/*
 * Copyright (C) 2008 Google Inc.
 *
 * 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.ryanharter.auto.value.gson.internal;

import com.google.errorprone.annotations.CheckReturnValue;
import com.ryanharter.auto.value.gson.internal.Util.ParameterizedTypeImpl;
import com.ryanharter.auto.value.gson.internal.Util.WildcardTypeImpl;
import java.lang.reflect.Array;
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.lang.reflect.WildcardType;
import java.util.Arrays;
import org.jetbrains.annotations.Nullable;

import static com.ryanharter.auto.value.gson.internal.Util.EMPTY_TYPE_ARRAY;

/** Factory methods for types. Adapted from <a href="https://git.io/fhWvz">Moshi</a>. */
@CheckReturnValue
public final class WildcardUtil {
  private WildcardUtil() {
  }

  /**
   * Returns a type that represents an unknown type that extends {@code bound}. For example, if
   * {@code bound} is {@code CharSequence.class}, this returns {@code ? extends CharSequence}. If
   * {@code bound} is {@code Object.class}, this returns {@code ?}, which is shorthand for {@code
   * ? extends Object}.
   */
  public static WildcardType subtypeOf(Type bound) {
    return new WildcardTypeImpl(new Type[] { bound }, EMPTY_TYPE_ARRAY);
  }

  /**
   * Returns a type that represents an unknown supertype of {@code bound}. For example, if {@code
   * bound} is {@code String.class}, this returns {@code ? super String}.
   */
  public static WildcardType supertypeOf(Type bound) {
    return new WildcardTypeImpl(new Type[] { Object.class }, new Type[] { bound });
  }

  static Class<?> getRawType(Type type) {
    if (type instanceof Class<?>) {
      // type is a normal class.
      return (Class<?>) type;

    } else if (type instanceof ParameterizedType) {
      ParameterizedType parameterizedType = (ParameterizedType) type;

      // I'm not exactly sure why getRawType() returns Type instead of Class. Neal isn't either but
      // suspects some pathological case related to nested classes exists.
      Type rawType = parameterizedType.getRawType();
      return (Class<?>) rawType;

    } else if (type instanceof GenericArrayType) {
      Type componentType = ((GenericArrayType) type).getGenericComponentType();
      return Array.newInstance(getRawType(componentType), 0).getClass();

    } else if (type instanceof TypeVariable) {
      // We could use the variable's bounds, but that won't work if there are multiple. having a raw
      // type that's more general than necessary is okay.
      return Object.class;

    } else if (type instanceof WildcardType) {
      return getRawType(((WildcardType) type).getUpperBounds()[0]);

    } else {
      String className = type == null ? "null" : type.getClass().getName();
      throw new IllegalArgumentException("Expected a Class, ParameterizedType, or "
          + "GenericArrayType, but <" + type + "> is of type " + className);
    }
  }

  /** Returns true if {@code a} and {@code b} are equal. */
  static boolean equals(@Nullable Type a, @Nullable Type b) {
    if (a == b) {
      return true; // Also handles (a == null && b == null).

    } else if (a instanceof Class) {
      if (b instanceof GenericArrayType) {
        return equals(((Class) a).getComponentType(),
            ((GenericArrayType) b).getGenericComponentType());
      }
      return a.equals(b); // Class already specifies equals().

    } else if (a instanceof ParameterizedType) {
      if (!(b instanceof ParameterizedType)) return false;
      ParameterizedType pa = (ParameterizedType) a;
      ParameterizedType pb = (ParameterizedType) b;
      Type[] aTypeArguments = pa instanceof ParameterizedTypeImpl
          ? ((ParameterizedTypeImpl) pa).typeArguments
          : pa.getActualTypeArguments();
      Type[] bTypeArguments = pb instanceof ParameterizedTypeImpl
          ? ((ParameterizedTypeImpl) pb).typeArguments
          : pb.getActualTypeArguments();
      return equals(pa.getOwnerType(), pb.getOwnerType())
          && pa.getRawType().equals(pb.getRawType())
          && Arrays.equals(aTypeArguments, bTypeArguments);

    } else if (a instanceof GenericArrayType) {
      if (b instanceof Class) {
        return equals(((Class) b).getComponentType(),
            ((GenericArrayType) a).getGenericComponentType());
      }
      if (!(b instanceof GenericArrayType)) return false;
      GenericArrayType ga = (GenericArrayType) a;
      GenericArrayType gb = (GenericArrayType) b;
      return equals(ga.getGenericComponentType(), gb.getGenericComponentType());

    } else if (a instanceof WildcardType) {
      if (!(b instanceof WildcardType)) return false;
      WildcardType wa = (WildcardType) a;
      WildcardType wb = (WildcardType) b;
      return Arrays.equals(wa.getUpperBounds(), wb.getUpperBounds())
          && Arrays.equals(wa.getLowerBounds(), wb.getLowerBounds());

    } else if (a instanceof TypeVariable) {
      if (!(b instanceof TypeVariable)) return false;
      TypeVariable<?> va = (TypeVariable<?>) a;
      TypeVariable<?> vb = (TypeVariable<?>) b;
      return va.getGenericDeclaration() == vb.getGenericDeclaration()
          && va.getName().equals(vb.getName());

    } else {
      // This isn't a supported type.
      return false;
    }
  }
}
