[LL FIR] introduce CompositeKotlinDeclarationProvider

^KT-57930

analysis/low-level-api-fir/src/org/jetbrains/kotlin/analysis/low/level/api/fir/project/structure/CompositeKotlinDeclarationProvider.kt

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2010-2023 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.analysis.low.level.api.fir.project.structure
+
+import org.jetbrains.kotlin.analysis.providers.KotlinDeclarationProvider
+import org.jetbrains.kotlin.name.CallableId
+import org.jetbrains.kotlin.name.ClassId
+import org.jetbrains.kotlin.name.FqName
+import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.psi.*
+
+internal class CompositeKotlinDeclarationProvider
+private constructor(
+    private val providers: List<KotlinDeclarationProvider>
+) : KotlinDeclarationProvider() {
+
+    override fun getClassLikeDeclarationByClassId(classId: ClassId): KtClassLikeDeclaration? {
+        return providers.firstNotNullOfOrNull { it.getClassLikeDeclarationByClassId(classId) }
+    }
+
+    override fun getAllClassesByClassId(classId: ClassId): Collection<KtClassOrObject> {
+        return providers.flatMap { it.getAllClassesByClassId(classId) }
+    }
+
+    override fun getAllTypeAliasesByClassId(classId: ClassId): Collection<KtTypeAlias> {
+        return providers.flatMap { it.getAllTypeAliasesByClassId(classId) }
+    }
+
+    override fun getTopLevelKotlinClassLikeDeclarationNamesInPackage(packageFqName: FqName): Set<Name> {
+        return providers.flatMapTo(mutableSetOf()) { it.getTopLevelKotlinClassLikeDeclarationNamesInPackage(packageFqName) }
+    }
+
+    override fun getTopLevelProperties(callableId: CallableId): Collection<KtProperty> {
+        return providers.flatMapTo(mutableListOf()) { it.getTopLevelProperties(callableId) }
+    }
+
+    override fun getTopLevelFunctions(callableId: CallableId): Collection<KtNamedFunction> {
+        return providers.flatMapTo(mutableListOf()) { it.getTopLevelFunctions(callableId) }
+    }
+
+    override fun getTopLevelCallableFiles(callableId: CallableId): Collection<KtFile> {
+        return providers.flatMapTo(mutableListOf()) { it.getTopLevelCallableFiles(callableId) }
+    }
+
+    override fun getTopLevelCallableNamesInPackage(packageFqName: FqName): Set<Name> {
+        return providers.flatMapTo(mutableSetOf()) { it.getTopLevelCallableNamesInPackage(packageFqName) }
+    }
+
+    override fun findFilesForFacadeByPackage(packageFqName: FqName): Collection<KtFile> {
+        return providers.flatMapTo(mutableListOf()) { it.findFilesForFacadeByPackage(packageFqName) }
+    }
+
+    override fun findFilesForFacade(facadeFqName: FqName): Collection<KtFile> {
+        return providers.flatMapTo(mutableListOf()) { it.findFilesForFacade(facadeFqName) }
+    }
+
+    override fun findInternalFilesForFacade(facadeFqName: FqName): Collection<KtFile> {
+        return providers.flatMapTo(mutableListOf()) { it.findInternalFilesForFacade(facadeFqName) }
+    }
+
+    companion object {
+        fun create(providers: List<KotlinDeclarationProvider>): KotlinDeclarationProvider {
+            return when (providers.size) {
+                0 -> EmptyKotlinDeclarationProvider
+                1 -> providers.single()
+                else -> CompositeKotlinDeclarationProvider(providers)
+            }
+        }
+    }
+}