use json polymorphic serialization to serialize ScreenParams. remove …

…paramsAsString

composables/src/commonMain/kotlin/eu/baroncelli/dkmpsample/composables/navigation/Router.kt

@@ -12,7 +12,7 @@ import eu.baroncelli.dkmpsample.composables.navigation.templates.TwoPane
 import eu.baroncelli.dkmpsample.shared.viewmodel.*
 import eu.baroncelli.dkmpsample.shared.viewmodel.screens.Level1Navigation
 import eu.baroncelli.dkmpsample.shared.viewmodel.screens.Screen
-
+import eu.baroncelli.dkmpsample.shared.viewmodel.screens.ScreenParams
 
 
 @Composable

composables/src/commonMain/kotlin/eu/baroncelli/dkmpsample/composables/navigation/ScreenPicker.kt

@@ -4,17 +4,18 @@ import androidx.compose.foundation.layout.Box
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
-import eu.baroncelli.dkmpsample.composables.screens.countrydetail.CountryDetailScreen
 import eu.baroncelli.dkmpsample.composables.screens.countrieslist.CountriesListScreen
 import eu.baroncelli.dkmpsample.composables.screens.countrieslist.CountriesListTwoPaneDefaultDetail
+import eu.baroncelli.dkmpsample.composables.screens.countrydetail.CountryDetailScreen
 import eu.baroncelli.dkmpsample.shared.viewmodel.Navigation
 import eu.baroncelli.dkmpsample.shared.viewmodel.ScreenIdentifier
-import eu.baroncelli.dkmpsample.shared.viewmodel.ScreenParams
+import eu.baroncelli.dkmpsample.shared.viewmodel.screens.CountryDetailParams
 import eu.baroncelli.dkmpsample.shared.viewmodel.screens.Screen
-import eu.baroncelli.dkmpsample.shared.viewmodel.screens.Screen.*
+import eu.baroncelli.dkmpsample.shared.viewmodel.screens.Screen.CountriesList
+import eu.baroncelli.dkmpsample.shared.viewmodel.screens.Screen.CountryDetail
+import eu.baroncelli.dkmpsample.shared.viewmodel.screens.ScreenParams
 import eu.baroncelli.dkmpsample.shared.viewmodel.screens.countrieslist.CountriesListState
 import eu.baroncelli.dkmpsample.shared.viewmodel.screens.countrieslist.selectFavorite
-import eu.baroncelli.dkmpsample.shared.viewmodel.screens.countrydetail.CountryDetailParams
 import eu.baroncelli.dkmpsample.shared.viewmodel.screens.countrydetail.CountryDetailState
 
 
@@ -50,7 +51,6 @@ fun Navigation.ScreenPicker(
 }
 
 
-
 @Composable
 fun Navigation.TwoPaneDefaultDetail(
     screenIdentifier: ScreenIdentifier
@@ -61,7 +61,7 @@ fun Navigation.TwoPaneDefaultDetail(
         CountriesList ->
             CountriesListTwoPaneDefaultDetail()
 
-        else -> Box{}
+        else -> Box {}
     }
 
 }

shared/src/commonMain/kotlin/eu/baroncelli/dkmpsample/shared/datalayer/sources/localsettings/MySettings.kt

@@ -5,7 +5,7 @@ import com.russhwolf.settings.long
 import com.russhwolf.settings.string
 import eu.baroncelli.dkmpsample.shared.viewmodel.screens.Level1Navigation
 
-class MySettings (s : Settings) {
+class MySettings(private val s: Settings) {
 
 
     // here we define all our local settings properties,
@@ -14,5 +14,5 @@ class MySettings (s : Settings) {
     var listCacheTimestamp by s.long(defaultValue = 0)
     var savedLevel1URI by s.string(defaultValue = Level1Navigation.AllCountries.screenIdentifier.URI)
 
-
+    fun clear() = s.clear()
 }

shared/src/commonMain/kotlin/eu/baroncelli/dkmpsample/shared/viewmodel/Navigation.kt

