feat: Introduce Result type and update UI states

This commit introduces a generic `Result` sealed interface to represent success, error, and loading states for asynchronous operations. It also updates the home screen UI and ViewModel to utilize this `Result` type for displaying different states.

Key changes:
- Added `Result.kt` in `core:util` defining the `Result` sealed interface and an `asResult()` Flow extension.
- Updated `HomeScreenViewModel` to use `asResult()` and map the `ObserveAirportsUseCase` output to `HomeUiState` (Loading, Success, Error).
- Modified `HomeUiState` to be a sealed interface with `Loading`, `Success`, and `Error` subtypes.
- Updated `HomeScreen` to handle different `HomeUiState` values and display appropriate UI (Loading text, Error text, or list of airports).
- Added `core.util` dependency to `ui:home`.
- Updated Moshi and Retrofit Moshi converter dependencies in `model/data/api/build.gradle.kts` and `gradle/libs.versions.toml`.
- Added `moshi` and `moshiKotlinCodegen` versions to `gradle/libs.versions.toml`.
- Removed `converter-moshi` and added `retrofit-converter-moshi` in `gradle/libs.versions.toml`.
- Added `ksp(libs.moshi.kotlin.codegen)` to `model/data/api/build.gradle.kts`.
- Added `INTERNET` permission to `app/src/main/AndroidManifest.xml`.
- Updated `ObserveAirportsUseCaseImpl` to use `cacheKey` when setting airports info and to fetch airports for "pl" (lowercase).
- Added `.editorconfig` file with Kotlin trailing comma settings.

.editorconfig

@@ -0,0 +1,4 @@
+[*.{kt,kts}]
+ij_kotlin_allow_trailing_comma = true
+ij_kotlin_allow_trailing_comma_on_call_site = true
+

app/src/main/AndroidManifest.xml

@@ -2,6 +2,8 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools">
 
+    <uses-permission android:name="android.permission.INTERNET" />
+
     <application
         android:name=".MyApplication"
         android:allowBackup="true"

core/util/src/main/kotlin/dev/adriankuta/flights/core/util/Result.kt

@@ -0,0 +1,16 @@
+package dev.adriankuta.flights.core.util
+
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.catch
+import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.onStart
+
+sealed interface Result<out T> {
+    data class Success<T>(val data: T) : Result<T>
+    data class Error(val exception: Throwable) : Result<Nothing>
+    data object Loading : Result<Nothing>
+}
+
+fun <T> Flow<T>.asResult(): Flow<Result<T>> = map<T, Result<T>> { Result.Success(it) }
+    .onStart { emit(Result.Loading) }
+    .catch { emit(Result.Error(it)) }

gradle/libs.versions.toml

@@ -33,6 +33,8 @@ kotlinxSerializationJson = "1.8.1"
 ksp = "2.1.21-2.0.1" # https://github.com/google/ksp/releases
 material = "1.12.0"
 mockk = "1.14.2" # https://github.com/mockk/mockk/releases
+moshi = "1.15.2"
+moshiKotlinCodegen = "1.15.2"
 okhttpBom = "4.12.0"
 retrofit = "3.0.0"
 secrets = "2.0.1"
@@ -73,7 +75,6 @@ androidx-test-uiautomator = { module = "androidx.test.uiautomator:uiautomator",
 androidx-ui-text-google-fonts = { module = "androidx.compose.ui:ui-text-google-fonts", version.ref = "uiTextGoogleFonts" }
 app-update-ktx = { module = "com.google.android.play:app-update-ktx", version.ref = "appUpdateKtx" }
 appcompat = { group = "androidx.appcompat", name = "appcompat", version.ref = "appcompat" }
-converter-moshi = { module = "com.squareup.retrofit2:converter-moshi", version.ref = "converterMoshi" }
 detekt-compose = { module = "io.nlopez.compose.rules:detekt", version.ref = "detektCompose" }
 detekt-ktlint = { module = "io.gitlab.arturbosch.detekt:detekt-formatting", version.ref = "detekt" }
 gson = { group = "com.google.code.gson", name = "gson", version.ref = "gson" }
@@ -89,10 +90,13 @@ kotlinx-datetime = { module = "org.jetbrains.kotlinx:kotlinx-datetime", version.
 kotlinx-serialization-json = { group = "org.jetbrains.kotlinx", name = "kotlinx-serialization-json", version.ref = "kotlinxSerializationJson" }
 material = { group = "com.google.android.material", name = "material", version.ref = "material" }
 mockk-android = { module = "io.mockk:mockk-android", version.ref = "mockk" }
+moshi = { module = "com.squareup.moshi:moshi", version.ref = "moshi" }
+moshi-kotlin-codegen = { module = "com.squareup.moshi:moshi-kotlin-codegen", version.ref = "moshiKotlinCodegen" }
 okhttp = { module = "com.squareup.okhttp3:okhttp" }
 okhttp-bom = { module = "com.squareup.okhttp3:okhttp-bom", version.ref = "okhttpBom" }
 okhttp-logging-interceptor = { module = "com.squareup.okhttp3:logging-interceptor" }
 retrofit = { module = "com.squareup.retrofit2:retrofit", version.ref = "retrofit" }
+retrofit-converter-moshi = { module = "com.squareup.retrofit2:converter-moshi", version.ref = "converterMoshi" }
 timber = { group = "com.jakewharton.timber", name = "timber", version.ref = "timber" }
 truth = { module = "com.google.truth:truth", version.ref = "truth" }
 

model/data/api/build.gradle.kts

@@ -12,10 +12,12 @@ dependencies {
 
     implementation(platform(libs.okhttp.bom))
 
