frontend/src/pages/SignIn.jsx

import React, { useEffect } from 'react';
import { useSearchParams } from 'react-router-dom';
import { Loader2, Zap } from 'lucide-react';
import { Button } from '@/components/ui/button';
import { cn } from '@/lib/utils';
import { APP_NAME, APP_TAGLINE } from '@/lib/branding';
import { useAuth } from '@/context/AuthContext';

export default function SignIn() {
    const { phase, googleOn } = useAuth();
    const [searchParams, setSearchParams] = useSearchParams();

    useEffect(() => {
        const err = searchParams.get('auth_error');
        if (!err) return;
        if (err === 'access_denied') {
            console.info('Google sign-in was cancelled.');
        } else if (err === 'invite_email_mismatch') {
            console.warn(
                'Invitation email does not match your Google account. Sign in with the invited address.'
            );
        } else {
            console.warn('Google sign-in error:', err);
        }
        const next = new URLSearchParams(searchParams);
        next.delete('auth_error');
        setSearchParams(next, { replace: true });
    }, [searchParams, setSearchParams]);

    const inviteParam = searchParams.get('invite');
    const googleHref = inviteParam
        ? `/api/auth/google?invite=${encodeURIComponent(inviteParam)}`
        : '/api/auth/google';

    if (phase === 'loading') {
        return (
            <div className="flex min-h-[100dvh] items-center justify-center bg-gradient-to-br from-slate-50 via-white to-violet-50">
                <Loader2 className="h-10 w-10 animate-spin text-violet-600" aria-label="Loading" />
            </div>
        );
    }

    if (phase === 'error') {
        return (
            <div className="flex min-h-[100dvh] items-center justify-center bg-gradient-to-br from-slate-50 via-white to-violet-50 px-4">
                <div className="max-w-md rounded-2xl border border-slate-200 bg-white p-8 text-center shadow-sm">
                    <p className="text-slate-700">Could not reach the server. Refresh and try again.</p>
                </div>
            </div>
        );
    }

    if (!googleOn) {
        return (
            <div className="flex min-h-[100dvh] items-center justify-center bg-gradient-to-br from-slate-50 via-white to-violet-50 px-4">
                <div className="max-w-md rounded-2xl border border-amber-200 bg-white p-8 text-center shadow-sm">
                    <p className="font-medium text-slate-800">Google sign-in is not configured</p>
                    <p className="mt-2 text-sm text-slate-600">
                        Set GOOGLE_CLIENT_ID and GOOGLE_CLIENT_SECRET on the server to enable access.
                    </p>
                </div>
            </div>
        );
    }

    return (
        <div className="flex min-h-[100dvh] flex-col items-center justify-center bg-gradient-to-br from-slate-50 via-white to-violet-50 px-4 py-12">
            <div className="w-full max-w-md rounded-2xl border border-slate-200 bg-white p-8 shadow-lg shadow-violet-100/50 sm:p-10">
                <div className="mb-8 flex flex-col items-center text-center">
                    <div className="mb-4 flex h-14 w-14 items-center justify-center rounded-2xl bg-gradient-to-br from-violet-600 to-purple-600 shadow-lg shadow-violet-200">
                        <Zap className="h-7 w-7 text-white" aria-hidden />
                    </div>
                    <h1 className="text-2xl font-bold text-slate-800">{APP_NAME}</h1>
                    <p className="mt-2 text-sm text-slate-500">{APP_TAGLINE}</p>
                </div>

                <p className="mb-6 text-center text-slate-600">
                    Sign in with your Google account to access campaigns, contacts, leads, and deals.
                </p>

                {inviteParam ? (
                    <p className="mb-6 rounded-lg bg-violet-50 px-4 py-3 text-center text-sm text-violet-800">
                        You have a workspace invitation. Sign in with the email address that received the
                        invite.
                    </p>
                ) : null}

                <Button
                    asChild
                    size="lg"
                    className={cn(
                        'w-full gap-3 bg-white text-slate-800 border border-slate-200 shadow-sm',
                        'hover:bg-slate-50'
                    )}
                    variant="outline"
                >
                    <a href={googleHref} className="inline-flex items-center justify-center gap-3">
                        <GoogleMark className="h-5 w-5 shrink-0" />
                        <span>Sign in with Google</span>
                    </a>
                </Button>
            </div>
        </div>
    );
}

function GoogleMark({ className }) {
    return (
        <svg className={className} viewBox="0 0 24 24" aria-hidden>
            <path
                fill="#4285F4"
                d="M22.56 12.25c0-.78-.07-1.53-.2-2.25H12v4.26h5.92c-.26 1.37-1.04 2.53-2.21 3.31v2.77h3.57c2.08-1.92 3.28-4.74 3.28-8.09z"
            />
            <path
                fill="#34A853"
                d="M12 23c2.97 0 5.46-.98 7.28-2.66l-3.57-2.77c-.98.66-2.23 1.06-3.71 1.06-2.86 0-5.29-1.93-6.16-4.53H2.18v2.84C3.99 20.53 7.7 23 12 23z"
            />
            <path
                fill="#FBBC05"
                d="M5.84 14.09c-.22-.66-.35-1.36-.35-2.09s.13-1.43.35-2.09V7.07H2.18C1.43 8.55 1 10.22 1 12s.43 3.45 1.18 4.93l2.85-2.22.81-.62z"
            />
            <path
                fill="#EA4335"
                d="M12 5.38c1.62 0 3.06.56 4.21 1.64l3.15-3.15C17.45 2.09 14.97 1 12 1 7.7 1 3.99 3.47 2.18 7.07l3.66 2.84c.87-2.6 3.3-4.53 6.16-4.53z"
            />
        </svg>
    );
}