/*
 * Copyright 2016 The Bazel Authors. All rights reserved.
 *
 * 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
 *
 *    http://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.
 */
package com.google.idea.blaze.base.lang.projectview.completion;

import static com.intellij.patterns.PlatformPatterns.psiElement;

import com.google.common.collect.Ordering;
import com.google.idea.blaze.base.lang.projectview.language.ProjectViewLanguage;
import com.google.idea.blaze.base.lang.projectview.psi.ProjectViewPsiListSection;
import com.google.idea.blaze.base.model.primitives.LanguageClass;
import com.google.idea.blaze.base.model.primitives.WorkspaceType;
import com.google.idea.blaze.base.projectview.section.sections.AdditionalLanguagesSection;
import com.google.idea.blaze.base.sync.SyncCache;
import com.google.idea.blaze.base.sync.projectview.LanguageSupport;
import com.intellij.codeInsight.completion.AutoCompletionContext;
import com.intellij.codeInsight.completion.AutoCompletionDecision;
import com.intellij.codeInsight.completion.CompletionContributor;
import com.intellij.codeInsight.completion.CompletionParameters;
import com.intellij.codeInsight.completion.CompletionProvider;
import com.intellij.codeInsight.completion.CompletionResultSet;
import com.intellij.codeInsight.completion.CompletionType;
import com.intellij.codeInsight.lookup.LookupElement;
import com.intellij.codeInsight.lookup.LookupElementBuilder;
import com.intellij.openapi.project.Project;
import com.intellij.patterns.StandardPatterns;
import com.intellij.util.ProcessingContext;
import java.util.List;
import java.util.stream.Collectors;

/** Code completion for additional language types. */
public class AdditionalLanguagesCompletionContributor extends CompletionContributor {

  @Override
  public AutoCompletionDecision handleAutoCompletionPossibility(AutoCompletionContext context) {
    // auto-insert the obvious only case; else show other cases.
    final LookupElement[] items = context.getItems();
    if (items.length == 1) {
      return AutoCompletionDecision.insertItem(items[0]);
    }
    return AutoCompletionDecision.SHOW_LOOKUP;
  }

  public AdditionalLanguagesCompletionContributor() {
    extend(
        CompletionType.BASIC,
        psiElement()
            .withLanguage(ProjectViewLanguage.INSTANCE)
            .inside(
                psiElement(ProjectViewPsiListSection.class)
                    .withText(
                        StandardPatterns.string()
                            .startsWith(AdditionalLanguagesSection.KEY.getName()))),
        new CompletionProvider<CompletionParameters>() {
          @Override
          protected void addCompletions(
              CompletionParameters parameters,
              ProcessingContext context,
              CompletionResultSet result) {
            for (LanguageClass type :
                availableAdditionalLanguages(parameters.getEditor().getProject())) {
              result.addElement(LookupElementBuilder.create(type.getName()));
            }
          }
        });
  }

  private static List<LanguageClass> availableAdditionalLanguages(Project project) {
    List<LanguageClass> langs =
        SyncCache.getInstance(project)
            .get(
                AdditionalLanguagesCompletionContributor.class,
                (proj, projectData) ->
                    additionalLanguages(projectData.workspaceLanguageSettings.getWorkspaceType()));
    return langs == null ? additionalLanguages(LanguageSupport.getDefaultWorkspaceType()) : langs;
  }

  private static List<LanguageClass> additionalLanguages(WorkspaceType workspaceType) {
    return LanguageSupport.availableAdditionalLanguages(workspaceType)
        .stream()
        .sorted(Ordering.usingToString())
        .collect(Collectors.toList());
  }
}