build-system/gradle-core/src/main/java/com/android/build/gradle/external/cmake/server/ServerProtocolV1.java - platform/tools/base - Git at Google

 /*
  * Copyright (C) 2017 The Android Open Source Project
  *
  * 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.android.build.gradle.external.cmake.server;

 import com.android.annotations.NonNull;
 import com.android.annotations.VisibleForTesting;
 import com.android.build.gradle.external.cmake.server.receiver.InteractiveMessage;
 import com.android.build.gradle.external.cmake.server.receiver.InteractiveProgress;
 import com.android.build.gradle.external.cmake.server.receiver.ServerReceiver;
 import com.google.gson.Gson;
 import com.google.gson.GsonBuilder;
 import java.io.BufferedReader;
 import java.io.BufferedWriter;
 import java.io.File;
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.io.OutputStreamWriter;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;

 /**
  * Implementation of version 1 of Cmake server for Cmake versions 3.7.1. Cmake server or a long
  * running mode which allows a client to configure and request buildsystem information generated by
  * Cmake. More info: https://cmake.org/cmake/help/v3.7/manual/cmake-server.7.html
  */
 public class ServerProtocolV1 implements Server {
     // Messages sent to and from the Cmake server are wrapped in the header and footer strings.
     public static final String CMAKE_SERVER_HEADER_MSG = "[== \"CMake Server\" ==[";
     public static final String CMAKE_SERVER_FOOTER_MSG = "]== \"CMake Server\" ==]";

     // When configuring a given project, Cmake server reports progress and these could contain
     // compiler information. The compiler info is contained within these prefix/suffix messages.
     // Note: These progress messages will be used as a fallback to determine the compiler info only
     // when compile_commands.json file is not present.
     public static final String CMAKE_SERVER_C_COMPILER_PREFIX = "Check for working C compiler: ";
     public static final String CMAKE_SERVER_CXX_COMPILER_PREFIX =
             "Check for working CXX compiler: ";
     public static final String CMAKE_SERVER_C_COMPILER_SUFFIX = " -- works";

     // Reader and writers to communicate with Cmake server.
     private BufferedReader input;
     private BufferedWriter output;
     // Cmake's install path.
     private final File cmakeInstallPath;
     // Messages, signals etc received from Cmake server.
     private final ServerReceiver serverReceiver;
     // Cached hello result, used to get Cmake server versions.
     private HelloResult helloResult = null;
     // Indicates if we are connected to the Cmake server.
     private boolean connected = false;
     // Indicates if we have configured the given project.
     private boolean configured = false;
     // Indicates if we have computed the given project.
     private boolean computed = false;

     // Interactive messages received when configuring the project.
     private List<InteractiveMessage> configureMessages;
     // Process builder used primarily for testing.
     Process process = null;

     ServerProtocolV1(@NonNull File cmakeInstallPath, @NonNull ServerReceiver serverReceiver) {
         this.cmakeInstallPath = cmakeInstallPath;
         this.serverReceiver = serverReceiver;
     }

     /**
      * This constructor is used only for testing purpose, to pass mock process, buffered
      * input/output etc.
      */
     @VisibleForTesting
     ServerProtocolV1(
             @NonNull File cmakeInstallPath,
             @NonNull ServerReceiver serverReceiver,
             Process process,
             BufferedReader input,
             BufferedWriter output) {
         this.cmakeInstallPath = cmakeInstallPath;
         this.serverReceiver = serverReceiver;
         this.process = process;
         this.input = input;
         this.output = output;
     }

     @Override
     public void finalize() {
         try {
             disconnect();
         } catch (IOException e) {
             diagnostic("Error when disconnecting from Cmake server: %s", e.toString());
         }
     }

     @Override
     public boolean connect() throws IOException {
         init();
         helloResult = decodeResponse(HelloResult.class);
         connected = ServerUtils.isHelloResultValid(helloResult);
         return connected;
     }

     @Override
     public void disconnect() throws IOException {
         if (input != null) {
             input.close();
             input = null;
         }
         if (output != null) {
             output.close();
             output = null;
         }

         if (process != null) {
             process.destroy();
             process = null;
         }

         connected = false;
         configured = false;
         computed = false;
         configureMessages = null;
         helloResult = null;
     }

