/**
 * Checkout Analytics - Multi-step checkout funnel tracking
 *
 * Tracks the entire checkout process from cart to purchase confirmation.
 */

import type { AnalyticsClient } from '@analytics/client';

import type { Cart, CartItem } from './cart-analytics';

// ─────────────────────────────────────────────────────────────────────────────
// Types
// ─────────────────────────────────────────────────────────────────────────────

export type CheckoutStep =
  | 'cart_review'
  | 'shipping_info'
  | 'shipping_method'
  | 'payment_info'
  | 'review_order'
  | 'purchase_complete';

export interface ShippingInfo {
  country: string;
  region?: string;
  city?: string;
  postalCode?: string;
}

export interface ShippingMethod {
  id: string;
  name: string;
  price: number;
  estimatedDays?: number;
}

export interface PaymentMethod {
  type: 'card' | 'paypal' | 'apple_pay' | 'google_pay' | 'bank_transfer' | string;
  lastFour?: string;
}

export interface Order {
  id: string;
  items: CartItem[];
  subtotal: number;
  shipping: number;
  tax: number;
  total: number;
  currency: string;
  paymentMethod: PaymentMethod;
  shippingMethod: ShippingMethod;
}

// ─────────────────────────────────────────────────────────────────────────────
// Step Tracking
// ─────────────────────────────────────────────────────────────────────────────

const STEP_ORDER: CheckoutStep[] = [
  'cart_review',
  'shipping_info',
  'shipping_method',
  'payment_info',
  'review_order',
  'purchase_complete',
];

/**
 * Track checkout step completion.
 */
export function trackCheckoutStep(
  client: AnalyticsClient,
  step: CheckoutStep,
  cart: Cart,
  metadata?: Record<string, unknown>,
): void {
  const stepIndex = STEP_ORDER.indexOf(step);

  client.trackEngagement({
    type: 'ecommerce',
    action: 'checkout_step',
    metadata: {
      step,
      stepNumber: stepIndex + 1,
      totalSteps: STEP_ORDER.length,
      funnelId: 'checkout',
      cartValue: cart.subtotal,
      itemCount: cart.items.length,
      currency: cart.currency,
      ...metadata,
    },
  });
}

/**
 * Track when user enters shipping information.
 */
export function trackShippingInfo(
  client: AnalyticsClient,
  shipping: ShippingInfo,
  cart: Cart,
): void {
  trackCheckoutStep(client, 'shipping_info', cart, {
    country: shipping.country,
    region: shipping.region,
    // Don't include city/postalCode for privacy
  });
}

/**
 * Track shipping method selection.
 */
export function trackShippingMethodSelect(
  client: AnalyticsClient,
  method: ShippingMethod,
  cart: Cart,
): void {
  trackCheckoutStep(client, 'shipping_method', cart, {
    shippingMethodId: method.id,
    shippingMethodName: method.name,
    shippingCost: method.price,
    estimatedDays: method.estimatedDays,
  });
}

/**
 * Track payment method selection.
 */
export function trackPaymentMethodSelect(
  client: AnalyticsClient,
  method: PaymentMethod,
  cart: Cart,
): void {
  trackCheckoutStep(client, 'payment_info', cart, {
    paymentType: method.type,
    // Never include card details, only type
  });
}

// ─────────────────────────────────────────────────────────────────────────────
// Purchase Tracking
// ─────────────────────────────────────────────────────────────────────────────

/**
 * Track successful purchase.
 *
 * This is the primary conversion event for e-commerce.
 */
export function trackPurchase(client: AnalyticsClient, order: Order): void {
  client.trackEngagement({
    type: 'ecommerce',
    action: 'purchase',
    metadata: {
      orderId: order.id,
      subtotal: order.subtotal,
      shipping: order.shipping,
      tax: order.tax,
      total: order.total,
      currency: order.currency,
      itemCount: order.items.length,
      paymentType: order.paymentMethod.type,
      shippingMethod: order.shippingMethod.name,
      // Key conversion metrics
      isConversion: true,
      conversionValue: order.total,
      funnelId: 'checkout',
      funnelStep: 'purchase_complete',
      // Product breakdown
      products: order.items.map((item) => ({
        productId: item.id,
        productName: item.name,
        quantity: item.quantity,
        price: item.price,
        itemTotal: item.price * item.quantity,
      })),
    },
  });
}

/**
 * Track checkout abandonment.
 *
 * Call when user leaves checkout without completing purchase.
 */
export function trackCheckoutAbandonment(
  client: AnalyticsClient,
  lastStep: CheckoutStep,
  cart: Cart,
  reason?: 'navigation' | 'error' | 'timeout' | 'browser_close',
): void {
  const stepIndex = STEP_ORDER.indexOf(lastStep);

  client.trackEngagement({
    type: 'ecommerce',
    action: 'checkout_abandonment',
    metadata: {
      lastStep,
      stepNumber: stepIndex + 1,
      totalSteps: STEP_ORDER.length,
      funnelId: 'checkout',
      abandonedValue: cart.subtotal,
      itemCount: cart.items.length,
      currency: cart.currency,
      reason,
      products: cart.items.map((item) => ({
        productId: item.id,
        quantity: item.quantity,
      })),
    },
  });
}

/**
 * Track payment failure.
 */
export function trackPaymentFailure(
  client: AnalyticsClient,
  cart: Cart,
  errorType: 'declined' | 'invalid' | 'network' | 'fraud' | string,
  paymentMethod: PaymentMethod,
): void {
  client.trackEngagement({
    type: 'ecommerce',
    action: 'payment_failure',
    metadata: {
      errorType,
      paymentType: paymentMethod.type,
      cartValue: cart.subtotal,
      currency: cart.currency,
      itemCount: cart.items.length,
    },
  });
}

// ─────────────────────────────────────────────────────────────────────────────
// React Hook
// ─────────────────────────────────────────────────────────────────────────────

/**
 * Hook for checkout funnel tracking.
 *
 * @example
 * ```tsx
 * function CheckoutPage() {
 *   const { trackStep, trackPurchase, trackAbandonment } = useCheckoutFunnel(cart);
 *
 *   return (
 *     <CheckoutWizard
 *       onStepComplete={(step) => trackStep(step)}
 *       onPurchase={(order) => trackPurchase(order)}
 *     />
 *   );
 * }
 * ```
 */
export function createCheckoutTracker(client: AnalyticsClient, cart: Cart) {
  return {
    trackStep: (step: CheckoutStep, metadata?: Record<string, unknown>) => {
      trackCheckoutStep(client, step, cart, metadata);
    },

    trackShipping: (info: ShippingInfo) => {
      trackShippingInfo(client, info, cart);
    },

    trackShippingMethod: (method: ShippingMethod) => {
      trackShippingMethodSelect(client, method, cart);
    },

    trackPaymentMethod: (method: PaymentMethod) => {
      trackPaymentMethodSelect(client, method, cart);
    },

    trackPurchase: (order: Order) => {
      trackPurchase(client, order);
    },

    trackAbandonment: (
      lastStep: CheckoutStep,
      reason?: 'navigation' | 'error' | 'timeout' | 'browser_close',
    ) => {
      trackCheckoutAbandonment(client, lastStep, cart, reason);
    },

    trackPaymentError: (
      errorType: 'declined' | 'invalid' | 'network' | 'fraud' | string,
      paymentMethod: PaymentMethod,
    ) => {
      trackPaymentFailure(client, cart, errorType, paymentMethod);
    },
  };
}