Fp Data Transforms

// API response
interface ApiOrder {
  order_id: string;
  customer: {
    id: string;
    full_name: string;
  };
  line_items: Array<{
    product_id: string;
    product_name: string;
    qty: number;
    unit_price: number;
  }>;
  order_date: string;
  status: 'pending' | 'processing' | 'shipped' | 'delivered';
}

// What the UI needs
interface OrderSummary {
  id: string;
  customerName: string;
  itemCount: number;
  total: number;
  formattedTotal: string;
  date: string;
  statusLabel: string;
  statusColor: string;
}

// Transformation
const STATUS_CONFIG: Record<string, { label: string; color: string }> = {
  pending: { label: 'Pending', color: 'yellow' },
  processing: { label: 'Processing', color: 'blue' },
  shipped: { label: 'Shipped', color: 'purple' },
  delivered: { label: 'Delivered', color: 'green' },
};

const formatCurrency = (cents: number): string =>
  `$${(cents / 100).toFixed(2)}`;

const formatDate = (iso: string): string =>
  new Date(iso).toLocaleDateString('en-US', {
    month: 'short',
    day: 'numeric',
    year: 'numeric',
  });

const toOrderSummary = (order: ApiOrder): OrderSummary => {
  const total = order.line_items.reduce(
    (sum, item) => sum + item.qty * item.unit_price,
    0
  );

  const status = STATUS_CONFIG[order.status] ?? STATUS_CONFIG.pending;

  return {
    id: order.order_id,
    customerName: order.customer.full_name,
    itemCount: order.line_items.reduce((sum, item) => sum + item.qty, 0),
    total,
    formattedTotal: formatCurrency(total),
    date: formatDate(order.order_date),
    statusLabel: status.label,
    statusColor: status.color,
  };
};

// Transform all orders
const toOrderSummaries = (orders: ApiOrder[]): OrderSummary[] =>
  orders.map(toOrderSummary);

interface AppSettings {
  theme: {
    mode: 'light' | 'dark' | 'system';
    primaryColor: string;
    fontSize: 'small' | 'medium' | 'large';
  };
  notifications: {
    email: boolean;
    push: boolean;
    sms: boolean;
    frequency: 'immediate' | 'daily' | 'weekly';
  };
  privacy: {
    showProfile: boolean;
    showActivity: boolean;
    allowAnalytics: boolean;
  };
}

type DeepPartial<T> = {
  [P in keyof T]?: T[P] extends object ? DeepPartial<T[P]> : T[P];
};

const DEFAULT_SETTINGS: AppSettings = {
  theme: {
    mode: 'system',
    primaryColor: '#007bff',
    fontSize: 'medium',
  },
  notifications: {
    email: true,
    push: true,
    sms: false,
    frequency: 'immediate',
  },
  privacy: {
    showProfile: true,
    showActivity: true,
    allowAnalytics: true,
  },
};

const deepMergeSettings = (
  defaults: AppSettings,
  user: DeepPartial<AppSettings>
): AppSettings => ({
  theme: { ...defaults.theme, ...user.theme },
  notifications: { ...defaults.notifications, ...user.notifications },
  privacy: { ...defaults.privacy, ...user.privacy },
});

// Usage
const userPreferences: DeepPartial<AppSettings> = {
  theme: { mode: 'dark' },
  notifications: { sms: true, frequency: 'daily' },
};

const finalSettings = deepMergeSettings(DEFAULT_SETTINGS, userPreferences);

interface Order {
  id: string;
  customerId: string;
  customerName: string;
  items: Array<{ name: string; price: number; quantity: number }>;
  date: string;
}

interface CustomerOrderSummary {
  customerId: string;
  customerName: string;
  orderCount: number;
  totalSpent: number;
  orders: Order[];
}

const calculateOrderTotal = (order: Order): number =>
  order.items.reduce((sum, item) => sum + item.price * item.quantity, 0);

const groupOrdersByCustomer = (orders: Order[]): CustomerOrderSummary[] => {
  const grouped = groupBy((order: Order) => order.customerId)(orders);

  return Object.entries(grouped).map(([customerId, customerOrders]) => ({
    customerId,
    customerName: customerOrders[0].customerName,
    orderCount: customerOrders.length,
    totalSpent: customerOrders.reduce(
      (sum, order) => sum + calculateOrderTotal(order),
      0
    ),
    orders: customerOrders,
  }));
};

interface AppConfig {
  services?: {
    api?: {
      endpoints?: {
        users?: string;
        orders?: string;
        products?: string;
      };
      auth?: {
        type?: 'bearer' | 'basic' | 'oauth';
        token?: string;
      };
    };
    database?: {
      primary?: {
        host?: string;
        port?: number;
        name?: string;
      };
    };
  };
}

import * as O from 'fp-ts/Option';
import { pipe } from 'fp-ts/function';

// Create a type-safe config accessor
const getConfigValue = <T>(
  config: AppConfig,
  path: (config: AppConfig) => T | undefined,
  defaultValue: T
): T => path(config) ?? defaultValue;

// Usage with optional chaining (simplest)
const apiUsersEndpoint = getConfigValue(
  config,
  c => c.services?.api?.endpoints?.users,
  '/api/users'
);

// For more complex scenarios, use Option
const getEndpoint = (config: AppConfig, name: 'users' | 'orders' | 'products'): string =>
  pipe(
    O.fromNullable(config.services),
    O.flatMap(s => O.fromNullable(s.api)),
    O.flatMap(a => O.fromNullable(a.endpoints)),
    O.flatMap(e => O.fromNullable(e[name])),
    O.getOrElse(() => `/api/${name}`)
  );

// Reusable pattern for multiple values
const getDbConfig = (config: AppConfig) => ({
  host: config.services?.database?.primary?.host ?? 'localhost',
  port: config.services?.database?.primary?.port ?? 5432,
  name: config.services?.database?.primary?.name ?? 'app',
});

// Native is fine here
const activeUserNames = users
  .filter(u => u.isActive)
  .map(u => u.name);