refactor(gradle): Inline the code from gradle-model

Stop sharing the model between the legacy `Gradle` package manager and
`GradleInspector`, to prepare for changing the representation of the
dependency tree structure to fix an issue with `GradleInspector`.

With a shared model also `Gradle` would need to be aligned, which would
result in a (too) large commit, quite a bit of development effort and
not least impose the risk of introducing new bugs into `Gradle`. It is
planned to remove `Gradle` once `GradleInspector` covers all its
features, which is why it does not make sense to put much effort into
`Gradle` anymore. So, decouple the implementations entirely to reflect
these priorities.

Signed-off-by: Frank Viernau <frank.viernau@gmail.com>

Author: fviernau

plugins/package-managers/gradle/build.gradle.kts

@@ -30,7 +30,6 @@ dependencies {
     implementation(libs.maven.core)
     implementation(libs.maven.resolver.api)
     implementation(projects.downloader)
-    implementation(projects.plugins.packageManagers.gradleModel)
     implementation(projects.plugins.packageManagers.mavenPackageManager)
     implementation(projects.utils.commonUtils)
     implementation(projects.utils.ortUtils)

plugins/package-managers/gradle/src/main/kotlin/Extensions.kt

@@ -0,0 +1,39 @@
+/*
+ * Copyright (C) 2021 The ORT Project Copyright Holders <https://github.com/oss-review-toolkit/ort/blob/main/NOTICE>
+ *
+ * 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
+ *
+ *     https://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
+ * License-Filename: LICENSE
+ */
+
+package org.ossreviewtoolkit.plugins.packagemanagers.gradle
+
+import OrtComponent
+
+/**
+ * The type of this Gradle dependency. In case of a project, it is [projectType]. Otherwise it is "Maven" unless there
+ * is no POM, then it is "Unknown".
+ */
+internal fun OrtComponent.getIdentifierType(projectType: String) =
+    when {
+        isProjectDependency -> projectType
+        pomFile != null -> "Maven"
+        else -> "Unknown"
+    }
+
+/**
+ * A flag to indicate whether this Gradle dependency refers to a project, or to a package.
+ */
+internal val OrtComponent.isProjectDependency: Boolean
+    get() = localPath != null

plugins/package-managers/gradle/src/main/kotlin/GradleDependencyHandler.kt

@@ -34,8 +34,6 @@ import org.ossreviewtoolkit.model.PackageLinkage
 import org.ossreviewtoolkit.model.Severity
 import org.ossreviewtoolkit.model.createAndLogIssue
 import org.ossreviewtoolkit.model.utils.DependencyHandler
-import org.ossreviewtoolkit.plugins.packagemanagers.gradlemodel.getIdentifierType
-import org.ossreviewtoolkit.plugins.packagemanagers.gradlemodel.isProjectDependency
 import org.ossreviewtoolkit.plugins.packagemanagers.maven.utils.MavenSupport
 import org.ossreviewtoolkit.plugins.packagemanagers.maven.utils.identifier
 import org.ossreviewtoolkit.utils.common.collectMessages

plugins/package-managers/gradle/src/main/kotlin/GradleModel.kt

@@ -0,0 +1,79 @@
+/*
+ * Copyright (C) 2017 The ORT Project Copyright Holders <https://github.com/oss-review-toolkit/ort/blob/main/NOTICE>
+ *
+ * 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
+ *
+ *     https://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
+ * License-Filename: LICENSE
+ */
+
+// As it is not possible to declare a package in "init.gradle" also no package is declared here.
+
+// The following interfaces have to match those in "plugins/package-managers/gradle/src/main/resources/init.gradle"
+// because they are used to deserialize the model produced there.
+
+internal interface OrtDependencyTreeModel {
+    val group: String
+    val name: String
+    val version: String
+    val configurations: List<OrtConfiguration>
+    val repositories: List<OrtRepository>
+    val errors: List<String>
+    val warnings: List<String>
+}
+
+internal interface OrtConfiguration {
+    val name: String
+    val dependencies: List<OrtComponent>
+}
+
+internal interface OrtComponentIdentifier {
+    val groupId: String
+    val artifactId: String
+    val version: String
+}
+
+internal interface OrtComponent {
+    val componentId: OrtComponentIdentifier
+    val classifier: String
+    val extension: String
+    val variants: Map<String, Map<String, String>>
+    val dependencies: List<OrtComponent>
+    val error: String?
+    val warning: String?
+    val pomFile: String?
+    val mavenModel: OrtMavenModel?
+    val localPath: String?
+}
+
+internal interface OrtMavenModel {
+    val licenses: Set<String>
+    val authors: Set<String>
+    val description: String?
+    val homepageUrl: String?
+    val vcs: OrtVcsModel?
+}
+
+internal interface OrtVcsModel {
+    val connection: String
+    val tag: String
+    val browsableUrl: String
+}
+
+internal interface OrtRepository {
+    val url: String
+    val username: String?
+    val password: String?
+    val headerName: String?
+    val headerValue: String?
+}