     @Override
     public boolean isConnected() {
         return connected;
     }

     @NonNull
     @Override
     public List<ProtocolVersion> getSupportedVersion() {
         if (helloResult == null || helloResult.supportedProtocolVersions == null) {
             return null;
         }
         List<ProtocolVersion> result = new ArrayList<>();
         for (ProtocolVersion protocolVersion : helloResult.supportedProtocolVersions) {
             if (protocolVersion.major == 1 && protocolVersion.minor == 0) {
                 result.add(protocolVersion);
                 break;
             }
         }
         return result;
     }

     @NonNull
     @Override
     public HandshakeResult handshake(@NonNull HandshakeRequest handshakeRequest)
             throws IOException {
         if (!connected) {
             throw new RuntimeException("Not connected to Cmake server.");
         }
         writeMessage(new GsonBuilder().setPrettyPrinting().create().toJson(handshakeRequest));
         return decodeResponse(HandshakeResult.class);
     }

     @NonNull
     @Override
     public ConfigureCommandResult configure(@NonNull String... cacheArguments) throws IOException {
         if (!connected) {
             throw new RuntimeException("Not connected to Cmake server.");
         }

         ConfigureRequest configureRequest = new ConfigureRequest();

         // Insert a blank element to work around a bug in Cmake 3.7.1 where the first element is
         // ignored.
         configureRequest.cacheArguments = new String[cacheArguments.length + 1];
         configureRequest.cacheArguments[0] = "";
         System.arraycopy(
                 cacheArguments, 0, configureRequest.cacheArguments, 1, cacheArguments.length);

         writeMessage(new GsonBuilder().setPrettyPrinting().create().toJson(configureRequest));
         configureMessages = new ArrayList<>();
         ConfigureResult configureResult = decodeResponse(ConfigureResult.class, configureMessages);
         configured = ServerUtils.isConfigureResultValid(configureResult);

         return new ConfigureCommandResult(
                 configureResult,
                 !configureMessages.isEmpty()
                         ? getInteractiveMessagesAsString(configureMessages)
                         : "");
     }

     @NonNull
     @Override
     public ComputeResult compute() throws IOException {
         if (!connected) {
             throw new RuntimeException("Not connected to Cmake server.");
         }

         if (!configured) {
             throw new RuntimeException(
                     "Cmake server has not been configured successfully, unable to compute.");
         }

         writeMessage("{\"type\":\"compute\"}");
         ComputeResult computeResult = decodeResponse(ComputeResult.class);
         computed = ServerUtils.isComputedResultValid(computeResult);
         return computeResult;
     }

     @NonNull
     @Override
     public CodeModel codemodel() throws IOException {
         if (!connected) {
             throw new RuntimeException("Not connected to Cmake server.");
         }

         if (!computed) {
             throw new RuntimeException("Need to compute before requesting for codemodel.");
         }

         writeMessage("{\"type\":\"codemodel\"}");
         return decodeResponse(CodeModel.class);
     }

     @NonNull
     @Override
     public CacheResult cache() throws IOException {
         if (!connected) {
             throw new RuntimeException("Not connected to Cmake server.");
         }

         CacheRequest request = new CacheRequest();
         writeMessage(new GsonBuilder().setPrettyPrinting().create().toJson(request));
         return decodeResponse(CacheResult.class);
     }

     @NonNull
     @Override
     public GlobalSettings globalSettings() throws IOException {
         if (!connected) {
             throw new RuntimeException("Not connected to Cmake server.");
         }

         writeMessage("{\"type\":\"globalSettings\"}");
         return decodeResponse(GlobalSettings.class);
     }

     @NonNull
     @Override
     public String getCCompilerExecutable() {
         final String prefixMessage = "Check for working C compiler: ";
         final String suffixMessage = " -- works";

         return hackyGetLangExecutable(prefixMessage, suffixMessage);
     }

     @NonNull
     @Override
     public String getCppCompilerExecutable() {
         final String prefixMessage = "Check for working CXX compiler: ";
         final String suffixMessage = " -- works";

         return hackyGetLangExecutable(prefixMessage, suffixMessage);
     }

     @NonNull
     @Override
     public String getCmakePath() {
         return cmakeInstallPath.getAbsolutePath();
     }

     @NonNull
     public HelloResult getHelloResult() {
         return helloResult;
     }

