feature: Limit Maximum Number of Logs

Closes: #19
Signed-Off-By: Andre Weber <andre.weber3@etas.com>

app/src/main/kotlin/org/eclipse/kuksa/testapp/databroker/view/DataBrokerView.kt

@@ -392,26 +392,30 @@ fun DataBrokerOutput(viewModel: OutputViewModel, modifier: Modifier = Modifier)
     val shape = RoundedCornerShape(20.dp, 20.dp, 0.dp, 0.dp)
     val scrollState = rememberScrollState(0)
 
+    val output = viewModel.output
+
     Surface(
         modifier = modifier.height(500.dp),
         color = MaterialTheme.colorScheme.primary,
         shape = shape,
     ) {
         Column(modifier = Modifier.verticalScroll(scrollState)) {
             Headline(name = "Output", color = Color.White)
-            Text(
-                modifier = Modifier
-                    .fillMaxHeight()
-                    .fillMaxWidth()
-                    .padding(start = DefaultElementPadding, end = DefaultElementPadding),
-                text = viewModel.output,
-                textAlign = TextAlign.Start,
-                onTextLayout = {
-                    scope.launch {
-                        scrollState.animateScrollTo(scrollState.maxValue)
-                    }
-                },
-            )
+            output.forEach { outputElement ->
+                Text(
+                    modifier = Modifier
+                        .fillMaxHeight()
+                        .fillMaxWidth()
+                        .padding(start = DefaultElementPadding, end = DefaultElementPadding),
+                    text = outputElement,
+                    textAlign = TextAlign.Start,
+                    onTextLayout = {
+                        scope.launch {
+                            scrollState.animateScrollTo(scrollState.maxValue)
+                        }
+                    },
+                )
+            }
         }
     }
 }

app/src/main/kotlin/org/eclipse/kuksa/testapp/databroker/viewmodel/OutputViewModel.kt

@@ -23,21 +23,30 @@ import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.setValue
 import androidx.lifecycle.ViewModel
+import org.eclipse.kuksa.testapp.util.MaxElementSet
 import java.time.LocalDateTime
 import java.time.format.DateTimeFormatter
 
+private const val MAX_NUMBER_LOG_ENTRIES = 100
+
 class OutputViewModel : ViewModel() {
-    var output: String by mutableStateOf("")
+    private val maxElementSet = MaxElementSet<String>(MAX_NUMBER_LOG_ENTRIES)
+
+    var output: List<String> by mutableStateOf(listOf())
         private set
 
     fun appendOutput(text: String) {
-        val emptyLines = if (output.isEmpty()) "\n" else "\n\n"
-        val dateFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm")
+        val emptyLines = if (maxElementSet.isEmpty()) "\n" else "\n\n"
+        val dateFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss:SSS")
         val date = LocalDateTime.now().format(dateFormatter)
-        output += "$emptyLines- $date\n $text"
+        maxElementSet += "$emptyLines- $date\n $text"
+
+        output = maxElementSet.toList()
     }
 
     fun clear() {
-        output = ""
+        maxElementSet.clear()
+
+        output = maxElementSet.toList()
     }
 }

app/src/main/kotlin/org/eclipse/kuksa/testapp/util/MaxElementSet.kt

@@ -0,0 +1,83 @@
+/*
+ * Copyright (c) 2023 Contributors to the Eclipse Foundation
+ *
+ * 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.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ */
+
+package org.eclipse.kuksa.testapp.util
+
+class MaxElementSet<T>(private val maxNumberEntries: Int = Int.MAX_VALUE) : MutableSet<T> {
+
+    private val map: LinkedHashMap<T, Boolean> = object : LinkedHashMap<T, Boolean>() {
+        override fun removeEldestEntry(eldest: MutableMap.MutableEntry<T, Boolean>?): Boolean {
+            return size > maxNumberEntries
+        }
+    }
+
+    override val size: Int
+        get() = map.size
+
+    override fun contains(element: T): Boolean {
+        return map[element] == true
+    }
+
+    override fun containsAll(elements: Collection<T>): Boolean {
+        var containsAll = true
+        elements.forEach { element ->
+            containsAll = containsAll && contains(element)
+        }
+        return containsAll
+    }
+
+    override fun add(element: T): Boolean {
+        map[element] = true
+        return true
+    }
+
+    override fun addAll(elements: Collection<T>): Boolean {
+        val associatedElements = elements.associateWith { true }
+
+        map.putAll(associatedElements)
+        return true
+    }
+
+    override fun clear() {
+        map.clear()
+    }
+
+    override fun isEmpty(): Boolean {
+        return map.isEmpty()
+    }
+
+    override fun iterator(): MutableIterator<T> {
+        return map.keys.iterator()
+    }
+
+    override fun retainAll(elements: Collection<T>): Boolean {
+        throw UnsupportedOperationException("not supported")
+    }
+
+    override fun removeAll(elements: Collection<T>): Boolean {
+        elements.forEach { element ->
+            map.remove(element)
+        }
+        return true
+    }
+
+    override fun remove(element: T): Boolean {
+        return map.remove(element) != null
+    }
+}

app/src/test/kotlin/org/eclipse/kuksa/testapp/util/MaxElementSetTest.kt

@@ -0,0 +1,86 @@
+/*
+ * Copyright (c) 2023 Contributors to the Eclipse Foundation
+ *
+ * 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.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ */
+
+package org.eclipse.kuksa.testapp.util
+
+import io.kotest.core.spec.style.BehaviorSpec
+import io.kotest.matchers.shouldBe
+
+class MaxElementSetTest : BehaviorSpec({
+    given("An Instance of MaxElementSet with Type TestElement and maxNumberEntries of 100") {
+        val classUnderTest = MaxElementSet<TestElement>(100)
+
+        `when`("Adding 100 elements") {
+            val testElements = mutableListOf<TestElement>()
+            repeat(100) {
+                val testElement = TestElement()
+
+                testElements.add(testElement)
+                classUnderTest.add(testElement)
+            }
+
+            then("All 100 elements are added successfully") {
+                classUnderTest.size shouldBe 100
+            }
+
+            then("The order is kept intact") {
+                classUnderTest.withIndex().forEach {
+                    val index = it.index
+                    val value = it.value
+
+                    value shouldBe testElements[index]
+                }
+            }
+        }
+    }
+
+    given("An Instance of MaxElementSet with Type TestElement and maxNumberEntries of 10") {
+        val classUnderTest = MaxElementSet<TestElement>(10)
+
+        `when`("Trying to add the same element twice") {
+            val testElement = TestElement()
+            classUnderTest.add(testElement)
+            classUnderTest.add(testElement)
+
+            then("It is only added once") {
+                classUnderTest.size shouldBe 1
+            }
+        }
+
+        `when`("Adding more than 10 elements (100)") {
+            val testElements = mutableListOf<TestElement>()
+            repeat(100) {
+                val testElement = TestElement()
+
+                testElements.add(testElement)
+                classUnderTest.add(testElement)
+            }
+
+            then("Only the last 10 Elements are kept") {
+                classUnderTest.size shouldBe 10
+
+                val subList = testElements.subList(90, 100)
+                val containsLastTenElements = classUnderTest.containsAll(subList)
+                containsLastTenElements shouldBe true
+            }
+        }
+    }
+})
+
+class TestElement