// Copyright 2024 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

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// See the License for the specific language governing permissions and

// limitations under the License.

package codelab;

import com.google.rpc.context.AttributeContext;

import dev.cel.common.CelAbstractSyntaxTree;

import dev.cel.common.CelFunctionDecl;

import dev.cel.common.CelOverloadDecl;

import dev.cel.common.CelValidationException;

import dev.cel.common.CelValidationResult;

import dev.cel.common.types.SimpleType;

import dev.cel.compiler.CelCompiler;

import dev.cel.compiler.CelCompilerFactory;

import dev.cel.parser.CelStandardMacro;

import dev.cel.runtime.CelEvaluationException;

import dev.cel.runtime.CelRuntime;

import dev.cel.runtime.CelRuntimeFactory;

import dev.cel.validator.CelValidator;

import dev.cel.validator.CelValidatorFactory;

/**

* Exercise9 demonstrates how to author a custom AST validator to perform domain specific

* validations.

*

* <p>Given a `google.rpc.context.AttributeContext.Request` message, validate that its fields follow

* the expected HTTP specification.

*

* <p>Given an expression containing an expensive function call, validate that it is not nested

* within a macro.

*/

final class Exercise9 {

private static final CelCompiler CEL_COMPILER =

CelCompilerFactory.standardCelCompilerBuilder()

.setStandardMacros(CelStandardMacro.ALL)

.addFunctionDeclarations(

CelFunctionDecl.newFunctionDeclaration(

"is_prime_number",

CelOverloadDecl.newGlobalOverload(

"is_prime_number_int",

"Invokes an expensive RPC call to check if the value is a prime number.",

SimpleType.BOOL,

SimpleType.INT)))

.addMessageTypes(AttributeContext.Request.getDescriptor())

.build();

private static final CelRuntime CEL_RUNTIME =

CelRuntimeFactory.standardCelRuntimeBuilder()

.addMessageTypes(AttributeContext.Request.getDescriptor())

.build();

private static final CelValidator CEL_VALIDATOR =

CelValidatorFactory.standardCelValidatorBuilder(CEL_COMPILER, CEL_RUNTIME)

// Add your custom AST validators here

.build();

/**

* Compiles the input expression.

*

* @throws CelValidationException If the expression contains parsing or type-checking errors.

*/

CelAbstractSyntaxTree compile(String expression) throws CelValidationException {

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

}

/** Validates a type-checked AST. */

CelValidationResult validate(CelAbstractSyntaxTree checkedAst) {

return CEL_VALIDATOR.validate(checkedAst);

}

/** Evaluates the compiled AST. */

Object eval(CelAbstractSyntaxTree ast) throws CelEvaluationException {

return CEL_RUNTIME.createProgram(ast).eval();

}

/**

* Performs general validation on AttributeContext.Request message. The validator raises errors if

* the HTTP request is malformed and semantically invalid (e.g: contains disallowed HTTP methods).

* Warnings are presented if there's potential problems with the contents of the request (e.g:

* using "http" instead of "https" for scheme).

*/

static final class AttributeContextRequestValidator {

// Implement validate method here

}

/** Prevents nesting an expensive function call within a macro. */

static final class ComprehensionSafetyValidator {

// Implement validate method here

}

}