     // Helper functions

     /**
      * Ideally, we should use compile_commands.json generated by Cmake to get C and Cxx compiler
      * information. If for whatever reason the file is not present (or not generated), we fall back
      * to check the progress messages generated Cmake server when configuring, to get the desired
      * information.
      *
      * @param prefixMessage - prefix string to search
      * @param suffixMessage - suffix string to search
      * @return C/CXX compiler
      */
     private String hackyGetLangExecutable(
             @NonNull String prefixMessage, @NonNull String suffixMessage) {
         if (configureMessages == null || configureMessages.isEmpty()) {
             return null;
         }

         for (InteractiveMessage message : configureMessages) {
             if (message.message == null
                     || !message.message.startsWith(prefixMessage)
                     || !message.message.endsWith(suffixMessage)) {
                 continue;
             }
             return message.message.substring(
                     prefixMessage.length(), message.message.length() - suffixMessage.length());
         }

         return null;
     }

     /**
      * Initializes the server.
      *
      * @throws IOException I/O failure
      */
     private void init() throws IOException {
         if (process == null) {
             ProcessBuilder processBuilder = getCmakeServerProcessBuilder();
             processBuilder.environment().putAll(new ProcessBuilder().environment());
             process = processBuilder.start();
         }

         if (input == null) {
             input = new BufferedReader(new InputStreamReader(process.getInputStream()));
         }
         if (output == null) {
             output = new BufferedWriter(new OutputStreamWriter(process.getOutputStream()));
         }
     }

     /**
      * Prints diagnostic messages.
      *
      * @param format - diagnostic message format
      * @param args - diagnostic message arguments
      */
     private void diagnostic(String format, Object... args) {
         if (serverReceiver.getDiagnosticReceiver() != null) {
             serverReceiver.getDiagnosticReceiver().receive(String.format(format, args));
         }
     }

     /**
      * Constructs a Cmake server process builder.
      *
      * @return process builder
      */
     private ProcessBuilder getCmakeServerProcessBuilder() {
         final String cmakeBinPath = new File(this.cmakeInstallPath, "cmake").getPath();
         return new ProcessBuilder(cmakeBinPath, "-E", "server", "--experimental", "--debug");
     }

     /**
      * Decodes the responses received during Cmake server interactions for a given request.
      *
      * @param clazz Class object that represents the response class
      * @return decoded response
      * @throws IOException I/O failure
      */
     private <T> T decodeResponse(Class<T> clazz) throws IOException {
         return decodeResponse(clazz, null);
     }

     private <T> T decodeResponse(Class<T> clazz, List<InteractiveMessage> interactiveMessages)
             throws IOException {
         Gson gson = new GsonBuilder().create();
         String message = readMessage();
         String messageType = gson.fromJson(message, TypeOfMessage.class).type;

         final List supportedTypes = Arrays.asList("message", "progress", "signal");
         // Process supported interactive messages.
         // For a given command, the CMake server would respond with message types
         // 0 or more of (message | progress | signal)
         // and finally terminates with a message with message types
         // (hello | reply | error)
         // More info:
         // https://cmake.org/cmake/help/v3.7/manual/cmake-server.7.html#general-message-layout
         while (supportedTypes.contains(messageType)) {
             switch (messageType) {
                 case "message":
                     if (serverReceiver.getMessageReceiver() != null) {
                         InteractiveMessage interactiveMessage =
                                 gson.fromJson(message, InteractiveMessage.class);
                         serverReceiver.getMessageReceiver().receive(interactiveMessage);
                         // Record the interactive messages only if need be.
                         if (interactiveMessages != null) {
                             serverReceiver.getMessageReceiver().receive(interactiveMessage);
                             interactiveMessages.add(interactiveMessage);
                         }
                     }
                     break;
                 case "progress":
                     if (serverReceiver.getProgressReceiver() != null) {
                         serverReceiver
                                 .getProgressReceiver()
                                 .receive(gson.fromJson(message, InteractiveProgress.class));
                         break;
                     }
                     break;
                 case "signal":
                     if (serverReceiver.getProgressReceiver() != null) {
                         serverReceiver
                                 .getProgressReceiver()
                                 .receive(gson.fromJson(message, InteractiveProgress.class));
                         break;
                     }
             }
             message = readMessage();
             messageType = gson.fromJson(message, TypeOfMessage.class).type;
         }

