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# Enterprise API Engine (`@repo/core-api`)

The platform-agnostic API engine for the monorepo. Provides an isolated HTTP client factory, a unified observability pipeline (Grafana Faro + OpenTelemetry), and a generic data services engine.

**This package enforces App Autonomy (IoC).** The core provides the engine and interceptor pipelines, but the consuming applications (`apps/web`, `apps/landing`) inject their own specific configurations, authentication tokens, and error handling behaviors.

---

## Architecture Overview
```mermaid
graph TD
    %% ─── Styling Definitions (Dark-Mode Friendly Enterprise Palette) ───
    classDef appEntity fill:#dbeafe,stroke:#3b82f6,stroke-width:2px,color:#1e3a8a
    classDef coreEngine fill:#6366f1,stroke:#4338ca,stroke-width:2px,color:#ffffff
    classDef dataService fill:#10b981,stroke:#047857,stroke-width:2px,color:#ffffff
    classDef observability fill:#f59e0b,stroke:#b45309,stroke-width:2px,color:#ffffff
    classDef errorNode fill:#f43f5e,stroke:#be123c,stroke-width:2px,color:#ffffff

    %% ─── Subgraphs ───
    subgraph Apps ["apps/* (App Autonomy)"]
        WEB([apps/web])
        LAND([apps/landing])
        DESK([apps/desktop])
    end

    subgraph Core ["@repo/core-api (Engine)"]
        subgraph HTTP ["http-client"]
            FACTORY[createHttpClient]
        end
        subgraph OBS ["observability"]
            FARO[faroAdapter]
        end
        subgraph DATA ["data-services"]
            BASE[BaseRemoteDataServices]
            COMMON[CommonRemoteDataServices]
        end
        subgraph ERRORS ["errors"]
            API_ERR[ApiError]
        end
    end

    %% ─── Flow & Relationships ───
    WEB & LAND & DESK ===>|instantiates| FACTORY
    WEB & LAND & DESK ===>|extends| COMMON
    
    COMMON --->|executes via| FACTORY
    FACTORY -.->|reports via| FARO
    FACTORY -.->|throws| API_ERR

    %% ─── Apply Styles ───
    class WEB,LAND,DESK appEntity;
    class FACTORY coreEngine;
    class BASE,COMMON dataService;
    class FARO observability;
    class API_ERR errorNode;

    %% ─── Subgraph Backgrounds (Transparent for Native GitHub Support) ───
    style Apps fill:transparent,stroke:#3b82f6,stroke-width:2px,stroke-dasharray: 5 5
    style Core fill:transparent,stroke:#94a3b8,stroke-width:2px,stroke-dasharray: 5 5
    
    %% Nested subgraphs also need transparent backgrounds to prevent glaring white boxes in dark mode
    style HTTP fill:transparent,stroke:#cbd5e1,stroke-width:1px,stroke-dasharray: 5 5
    style OBS fill:transparent,stroke:#cbd5e1,stroke-width:1px,stroke-dasharray: 5 5
    style DATA fill:transparent,stroke:#cbd5e1,stroke-width:1px,stroke-dasharray: 5 5
    style ERRORS fill:transparent,stroke:#cbd5e1,stroke-width:1px,stroke-dasharray: 5 5
  ```

### Data Flow Lifecycle

Every HTTP request flows through this precise interceptor pipeline:

```mermaid
sequenceDiagram
    autonumber

    %% ─── Dark-Mode Friendly RGBA Boxes ───
    box rgba(59, 130, 246, 0.1) App Layer (Consumers)
        participant C as UI Component
    end

    box rgba(148, 163, 184, 0.1) Core Engine (@repo/core-api)
        participant S as Data Service
        participant H as HTTP Client
        participant F as Faro Adapter
    end

    box rgba(16, 185, 129, 0.1) App Logic (IoC)
        participant A as App Hooks
    end

    box rgba(245, 158, 11, 0.1) External
        participant N as Network
    end

    %% ─── Execution Flow ───
    C->>S: getMany()
    S->>H: request()
    H->>F: onRequestStart() (Log + Span)
    H->>A: hooks.onRequest() (Inject Token)
    A->>N: fetch/XHR
    
    alt Success (2xx)
        N-->>A: return Response
        A->>F: onRequestEnd() (Close Span)
        F->>A: hooks.onResponse()
        A-->>S: return data
    else Error (4xx / 5xx)
        N-->>A: return Rejection
        A->>F: onRequestError() (Log Error)
        F->>A: hooks.onResponseError() (Redirect/Refresh)
        A-->>S: throw ApiError
    end
```

> [!IMPORTANT]
> Observability adapter errors are **caught internally** via try-catch in the interceptor chain. An adapter crash will never swallow or replace the original API error — the UI always receives the correct rejection.

