db, email, VerificationPurpose.REGISTER)
    code_record, code = _create_code_record(
        db,
        email=email,
        purpose=VerificationPurpose.REGISTER,
        expire_minutes=REGISTER_CODE_EXPIRE_MINUTES,
    )

    email_sent = await send_html_email(
        to_email=email,
        subject="InsightRadar Registration Code",
        html_content=_build_verification_email(code, "registration", REGISTER_CODE_EXPIRE_MINUTES),
    )
    if not email_sent:
        code_record.is_used = True
        db.add(code_record)
        db.commit()
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail="Failed to send verification code",
        )

    return MessageResponse(message="Verification code sent")


@router.post("/login/send-code", response_model=MessageResponse)
async def send_login_code(payload: LoginCodeSendRequest, db: Session = Depends(get_db)):
    email = _normalize_email(payload.email)
    user = db.query(AppUser).filter(AppUser.email == email).first()

    if not user:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Email is not registered")

    _invalidate_unused_codes(db, email, VerificationPurpose.LOGIN)
    code_record, code = _create_code_record(
        db,
        email=email,
        purpose=VerificationPurpose.LOGIN,
        expire_minutes=LOGIN_CODE_EXPIRE_MINUTES,
    )

    email_sent = await send_html_email(
        to_email=email,
        subject="InsightRadar Login Code",
        html_content=_build_verification_email(code, "login", LOGIN_CODE_EXPIRE_MINUTES),
    )
    if not email_sent:
        code_record.is_used = True
        db.add(code_record)
        db.commit()
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail="Failed to send verification code",
        )

    return MessageResponse(message="Verification code sent")


@router.post(
    "/register",
    response_model=AuthTokenResponse,
    status_code=status.HTTP_201_CREATED,
)
async def register(payload: RegisterRequest, db: Session = Depends(get_db)):
    email = _normalize_email(payload.email)
    existing_user = db.query(AppUser).filter(AppUser.email == email).first()
    if existing_user:
        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="Email is already registered")

    now = utcnow()
    code_record = db.query(EmailVerificationCode).filter(
        EmailVerificationCode.email == email,
        EmailVerificationCode.purpose == VerificationPurpose.REGISTER,
        EmailVerificationCode.is_used.is_(False),
        EmailVerificationCode.expires_at >= now,
    ).order_by(EmailVerificationCode.created_at.desc()).first()

    if not code_record:
        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="Verification code does not exist or expired")

    if not verify_verification_code(payload.verification_code, code_record.code_hash):
        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="Invalid verification code")

    nickname = payload.nickname or email.split("@")[0]
    user = AppUser(
        email=email,
        password_hash=hash_password(payload.password),
        nickname=nickname,
        metadata_={"email_verified_at": now.isoformat()},
    )

    code_record.is_used = True
    db.add(user)
    db.add(code_record)
    db.commit()
    db.refresh(user)

    return _build_auth_response(user)


@router.post("/login", response_model=AuthTokenResponse)
async def login(payload: LoginRequest, db: Session = Depends(get_db)):
    email = _normalize_email(payload.email)
    user = db.query(AppUser).filter(AppUser.email == email).first()

    if not user or not user.password_hash:
        raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="Invalid email or password")

    if not verify_password(payload.password, user.password_hash):
        raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="Invalid email or password")

    return _build_auth_response(user)


@router.post("/login/code", response_model=AuthTokenResponse)
async def login_with_code(payload: LoginWithCodeRequest, db: Session = Depends(get_db)):
    email = _normalize_email(payload.email)
    user = db.query(AppUser).filter(AppUser.email == email).first()

    if not user:
        raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="Invalid email or verification code")

    now = utcnow()
    code_record = db.query(EmailVerificationCode).filter(
        EmailVerificationCode.email == email,
        EmailVerificationCode.purpose == VerificationPurpose.LOGIN,
        EmailVerificationCode.is_used.is_(False),
        EmailVerificationCode.expires_at >= now,
    ).order_by(EmailVerificationCode.created_at.desc()).first()

    if not code_record:
        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="Verification code does not exist or expired")

    if not verify_verification_code(payload.verification_code, code_record.code_hash):
        raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="Invalid email or verification code")

    code_record.is_used = True
    db.add(code_record)
    db.commit()

    return _build_auth_response(user)