import { useState } from 'react'
import { Link } from 'react-router-dom'
import { CreditCard, AlertCircle, Loader2, ExternalLink, Crown } from 'lucide-react'

import { billingApi } from '@/api/billing'
import { Button } from '@/components/ui/Button'
import { PageMeta } from '@/components/common/PageMeta'
import { useBillingStore } from '@/store/billingStore'
import { BillingPortalError } from '@/types/billing'
import { toast } from '@/lib/toast'
import { cn } from '@/lib/utils'

function formatDate(value: string | null | undefined): string {
  if (!value) return '—'
  return new Date(value).toLocaleDateString(undefined, {
    year: 'numeric',
    month: 'short',
    day: 'numeric',
  })
}

function statusLabel(status: string): string {
  switch (status) {
    case 'trialing':
      return 'Trialing'
    case 'active':
      return 'Active'
    case 'past_due':
      return 'Past due'
    case 'canceled':
      return 'Canceled'
    case 'incomplete':
      return 'Incomplete'
    case 'complimentary':
      return 'Complimentary'
    default:
      return status
  }
}

function statusToneClass(status: string): string {
  switch (status) {
    case 'active':
    case 'complimentary':
      return 'text-success'
    case 'trialing':
      return 'text-info'
    case 'past_due':
    case 'incomplete':
      return 'text-warning'
    case 'canceled':
      return 'text-danger'
    default:
      return 'text-muted-foreground'
  }
}

export function BillingPage() {
  const subscription = useBillingStore((s) => s.subscription)
  const planBilling = useBillingStore((s) => s.planBilling)
  const isLoading = useBillingStore((s) => s.isLoading)

  const [openingPortal, setOpeningPortal] = useState(false)

  const status = subscription?.status ?? null
  const isComplimentary = status === 'complimentary'
  const isTrialing = status === 'trialing'
  const isPastDue = status === 'past_due'
  const isCanceled = status === 'canceled'

  const handleOpenPortal = async () => {
    setOpeningPortal(true)
    try {
      const { url } = await billingApi.getPortalSession()
      window.location.href = url
    } catch (err) {
      if (err instanceof BillingPortalError) {
        if (err.code === 'no_stripe_customer') {
          toast.error('Complete checkout first to access billing portal.')
        } else {
          toast.error('Billing portal is not available right now.')
        }
      } else {
        toast.error('Failed to open billing portal.')
      }
      setOpeningPortal(false)
    }
  }

  if (isLoading && !subscription) {
    return (
      <div className="flex justify-center py-12">
        <Loader2 className="h-6 w-6 animate-spin text-muted-foreground" />
      </div>
    )
  }

  return (
    <>
      <PageMeta title="Billing" />
      <div>
        {/* ── Header ─────────────────────────────────────────────────────── */}
        <div className="mb-8">
          <div className="flex items-center gap-3">
            <CreditCard className="h-8 w-8 text-muted-foreground" />
            <h1 className="text-2xl font-bold font-heading text-foreground sm:text-3xl">
              Billing
            </h1>
          </div>
          <p className="mt-2 text-muted-foreground">
            Manage your subscription, payment method, and billing history.
          </p>
        </div>

        {/* ── Past-due banner ────────────────────────────────────────────── */}
        {isPastDue && (
          <div
            data-testid="past-due-banner"
            className={cn(
              'mb-6 flex flex-wrap items-start gap-3 rounded-lg border border-warning/30',
              'bg-warning-dim p-4 text-foreground',
            )}
          >
            <AlertCircle className="mt-0.5 h-5 w-5 shrink-0 text-warning" />
            <div className="flex-1 min-w-0">
              <p className="text-sm font-medium">Your last payment failed.</p>
              <p className="mt-0.5 text-xs text-muted-foreground">
                Update your payment method to keep access to ResolutionFlow.
              </p>
            </div>
            <Button
              size="sm"
              loading={openingPortal}
              onClick={handleOpenPortal}
              data-testid="past-due-update-payment"
            >
              Update payment method
            </Button>
          </div>
        )}

        {/* ── Subscription summary card ──────────────────────────────────── */}
        <div className="card-flat max-w-xl space-y-5 p-6">
          <div className="flex items-baseline justify-between gap-3">
            <div>
              <div className="flex items-center gap-2">
                <Crown className="h-4 w-4 text-muted-foreground" />
                <span className="text-sm font-medium text-foreground">
                  {planBilling?.display_name ?? 'No active plan'}
                </span>
              </div>
              {subscription && (
                <div
                  className={cn(
                    'mt-1 text-xs',
                    statusToneClass(subscription.status),
                  )}
                >
                  {statusLabel(subscription.status)}
                  {subscription.cancel_at_period_end && ' · cancels at period end'}
                </div>
              )}
            </div>
            {subscription?.seat_limit != null && (
              <div className="text-right">
                <div className="text-xs text-muted-foreground">Seats</div>
                <div className="text-sm tabular-nums text-foreground">
                  {subscription.seat_limit}
                </div>
              </div>
            )}
          </div>

          <div className="grid grid-cols-1 gap-3 border-t border-border pt-4 sm:grid-cols-2">
            <div>
              <div className="text-xs text-muted-foreground">
                {isCanceled ? 'Ends' : isTrialing ? 'Trial ends' : 'Next renewal'}
              </div>
              <div className="text-sm tabular-nums text-foreground">
                {isComplimentary ? '—' : formatDate(subscription?.current_period_end)}
              </div>
            </div>
            <div>
              <div className="text-xs text-muted-foreground">Plan started</div>
              <div className="text-sm tabular-nums text-foreground">
                {formatDate(subscription?.current_period_start)}
              </div>
            </div>
          </div>

          {/* State-specific messaging ------------------------------------ */}
          {isComplimentary && (
            <div
              data-testid="complimentary-message"
              className="rounded-md bg-success-dim p-3 text-xs text-success"
            >
              Complimentary Pro — no billing required.
            </div>
          )}

          {isTrialing && (
            <div
              data-testid="trial-message"
              className="rounded-md bg-info-dim p-3 text-xs text-info"
            >
              Trial ends {formatDate(subscription?.current_period_end)} — pick a plan
              to continue.
            </div>
          )}

          {isCanceled && (
            <div
              data-testid="canceled-message"
              className="rounded-md bg-muted p-3 text-xs text-muted-foreground"
            >
              Subscription canceled. Reactivate by picking a plan.
            </div>
          )}
        </div>

        {/* ── Actions ────────────────────────────────────────────────────── */}
        {!isComplimentary && (
          <div className="mt-6 flex max-w-xl flex-wrap gap-3">
            {(isTrialing || isCanceled) && (
              <Link
                to="/account/billing/select-plan"
                data-testid="select-plan-link"
                className={cn(
                  'inline-flex items-center gap-2 rounded-lg bg-primary px-4 py-2',
                  'text-sm font-semibold text-white hover:brightness-110',
                )}
              >
                Pick a plan
              </Link>
            )}

            {!isTrialing && !isCanceled && (
              <Link
                to="/account/billing/select-plan"
                data-testid="change-plan-link"
                className={cn(
                  'inline-flex items-center gap-2 rounded-lg border border-border',
                  'bg-input px-4 py-2 text-sm font-medium text-foreground',
                  'hover:border-border-hover',
                )}
              >
                Change plan
              </Link>
            )}

            <Button
              variant="secondary"
              loading={openingPortal}
              onClick={handleOpenPortal}
              data-testid="manage-billing-button"
            >
              <ExternalLink className="h-4 w-4" />
              Manage billing
            </Button>
          </div>
        )}
      </div>
    </>
  )
}

export default BillingPage