// Billing client: fetches subscription status, kicks off checkout/portal
// flows, and owns the global "upgrade required" prompt shown by the
// 402 interceptor in useApi. State is shared across components via
// useState so the prompt can be triggered from any handler.

export interface BillingStatus {
  tier: 'free' | 'pro' | 'business'
  status: string
  current_period_end?: string
  cancel_at_period_end: boolean
  limits: {
    events_per_month: number
    guests_per_event: number
  }
  usage: {
    events_this_month: number
  }
  portal_available: boolean
}

// UpgradePrompt mirrors the 402 body the backend returns when a limit is
// hit. Shown globally as a modal until dismissed or acted upon.
export interface UpgradePrompt {
  error: string
  reason: string
  tier: string
  used: number
  limit: number
  upgrade_url: string
}

const FREE_DEFAULT: BillingStatus = {
  tier: 'free',
  status: 'active',
  cancel_at_period_end: false,
  limits: { events_per_month: 1, guests_per_event: 50 },
  usage: { events_this_month: 0 },
  portal_available: false,
}

export function useBilling() {
  const status = useState<BillingStatus | null>('gg-billing-status', () => null)
  const loading = useState<boolean>('gg-billing-loading', () => false)
  const prompt = useState<UpgradePrompt | null>('gg-upgrade-prompt', () => null)

  async function fetchStatus(): Promise<BillingStatus> {
    loading.value = true
    try {
      const res = await useApi<BillingStatus>('/billing/status')
      status.value = res
      return res
    } catch (e: any) {
      // 401/refresh edge → caller redirected to /login by useApi. If the
      // backend has billing wired but the response is malformed, fall
      // back to free defaults so the page renders something usable.
      status.value = FREE_DEFAULT
      return FREE_DEFAULT
    } finally {
      loading.value = false
    }
  }

  async function startCheckout(tier: 'pro' | 'business'): Promise<void> {
    const res = await useApi<{ url: string }>('/billing/checkout-session', {
      method: 'POST',
      body: { tier },
    })
    if (import.meta.client) window.location.href = res.url
  }

  async function openPortal(): Promise<void> {
    const res = await useApi<{ url: string }>('/billing/portal', { method: 'POST' })
    if (import.meta.client) window.location.href = res.url
  }

  function showUpgradePrompt(info: UpgradePrompt) {
    prompt.value = info
  }
  function dismissUpgradePrompt() {
    prompt.value = null
  }

  return {
    status,
    loading,
    prompt,
    fetchStatus,
    startCheckout,
    openPortal,
    showUpgradePrompt,
    dismissUpgradePrompt,
  }
}

// Static pricing copy. Keep in sync with internal/billing/tiers.go.
// One source of truth for the marketing-page-style cards in
// /dashboard/billing and the UpgradeModal.
export interface TierCard {
  id: 'free' | 'pro' | 'business'
  name: string
  price: string
  priceSubtitle: string
  tagline: string
  features: string[]
  highlight?: boolean
}

export const TIER_CARDS: TierCard[] = [
  {
    id: 'free',
    name: 'Free',
    price: '$0',
    priceSubtitle: 'forever',
    tagline: 'Try GuestGuard with a single event.',
    features: [
      '1 event per month',
      'Up to 50 guests per event',
      'Branded email invitations',
      'Real-time RSVP dashboard',
    ],
  },
  {
    id: 'pro',
    name: 'Pro',
    price: '$49',
    priceSubtitle: 'per month',
    tagline: 'For active hosts running several events.',
    features: [
      '10 events per month',
      'Up to 1,000 guests per event',
      'WhatsApp + email invitations',
      'CSV import + bulk send',
      'Priority email support',
    ],
    highlight: true,
  },
  {
    id: 'business',
    name: 'Business',
    price: '$199',
    priceSubtitle: 'per month',
    tagline: 'For agencies and corporate events teams.',
    features: [
      'Unlimited events',
      'Up to 5,000 guests per event',
      'Everything in Pro',
      'Signed DPA on request',
      'SLA with response targets',
    ],
  },
]