import { sendEmail } from '@/lib/mail'

function formatTrialEnd(date: Date, locale: string): string {
  try {
    return new Intl.DateTimeFormat(locale, {
      day: 'numeric',
      month: 'long',
      year: 'numeric',
    }).format(date)
  } catch {
    return date.toISOString().slice(0, 10)
  }
}

/**
 * Best-effort reminder ~3 days before Stripe ends a trial.
 * Failures are logged by the caller; never throw to the webhook.
 */
export async function sendTrialEndingReminder(opts: {
  to: string
  name?: string | null
  trialEndsAt: Date
  billingUrl: string
  locale?: string
}): Promise<{ success: boolean; error?: string }> {
  const locale = opts.locale?.startsWith('fr') ? 'fr' : 'en'
  const endLabel = formatTrialEnd(opts.trialEndsAt, locale === 'fr' ? 'fr-FR' : 'en-US')
  const greet = opts.name?.trim() ? opts.name.trim() : locale === 'fr' ? 'Bonjour' : 'Hi'

  const subject =
    locale === 'fr'
      ? 'Votre essai Memento se termine bientôt'
      : 'Your Memento trial is ending soon'

  const html =
    locale === 'fr'
      ? `
        <p>${greet},</p>
        <p>Votre période d'essai Memento se termine le <strong>${endLabel}</strong>.</p>
        <p>Après cette date, votre abonnement démarrera automatiquement avec le moyen de paiement enregistré.</p>
        <p>Pour gérer votre abonnement ou votre carte&nbsp;:</p>
        <p><a href="${opts.billingUrl}">Ouvrir la facturation</a></p>
        <p>— L'équipe Memento</p>
      `
      : `
        <p>${greet},</p>
        <p>Your Memento trial ends on <strong>${endLabel}</strong>.</p>
        <p>After that date, your subscription will start automatically using the payment method on file.</p>
        <p>To manage your subscription or card:</p>
        <p><a href="${opts.billingUrl}">Open billing settings</a></p>
        <p>— The Memento team</p>
      `

  return sendEmail({ to: opts.to, subject, html })
}