Update README.md

Author: javaherisaber

README.md

@@ -23,8 +23,99 @@ dependencies {
 }
 ```
 
-## Todo
+## How to use
 
-- Add example usage and demo gif
-- Use builder design pattern to simplify constructor
-- Split codes to more classes
+### 1. Create json file of your api response lets say `picsum_list.json` and put it in `assets/mock_json` directory
+
+```json
+[
+  {
+    "id": "1016",
+    "author": "Andrew Ridley",
+    "width": 3844,
+    "height": 2563,
+    "url": "https://unsplash.com/photos/_h7aBovKia4",
+    "download_url": "https://picsum.photos/id/1018/3914/2935"
+  },
+  {
+    "id": "1018",
+    "author": "Andrew Ridley",
+    "width": 3914,
+    "height": 2935,
+    "url": "https://unsplash.com/photos/Kt5hRENuotI",
+    "download_url": "https://picsum.photos/id/1018/3914/2935"
+  },
+  {
+    "id": "1019",
+    "author": "Patrick Fore",
+    "width": 5472,
+    "height": 3648,
+    "url": "https://unsplash.com/photos/V6s1cmE39XM",
+    "download_url": "https://picsum.photos/id/1019/5472/3648"
+  }
+]
+```
+
+### 2. Define your api interface and annotate endpoint with `@mock("picsum_list.json")` so that Mockfit can generate config for you
+```kotlin
+interface Api {
+
+    @Mock("picsum_list.json")
+    @GET("list")
+    fun getListOfPicsums(
+        @Query("page") page: Int,
+        @Query("limit") limit: Int
+    ): Call<List<Picsum>>
+}
+```
+
+### 3. Add `MockfitInterceptor` to retrofit configuration
+```kotlin
+class RemoteDataSource(private val context: Context) {
+
+    fun api(): Api {
+        val mockFitInterceptor = provideMockFitInterceptor(context)
+        val okHttpClient = provideOkHttpClient(mockFitInterceptor)
+        val retrofit = provideRetrofit(okHttpClient)
+        return retrofit.create(Api::class.java)
+    }
+
+    private fun provideRetrofit(okHttpClient: OkHttpClient): Retrofit = Retrofit.Builder()
+        .baseUrl(BASE_URL)
+        .addConverterFactory(GsonConverterFactory.create())
+        .client(okHttpClient)
+        .build()
+
+    private fun provideMockFitInterceptor(context: Context) = MockFitInterceptor(
+        bodyFactory = { input -> context.resources.assets.open(input) }, // read asset file
+        logger = { tag, message -> Log.d(tag, message) }, // pass logger to log events in logcat
+        baseUrl = BASE_URL, // base url of your api
+        requestPathToJsonMap = REQUEST_TO_JSON, // autogenerated constant, just press build button
+        mockFilesPath = MOCK_FILES_PATH, // path to json files
+        mockFitEnable = true, // master setting to enable or disable mocking
+        apiEnableMock = true, // enable or disable mock when there are includes and excludes configs
+        apiIncludeIntoMock = arrayOf(), // include endpoint if `apiEnableMock` is false
+        apiExcludeFromMock = arrayOf(), // exclude endpoint if `apiEnableMock` is true 
+        apiResponseLatency = 500L // latency of retrieving data
+    )
+
+    private fun provideOkHttpClient(mockFitInterceptor: MockFitInterceptor) = OkHttpClient.Builder()
+        .addInterceptor(mockFitInterceptor)
+        .connectTimeout(CONNECT_TIMEOUT, TimeUnit.SECONDS)
+        .writeTimeout(WRITE_TIMEOUT, TimeUnit.SECONDS)
+        .readTimeout(READ_TIMEOUT, TimeUnit.SECONDS)
+        .build()
+
+    companion object {
+        private const val BASE_URL = "https://picsum.photos/v2/"
+        private const val MOCK_FILES_PATH = "mock_json" // located at assets/mock_json/
+        private const val CONNECT_TIMEOUT = 20L
+        private const val WRITE_TIMEOUT = 20L
+        private const val READ_TIMEOUT = 30L
+    }
+}
+```
+
+Now you can see your mock data in UI:
+
+<img src="https://user-images.githubusercontent.com/29440700/115327793-ce226080-a1a4-11eb-814b-5f58afbb5af6.png" width="256" height="455">