feat(devins-java): add package name completion #101

Add the ability to suggest package names for completion in the `JavaCustomDevInsCompletionProvider`. This feature was added to enhance the user experience when working with Java code.

java/src/main/kotlin/cc/unitmesh/idea/provider/JavaCustomDevInsCompletionProvider.kt

@@ -1,34 +1,46 @@
 package cc.unitmesh.idea.provider
 
 import cc.unitmesh.devti.provider.devins.DevInsCompletionProvider
-import com.intellij.codeInsight.completion.CompletionParameters
-import com.intellij.codeInsight.completion.CompletionResultSet
-import com.intellij.codeInsight.completion.CompletionUtil
-import com.intellij.codeInsight.completion.JavaClassNameCompletionContributor
+import com.intellij.codeInsight.completion.*
 import com.intellij.codeInsight.lookup.LookupElement
+import com.intellij.codeInsight.lookup.LookupElementBuilder
 import com.intellij.ide.highlighter.JavaFileType
 import com.intellij.openapi.project.Project
+import com.intellij.psi.PsiManager
+import com.intellij.psi.PsiPackageStatement
 import com.intellij.psi.search.FileTypeIndex
 import com.intellij.psi.search.ProjectScope
+import com.intellij.psi.util.PsiTreeUtil
 import com.intellij.util.SmartList
 
 class JavaCustomDevInsCompletionProvider : DevInsCompletionProvider {
+
     override fun lookupSymbol(
         project: Project,
         parameters: CompletionParameters,
         result: CompletionResultSet,
     ): Iterable<LookupElement> {
         val lookupElements: MutableList<LookupElement> = SmartList()
-        val searchScope = ProjectScope.getContentScope(project)
+        val searchScope = ProjectScope.getProjectScope(project)
         val javaFiles = FileTypeIndex.getFiles(JavaFileType.INSTANCE, searchScope)
         if (javaFiles.isEmpty()) return lookupElements
 
         val prefixMatcher = CompletionUtil.findReferenceOrAlphanumericPrefix(parameters)
         result.withPrefixMatcher(prefixMatcher)
 
-        // TODO: fix this
-        JavaClassNameCompletionContributor
-            .addAllClasses(parameters, true, result.prefixMatcher, lookupElements::add)
+        val text = parameters.position.text.removePrefix(CompletionUtilCore.DUMMY_IDENTIFIER_TRIMMED)
+
+        val packageStatements = javaFiles.mapNotNull {
+            val psi = PsiManager.getInstance(project).findFile(it) ?: return@mapNotNull null
+            PsiTreeUtil.getChildrenOfTypeAsList(psi, PsiPackageStatement::class.java).firstOrNull()
+        }
+
+        packageStatements.forEach {
+            val packageName = it.packageName
+            if (packageName != null && packageName.startsWith(text)) {
+                lookupElements.add(LookupElementBuilder.create(packageName))
+            }
+        }
 
         return lookupElements
     }