package org.checkerframework.framework.ajava;

import com.github.javaparser.ParseProblemException;
import com.github.javaparser.StaticJavaParser;
import com.github.javaparser.ast.NodeList;
import com.github.javaparser.ast.expr.AnnotationExpr;
import com.github.javaparser.ast.expr.ArrayInitializerExpr;
import com.github.javaparser.ast.expr.BooleanLiteralExpr;
import com.github.javaparser.ast.expr.CharLiteralExpr;
import com.github.javaparser.ast.expr.ClassExpr;
import com.github.javaparser.ast.expr.DoubleLiteralExpr;
import com.github.javaparser.ast.expr.Expression;
import com.github.javaparser.ast.expr.FieldAccessExpr;
import com.github.javaparser.ast.expr.IntegerLiteralExpr;
import com.github.javaparser.ast.expr.LongLiteralExpr;
import com.github.javaparser.ast.expr.MarkerAnnotationExpr;
import com.github.javaparser.ast.expr.MemberValuePair;
import com.github.javaparser.ast.expr.Name;
import com.github.javaparser.ast.expr.NameExpr;
import com.github.javaparser.ast.expr.NormalAnnotationExpr;
import com.github.javaparser.ast.expr.SingleMemberAnnotationExpr;
import com.github.javaparser.ast.expr.StringLiteralExpr;
import com.github.javaparser.ast.expr.UnaryExpr;
import com.github.javaparser.ast.type.ClassOrInterfaceType;
import java.util.List;
import java.util.Map;
import javax.lang.model.element.AnnotationMirror;
import javax.lang.model.element.AnnotationValue;
import javax.lang.model.element.AnnotationValueVisitor;
import javax.lang.model.element.ExecutableElement;
import javax.lang.model.element.TypeElement;
import javax.lang.model.element.VariableElement;
import javax.lang.model.type.DeclaredType;
import javax.lang.model.type.TypeKind;
import javax.lang.model.type.TypeMirror;
import org.checkerframework.checker.nullness.qual.Nullable;
import org.checkerframework.javacutil.AnnotationUtils;
import org.checkerframework.javacutil.BugInCF;
import org.checkerframework.javacutil.TypesUtils;

/**
 * Methods for converting a {@code AnnotationMirror} into a JavaParser {@code AnnotationExpr},
 * namely {@code annotationMirrorToAnnotationExpr}.
 */
public class AnnotationMirrorToAnnotationExprConversion {
  /**
   * Converts an AnnotationMirror into a JavaParser {@code AnnotationExpr}.
   *
   * @param annotation the annotation to convert
   * @return a JavaParser {@code AnnotationExpr} representing the same annotation with the same
   *     element values. The converted annotation will contain the annotation's fully qualified
   *     name.
   */
  public static AnnotationExpr annotationMirrorToAnnotationExpr(AnnotationMirror annotation) {
    Map<? extends ExecutableElement, ? extends AnnotationValue> values =
        annotation.getElementValues();
    Name name = createQualifiedName(AnnotationUtils.annotationName(annotation));
    if (values.isEmpty()) {
      return new MarkerAnnotationExpr(name);
    }

    NodeList<MemberValuePair> convertedValues = convertAnnotationValues(values);
    if (convertedValues.size() == 1
        && convertedValues.get(0).getName().asString().equals("value")) {
      return new SingleMemberAnnotationExpr(name, convertedValues.get(0).getValue());
    }

    return new NormalAnnotationExpr(name, convertedValues);
  }

  /**
   * Converts a mapping of (annotation element &rarr; value) into a list of key-value pairs
   * containing the JavaParser representations of the same values.
   *
   * @param values mapping of element values from an {@code AnnotationMirror}
   * @return a list of the key-value pairs in {@code values} converted to their JavaParser
   *     representations
   */
  private static NodeList<MemberValuePair> convertAnnotationValues(
      Map<? extends ExecutableElement, ? extends AnnotationValue> values) {
    NodeList<MemberValuePair> convertedValues = new NodeList<>();
    AnnotationValueConverterVisitor converter = new AnnotationValueConverterVisitor();
    for (ExecutableElement valueName : values.keySet()) {
      AnnotationValue value = values.get(valueName);
      convertedValues.add(
          new MemberValuePair(valueName.getSimpleName().toString(), value.accept(converter, null)));
    }

    return convertedValues;
  }

  /**
   * Given a fully qualified name, creates a JavaParser {@code Name} structure representing the same
   * name.
   *
   * @param name the fully qualified name to convert
   * @return a JavaParser {@code Name} holding {@code name}
   */
  private static Name createQualifiedName(String name) {
    String[] components = name.split("\\.");
    Name result = new Name(components[0]);
    for (int i = 1; i < components.length; i++) {
      result = new Name(result, components[i]);
    }

