Supabase → Firebase Migration: Connecting a Contact Form to Firestore Without a Backend

console.error : 'Supabase client library (supabase-js) is not loaded.'

rules_version = '2';

service cloud.firestore {
  match /databases/{database}/documents {

    match /contact_messages/{messageId} {
      // Lecture : admin uniquement (authentifié)
      allow read: if request.auth != null;

      // Écriture : publique, mais limitée
      allow create: if request.auth == null
        && request.resource.data.name is string
        && request.resource.data.name.size() >= 1
        && request.resource.data.name.size() <= 100
        && request.resource.data.email is string
        && request.resource.data.email.matches('.*@.*\\..*')
        && request.resource.data.email.size() <= 254
        && request.resource.data.subject is string
        && request.resource.data.subject.size() >= 3
        && request.resource.data.subject.size() <= 200
        && request.resource.data.message is string
        && request.resource.data.message.size() >= 10
        && request.resource.data.message.size() <= 5000
        && request.resource.data.created_at == request.time
        && request.resource.data.user_agent is string
        && request.resource.data.user_agent.size() <= 500;
    }
  }
}

<script type="module">
    import { initializeApp } from "https://www.gstatic.com/firebasejs/11.6.0/firebase-app.js";
    import { getFirestore, collection, addDoc, serverTimestamp }
      from "https://www.gstatic.com/firebasejs/11.6.0/firebase-firestore.js";

    const firebaseConfig = { /* valeurs réelles */ };
    const app = initializeApp(firebaseConfig);
    const db = getFirestore(app);

    window.__FIREBASE__ = { db, collection, addDoc, serverTimestamp };
</script>

document.addEventListener('DOMContentLoaded', function () {
    'use strict';

    const form = document.getElementById('contact-form');
    if (!form) return;

    const submitButton = form.querySelector('button[type="submit"]');
    const successMessage = document.getElementById('contact-success-message');
    const errorMessage = document.getElementById('contact-error-message');

    // Éléments de validation
    const nameInput = form.querySelector('input[name="name"]');
    const emailInput = form.querySelector('input[name="email"]');
    const phoneInput = form.querySelector('input[name="phone"]');
    const subjectInput = form.querySelector('input[name="subject"]');
    const messageInput = form.querySelector('textarea[name="message"]');
    const honeypotInput = form.querySelector('input[name="hp_name"]');

    /**
     * Attend que window.__FIREBASE__ soit disponible.
     * Timeout de 5 secondes — si le CDN Firebase est lent, on abandonne.
     */
    function waitForFirebase(timeoutMs = 5000) {
        return new Promise((resolve, reject) => {
            if (window.__FIREBASE__) {
                resolve(window.__FIREBASE__);
                return;
            }
            const start = Date.now();
            const interval = setInterval(() => {
                if (window.__FIREBASE__) {
                    clearInterval(interval);
                    resolve(window.__FIREBASE__);
                } else if (Date.now() - start > timeoutMs) {
                    clearInterval(interval);
                    reject(new Error('Firebase SDK non disponible après timeout'));
                }
            }, 100);
        });
    }

    // --- Validation (identique à l'existant) ---
    function validateForm() {
        nameInput.setCustomValidity('');
        emailInput.setCustomValidity('');
        if (phoneInput) phoneInput.setCustomValidity('');
        subjectInput.setCustomValidity('');
        messageInput.setCustomValidity('');

        if (nameInput.value.trim().length < 1) {
            nameInput.setCustomValidity('Veuillez saisir votre nom.');
        }
        const emailPattern = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
        if (!emailPattern.test(emailInput.value.trim())) {
            emailInput.setCustomValidity('Veuillez saisir une adresse email valide.');
        }
        if (phoneInput && phoneInput.value.trim() !== '') {
            const phonePattern = /^\d{10,15}$/;
            if (!phonePattern.test(phoneInput.value.trim())) {
                phoneInput.setCustomValidity('Veuillez saisir un numéro valide (10 à 15 chiffres).');
            }
        }
        if (subjectInput.value.trim().length < 3) {
            subjectInput.setCustomValidity('Veuillez saisir un sujet (3 caractères minimum).');
        }
        if (messageInput.value.trim().length < 10) {
            messageInput.setCustomValidity('Veuillez saisir un message (10 caractères minimum).');
        }

        form.classList.add('was-validated');
        return form.checkValidity();
    }

    // --- Handler de soumission ---
    form.addEventListener('submit', async function (event) {
        event.preventDefault();
        event.stopPropagation();

        if (!validateForm()) return;

        // Honeypot : si rempli, simuler un succès sans rien envoyer
        if (honeypotInput && honeypotInput.value.trim() !== '') {
            successMessage.style.display = 'block';
            form.reset();
            form.classList.remove('was-validated');
            return;
        }

        // UI : état d'envoi
        submitButton.disabled = true;
        submitButton.innerHTML = `
            <span class="spinner-border spinner-border-sm" role="status" aria-hidden="true"></span>
            Envoi en cours...
        `;
        successMessage.style.display = 'none';
        errorMessage.style.display = 'none';

        try {
            const fb = await waitForFirebase();
            const messagesCollection = fb.collection(fb.db, 'contact_messages');

            await fb.addDoc(messagesCollection, {
                name: nameInput.value.trim(),
                email: emailInput.value.trim(),
                phone: phoneInput ? phoneInput.value.trim() : '',
                subject: subjectInput.value.trim(),
                message: messageInput.value.trim(),
                created_at: fb.serverTimestamp(),
                user_agent: navigator.userAgent.substring(0, 500)
            });

            successMessage.style.display = 'block';
            form.reset();
            form.classList.remove('was-validated');

        } catch (error) {
            console.error('Erreur Firestore:', error);
            errorMessage.style.display = 'block';

        } finally {
            submitButton.disabled = false;
            submitButton.innerHTML = `
                <i class="bi bi-send me-2"></i>
                Envoyer le Message
            `;
        }
    }, false);
});