package com.jetbrains.lang.dart.ide.template.macro;

import com.google.common.annotations.VisibleForTesting;
import com.intellij.codeInsight.template.Expression;
import com.intellij.codeInsight.template.ExpressionContext;
import com.intellij.codeInsight.template.Result;
import com.intellij.codeInsight.template.TextResult;
import com.intellij.psi.PsiElement;
import com.intellij.psi.util.PsiTreeUtil;
import com.jetbrains.lang.dart.psi.*;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

public class DartMethodReturnTypeMacro extends DartMacroBase {
  @Override
  public String getName() {
    return "dartReturnType";
  }

  @Nullable
  @Override
  public Result calculateResult(@NotNull final Expression[] params, final ExpressionContext context) {
    final String returnType = getContainingFunctionReturnType(context.getPsiElementAtStartOffset());
    return returnType == null ? null : new TextResult(returnType);
  }

  @VisibleForTesting
  @Nullable
  public String getContainingFunctionReturnType(@Nullable final PsiElement element) {
    if (element == null) return null;
    final DartComponent parent = PsiTreeUtil.getParentOfType(element,
                                                             DartGetterDeclaration.class,
                                                             DartFunctionDeclarationWithBodyOrNative.class,
                                                             DartMethodDeclaration.class,
                                                             DartFunctionDeclarationWithBody.class);

    if (parent instanceof DartGetterDeclaration) {
      return getReturnTypeString(((DartGetterDeclaration)parent).getReturnType());
    }
    if (parent instanceof DartMethodDeclaration) {
      return getReturnTypeString(((DartMethodDeclaration)parent).getReturnType());
    }
    if (parent instanceof DartFunctionDeclarationWithBodyOrNative) {
      return getReturnTypeString(((DartFunctionDeclarationWithBodyOrNative)parent).getReturnType());
    }
    if (parent instanceof DartFunctionDeclarationWithBody) {
      return getReturnTypeString(((DartFunctionDeclarationWithBody)parent).getReturnType());
    }

    return null;
  }

  private static String getReturnTypeString(@Nullable final DartReturnType returnType) {
    return returnType == null ? null : returnType.getText();
  }
}