EditCalendarActvivity: Switch to compose state and kotlin flows

app/src/main/java/at/bitfire/icsdroid/model/EditCalendarModel.kt

@@ -0,0 +1,99 @@
+package at.bitfire.icsdroid.model
+
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
+import at.bitfire.icsdroid.db.dao.SubscriptionsDao
+import at.bitfire.icsdroid.db.entity.Credential
+import at.bitfire.icsdroid.db.entity.Subscription
+import kotlinx.coroutines.launch
+
+class EditCalendarModel(
+    val editSubscriptionModel: EditSubscriptionModel,
+    val subscriptionSettingsModel: SubscriptionSettingsModel,
+    val credentialsModel: CredentialsModel
+): ViewModel() {
+
+    private var initialSubscription: Subscription? = null
+    private var initialCredential: Credential? = null
+    private var initialRequiresAuthValue: Boolean? = null
+
+    init {
+        // Initialise view models and save their initial state
+        viewModelScope.launch {
+            editSubscriptionModel.subscriptionWithCredential.collect { data ->
+                if (data != null)
+                    onSubscriptionLoaded(data)
+            }
+        }
+    }
+
+    /**
+     * Whether user input is error free
+     */
+    val inputValid: Boolean
+        @Composable
+        get() = remember(subscriptionSettingsModel.uiState, credentialsModel.uiState) {
+            val title = subscriptionSettingsModel.uiState.title
+            val requiresAuth = credentialsModel.uiState.requiresAuth
+            val username = credentialsModel.uiState.username
+            val password = credentialsModel.uiState.password
+
+            val titleOK = !title.isNullOrBlank()
+            val authOK = if (requiresAuth)
+                !username.isNullOrBlank() && !password.isNullOrBlank()
+            else
+                true
+            titleOK && authOK
+        }
+
+    /**
+     * Whether there are unsaved user changes
+     */
+    val modelsDirty: Boolean
+        @Composable
+        get() = remember(subscriptionSettingsModel.uiState, credentialsModel.uiState) {
+            val requiresAuth = credentialsModel.uiState.requiresAuth
+
+            val credentialsDirty = initialRequiresAuthValue != requiresAuth ||
+                    initialCredential?.let { !credentialsModel.equalsCredential(it) } ?: false
+            val subscriptionsDirty = initialSubscription?.let {
+                !subscriptionSettingsModel.equalsSubscription(it)
+            } ?: false
+
+            credentialsDirty || subscriptionsDirty
+        }
+
+    /**
+     * Initialise view models and remember their initial state
+     */
+    private fun onSubscriptionLoaded(subscriptionWithCredential: SubscriptionsDao.SubscriptionWithCredential) {
+        val subscription = subscriptionWithCredential.subscription
+
+        subscriptionSettingsModel.setUrl(subscription.url.toString())
+        subscription.displayName.let {
+            subscriptionSettingsModel.setTitle(it)
+        }
+        subscription.color.let(subscriptionSettingsModel::setColor)
+        subscription.ignoreEmbeddedAlerts.let(subscriptionSettingsModel::setIgnoreAlerts)
+        subscription.defaultAlarmMinutes?.toString().let(subscriptionSettingsModel::setDefaultAlarmMinutes)
+        subscription.defaultAllDayAlarmMinutes?.toString()?.let(subscriptionSettingsModel::setDefaultAllDayAlarmMinutes)
+        subscription.ignoreDescription.let(subscriptionSettingsModel::setIgnoreDescription)
+
+        val credential = subscriptionWithCredential.credential
+        val requiresAuth = credential != null
+        credentialsModel.setRequiresAuth(requiresAuth)
+
+        if (credential != null) {
+            credential.username.let(credentialsModel::setUsername)
+            credential.password.let(credentialsModel::setPassword)
+        }
+
+        // Save state, before user makes changes
+        initialSubscription = subscription
+        initialCredential = credential
+        initialRequiresAuthValue = credentialsModel.uiState.requiresAuth
+    }
+
+}