    return result;
  }

  /**
   * A visitor that converts an annotation value from an {@code AnnotationMirror} to a JavaParser
   * node that can appear in an {@code AnnotationExpr}.
   */
  private static class AnnotationValueConverterVisitor
      implements AnnotationValueVisitor<Expression, Void> {
    @Override
    public Expression visit(AnnotationValue value, Void p) {
      // This is called only if the value couldn't be dispatched to any known type, which
      // should never happen.
      throw new BugInCF("Unknown annotation value type: " + value);
    }

    @Override
    public Expression visitAnnotation(AnnotationMirror value, Void p) {
      return AnnotationMirrorToAnnotationExprConversion.annotationMirrorToAnnotationExpr(value);
    }

    @Override
    public Expression visitArray(List<? extends AnnotationValue> value, Void p) {
      NodeList<Expression> valueExpressions = new NodeList<>();
      for (AnnotationValue arrayValue : value) {
        valueExpressions.add(arrayValue.accept(this, null));
      }

      return new ArrayInitializerExpr(valueExpressions);
    }

    @Override
    public Expression visitBoolean(boolean value, Void p) {
      return new BooleanLiteralExpr(value);
    }

    @Override
    public Expression visitByte(byte value, Void p) {
      // Annotation byte values are automatically cast to the correct type, so using an
      // integer literal here works.
      return toIntegerLiteralExpr(value);
    }

    @Override
    public Expression visitChar(char value, Void p) {
      return new CharLiteralExpr(value);
    }

    @Override
    public Expression visitDouble(double value, Void p) {
      return new DoubleLiteralExpr(value);
    }

    @Override
    public Expression visitEnumConstant(VariableElement value, Void p) {
      // The enclosing element of an enum constant is the enum type itself.
      TypeElement enumElt = (TypeElement) value.getEnclosingElement();
      String[] components = enumElt.getQualifiedName().toString().split("\\.");
      Expression enumName = new NameExpr(components[0]);
      for (int i = 1; i < components.length; i++) {
        enumName = new FieldAccessExpr(enumName, components[i]);
      }

      return new FieldAccessExpr(enumName, value.getSimpleName().toString());
    }

    @Override
    public Expression visitFloat(float value, Void p) {
      return new DoubleLiteralExpr(value + "f");
    }

    @Override
    public Expression visitInt(int value, Void p) {
      return toIntegerLiteralExpr(value);
    }

    @Override
    public Expression visitLong(long value, Void p) {
      if (value < 0) {
        return new UnaryExpr(new LongLiteralExpr(Long.toString(-value)), UnaryExpr.Operator.MINUS);
      }

      return new LongLiteralExpr(Long.toString(value));
    }

    @Override
    public Expression visitShort(short value, Void p) {
      // Annotation short values are automatically cast to the correct type, so using an
      // integer literal here works.
      return toIntegerLiteralExpr(value);
    }

    @Override
    public Expression visitString(String value, Void p) {
      return new StringLiteralExpr(value);
    }

    @Override
    public Expression visitType(TypeMirror value, Void p) {
      if (value.getKind() != TypeKind.DECLARED) {
        throw new BugInCF("Unexpected type for class expression: " + value);
      }

      DeclaredType type = (DeclaredType) value;
      ClassOrInterfaceType parsedType;
      try {
        parsedType = StaticJavaParser.parseClassOrInterfaceType(TypesUtils.getQualifiedName(type));
      } catch (ParseProblemException e) {
        throw new BugInCF("Invalid class or interface name: " + value, e);
      }

      return new ClassExpr(parsedType);
    }

    @Override
    public @Nullable Expression visitUnknown(AnnotationValue value, Void p) {
      return null;
    }

    /**
     * Creates a JavaParser expression node representing a literal with the given value.
     *
     * <p>JavaParser represents a negative literal with a {@code UnaryExpr} containing a {@code
     * IntegerLiteralExpr}, so this method won't necessarily return an {@code IntegerLiteralExpr}.
     *
     * @param value the value for the literal
     * @return a JavaParser expression representing {@code value}
     */
    private Expression toIntegerLiteralExpr(int value) {
      if (value < 0) {
        return new UnaryExpr(
            new IntegerLiteralExpr(Integer.toString(-value)), UnaryExpr.Operator.MINUS);
      }

      return new IntegerLiteralExpr(Integer.toString(value));
    }
  }
}