com.salesforce.jprotoc.Generator Maven / Gradle / Ivy

Go to download
/*
 *  Copyright (c) 2019, Salesforce.com, Inc.
 *  All rights reserved.
 *  Licensed under the BSD 3-Clause license.
 *  For full license text, see LICENSE.txt file in the repo root  or https://opensource.org/licenses/BSD-3-Clause
 */

package com.salesforce.jprotoc;

import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.StringWriter;
import java.util.Collections;
import java.util.List;
import java.util.stream.Stream;

import javax.annotation.Nonnull;

import com.github.mustachejava.DefaultMustacheFactory;
import com.github.mustachejava.Mustache;
import com.github.mustachejava.MustacheFactory;
import com.google.common.base.Charsets;
import com.google.common.base.Preconditions;
import com.google.protobuf.ByteString;
import com.google.protobuf.compiler.PluginProtos;

/**
 * Generator is the base class for all protoc generators managed by {@link ProtocPlugin}.
 */
public abstract class Generator {
	private static final MustacheFactory MUSTACHE_FACTORY = new DefaultMustacheFactory();

	/**
	 * Processes a generator request into a set of files to output.
	 *
	 * @deprecated use {@link #generateFiles(PluginProtos.CodeGeneratorRequest)} and return a List instead of a Stream.
	 * @param request The raw generator request from protoc.
	 * @return The completed files to write out.
	 */
	@Deprecated()
	public Stream generate(PluginProtos.CodeGeneratorRequest request) throws GeneratorException {
		return Stream.empty();
	}

	/**
	 * Processes a generator request into a set of files to output.
	 *
	 * @param request The raw generator request from protoc.
	 * @return The completed files to write out.
	 */
	public List generateFiles(PluginProtos.CodeGeneratorRequest request) throws GeneratorException {
		return Collections.emptyList();
	}

	/**
	 * Signals to protoc which additional generator features this Generator supports. By default, this method returns FEATURE_NONE. You must override this
	 * method and supply a value, like FEATURE_PROTO3_OPTIONAL.
	 *
	 * @return A list of enumerated features.
	 */
	protected List supportedFeatures() {
		return Collections.singletonList(PluginProtos.CodeGeneratorResponse.Feature.FEATURE_NONE);
	}

	/**
	 * Executes a mustache template against a generatorContext object to generate an output string.
	 * 
	 * @param resourcePath     Embedded resource template to use.
	 * @param generatorContext Context object to bind the template to.
	 * @return The string that results.
	 */
	protected String applyTemplate(@Nonnull String resourcePath, @Nonnull Object generatorContext) {
		Preconditions.checkNotNull(resourcePath, "resourcePath");
		Preconditions.checkNotNull(generatorContext, "generatorContext");

		InputStream resource = MustacheFactory.class.getClassLoader().getResourceAsStream(resourcePath);
		if (resource == null) {
			throw new RuntimeException("Could not find resource " + resourcePath);
		}

		InputStreamReader resourceReader = new InputStreamReader(resource, Charsets.UTF_8);
		Mustache template = MUSTACHE_FACTORY.compile(resourceReader, resourcePath);
		return template.execute(new StringWriter(), generatorContext).toString();
	}

	/**
	 * Creates a protobuf file message from a given name and content.
	 * 
	 * @param fileName    The name of the file to generate.
	 * @param fileContent The content of the generated file.
	 * @return The protobuf file.
	 */
	protected PluginProtos.CodeGeneratorResponse.File makeFile(String fileName, String fileContent) {
		return PluginProtos.CodeGeneratorResponse.File.newBuilder().setName(fileName).setContent(fileContent).build();
	}

	/**
	 * Creates a protobuf file message from a given name and content.
	 * 
	 * @param fileName    The name of the file to generate.
	 * @param fileContent The content of the generated file.
	 * @return The protobuf file.
	 */
	protected PluginProtos.CodeGeneratorResponse.File makeFile(String fileName, byte[] fileContent) {
		return PluginProtos.CodeGeneratorResponse.File.newBuilder().setName(fileName).setContentBytes(ByteString.copyFrom(fileContent)).build();
	}
}