build: Migrate to flat project structure

This change updates the project structure to become flattened.
Previously, the simulator, frontend and API each lived into their own
directory.

With this change, all modules of the project live in the top-level
directory of the repository. This should improve discoverability of
modules of the project.

5 files changed, 238 insertions, 0 deletions

diff --git a/opendc-harness/src/main/kotlin/org/opendc/harness/engine/discovery/Discovery.kt b/opendc-harness/src/main/kotlin/org/opendc/harness/engine/discovery/Discovery.kt
new file mode 100644
index 00000000..f7f73b38
--- /dev/null
+++ b/opendc-harness/src/main/kotlin/org/opendc/harness/engine/discovery/Discovery.kt
@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.harness.engine.discovery
+
+import kotlinx.coroutines.flow.Flow
+import org.opendc.harness.api.ExperimentDefinition
+
+/**
+ * Component responsible for scanning for [ExperimentDefinition]s.
+ */
+public interface Discovery {
+    /**
+     * Start discovery of experiments.
+     *
+     * @param request The [DiscoveryRequest] to determine the experiments to discover.
+     * @return A flow of [ExperimentDefinition]s that have been discovered by the implementation.
+     */
+    public fun discover(request: DiscoveryRequest): Flow<ExperimentDefinition>
+}
diff --git a/opendc-harness/src/main/kotlin/org/opendc/harness/engine/discovery/DiscoveryFilter.kt b/opendc-harness/src/main/kotlin/org/opendc/harness/engine/discovery/DiscoveryFilter.kt
new file mode 100644
index 00000000..219d09cd
--- /dev/null
+++ b/opendc-harness/src/main/kotlin/org/opendc/harness/engine/discovery/DiscoveryFilter.kt
@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.harness.engine.discovery
+
+import org.opendc.harness.api.ExperimentDefinition
+import java.util.function.Predicate
+
+/**
+ * A [DiscoveryFilter] decides how the selected experiments are filtered.
+ */
+public sealed class DiscoveryFilter {
+    /**
+     * Test whether the specified [ExperimentDefinition] should be selected.
+     */
+    public abstract fun test(definition: ExperimentDefinition): Boolean
+
+    /**
+     * Filter an experiment based on its name.
+     */
+    public data class Name(val predicate: Predicate<String>) : DiscoveryFilter() {
+        override fun test(definition: ExperimentDefinition): Boolean = predicate.test(definition.name)
+    }
+
+    /**
+     * Filter an experiment based on its metadata.
+     */
+    public data class Meta(val key: String, val predicate: Predicate<Any>) : DiscoveryFilter() {
+        override fun test(definition: ExperimentDefinition): Boolean =
+            definition.meta[key]?.let { predicate.test(it) } ?: false
+    }
+}
diff --git a/opendc-harness/src/main/kotlin/org/opendc/harness/engine/discovery/DiscoveryProvider.kt b/opendc-harness/src/main/kotlin/org/opendc/harness/engine/discovery/DiscoveryProvider.kt
new file mode 100644
index 00000000..fad255de
--- /dev/null
+++ b/opendc-harness/src/main/kotlin/org/opendc/harness/engine/discovery/DiscoveryProvider.kt
@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.harness.engine.discovery
+
+import org.opendc.harness.internal.CompositeDiscovery
+import java.util.*
+
+/**
+ * A provider interface for the [Discovery] component.
+ */
+public interface DiscoveryProvider {
+    /**
+     * A unique identifier for this discovery implementation.
+     *
+     * Each discovery implementation must provide a unique ID, so that they can be selected by the user.
+     * When in doubt, you may use the fully qualified name of your custom [Discovery] implementation class.
+     */
+    public val id: String
+
+    /**
+     * Factory method for creating a new [Discovery] instance.
+     */
+    public fun create(): Discovery
+
+    public companion object {
+        /**
+         * The available [DiscoveryProvider]s.
+         */
+        private val providers by lazy { ServiceLoader.load(DiscoveryProvider::class.java) }
+
+        /**
+         * Obtain the [DiscoveryProvider] with the specified [id] or return `null`.
+         */
+        public fun findById(id: String): DiscoveryProvider? {
+            return providers.find { it.id == id }
+        }
+
+        /**
+         * Obtain a composite [Discovery] that combines the results of all available providers.
+         */
+        public fun createComposite(): Discovery {
+            return CompositeDiscovery(providers)
+        }
+    }
+}
diff --git a/opendc-harness/src/main/kotlin/org/opendc/harness/engine/discovery/DiscoveryRequest.kt b/opendc-harness/src/main/kotlin/org/opendc/harness/engine/discovery/DiscoveryRequest.kt
new file mode 100644
index 00000000..5bc08dac
--- /dev/null
+++ b/opendc-harness/src/main/kotlin/org/opendc/harness/engine/discovery/DiscoveryRequest.kt
@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.harness.engine.discovery
+
+/**
+ * A request for discovering experiments according to the specified information.
+ *
+ * @param selectors The selectors for this discovery request.
+ * @param filters The filters for this discovery request.
+ */
+public data class DiscoveryRequest(
+    val selectors: List<DiscoverySelector> = emptyList(),
+    val filters: List<DiscoveryFilter> = emptyList(),
+)
diff --git a/opendc-harness/src/main/kotlin/org/opendc/harness/engine/discovery/DiscoverySelector.kt b/opendc-harness/src/main/kotlin/org/opendc/harness/engine/discovery/DiscoverySelector.kt
new file mode 100644
index 00000000..67681303
--- /dev/null
+++ b/opendc-harness/src/main/kotlin/org/opendc/harness/engine/discovery/DiscoverySelector.kt
@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.harness.engine.discovery
+
+import org.opendc.harness.api.ExperimentDefinition
+
+/**
+ * A [DiscoverySelector] defines the properties used to discover experiments.
+ */
+public sealed class DiscoverySelector {
+    /**
+     * Test whether the specified [ExperimentDefinition] should be selected.
+     */
+    public abstract fun test(definition: ExperimentDefinition): Boolean
+
+    /**
+     * Select an experiment based on its name.
+     */
+    public data class Name(val name: String) : DiscoverySelector() {
+        override fun test(definition: ExperimentDefinition): Boolean = definition.name == name
+    }
+
+    /**
+     * Select an experiment based on its metadata.
+     */
+    public data class Meta(val key: String, val value: Any) : DiscoverySelector() {
+        override fun test(definition: ExperimentDefinition): Boolean = definition.meta[key] == value
+    }
+}