/*
 * 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 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.*;
import com.intellij.codeInsight.lookup.LookupElement;
import com.intellij.psi.util.PsiTreeUtil;
import com.intellij.util.ProcessingContext;

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

/**
 * 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(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);
              }
            }
          }
        }
      }
    );
  }

}