         // Process the final message.
         switch (messageType) {
             case "hello":
             case "reply":
                 if (serverReceiver.getDeserializationMonitor() != null) {
                     serverReceiver.getDeserializationMonitor().receive(message, clazz);
                 }
                 return gson.fromJson(message, clazz);
             case "error":
                 if (serverReceiver.getMessageReceiver() != null) {
                     InteractiveMessage interactiveMessage =
                             gson.fromJson(message, InteractiveMessage.class);
                     serverReceiver.getMessageReceiver().receive(interactiveMessage);
                 }
                 return null;
             default:
                 throw new RuntimeException(
                         "Unsupported message type " + messageType + " received from CMake server.");
         }
     }

     /**
      * Appends the messages from the given list of InteractiveMessage to return it as a single
      * string.
      *
      * @param interactiveMessages - list of interactive messages received from Cmake server
      * @return A single string with all the messages from interactive messages.
      */
     private static String getInteractiveMessagesAsString(
             List<InteractiveMessage> interactiveMessages) {
         StringBuilder result = new StringBuilder();
         for (InteractiveMessage interactiveMessage : interactiveMessages) {
             result.append(interactiveMessage.message).append("\n");
         }

         return result.toString();
     }

     /**
      * Reads a line from Cmake server
      *
      * @return a line read from Cmake servers response
      * @throws IOException I/O failure
      */
     private String readLine() throws IOException {
         final String line = input.readLine();
         diagnostic(line + "\n");
         return line;
     }

     /**
      * Writes a string to Cmake server
      *
      * @throws IOException I/O failure
      */
     private void writeLine(String message) throws IOException {
         diagnostic("%s\n", message);
         output.write(message);
         output.newLine();
     }

     /**
      * Reads until the expected string is found. Skip unexpected (or non-conforming) messages if
      * need be until the expected string is found. Note: The CMake server sometimes writes
      * non-conforming messages (by deviating from the general message layout: https://goo.gl/d4XMmB)
      * to stdout, these are harmless (i.e., they don't break the build) and hence need to be
      * ignored.
      */
     private void readExpected(@NonNull String expectedString) throws IOException {
         String line = readLine();
         while (!line.equals(expectedString)) {
             // Skip a blank line if there is one.
             if (!line.isEmpty() && serverReceiver.getDiagnosticReceiver() != null) {
                 serverReceiver.getDiagnosticReceiver().receive(line);
             }
             line = readLine();
         }
     }

     /**
      * Reads a message send by CMake server. CMake Server sends the messages wrapped within a
      * defined header and footer string, this function reads everything inbetween the header and
      * footer and returns it. General message layout we expect from CMake Server:
      *
      * <p>[non-conforming messages from CMake Server]
      *
      * <p>[== "CMake Server" ==[
      *
      * <p>InteractiveMessage
      *
      * <p>[non-conforming messages from CMake Server]
      *
      * <p>]== "CMake Server" ==]
      *
      * @return The string contained within the header and footer
      * @throws IOException I/O failure
      */
     private String readMessage() throws IOException {
         readExpected(CMAKE_SERVER_HEADER_MSG);
         final String line = readLine();
         readExpected(CMAKE_SERVER_FOOTER_MSG);
         return line;
     }

     /**
      * Writes a message wrapped within the header and footer.
      *
      * @param message string to be sent to Cmake server
      * @throws IOException I/O failure
      */
     private void writeMessage(String message) throws IOException {
         writeLine(CMAKE_SERVER_HEADER_MSG);
         writeLine(message);
         writeLine(CMAKE_SERVER_FOOTER_MSG);
         output.flush();
     }
 }
	/*
	* Copyright (C) 2017 The Android Open Source Project
	*
	* 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.android.build.gradle.external.cmake.server;

	import com.android.annotations.NonNull;
	import com.android.annotations.VisibleForTesting;
	import com.android.build.gradle.external.cmake.server.receiver.InteractiveMessage;
	import com.android.build.gradle.external.cmake.server.receiver.InteractiveProgress;
	import com.android.build.gradle.external.cmake.server.receiver.ServerReceiver;
	import com.google.gson.Gson;
	import com.google.gson.GsonBuilder;
	import java.io.BufferedReader;
	import java.io.BufferedWriter;
	import java.io.File;
	import java.io.IOException;
	import java.io.InputStreamReader;
	import java.io.OutputStreamWriter;
	import java.util.ArrayList;
	import java.util.Arrays;
	import java.util.List;

