Introduce ORT result scanner infrastructre

As explained in the issue oss-review-toolkit#5324, we need a scanner with the capability to access and autonomously process the full ORT result into a scan result structure.

This pull request gives an insight on how we solved this requirement using the current ORT infrastructure. This has to be seen as an example and a base for further discussion on the ORT developer community.

Signed-off-by: Rainer Bieniek <extern.rainer.bieniek@porsche.de>

scanner/src/main/kotlin/OrtResultScanner.kt

@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2021 Porsche AG
+ *
+ * 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.scanner
+
+import org.ossreviewtoolkit.model.OrtResult
+import org.ossreviewtoolkit.model.Package
+import org.ossreviewtoolkit.model.ScanResult
+import org.ossreviewtoolkit.model.config.DownloaderConfiguration
+import org.ossreviewtoolkit.model.config.ScannerConfiguration
+
+/**
+ * A [Scanner] that operates on a complete [OrtResult]
+ */
+abstract class OrtResultScanner(
+    scannerName: String,
+    scannerConfig: ScannerConfiguration,
+    downloaderConfig: DownloaderConfiguration
+) : Scanner(scannerName, scannerConfig, downloaderConfig) {
+
+    /**
+     * This scanner operates on the level of a complete [OrtResult].
+     *
+     * Using it for package scanning is neither wanted nor supported and must be considered as an error.
+     */
+    final override suspend fun scanPackages(
+        packages: Set<org.ossreviewtoolkit.model.Package>,
+        labels: Map<String, String>
+    ): Map<org.ossreviewtoolkit.model.Package, List<ScanResult>> =
+        throw NotImplementedError("Not implemented on purpose")
+
+    /**
+     * Process a complete [OrtResult] and manage any scanning activities on projects and packages
+     * autonomous without any orchestration from ORT
+     */
+    abstract suspend fun scanOrtResult(
+        ortResult: OrtResult,
+        labels: Map<String, String>
+    ): Map<Package, List<ScanResult>>
+}

scanner/src/main/kotlin/Scanner.kt

@@ -102,33 +102,45 @@ fun scanOrtResult(
         .filter { it.pkg.id !in projectPackageIds }
         .map { it.pkg }
 
-    val scanResults = runBlocking {
-        val deferredProjectScan = async {
-            if (projectScanner == null) emptyMap()
-            else {
-                // Scan the projects from the ORT result.
-                val filteredProjectPackages = removeConcludedPackages(projectPackages, projectScanner)
-
-                if (filteredProjectPackages.isEmpty()) emptyMap()
-                else projectScanner.scanPackages(filteredProjectPackages, ortResult.labels).mapKeys { it.key.id }
+    val scanResults = if (packageScanner is OrtResultScanner) {
+        runBlocking {
+            val deferredScanResults = async {
+                packageScanner.scanOrtResult(ortResult, ortResult.labels).mapKeys { it.key.id }
             }
+
+            val scanResult = deferredScanResults.await()
+
+            scanResult
         }
+    } else {
+        runBlocking {
+            val deferredProjectScan = async {
+                if (projectScanner == null) emptyMap()
+                else {
+                    // Scan the projects from the ORT result.
+                    val filteredProjectPackages = removeConcludedPackages(projectPackages, projectScanner)
+
+                    if (filteredProjectPackages.isEmpty()) emptyMap()
+                    else projectScanner.scanPackages(filteredProjectPackages, ortResult.labels).mapKeys { it.key.id }
+                }
+            }
 
-        val deferredPackageScan = async {
-            if (packageScanner == null) emptyMap()
-            else {
-                // Scan the packages from the ORT result.
-                val filteredPackages = removeConcludedPackages(packages.toSet(), packageScanner)
+            val deferredPackageScan = async {
+                if (packageScanner == null) emptyMap()
+                else {
+                    // Scan the packages from the ORT result.
+                    val filteredPackages = removeConcludedPackages(packages.toSet(), packageScanner)
 
-                if (filteredPackages.isEmpty()) emptyMap()
-                else packageScanner.scanPackages(filteredPackages, ortResult.labels).mapKeys { it.key.id }
+                    if (filteredPackages.isEmpty()) emptyMap()
+                    else packageScanner.scanPackages(filteredPackages, ortResult.labels).mapKeys { it.key.id }
+                }
             }
-        }
 
-        val projectResults = deferredProjectScan.await()
-        val packageResults = deferredPackageScan.await()
+            val projectResults = deferredProjectScan.await()
+            val packageResults = deferredPackageScan.await()
 
-        projectResults + packageResults
+            projectResults + packageResults
+        }
     }.toSortedMap()
 
     // Add scan results from de-duplicated project packages to result.