import { useBillingStore } from '@/store/billingStore'

export type TrialBannerStage =
  | 'pristine'
  | 'warning'
  | 'urgent'
  | 'expired'
  | 'complimentary'
  | 'paid'
  | 'past_due'
  | 'canceled'

export interface TrialBannerResult {
  stage: TrialBannerStage | null
  daysRemaining: number | null
}

const MS_PER_DAY = 24 * 60 * 60 * 1000

/**
 * Derives the trial-banner display stage from the current subscription.
 *
 * Returns `{ stage: null, daysRemaining: null }` when subscription data is
 * not yet loaded — this prevents the banner flickering on initial render.
 *
 * Subscribes to `useBillingStore` so updates from `refetch()` after a Stripe
 * checkout propagate automatically.
 */
export function useTrialBanner(): TrialBannerResult {
  const subscription = useBillingStore((state) => state.subscription)

  if (!subscription) {
    return { stage: null, daysRemaining: null }
  }

  switch (subscription.status) {
    case 'complimentary':
      return { stage: 'complimentary', daysRemaining: null }
    case 'active':
      return { stage: 'paid', daysRemaining: null }
    case 'past_due':
      return { stage: 'past_due', daysRemaining: null }
    case 'canceled':
      return { stage: 'canceled', daysRemaining: null }
    case 'trialing': {
      const end = subscription.current_period_end
        ? new Date(subscription.current_period_end).getTime()
        : null
      if (end === null || Number.isNaN(end)) {
        // Trialing without a period end is malformed; treat as expired so the
        // upgrade prompt still surfaces rather than silently swallowing it.
        return { stage: 'expired', daysRemaining: null }
      }
      const now = Date.now()
      if (end <= now) {
        return { stage: 'expired', daysRemaining: 0 }
      }
      const msRemaining = end - now
      // Use fractional days for stage thresholds so exactly 24h remaining
      // sits on the warning side (1.0), not urgent. The displayed integer
      // countdown still uses Math.ceil so "0.5 days" renders as "1 day".
      const fractionalDays = msRemaining / MS_PER_DAY
      const daysRemaining = Math.ceil(fractionalDays)
      // Spec thresholds:
      //   >3 days remaining → pristine
      //   1–3 days          → warning (inclusive of exactly 1)
      //   <1 day            → urgent
      let stage: TrialBannerStage = 'pristine'
      if (fractionalDays < 1) stage = 'urgent'
      else if (fractionalDays <= 3) stage = 'warning'
      return { stage, daysRemaining }
    }
    case 'incomplete':
      // Not in the spec's matrix; surface as null so the banner stays hidden
      // until checkout actually resolves.
      return { stage: null, daysRemaining: null }
    default: {
      // Defensive fallthrough for unknown statuses — keep the banner hidden.
      const _exhaustive: never = subscription.status as never
      void _exhaustive
      return { stage: null, daysRemaining: null }
    }
  }
}

export default useTrialBanner