-    implementation(libs.converter.moshi)
+    implementation(libs.moshi)
     implementation(libs.okhttp)
     implementation(libs.okhttp.logging.interceptor)
     implementation(libs.retrofit)
+    implementation(libs.retrofit.converter.moshi)
+    ksp(libs.moshi.kotlin.codegen)
 
     implementation(libs.timber)
     implementation(libs.gson)

model/repository/src/main/kotlin/dev/adriankuta/flights/model/repository/usecases/ObserveAirportsUseCaseImpl.kt

@@ -15,9 +15,9 @@ internal class ObserveAirportsUseCaseImpl @Inject constructor(
     private val airportsDatasource: AirportsDatasource,
 ) : ObserveAirportsUseCase {
     override fun invoke(): Flow<List<AirportInfo>?> = loadData(
-        onCacheInvalidated = {
-            val response = airportService.getAirports("PL")
-            airportsDatasource.setAirportsInfo(response, "PL")
+        onCacheInvalidated = { cacheKey ->
+            val response = airportService.getAirports("pl")
+            airportsDatasource.setAirportsInfo(response, cacheKey)
         },
         observeCache = {
             airportsDatasource.airports

ui/home/build.gradle.kts

@@ -9,6 +9,7 @@ android {
 }
 
 dependencies {
+    implementation(projects.core.util)
     implementation(projects.ui.designsystem)
     implementation(projects.domain.search)
 

ui/home/src/main/kotlin/dev/adriankuta/flights/ui/home/HomeScreen.kt

@@ -8,7 +8,6 @@ import androidx.compose.runtime.getValue
 import androidx.compose.ui.Modifier
 import androidx.hilt.navigation.compose.hiltViewModel
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
-import dev.adriankuta.flights.domain.types.AirportInfo
 import dev.adriankuta.flights.ui.designsystem.theme.FlightsTheme
 import dev.adriankuta.flights.ui.designsystem.theme.PreviewDevices
 
@@ -19,18 +18,24 @@ internal fun HomeScreen(
     val homeUiState by viewModel.uiState.collectAsStateWithLifecycle()
 
     HomeScreen(
-        airports = homeUiState.airports
+        uiState = homeUiState,
     )
 }
 
 @Composable
 private fun HomeScreen(
-    airports: List<AirportInfo>,
+    uiState: HomeUiState,
     modifier: Modifier = Modifier,
 ) {
-    LazyColumn {
-        items(airports) { airport ->
-            Text(airport.name)
+    LazyColumn(
+        modifier = modifier,
+    ) {
+        when (uiState) {
+            is HomeUiState.Error -> item { Text("Error") }
+            HomeUiState.Loading -> item { Text("Loading") }
+            is HomeUiState.Success -> items(uiState.airports) { airport ->
+                Text(airport.name)
+            }
         }
     }
 }
@@ -40,7 +45,7 @@ private fun HomeScreen(
 private fun HomeScreenPreview() {
     FlightsTheme {
         HomeScreen(
-            airports = listOf()
+            uiState = HomeUiState.Loading,
         )
     }
 }

ui/home/src/main/kotlin/dev/adriankuta/flights/ui/home/HomeScreenViewModel.kt

@@ -3,17 +3,15 @@ package dev.adriankuta.flights.ui.home
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import dagger.hilt.android.lifecycle.HiltViewModel
+import dev.adriankuta.flights.core.util.Result
+import dev.adriankuta.flights.core.util.asResult
 import dev.adriankuta.flights.domain.search.ObserveAirportsUseCase
 import dev.adriankuta.flights.domain.types.AirportInfo
-import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.SharingStarted
-import kotlinx.coroutines.flow.flatMapLatest
-import kotlinx.coroutines.flow.flow
 import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.stateIn
 import javax.inject.Inject
-import kotlin.time.Duration.Companion.seconds
 
 @HiltViewModel
 class HomeScreenViewModel @Inject constructor(
@@ -26,7 +24,7 @@ class HomeScreenViewModel @Inject constructor(
         .stateIn(
             scope = viewModelScope,
             started = SharingStarted.WhileSubscribed(5_000),
-            initialValue = HomeUiState(),
+            initialValue = HomeUiState.Loading,
         )
 }
 
@@ -34,14 +32,19 @@ private fun homeUiState(
     useCase: ObserveAirportsUseCase
 ): Flow<HomeUiState> {
 
-    return flow {
-        delay(15.seconds)
-        emit("")
-    }.flatMapLatest { useCase() }.map {
-        HomeUiState(it.orEmpty())
-    }
+    return useCase()
+        .asResult()
+        .map { result ->
+            when (result) {
+                is Result.Error -> HomeUiState.Error(result.exception)
+                Result.Loading -> HomeUiState.Loading
+                is Result.Success -> HomeUiState.Success(result.data.orEmpty())
+            }
+        }
 }
 
-internal data class HomeUiState(
-    val airports: List<AirportInfo> = emptyList()
-)
+internal sealed interface HomeUiState {
+    data object Loading : HomeUiState
+    data class Success(val airports: List<AirportInfo>) : HomeUiState
+    data class Error(val exception: Throwable) : HomeUiState
+}