---

## HTTP Client

### `createHttpClient(config, hooks?)`

Creates an **isolated** Axios instance. Each app receives its own interceptor chain — no globals are shared or mutated.

```typescript
import { createHttpClient } from '@repo/core-api/http-client';
import { faroAdapter } from '@repo/core-api/observability';

export const apiClient = createHttpClient(
  {
    baseURL: import.meta.env.VITE_API_URL ?? 'http://localhost:8080/api/v1',
    timeout: 15000,
    observability: faroAdapter,
  },
  {
    onRequest: async (config) => {
      const token = localStorage.getItem('access_token');
      if (token) config.headers.Authorization = `Bearer ${token}`;
      return config;
    },
    onResponseError: async (error) => {
      if (error.response?.status === 401) {
        localStorage.removeItem('access_token');
        window.location.href = '/auth/login';
      }
      throw error;
    },
  },
);
```

### Configuration

| Property | Type | Default | Description |
|---|---|---|---|
| `baseURL` | `string` | *required* | Base URL for all requests |
| `timeout` | `number` | `15000` | Default request timeout (ms) |
| `defaultHeaders` | `Record<string, string>` | `{}` | Headers applied to every request |
| `observability` | `IObservabilityAdapter` | `noopAdapter` | Observability adapter (Faro or no-op) |

### Interceptor Hooks

| Hook | Signature | Purpose |
|---|---|---|
| `onRequest` | `(config) => config` | Inject auth tokens, tenant headers |
| `onResponse` | `(response) => response` | Transform response shapes |
| `onResponseError` | `(error) => never` | App-specific error handling (e.g., 401 redirect) |

---

## Observability

### Strategy: Opt-In Custom Spans + Faro/Loki Baseline

The observability layer operates in two complementary modes:

| Mode | Activation | What it does |
|---|---|---|
| **Baseline** (always on) | Automatic | Pushes structured logs to Faro/Loki on every request with `module.key`, `module.action`, HTTP method, and URL |
| **Custom Span** (opt-in) | Via `telemetryContext.customSpanName` | Creates an explicit OTel span with custom tags, visible in Grafana Tempo |

> [!NOTE]
> `trace.getActiveSpan()` returns `undefined` inside Axios interceptors due to browser XHR/Fetch lifecycle race conditions with Faro's `TracingInstrumentation`. The adapter does **not** attempt to enrich auto-instrumented spans. HTTP span capture is handled entirely by `TracingInstrumentation` auto-instrumentation.

### Initialization

Call `initTelemetry()` **once** at the top of your app's entry point, before any React code:

```typescript
import { initTelemetry } from '@repo/core-api/observability/setup';

initTelemetry({
  appName: 'fe-monorepo-web',
  appVersion: '1.0.0',
  telemetryUrl: '[https://telemetry.eigen.co.id/collect](https://telemetry.eigen.co.id/collect)',
  environment: 'production',
  // Optional: direct OTLP export to Grafana Tempo
  otlpTraceUrl: '[https://telemetry.eigen.co.id/v1/traces](https://telemetry.eigen.co.id/v1/traces)',
});
```

### `TelemetryConfig`

| Property | Type | Required | Description |
|---|---|---|---|
| `appName` | `string` | ✅ | Application name for Faro + OTel resource attributes |
| `appVersion` | `string` | ✅ | SemVer version |
| `telemetryUrl` | `string` | ✅ | Grafana Faro collector URL |
| `environment` | `string` | ✅ | Deployment environment (`production`, `staging`, `development`) |
| `otlpTraceUrl` | `string` | — | Separate OTLP trace endpoint for direct Tempo ingestion |
| `propagateTraceHeaderCorsUrls` | `Array<string \| RegExp>` | — | CORS patterns for W3C trace context propagation (default: `[/.*/]`) |

### Audit Headers

Every request dispatched through `BaseRemoteDataServices` automatically attaches two business audit headers:

| Header | Source | Purpose |
|---|---|---|
| `ex-module-key` | `DataServicesConfig.moduleKey` | Identifies the business module (e.g., `BOOKING`) |
| `ex-module-action` | `RequestDescriptor.action` | Identifies the operation (e.g., `READ`, `CREATE`) |

These headers are extracted by the `faroAdapter` and included in all Faro `pushLog`, `pushError`, and `pushEvent` calls as top-level context — making them directly queryable in **LogQL (Loki)**.

