"""Authentication router — multi-user SaaS with local + Google OAuth."""

import secrets
import uuid
from datetime import datetime, timedelta
from typing import Optional

import httpx
from fastapi import APIRouter, Depends, HTTPException
from fastapi.responses import RedirectResponse
from pydantic import BaseModel
from sqlalchemy.orm import Session

from ..auth import (
    create_access_token,
    get_current_user,
    get_user_by_email,
    hash_password,
    verify_password,
)
from ..config import settings
from ..database import get_db
from ..models import SubscriptionCode, User

router = APIRouter(prefix="/api/auth", tags=["auth"])


# === Schemas ===

class RegisterRequest(BaseModel):
    email: str
    password: str
    display_name: Optional[str] = None


class LoginRequest(BaseModel):
    email: Optional[str] = None
    username: Optional[str] = None  # backward compat
    password: str


class RedeemCodeRequest(BaseModel):
    code: str


def _user_response(user: User) -> dict:
    return {
        "id": user.id,
        "email": user.email,
        "username": user.username,
        "display_name": user.display_name,
        "avatar_url": user.avatar_url,
        "subscription_plan": user.subscription_plan or "freemium",
        "subscription_expires_at": user.subscription_expires_at.isoformat() if user.subscription_expires_at else None,
        "is_admin": bool(user.is_admin),
        "posts_generated_this_month": user.posts_generated_this_month or 0,
    }


# === Endpoints ===

@router.post("/register")
def register(request: RegisterRequest, db: Session = Depends(get_db)):
    """Register a new user with email + password."""
    # Check email uniqueness
    existing = get_user_by_email(db, request.email)
    if existing:
        raise HTTPException(status_code=400, detail="Email già registrata.")

    # Build username from email for backward compat
    username_base = request.email.split("@")[0]
    username = username_base
    counter = 1
    while db.query(User).filter(User.username == username).first():
        username = f"{username_base}{counter}"
        counter += 1

    user = User(
        username=username,
        hashed_password=hash_password(request.password),
        email=request.email,
        display_name=request.display_name or username,
        auth_provider="local",
        subscription_plan="freemium",
        is_admin=False,
    )
    db.add(user)
    db.commit()
    db.refresh(user)

    token = create_access_token({"sub": user.username, "user_id": user.id})
    return {
        "access_token": token,
        "token_type": "bearer",
        "user": _user_response(user),
    }


@router.post("/login")
def login(request: LoginRequest, db: Session = Depends(get_db)):
    """Login with email (or legacy username) + password."""
    user = None

    if request.email:
        user = get_user_by_email(db, request.email)
    elif request.username:
        # Backward compat: check username OR email
        user = db.query(User).filter(User.username == request.username).first()
        if not user:
            user = get_user_by_email(db, request.username)

    if not user or not verify_password(request.password, user.hashed_password):
        raise HTTPException(status_code=401, detail="Credenziali non valide.")

    token = create_access_token({"sub": user.username, "user_id": user.id})
    return {
        "access_token": token,
        "token_type": "bearer",
        "user": _user_response(user),
    }


@router.get("/me")
def me(user: User = Depends(get_current_user)):
    """Get current authenticated user info."""
    return _user_response(user)


@router.post("/logout")
def logout():
    """Logout — client should remove the token."""
    return {"message": "ok"}


# === Google OAuth ===

@router.get("/oauth/google")
def oauth_google_start():
    """Redirect to Google OAuth consent screen."""
    if not settings.google_client_id:
        raise HTTPException(status_code=501, detail="Google OAuth non configurato.")

    state_token = str(uuid.uuid4())
    params = {
        "client_id": settings.google_client_id,
        "redirect_uri": f"{settings.app_url}/api/auth/oauth/google/callback",
        "response_type": "code",
        "scope": "openid email profile",
        "state": state_token,
        "access_type": "offline",
    }
    query = "&".join(f"{k}={v}" for k, v in params.items())
    auth_url = f"https://accounts.google.com/o/oauth2/v2/auth?{query}"
    return RedirectResponse(url=auth_url)


@router.get("/oauth/google/callback")
async def oauth_google_callback(code: str, state: Optional[str] = None, db: Session = Depends(get_db)):
    """Exchange Google OAuth code for token, create/find user, redirect with JWT."""
    if not settings.google_client_id or not settings.google_client_secret:
        raise HTTPException(status_code=501, detail="Google OAuth non configurato.")

