from __future__ import annotations

import secrets
from datetime import datetime, timedelta, timezone

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

from app.core.config import settings
from app.core.security import create_jwt, hash_password, verify_password
from app.db.session import get_db
from app.models.otp_session import OtpSession
from app.models.request import Request
from app.schemas.public import OtpSend, OtpVerify

router = APIRouter()

OTP_TTL_MINUTES = 10
OTP_MAX_ATTEMPTS = 5
OTP_CREATE_PURPOSE = "CREATE_REQUEST"
OTP_VIEW_PURPOSE = "VIEW_REQUEST"
ALLOWED_PURPOSES = {OTP_CREATE_PURPOSE, OTP_VIEW_PURPOSE}


def _now_utc() -> datetime:
    return datetime.now(timezone.utc)


def _as_utc(dt: datetime | None) -> datetime:
    if dt is None:
        return _now_utc()
    if dt.tzinfo is None:
        return dt.replace(tzinfo=timezone.utc)
    return dt.astimezone(timezone.utc)


def _normalize_purpose(raw: str | None) -> str:
    return str(raw or "").strip().upper()


def _normalize_phone(raw: str | None) -> str:
    phone = str(raw or "").strip()
    if not phone:
        return ""
    allowed = {"+", "(", ")", "-", " "}
    digits = [ch for ch in phone if ch.isdigit() or ch in allowed]
    return "".join(digits).strip()


def _normalize_track(raw: str | None) -> str:
    return str(raw or "").strip().upper()


def _generate_code() -> str:
    return f"{secrets.randbelow(1_000_000):06d}"


def _set_public_cookie(response: Response, *, subject: str, purpose: str) -> None:
    token = create_jwt(
        {"sub": subject, "purpose": purpose},
        settings.PUBLIC_JWT_SECRET,
        timedelta(days=settings.PUBLIC_JWT_TTL_DAYS),
    )
    response.set_cookie(
        key=settings.PUBLIC_COOKIE_NAME,
        value=token,
        httponly=True,
        secure=False,
        samesite="lax",
        max_age=settings.PUBLIC_JWT_TTL_DAYS * 24 * 3600,
    )


def _mock_sms_send(phone: str, code: str, purpose: str, track_number: str | None = None) -> dict:
    # Dev-only behavior: emit OTP in console instead of sending real SMS.
    print(f"[OTP MOCK] purpose={purpose} phone={phone} track={track_number or '-'} code={code}")
    return {
        "provider": "mock_sms",
        "status": "accepted",
        "message": "SMS provider response mocked",
    }


@router.post("/send")
def send_otp(payload: OtpSend, db: Session = Depends(get_db)):
    purpose = _normalize_purpose(payload.purpose)
    if purpose not in ALLOWED_PURPOSES:
        raise HTTPException(status_code=400, detail="Некорректная цель OTP")

    track_number: str | None = None
    phone = ""
    if purpose == OTP_CREATE_PURPOSE:
        phone = _normalize_phone(payload.client_phone)
        if not phone:
            raise HTTPException(status_code=400, detail='Поле "client_phone" обязательно для CREATE_REQUEST')
    else:
        track_number = _normalize_track(payload.track_number)
        if not track_number:
            raise HTTPException(status_code=400, detail='Поле "track_number" обязательно для VIEW_REQUEST')
        request = db.query(Request).filter(Request.track_number == track_number).first()
        if request is None:
            raise HTTPException(status_code=404, detail="Заявка не найдена")
        phone = _normalize_phone(request.client_phone)
        if not phone:
            raise HTTPException(status_code=400, detail="У заявки отсутствует номер телефона")

    code = _generate_code()
    now = _now_utc()
    expires_at = now + timedelta(minutes=OTP_TTL_MINUTES)

    existing_query = db.query(OtpSession).filter(
        OtpSession.purpose == purpose,
        OtpSession.phone == phone,
        OtpSession.track_number == track_number,
    )
    existing_query.delete(synchronize_session=False)

    row = OtpSession(
        purpose=purpose,
        track_number=track_number,
        phone=phone,
        code_hash=hash_password(code),
        attempts=0,
        expires_at=expires_at,
        responsible="Система OTP",
    )
    db.add(row)
    db.commit()
    db.refresh(row)

    sms_response = _mock_sms_send(phone, code, purpose, track_number)
    return {
        "status": "sent",
        "purpose": purpose,
        "track_number": track_number,
        "ttl_seconds": OTP_TTL_MINUTES * 60,
        "sms_response": sms_response,
    }


@router.post("/verify")
def verify_otp(payload: OtpVerify, response: Response, db: Session = Depends(get_db)):
    purpose = _normalize_purpose(payload.purpose)
    if purpose not in ALLOWED_PURPOSES:
        raise HTTPException(status_code=400, detail="Некорректная цель OTP")

    track_number: str | None = None
    phone: str | None = None
    if purpose == OTP_CREATE_PURPOSE:
        phone = _normalize_phone(payload.client_phone)
        if not phone:
            raise HTTPException(status_code=400, detail='Поле "client_phone" обязательно для CREATE_REQUEST')
    else:
        track_number = _normalize_track(payload.track_number)
        if not track_number:
            raise HTTPException(status_code=400, detail='Поле "track_number" обязательно для VIEW_REQUEST')

    query = db.query(OtpSession).filter(
        OtpSession.purpose == purpose,
        OtpSession.track_number == track_number,
    )
    if phone is not None:
        query = query.filter(OtpSession.phone == phone)

    row = query.order_by(OtpSession.created_at.desc()).first()
    if row is None:
        raise HTTPException(status_code=400, detail="OTP не найден или истек")

    now = _now_utc()
    if _as_utc(row.expires_at) <= now:
        db.delete(row)
        db.commit()
        raise HTTPException(status_code=400, detail="OTP не найден или истек")

    if int(row.attempts or 0) >= OTP_MAX_ATTEMPTS:
        raise HTTPException(status_code=429, detail="Превышено количество попыток")

    code = str(payload.code or "").strip()
    if not code or not verify_password(code, row.code_hash):
        row.attempts = int(row.attempts or 0) + 1
        db.add(row)
        db.commit()
        raise HTTPException(status_code=400, detail="Неверный OTP-код")

    subject = row.phone if purpose == OTP_CREATE_PURPOSE else str(row.track_number or "")
    if not subject:
        raise HTTPException(status_code=400, detail="Некорректная OTP-сессия")

    _set_public_cookie(response, subject=subject, purpose=purpose)

    db.delete(row)
    db.commit()
    return {"status": "verified", "purpose": purpose}