### Span Safety Guarantees

| Guarantee | Mechanism |
|---|---|
| **No span leaks** | `safeEndSpan()` always closes the span and detaches the reference from config |
| **No double-close on retry** | Span reference is deleted from config after `span.end()` |
| **No error swallowing** | All adapter calls are wrapped in try-catch in `create-http-client.ts` |
| **No crash on timeout** | `null`/`undefined` config guards on all `error.config` access |

---

## Data Services

### `CommonRemoteDataServices<E>`

A concrete, ready-to-use data services class that provides full CRUD and lifecycle operations. Extends `BaseRemoteDataServices<E>`.

```typescript
import { CommonRemoteDataServices } from '@repo/core-api/data-services';
import type { BaseEntity } from '@repo/core-api/data-services';
import { apiClient } from '@/lib/api-client';

interface BookingEntity extends BaseEntity {
  bookingCode: string;
  customerName: string;
  status: 'pending' | 'confirmed' | 'cancelled';
}

export const bookingServices = new CommonRemoteDataServices<BookingEntity>(
  apiClient,
  {
    apiUrl: '/bookings',
    moduleKey: 'BOOKING',
  },
);
```

### Available Operations

| Method | HTTP | URL Template | Description |
|---|---|---|---|
| `getMany(config?)` | GET | `/bookings` | Fetch paginated list |
| `getOne(id, config?)` | GET | `/bookings/:id` | Fetch single entity |
| `create(data, config?)` | POST | `/bookings` | Create new entity |
| `edit(id, data, config?)` | PUT | `/bookings/:id` | Update entity |
| `delete(id, config?)` | DELETE | `/bookings/:id` | Delete entity |
| `batchDelete(ids, config?)` | DELETE | `/bookings/batch` | Delete multiple |
| `activate(id)` | PATCH | `/bookings/:id/activate` | Activate entity |
| `deactivate(id)` | PATCH | `/bookings/:id/deactivate` | Deactivate entity |
| `confirmProcessData(id)` | PATCH | `/bookings/:id/confirm-process-data` | Confirm data processing |
| `confirmProcessTransaction(id)` | PATCH | `/bookings/:id/confirm-process-transaction` | Confirm transaction |
| `cancelProcessTransaction(id)` | PATCH | `/bookings/:id/cancel-process-transaction` | Cancel transaction |
| `rollbackProcessTransaction(id)` | PATCH | `/bookings/:id/rollback-process-transaction` | Rollback transaction |
| `holdProcessTransaction(id)` | PATCH | `/bookings/:id/hold-process-transaction` | Hold transaction |

All batch variants (`batchActivate`, `batchDeactivate`, etc.) are also available.

### Escape Hatch: `customRequest<T>(config)`

For non-standard endpoints that don't fit the CRUD pattern:

```typescript
const taxResult = await bookingServices.customRequest<TaxCalculation>({
  url: '/bookings/42/calculate-tax',
  method: 'POST',
  data: { items: [...] },
});
```

---

## Application Setup Guide

### 1. Initialize Telemetry (Entry Point)

```typescript
// apps/web/src/main.tsx — MUST be the first import
import { initTelemetry } from '@repo/core-api/observability/setup';

initTelemetry({
  appName: import.meta.env.VITE_APP_NAME || 'fe-monorepo-web',
  appVersion: import.meta.env.VITE_APP_VERSION || '0.0.0',
  telemetryUrl: import.meta.env.VITE_FARO_URL || '[https://telemetry.eigen.co.id/collect](https://telemetry.eigen.co.id/collect)',
  otlpTraceUrl: import.meta.env.VITE_OTLP_TRACE_URL || '[https://telemetry.eigen.co.id/v1/traces](https://telemetry.eigen.co.id/v1/traces)',
  environment: import.meta.env.VITE_ENV || 'development',
});

// ... rest of React bootstrap
```

### 2. Create the HTTP Client

```typescript
// apps/web/src/lib/api-client.ts
import { createHttpClient } from '@repo/core-api/http-client';
import { faroAdapter } from '@repo/core-api/observability';

export const apiClient = createHttpClient({
  baseURL: import.meta.env.VITE_API_URL ?? 'http://localhost:8080/api/v1',
  timeout: 15000,
  observability: faroAdapter,
});
```

### 3. Create a Data Service

```typescript
// features/booking/data/booking.data-services.ts
import { CommonRemoteDataServices } from '@repo/core-api/data-services';
import type { BaseEntity } from '@repo/core-api/data-services';
import { apiClient } from '@/lib/api-client';

export interface BookingEntity extends BaseEntity {
  bookingCode: string;
  customerName: string;
  status: 'pending' | 'confirmed' | 'cancelled';
  totalAmount: number;
}

export const bookingServices = new CommonRemoteDataServices<BookingEntity>(
  apiClient,
  { apiUrl: '/bookings', moduleKey: 'BOOKING' },
);
```