    # Exchange code for tokens
    async with httpx.AsyncClient() as client:
        token_resp = await client.post(
            "https://oauth2.googleapis.com/token",
            data={
                "code": code,
                "client_id": settings.google_client_id,
                "client_secret": settings.google_client_secret,
                "redirect_uri": f"{settings.app_url}/api/auth/oauth/google/callback",
                "grant_type": "authorization_code",
            },
        )
        if token_resp.status_code != 200:
            raise HTTPException(status_code=400, detail="Errore scambio token Google.")
        token_data = token_resp.json()

        # Get user info
        userinfo_resp = await client.get(
            "https://www.googleapis.com/oauth2/v3/userinfo",
            headers={"Authorization": f"Bearer {token_data['access_token']}"},
        )
        if userinfo_resp.status_code != 200:
            raise HTTPException(status_code=400, detail="Errore recupero profilo Google.")
        google_user = userinfo_resp.json()

    google_id = google_user.get("sub")
    email = google_user.get("email")
    name = google_user.get("name")
    picture = google_user.get("picture")

    # Find existing user by google_id or email
    user = db.query(User).filter(User.google_id == google_id).first()
    if not user and email:
        user = get_user_by_email(db, email)

    if user:
        # Update google_id and avatar if missing
        if not user.google_id:
            user.google_id = google_id
        if not user.avatar_url and picture:
            user.avatar_url = picture
        db.commit()
    else:
        # Create new user
        username_base = (email or google_id).split("@")[0]
        username = username_base
        counter = 1
        while db.query(User).filter(User.username == username).first():
            username = f"{username_base}{counter}"
            counter += 1

        user = User(
            username=username,
            hashed_password=hash_password(secrets.token_urlsafe(32)),
            email=email,
            display_name=name or username,
            avatar_url=picture,
            auth_provider="google",
            google_id=google_id,
            subscription_plan="freemium",
            is_admin=False,
        )
        db.add(user)
        db.commit()
        db.refresh(user)

    jwt_token = create_access_token({"sub": user.username, "user_id": user.id})
    redirect_url = f"{settings.app_url}/auth/callback?token={jwt_token}"
    return RedirectResponse(url=redirect_url)


# === Subscription code redemption ===

@router.post("/redeem")
def redeem_code(
    request: RedeemCodeRequest,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    """Redeem a Pro subscription code."""
    code = db.query(SubscriptionCode).filter(
        SubscriptionCode.code == request.code.upper().strip()
    ).first()

    if not code:
        raise HTTPException(status_code=404, detail="Codice non trovato.")
    if code.used_by_user_id is not None:
        raise HTTPException(status_code=400, detail="Codice già utilizzato.")

    # Calculate new expiry
    now = datetime.utcnow()
    current_expiry = current_user.subscription_expires_at
    if current_user.subscription_plan == "pro" and current_expiry and current_expiry > now:
        # Extend existing pro subscription
        base_date = current_expiry
    else:
        base_date = now

    new_expiry = base_date + timedelta(days=30 * code.duration_months)

    # Update user
    current_user.subscription_plan = "pro"
    current_user.subscription_expires_at = new_expiry

    # Mark code as used
    code.used_by_user_id = current_user.id
    code.used_at = now

    db.commit()
    db.refresh(current_user)

    return {
        "subscription_plan": current_user.subscription_plan,
        "subscription_expires_at": current_user.subscription_expires_at.isoformat(),
    }