@@ -46,7 +46,16 @@ class Navigation(val stateManager : StateManager) {
     fun getStartScreenIdentifier() : ScreenIdentifier {
         var startScreenIdentifier = navigationSettings.homeScreen.screenIdentifier
         if (navigationSettings.saveLastLevel1Screen) {
-            startScreenIdentifier = ScreenIdentifier.getByURI(savedLevel1URI) ?: startScreenIdentifier
+            startScreenIdentifier = try {
+                ScreenIdentifier.getByURI(savedLevel1URI) ?: startScreenIdentifier
+            } catch (e: ScreenParamsDeserializationException) {
+                stateManager.dataRepository.localSettings.clear()
+                throw ScreenParamsDeserializationException(
+                    "Failed to deserialize params for screen: ${startScreenIdentifier.screen.asString}. " +
+                            "Local settings have been reset. Please restart the app.",
+                    e
+                )
+            }
         }
         return startScreenIdentifier
     }

shared/src/commonMain/kotlin/eu/baroncelli/dkmpsample/shared/viewmodel/ScreenIdentifier.kt

@@ -3,76 +3,88 @@ package eu.baroncelli.dkmpsample.shared.viewmodel
 import eu.baroncelli.dkmpsample.shared.viewmodel.screens.Level1Navigation
 import eu.baroncelli.dkmpsample.shared.viewmodel.screens.Screen
 import eu.baroncelli.dkmpsample.shared.viewmodel.screens.ScreenInitSettings
-import kotlinx.serialization.decodeFromString
+import eu.baroncelli.dkmpsample.shared.viewmodel.screens.ScreenParams
+import kotlinx.serialization.encodeToString
 import kotlinx.serialization.json.Json
 
 typealias URI = String
 
+class ScreenParamsDeserializationException(message: String? = null, cause: Throwable? = null) :
+    Exception(message, cause)
+
 class ScreenIdentifier private constructor(
-    val screen : Screen,
+    val screen: Screen,
     var params: ScreenParams? = null,
-    var paramsAsString: String? = null,
 ) {
-
-    val URI : URI
+    val URI: URI
         get() = returnURI()
 
+
     companion object Factory {
+
+        internal val json = Json
+
         fun get(screen: Screen, params: ScreenParams?): ScreenIdentifier {
-            return ScreenIdentifier(screen, params, null)
+            return ScreenIdentifier(screen, params)
         }
+
         fun getByURI(URI: String): ScreenIdentifier? {
-            val parts = URI.split(":")
-            Screen.values().forEach {
-                if (it.asString == parts[0]) {
-                    return ScreenIdentifier(it, null, parts[1])
+            val splitAt = URI.indexOf(':')
+            val part0 = URI.substring(0, splitAt)
+            val part1 = URI.substring(splitAt + 1)
+            Screen.entries.forEach {
+                if (it.asString == part0) {
+                    val jsonString = if (part1 == "null") null else part1
+                    val params: ScreenParams? = try {
+                        jsonString?.let { json.decodeFromString(jsonString) }
+                    } catch (t: Throwable) {
+                        throw ScreenParamsDeserializationException(
+                            "Failed to deserialize params for screen: ${it.asString}",
+                            t
+                        )
+                    }
+                    return get(it, params)
                 }
             }
             return null
         }
 
     }
 
-    private fun returnURI() : String {
-        if (paramsAsString != null) {
-            return screen.asString + ":" + paramsAsString
+    private fun returnURI(): String {
+        val paramsString = if (params != null) {
+            json.encodeToString(params)
+        } else {
+            "null"
         }
-        val toString = params.toString() // returns `ClassParams(A=1&B=2)`
-        val startIndex = toString.indexOf("(")
-        val paramsString = toString.substring(startIndex + 1, toString.length - 1)
-        return screen.asString  + ":" + paramsString
+        return screen.asString + ":" + paramsString
     }
 
     // unlike the "params" property, this reified function returns the specific type and not the generic "ScreenParams" interface type
-    inline fun <reified T: ScreenParams> params() : T {
-        if (params == null && paramsAsString != null) {
-            val jsonValues = paramsStrToJson(paramsAsString!!)
-            params = Json.decodeFromString<T>("""{$jsonValues}""")
-        }
-        return params as T
-    }
-
-    fun paramsStrToJson(paramsAsString: String) : String {
-        // converts `A=1&B=1` into `"A":"1","B":"2"`
-        val elements = paramsAsString.split("&")
-        var jsonValues = ""
-        elements.forEach {
-            if (jsonValues!="") {
-                jsonValues += ","
+    inline fun <reified T : ScreenParams> params(): T {
+        return try {
+            params as T
+        } catch (t: Throwable) {
+            if (screen.navigationLevel == 1) {
+                val defaultParams = Level1Navigation.entries.first {
+                    it.screenIdentifier.screen.asString == screen.asString
+                }.screenIdentifier.params
+                debugLogger.log(
+                    "Warning: Failed to cast params: $params as ${T::class} returning default L1 params for screen: " + "$defaultParams"
+                )
+                defaultParams as T
+            } else {
+                throw t
             }
-            val parts = it.split("=")
-            jsonValues += "\"${parts[0]}\":\"${parts[1]}\""
         }
-        return jsonValues
     }
 
