Create a reusable selectusers feature module

features/selectusers/impl/src/main/AndroidManifest.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ Copyright (c) 2023 New Vector Ltd
+  ~
+  ~ Licensed under the Apache License, Version 2.0 (the "License");
+  ~ you may not use this file except in compliance with the License.
+  ~ You may obtain a copy of the License at
+  ~
+  ~     http://www.apache.org/licenses/LICENSE-2.0
+  ~
+  ~ Unless required by applicable law or agreed to in writing, software
+  ~ distributed under the License is distributed on an "AS IS" BASIS,
+  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  ~ See the License for the specific language governing permissions and
+  ~ limitations under the License.
+  -->
+
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+
+</manifest>

features/selectusers/impl/src/main/kotlin/io/element/android/features/selectusers/impl/DefaultSelectUsersPresenter.kt

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+/*
+ * Copyright (c) 2023 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.element.android.features.selectusers.impl
+
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.MutableState
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.saveable.rememberSaveable
+import androidx.compose.runtime.setValue
+import com.squareup.anvil.annotations.ContributesBinding
+import io.element.android.features.selectusers.api.SelectUsersEvents
+import io.element.android.features.selectusers.api.SelectUsersPresenter
+import io.element.android.features.selectusers.api.SelectUsersState
+import io.element.android.libraries.di.SessionScope
+import io.element.android.libraries.matrix.api.core.MatrixPatterns
+import io.element.android.libraries.matrix.api.core.UserId
+import io.element.android.libraries.matrix.ui.model.MatrixUser
+import kotlinx.collections.immutable.ImmutableList
+import kotlinx.collections.immutable.persistentListOf
+import kotlinx.collections.immutable.toImmutableList
+import javax.inject.Inject
+
+// TODO add unit tests
+@ContributesBinding(SessionScope::class)
+class DefaultSelectUsersPresenter @Inject constructor() : SelectUsersPresenter {
+
+    @Composable
+    override fun present(): SelectUsersState {
+        val selectedUsers: MutableState<ImmutableList<MatrixUser>> = remember { mutableStateOf(persistentListOf()) }
+        var searchQuery by rememberSaveable { mutableStateOf("") }
+        val searchResults: MutableState<ImmutableList<MatrixUser>> = remember {
+            mutableStateOf(persistentListOf())
+        }
+
+        fun handleEvents(event: SelectUsersEvents) {
+            when (event) {
+                is SelectUsersEvents.UpdateSearchQuery -> searchQuery = event.query
+                is SelectUsersEvents.AddToSelection -> selectedUsers.value = selectedUsers.value.plus(event.matrixUser).toImmutableList()
+                is SelectUsersEvents.RemoveFromSelection -> selectedUsers.value = selectedUsers.value.minus(event.matrixUser).toImmutableList()
+            }
+        }
+
+        LaunchedEffect(searchQuery) {
+            searchResults.value = if (MatrixPatterns.isUserId(searchQuery)) {
+                persistentListOf(MatrixUser(UserId(searchQuery)))
+            } else {
+                persistentListOf()
+            }
+            if (searchQuery.isNotEmpty()) {
+                searchResults.value = performSearch(searchQuery)
+            }
+        }
+
+        return SelectUsersState(
+            searchQuery = searchQuery,
+            searchResults = searchResults.value,
+            selectedUsers = selectedUsers.value,
+            eventSink = ::handleEvents,
+        )
+    }
+
+    private fun performSearch(query: String): ImmutableList<MatrixUser> {
+        val isMatrixId = MatrixPatterns.isUserId(query)
+        val results = mutableListOf<MatrixUser>()// TODO trigger /search request
+        if (isMatrixId && results.none { it.id.value == query }) {
+            val getProfileResult: MatrixUser? = null // TODO trigger /profile request
+            val profile = getProfileResult ?: MatrixUser(UserId(query))
+            results.add(0, profile)
+        }
+        return results.toImmutableList()
+    }
+}