// 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 codelab;

import com.google.rpc.context.AttributeContext.Request;

import dev.cel.common.CelAbstractSyntaxTree;

import dev.cel.common.CelValidationException;

import dev.cel.common.types.SimpleType;

import dev.cel.common.types.StructTypeReference;

import dev.cel.compiler.CelCompiler;

import dev.cel.compiler.CelCompilerFactory;

import dev.cel.runtime.CelEvaluationException;

import dev.cel.runtime.CelRuntime;

import dev.cel.runtime.CelRuntimeFactory;

import java.util.Map;

/**

* Exercise4 demonstrates how to extend CEL with custom functions.

*

* <p>Declare a "contains" member function on map types that return a boolean indicating whether the

* map contains the key-value pair.

*/

final class Exercise4 {

/**

* Compiles the input expression.

*

* @throws IllegalArgumentException If the expression is malformed due to syntactic or semantic

* errors.

*/

CelAbstractSyntaxTree compile(String expression) {

CelCompiler celCompiler =

CelCompilerFactory.standardCelCompilerBuilder()

.addVar("request", StructTypeReference.create(Request.getDescriptor().getFullName()))

.addMessageTypes(Request.getDescriptor())

.setResultType(SimpleType.BOOL)

// Provide the custom `contains` function declaration here.

.build();

try {

return celCompiler.compile(expression).getAst();

} catch (CelValidationException e) {

throw new IllegalArgumentException("Failed to compile expression.", e);

}

}

/**

* Evaluates the compiled AST with the user provided parameter values.

*

* @throws IllegalArgumentException If the compiled expression in AST fails to evaluate.

*/

Object eval(CelAbstractSyntaxTree ast, Map<String, ?> parameterValues) {

CelRuntime celRuntime =

CelRuntimeFactory.standardCelRuntimeBuilder()

// Provide the custom `contains` function implementation here.

.build();

try {

CelRuntime.Program program = celRuntime.createProgram(ast);

return program.eval(parameterValues);

} catch (CelEvaluationException e) {

throw new IllegalArgumentException("Evaluation error has occurred.", e);

}

}

}