-
-    fun getScreenInitSettings(stateManager: StateManager) : ScreenInitSettings {
-        return screen.initSettings(stateManager,this)
+    fun getScreenInitSettings(stateManager: StateManager): ScreenInitSettings {
+        return screen.initSettings(stateManager, this)
     }
 
-    fun level1VerticalBackstackEnabled() : Boolean {
-        Level1Navigation.values().forEach {
+    fun level1VerticalBackstackEnabled(): Boolean {
+        Level1Navigation.entries.forEach {
             if (it.screenIdentifier.URI == this.URI && it.rememberVerticalStack) {
                 return true
             }

shared/src/commonMain/kotlin/eu/baroncelli/dkmpsample/shared/viewmodel/StateManager.kt

@@ -9,7 +9,6 @@ import kotlin.reflect.KClass
 
 
 interface ScreenState
-interface ScreenParams
 
 class StateManager(repo: Repository) {
 

shared/src/commonMain/kotlin/eu/baroncelli/dkmpsample/shared/viewmodel/screens/NavigationSettings.kt

@@ -1,9 +1,9 @@
 package eu.baroncelli.dkmpsample.shared.viewmodel.screens
 
 import eu.baroncelli.dkmpsample.shared.viewmodel.ScreenIdentifier
-import eu.baroncelli.dkmpsample.shared.viewmodel.screens.Screen.*
-import eu.baroncelli.dkmpsample.shared.viewmodel.screens.countrieslist.CountriesListParams
-import eu.baroncelli.dkmpsample.shared.viewmodel.screens.countrieslist.CountriesListType.*
+import eu.baroncelli.dkmpsample.shared.viewmodel.screens.Screen.CountriesList
+import eu.baroncelli.dkmpsample.shared.viewmodel.screens.countrieslist.CountriesListType.ALL
+import eu.baroncelli.dkmpsample.shared.viewmodel.screens.countrieslist.CountriesListType.FAVORITES
 
 
 // CONFIGURATION SETTINGS
@@ -18,6 +18,6 @@ object navigationSettings {
 // LEVEL 1 NAVIGATION OF THE APP
 
 enum class Level1Navigation(val screenIdentifier: ScreenIdentifier, val rememberVerticalStack: Boolean = false) {
-    AllCountries( ScreenIdentifier.get(CountriesList, CountriesListParams(listType = ALL)), true),
-    FavoriteCountries( ScreenIdentifier.get(CountriesList, CountriesListParams(listType = FAVORITES)), true),
+    AllCountries(ScreenIdentifier.get(CountriesList, CountriesListParams(listType = ALL)), true),
+    FavoriteCountries(ScreenIdentifier.get(CountriesList, CountriesListParams(listType = FAVORITES)), true),
 }

shared/src/commonMain/kotlin/eu/baroncelli/dkmpsample/shared/viewmodel/screens/ScreenParams.kt

@@ -0,0 +1,25 @@
+package eu.baroncelli.dkmpsample.shared.viewmodel.screens
+
+
+import eu.baroncelli.dkmpsample.shared.viewmodel.screens.countrieslist.CountriesListType
+import kotlinx.serialization.Serializable
+
+/***
+ * [ScreenParams] is an interface which defines the parameters to the passed to the screen if any are needed.
+ * Each class which implements it should be a data class and should always be set as [Serializable]
+ *
+ * Note: we are defining all implementations here instead of inside a screen's
+ * eu.baroncelli.dkmpsample.shared.viewmodel.screens.`screen-name` subpackage, because all classes implementing
+ * a sealed interface must be in the same package. The reason we are using a sealed interface is that it
+ * allows the list of ScreenParams subclasses that can be serialized in a polymorphic way to be
+ * determined at compile time vs having to explicitly registered them at runtime.
+ * See: https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/polymorphism.md#open-polymorphism
+ */
+@Serializable
+sealed interface ScreenParams
+
+@Serializable
+data class CountriesListParams(val listType: CountriesListType) : ScreenParams
+
+@Serializable
+data class CountryDetailParams(val countryName: String) : ScreenParams

shared/src/commonMain/kotlin/eu/baroncelli/dkmpsample/shared/viewmodel/screens/countrieslist/CountriesListInit.kt

