Added the actual quickfix missing imports class.

Author: themkat

server/src/main/kotlin/org/javacs/kt/codeaction/quickfix/AddMissingImportsQuickFix.kt

@@ -0,0 +1,59 @@
+package org.javacs.kt.codeaction.quickfix
+
+import org.eclipse.lsp4j.*
+import org.eclipse.lsp4j.jsonrpc.messages.Either
+import org.jetbrains.kotlin.psi.KtFile
+import org.javacs.kt.CompiledFile
+import org.javacs.kt.LOG
+import org.javacs.kt.index.SymbolIndex
+import org.javacs.kt.index.Symbol
+import org.javacs.kt.position.offset
+import org.javacs.kt.util.toPath
+import org.javacs.kt.codeaction.quickfix.diagnosticMatch
+import org.javacs.kt.imports.getImportTextEditEntry
+
+class AddMissingImportsQuickFix: QuickFix {
+    override fun compute(file: CompiledFile, index: SymbolIndex, range: Range, diagnostics: List<Diagnostic>): List<Either<Command, CodeAction>> {
+        val uri = file.parse.toPath().toUri().toString()
+        val unresolvedReferences = getUnresolvedReferencesFromDiagnostics(diagnostics) 
+        
+        return unresolvedReferences.flatMap { diagnostic ->
+            val diagnosticRange = diagnostic.range
+            val startCursor = offset(file.content, diagnosticRange.start)
+            val endCursor = offset(file.content, diagnosticRange.end)
+            val symbolName = file.content.substring(startCursor, endCursor)
+
+            getImportAlternatives(symbolName, file.parse, index).map { (importStr, edit) ->
+                val codeAction = CodeAction()
+                codeAction.title = "import ${importStr}"
+                codeAction.kind = CodeActionKind.QuickFix
+                codeAction.diagnostics = listOf(diagnostic)
+                codeAction.edit = WorkspaceEdit(mapOf(uri to listOf(edit)))
+                
+                Either.forRight(codeAction)
+            }
+        }
+    }
+
+    private fun getUnresolvedReferencesFromDiagnostics(diagnostics: List<Diagnostic>): List<Diagnostic> =
+        diagnostics.filter {
+            "UNRESOLVED_REFERENCE" == it.code.left.trim()
+        }
+
+    private fun getImportAlternatives(symbolName: String, file: KtFile, index: SymbolIndex): List<Pair<String, TextEdit>> {
+        // wildcard matcher to empty string, because we only want to match exactly the symbol itself, not anything extra
+        val queryResult = index.query(symbolName, wildcardMatcher = "")
+        
+        return queryResult
+            .filter { it.kind != Symbol.Kind.MODULE }
+            .filter {
+                // TODO: Visibility checker should be less liberal
+                it.visibility == Symbol.Visibility.PUBLIC
+                || it.visibility == Symbol.Visibility.PROTECTED
+                || it.visibility == Symbol.Visibility.INTERNAL
+            }
+            .map {
+                Pair(it.fqName.toString(), getImportTextEditEntry(file, it.fqName))
+            }
+    }
+}