// Copyright 2022 Google LLC

//

// 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

//

// https://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 dev.cel.common.types;

import static com.google.common.collect.ImmutableList.toImmutableList;

import com.google.common.collect.ImmutableList;

import com.google.errorprone.annotations.CanIgnoreReturnValue;

import com.google.errorprone.annotations.CheckReturnValue;

import com.google.errorprone.annotations.Immutable;

import java.util.function.Function;

/**

* Abstract representation of a CEL type which indicates its {@code CelKind}, {@code name}, and

* {@code parameters}.

*

* <p>Each type also exposes functions to generate a copy of the type containing fresh type

* variables, and a function for generating a new instance of the type with a different set of type

* parameters. These functions are critical for making type inferences.

*/

@Immutable

@CheckReturnValue

public abstract class CelType {

protected CelType() {}

/** Return the type {@code CelKind}. */

public abstract CelKind kind();

/**

* Return the type name.

*

* <p>For struct types this should be the fully qualified name. Be wary of introducing unqualified

* type names as they may collide with future CEL type.

*/

public abstract String name();

/** Return the type parameters. e.g. a map's key and value {@code CelType}. */

public ImmutableList<CelType> parameters() {

return ImmutableList.of();

}

/**

* Determine whether {@code this} type is assignable from the {@code other} type value.

*

* <p>Defaults to an equality test.

*/

public boolean isAssignableFrom(CelType other) {

return this.equals(other);

}

/**

* Instantiate a new copy of this type with alternative {@code parameters}.

*

* <p>If the {@code CelType} does not have any {@code parameters}, then the return value defaults

* to the original type instance.

*/

@CanIgnoreReturnValue

public CelType withParameters(ImmutableList<CelType> parameters) {

return this;

}

/**

* Instantiate a new copy of this type with alternative {@code parameters}.

*

* <p>If the {@code CelType} does not have any {@code parameters}, then the return value defaults

* to the original type instance.

*/

@CanIgnoreReturnValue

public CelType withFreshTypeParamVariables(Function<String, String> varNameGenerator) {

return withParameters(

parameters().stream()

.map(p -> p.withFreshTypeParamVariables(varNameGenerator))

.collect(toImmutableList()));

}

}