### 4. Consume in a React Component

```tsx
import { useState } from 'react';
import { bookingServices } from '../data/booking.data-services';
import type { BookingEntity } from '../data/booking.data-services';
import type { ApiResponse } from '@repo/core-api/http-client';
import { ApiError } from '@repo/core-api/errors';

export default function BookingSample() {
  const [result, setResult] = useState<ApiResponse<BookingEntity[]> | null>(null);
  const [error, setError] = useState<string | null>(null);

  const handleFetch = async () => {
    try {
      const response = await bookingServices.getMany<BookingEntity[]>({
        params: { page: 1, limit: 20 },
        // Optional: Per-request telemetry escape hatch
        telemetryContext: {
          customSpanName: 'booking.list.fetch',
          tags: { feature: 'booking', page: 1 },
          pushEventOnSuccess: 'booking_list_loaded',
        },
      });
      setResult(response);
    } catch (err) {
      if (err instanceof ApiError) {
        setError(`[${err.code}] ${err.message} (HTTP ${err.status})`);
      }
    }
  };

  return <button onClick={handleFetch}>Fetch Bookings</button>;
}
```

---

## Per-Request Telemetry (Escape Hatch)

### `TelemetryContext`

Attach to any request via the `telemetryContext` property to push custom spans and business events:

```typescript
interface TelemetryContext {
  /** Creates a custom OTel span wrapping this request (visible in Grafana Tempo). */
  customSpanName?: string;
  /** Custom tags enriching the span and Faro logs (prefixed with `custom.` on spans). */
  tags?: Record<string, string | number | boolean>;
  /** Pushes a named Faro event on success (visible in Grafana Faro dashboard). */
  pushEventOnSuccess?: string;
}
```

### Precedence

`telemetryContext` can be provided at two levels. The top-level `ExecuteOptions.telemetryContext` takes precedence over `config.telemetryContext`:

```typescript
// Top-level (preferred)
await bookingServices.getMany({
  telemetryContext: { customSpanName: 'booking.list.fetch' },
});

// Nested in config (also works)
await bookingServices.getMany({
  params: { page: 1 },
  telemetryContext: { customSpanName: 'booking.list.fetch' },
});
```

### What Happens at Each Stage

| Stage | Baseline (no telemetryContext) | With `customSpanName` |
|---|---|---|
| **Request Start** | Faro `pushLog` (DEBUG) with `module.key`, `module.action`, URL | + Creates OTel span with `http.method`, `http.url`, `custom.*` tags |
| **Request Success** | — | Closes span (OK). If `pushEventOnSuccess`, pushes Faro event |
| **Request Error** | Faro `pushError` + `pushLog` (ERROR) | + Closes span (ERROR), records exception |

---

## Error Handling

### `ApiError`

All non-2xx responses are normalized into structured `ApiError` instances:

```typescript
try {
  await bookingServices.getOne('42');
} catch (err) {
  if (err instanceof ApiError) {
    err.code;    // ApiErrorCode.NOT_FOUND
    err.status;  // 404
    err.message; // "Booking not found"
    err.data;    // Raw server response body
    err.toJSON(); // Serializable for logging
  }
}
```

### Error Codes

| Code | HTTP Status | Description |
|---|---|---|
| `BAD_REQUEST` | 400 | Invalid request parameters |
| `UNAUTHORIZED` | 401 | Missing or expired token |
| `FORBIDDEN` | 403 | Insufficient permissions |
| `NOT_FOUND` | 404 | Resource not found |
| `TIMEOUT` | — | Request timed out (`ECONNABORTED`) |
| `CANCELLED` | — | Request was cancelled (`ERR_CANCELED`) |
| `NETWORK_ERROR` | — | No response received |
| `SERVER_ERROR` | 500+ | Internal server error |

---

## Package Exports

| Import Path | Contents |
|---|---|
| `@repo/core-api/http-client` | `createHttpClient`, `ApiResponse`, `TelemetryContext`, Axios type re-exports |
| `@repo/core-api/observability` | `faroAdapter`, `noopObservabilityAdapter`, `IObservabilityAdapter`, `initTelemetry`, `getFaro`, `TelemetryConfig` |
| `@repo/core-api/observability/setup` | `initTelemetry`, `getFaro`, `TelemetryConfig` |
| `@repo/core-api/data-services` | `BaseRemoteDataServices`, `CommonRemoteDataServices`, types, constants |
| `@repo/core-api/errors` | `ApiError`, `ApiErrorCode` |