@@ -2,23 +2,18 @@ package eu.baroncelli.dkmpsample.shared.viewmodel.screens.countrieslist
 
 import eu.baroncelli.dkmpsample.shared.datalayer.functions.getCountriesListData
 import eu.baroncelli.dkmpsample.shared.datalayer.functions.getFavoriteCountriesMap
-import eu.baroncelli.dkmpsample.shared.viewmodel.ScreenParams
 import eu.baroncelli.dkmpsample.shared.viewmodel.StateManager
-import eu.baroncelli.dkmpsample.shared.viewmodel.debugLogger
 import eu.baroncelli.dkmpsample.shared.viewmodel.screens.CallOnInitValues
+import eu.baroncelli.dkmpsample.shared.viewmodel.screens.CountriesListParams
 import eu.baroncelli.dkmpsample.shared.viewmodel.screens.ScreenInitSettings
-import kotlinx.serialization.Serializable
 
 // INIZIALIZATION settings for this screen
 // this is what should be implemented:
 // - a data class implementing the ScreenParams interface, which defines the parameters to the passed to the screen
 // - Navigation extension function taking the ScreenParams class as an argument, return the ScreenInitSettings for this screen
 // to understand the initialization behaviour, read the comments in the ScreenInitSettings.kt file
 
-@Serializable // Note: ScreenParams should always be set as Serializable
-data class CountriesListParams(val listType: CountriesListType) : ScreenParams
-
-fun StateManager.initCountriesList(params: CountriesListParams) = ScreenInitSettings (
+fun StateManager.initCountriesList(params: CountriesListParams) = ScreenInitSettings(
     title = "Countries: " + params.listType.name,
     initState = { CountriesListState(isLoading = true) },
     callOnInit = {
@@ -38,7 +33,7 @@ fun StateManager.initCountriesList(params: CountriesListParams) = ScreenInitSett
         }
     },
     callOnInitAtEachNavigation = CallOnInitValues.CALL_BEFORE_SHOWING_SCREEN
-        // enabling in this way favourites can refresh at each navigation
-        // CALL_BEFORE_SHOWING_SCREEN is used, as favourites come from the local storage and not from the network
-        // (for more information about "callOnInitAtEachNavigation" values, look at "ScreenInitSettings" class definition)
+    // enabling in this way favourites can refresh at each navigation
+    // CALL_BEFORE_SHOWING_SCREEN is used, as favourites come from the local storage and not from the network
+    // (for more information about "callOnInitAtEachNavigation" values, look at "ScreenInitSettings" class definition)
 )

shared/src/commonMain/kotlin/eu/baroncelli/dkmpsample/shared/viewmodel/screens/countrydetail/CountryDetailInit.kt

@@ -1,20 +1,15 @@
 package eu.baroncelli.dkmpsample.shared.viewmodel.screens.countrydetail
 
 import eu.baroncelli.dkmpsample.shared.datalayer.functions.getCountryInfo
-import eu.baroncelli.dkmpsample.shared.viewmodel.Navigation
-import eu.baroncelli.dkmpsample.shared.viewmodel.ScreenParams
 import eu.baroncelli.dkmpsample.shared.viewmodel.StateManager
+import eu.baroncelli.dkmpsample.shared.viewmodel.screens.CountryDetailParams
 import eu.baroncelli.dkmpsample.shared.viewmodel.screens.ScreenInitSettings
-import kotlinx.serialization.Serializable
 
 
 // INIZIALIZATION settings for this screen
 // to understand the initialization behaviour, read the comments in the ScreenInitSettings.kt file
 
-@Serializable // Note: ScreenParams should always be set as Serializable
-data class CountryDetailParams(val countryName: String) : ScreenParams
-
-fun StateManager.initCountryDetail(params: CountryDetailParams) = ScreenInitSettings (
+fun StateManager.initCountryDetail(params: CountryDetailParams) = ScreenInitSettings(
     title = params.countryName,
     initState = { CountryDetailState(isLoading = true) },
     callOnInit = {