Add Demo code to README

README.md

@@ -11,7 +11,226 @@ _Recommendation: Use _it alongside Jetpack Compose_._
 
 ## Demo
 
-_:construction: WIP :construction:_
+### Imaginary Weather app :cloud::sunny::umbrella:
+
+> TL;DR: You'll find the code of the entire weather app below. If you're already sold to use Ivy FRP => skip to Installation.
+
+#### Data (boring)
+```Kotlin
+data class Temperature(
+    val value: Float,
+    val unit: TemperatureUnit
+)
+
+enum class TemperatureUnit {
+    CELSIUS, FAHRENHEIT
+}
+
+data class UserPreference(
+    val temperatureUnit: TemperatureUnit
+)
+```
+
+#### IO (boring)
+```Kotlin
+data class WeatherResponse(
+    val temperature: Temperature
+)
+
+interface WeatherService {
+    @GET("/api/weather")
+    suspend fun getWeather(): WeatherResponse
+}
+
+interface UserPreferenceService {
+    @GET("/preference/temp-unit")
+    suspend fun getTempUnit(): UserPreference
+
+    @POST("/preference/temp-unit")
+    suspend fun updateTempUnit(
+        @Query("unit") temperatureUnit: TemperatureUnit
+    )
+}
+```
+
+#### Actions
+**ConvertTempAct.kt**
+```Kotlin
+class ConvertTempAct @Inject constructor() : FPAction<ConvertTempAct.Input, Temperature>() {
+
+    override suspend fun Input.compose(): suspend () -> Temperature =
+        this asParamTo ::convertValue then { convertedValue ->
+            Temperature(convertedValue, toUnit)
+        }
+
+    private fun convertValue(input: Input): Float = with(input.temperature) {
+        if (unit == input.toUnit) value else {
+            when (input.toUnit) {
+                TemperatureUnit.CELSIUS -> fahrenheitToCelsius(value)
+                TemperatureUnit.FAHRENHEIT -> celsiusToFahrenheit(value)
+            }
+        }
+    }
+
+    //X°F = (Y°C × 9/5) + 32
+    private fun celsiusToFahrenheit(celsius: Float): Float = (celsius * 9 / 5) + 32
+
+    //X°C = (Y°F - 32) / (9/5)
+    private fun fahrenheitToCelsius(fahrenheit: Float): Float = (fahrenheit - 32) / (9 / 5)
+
+    data class Input(
+        val temperature: Temperature,
+        val toUnit: TemperatureUnit
+    )
+}
+```
+
+**CurrentTempAct.kt**
+```Kotlin
+class CurrentTempAct @Inject constructor(
+    private val weatherService: WeatherService,
+    private val convertTempAct: ConvertTempAct
+) : FPAction<TemperatureUnit, Res<String, Temperature>>() {
+    override suspend fun TemperatureUnit.compose(): suspend () -> Res<String, Temperature> = tryOp(
+        operation = weatherService::getWeather
+    ) mapSuccess { response ->
+        ConvertTempAct.Input(
+            temperature = response.temperature,
+            toUnit = this //TemperatureUnit
+        )
+    } mapSuccess convertTempAct mapError {
+        "Failed to fetch weather: ${it.message}"
+    }
+}
+```
+
+**UserPreferencesAct.kt**
+```Kotlin
+class UserPreferenceAct @Inject constructor(
+    private val userPreferenceService: UserPreferenceService
+) : FPAction<Unit, Res<String, UserPreference>>() {
+    override suspend fun Unit.compose(): suspend () -> Res<String, UserPreference> = tryOp(
+        operation = userPreferenceService::getTempUnit
+    ) mapError {
+        "Failed to fetch user's preference: ${it.message}"
+    }
+}
+```
+
+**UpdateUserPreferencesAct.kt**
+```Kotlin
+class UpdateUserPreferenceAct @Inject constructor(
+    private val userPreferenceService: UserPreferenceService
+) : FPAction<TemperatureUnit, Res<String, Unit>>() {
+    override suspend fun TemperatureUnit.compose(): suspend () -> Res<String, Unit> = tryOp(
+        operation = this asParamTo userPreferenceService::updateTempUnit
+    ) mapError {
+        "Failed to update user preference: ${it.message}"
+    }
+}
+```
+
+#### ViewModel
+
+**WeatherState.kt**
+```Kotlin
+sealed class WeatherState {
+    object Loading : WeatherState()
