/*
 * 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.language.semantics.BuildLanguageSpec;
import com.google.idea.blaze.base.lang.buildfile.language.semantics.BuildLanguageSpecProvider;
import com.google.idea.blaze.base.lang.buildfile.language.semantics.RuleDefinition;
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.FuncallExpression;
import com.google.idea.blaze.base.lang.buildfile.psi.util.PsiUtils;
import com.intellij.codeInsight.completion.*;
import com.intellij.codeInsight.lookup.LookupElement;
import com.intellij.codeInsight.lookup.LookupElementBuilder;
import com.intellij.icons.AllIcons;
import com.intellij.psi.PsiElement;
import com.intellij.util.ProcessingContext;

import javax.annotation.Nullable;

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

/**
 * Known attributes for built-in blaze functions.
 */
public class BuiltInFunctionAttributeCompletionContributor 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 BuiltInFunctionAttributeCompletionContributor() {
    extend(
      CompletionType.BASIC,
      psiElement()
        .withLanguage(BuildFileLanguage.INSTANCE)
        .inside(psiElement(FuncallExpression.class))
        .andNot(psiElement().afterLeaf("."))
        .andOr(
          psiElement().withSuperParent(2, FuncallExpression.class),
          psiElement().withSuperParent(2, Argument.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) {
          BuildLanguageSpec spec = BuildLanguageSpecProvider.getInstance().getLanguageSpec(parameters.getPosition().getProject());
          if (spec == null) {
            return;
          }
          RuleDefinition rule = spec.getRule(getEnclosingFuncallName(parameters.getPosition()));
          if (rule == null) {
            return;
          }
          for (String attributeName : rule.getKnownAttributeNames()) {
            result.addElement(
              LookupElementBuilder
                .create(attributeName)
                .withIcon(AllIcons.Nodes.Parameter));
          }
        }
      }
    );
  }

  @Nullable
  private static String getEnclosingFuncallName(PsiElement element) {
    FuncallExpression funcall = PsiUtils.getParentOfType(element, FuncallExpression.class);
    return funcall != null ? funcall.getFunctionName() : null;
  }

}