/*
 * 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.buildfile.completion;

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

import com.google.idea.blaze.base.lang.buildfile.language.BuildFileLanguage;
import com.google.idea.blaze.base.lang.buildfile.lexer.BuildToken;
import com.google.idea.blaze.base.lang.buildfile.lexer.TokenKind;
import com.google.idea.blaze.base.lang.buildfile.psi.Argument;
import com.google.idea.blaze.base.lang.buildfile.psi.ReferenceExpression;
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.psi.util.PsiTreeUtil;
import com.intellij.util.ProcessingContext;

/**
 * We can't rely solely keyword arg references, because as the user is typing a new keyword arg, the
 * PsiElement will be a ReferenceExpression (with different completion results not relevant to
 * keyword args).
 */
public class ArgumentCompletionContributor 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 ArgumentCompletionContributor() {
    extend(
        CompletionType.BASIC,
        psiElement()
            .withLanguage(BuildFileLanguage.INSTANCE)
            .withElementType(BuildToken.fromKind(TokenKind.IDENTIFIER))
            .withParents(ReferenceExpression.class, Argument.Positional.class)
            .andNot(psiComment())
            .andNot(psiElement().afterLeaf("="))
            .andNot(psiElement().afterLeaf(psiElement(BuildToken.fromKind(TokenKind.IDENTIFIER)))),
        new CompletionProvider<CompletionParameters>() {
          @Override
          protected void addCompletions(
              CompletionParameters parameters,
              ProcessingContext context,
              CompletionResultSet result) {
            Argument.Positional arg =
                PsiTreeUtil.getParentOfType(parameters.getPosition(), Argument.Positional.class);
            if (arg != null) {
              Object[] lookups = arg.getReference().getVariants();
              for (Object lookup : lookups) {
                if (lookup instanceof LookupElement) {
                  result.addElement((LookupElement) lookup);
                }
              }
            }
          }
        });
  }
}