+
+    data class Error(val errReason: String) : WeatherState()
+
+    data class Success(
+        val tempUnit: TemperatureUnit,
+        val temp: Float
+    ) : WeatherState()
+}
+```
+
+**WeatherEvent.kt**
+```Kotlin
+sealed class WeatherEvent {
+    object LoadWeather : WeatherEvent()
+
+    data class UpdateTempUnit(val unit: TemperatureUnit) : WeatherEvent()
+}
+```
+
+**WeatherViewModel.kt**
+```Kotlin
+@HiltViewModel
+class WeatherViewModel @Inject constructor(
+    private val userPreferenceAct: UserPreferenceAct,
+    private val updateUserPreferenceAct: UpdateUserPreferenceAct,
+    private val currentTempAct: CurrentTempAct,
+) : FRPViewModel<WeatherState, WeatherEvent>() {
+    override val _state: MutableStateFlow<WeatherState> = MutableStateFlow(WeatherState.Loading)
+
+    override suspend fun handleEvent(event: WeatherEvent): suspend () -> WeatherState =
+        when (event) {
+            is WeatherEvent.LoadWeather -> loadWeather()
+            is WeatherEvent.UpdateTempUnit -> updateTempUnit(event)
+        }
+
+    private suspend fun loadWeather(): suspend () -> WeatherState = suspend {
+        updateState { WeatherState.Loading }
+        Unit
+    } then userPreferenceAct mapSuccess {
+        it.temperatureUnit //loadTempFor() expects TemperatureUnit
+    } then ::loadTempFor
+
+    private suspend fun updateTempUnit(
+        event: WeatherEvent.UpdateTempUnit
+    ): suspend () -> WeatherState = suspend {
+        updateState { WeatherState.Loading }
+        event.unit
+    } then updateUserPreferenceAct mapSuccess {
+        event.unit
+    } then ::loadTempFor
+
+    private suspend fun loadTempFor(tempRes: Res<String, TemperatureUnit>) =
+        tempRes.lambda() thenIfSuccess currentTempAct thenInvokeAfter {
+            when (it) {
+                is Res.Ok -> WeatherState.Success(
+                    temp = it.data.value,
+                    tempUnit = it.data.unit
+                )
+                is Res.Err -> WeatherState.Error(errReason = it.error)
+            }
+        }
+}
+```
+
+#### UI
+
+**WeatherScreen.kt**
+```Kotlin
+data class WeatherScreen(
+    val title: String
+) : Screen
+
+@Composable
+fun BoxWithConstraintsScope.WeatherScreen(screen: WeatherScreen) {
+    FRP<WeatherState, WeatherEvent, WeatherViewModel>(
+        initialEvent = WeatherEvent.LoadWeather
+    ) { state, onEvent ->
+        UI(title = screen.title, state = state, onEvent = onEvent)
+    }
+}
+
+@Composable
+private fun UI(
+    title: String,
+    state: WeatherState,
+
+    onEvent: (WeatherEvent) -> Unit
+) {
+    //UI goes here.....
+    //When Celsius is clicked:
+    // onEvent(WeatherEvent.UpdateTempUnit(TemperatureUnit.CELSIUS))
+}
+```
+
+Find the full sample **[here](sample/src/main/java/com/ivy/sample/demo/weather)**.
 
 ### Key Features
 
@@ -23,7 +242,7 @@ _:construction: WIP :construction:_
 - `@Composable FRP<State, Event>(){ UI() }`: functional-reactive UI implementation in Jetpack
   Compose.
 - `Res.Ok / Res.Err` result type: monadic result type supporting success and error composition.
-    - `thenR`: calls the next function only on success (OK)
+    - `thenIfSuccess`: calls the next function only on success (OK)
     - `mapSuccess`: maps only the success type if the result is OK
     - `mapError`: maps only the error type if the result is Err
 
@@ -106,7 +325,7 @@ implementation("com.githubILIYANGERMANOV:ivy-frp:0.0.0")
 implementation 'com.githubILIYANGERMANOV:ivy-frp:0.0.0'
 ```
 
-## Usage
+## Docs
 
 ### _:construction: WIP... :construction:_
 

sample/src/main/java/com/ivy/sample/demo/weather/ui/WeatherViewModel.kt

@@ -55,5 +55,4 @@ class WeatherViewModel @Inject constructor(
                 is Res.Err -> WeatherState.Error(errReason = it.error)
             }
         }
-
 }