	/**
	* Implementation of version 1 of Cmake server for Cmake versions 3.7.1. Cmake server or a long
	* running mode which allows a client to configure and request buildsystem information generated by
	* Cmake. More info: https://cmake.org/cmake/help/v3.7/manual/cmake-server.7.html
	*/
	public class ServerProtocolV1 implements Server {
	// Messages sent to and from the Cmake server are wrapped in the header and footer strings.
	public static final String CMAKE_SERVER_HEADER_MSG = "[== \"CMake Server\" ==[";
	public static final String CMAKE_SERVER_FOOTER_MSG = "]== \"CMake Server\" ==]";

	// When configuring a given project, Cmake server reports progress and these could contain
	// compiler information. The compiler info is contained within these prefix/suffix messages.
	// Note: These progress messages will be used as a fallback to determine the compiler info only
	// when compile_commands.json file is not present.
	public static final String CMAKE_SERVER_C_COMPILER_PREFIX = "Check for working C compiler: ";
	public static final String CMAKE_SERVER_CXX_COMPILER_PREFIX =
	"Check for working CXX compiler: ";
	public static final String CMAKE_SERVER_C_COMPILER_SUFFIX = " -- works";

	// Reader and writers to communicate with Cmake server.
	private BufferedReader input;
	private BufferedWriter output;
	// Cmake's install path.
	private final File cmakeInstallPath;
	// Messages, signals etc received from Cmake server.
	private final ServerReceiver serverReceiver;
	// Cached hello result, used to get Cmake server versions.
	private HelloResult helloResult = null;
	// Indicates if we are connected to the Cmake server.
	private boolean connected = false;
	// Indicates if we have configured the given project.
	private boolean configured = false;
	// Indicates if we have computed the given project.
	private boolean computed = false;

	// Interactive messages received when configuring the project.
	private List<InteractiveMessage> configureMessages;
	// Process builder used primarily for testing.
	Process process = null;

	ServerProtocolV1(@NonNull File cmakeInstallPath, @NonNull ServerReceiver serverReceiver) {
	this.cmakeInstallPath = cmakeInstallPath;
	this.serverReceiver = serverReceiver;
	}

	/**
	* This constructor is used only for testing purpose, to pass mock process, buffered
	* input/output etc.
	*/
	@VisibleForTesting
	ServerProtocolV1(
	@NonNull File cmakeInstallPath,
	@NonNull ServerReceiver serverReceiver,
	Process process,
	BufferedReader input,
	BufferedWriter output) {
	this.cmakeInstallPath = cmakeInstallPath;
	this.serverReceiver = serverReceiver;
	this.process = process;
	this.input = input;
	this.output = output;
	}

	@Override
	public void finalize() {
	try {
	disconnect();
	} catch (IOException e) {
	diagnostic("Error when disconnecting from Cmake server: %s", e.toString());
	}
	}

	@Override
	public boolean connect() throws IOException {
	init();
	helloResult = decodeResponse(HelloResult.class);
	connected = ServerUtils.isHelloResultValid(helloResult);
	return connected;
	}

	@Override
	public void disconnect() throws IOException {
	if (input != null) {
	input.close();
	input = null;
	}
	if (output != null) {
	output.close();
	output = null;
	}

	if (process != null) {
	process.destroy();
	process = null;
	}

	connected = false;
	configured = false;
	computed = false;
	configureMessages = null;
	helloResult = null;
	}

	@Override
	public boolean isConnected() {
	return connected;
	}

	@NonNull
	@Override
	public List<ProtocolVersion> getSupportedVersion() {
	if (helloResult == null \|\| helloResult.supportedProtocolVersions == null) {
	return null;
	}
	List<ProtocolVersion> result = new ArrayList<>();
	for (ProtocolVersion protocolVersion : helloResult.supportedProtocolVersions) {
	if (protocolVersion.major == 1 && protocolVersion.minor == 0) {
	result.add(protocolVersion);
	break;
	}
	}
	return result;
	}

	@NonNull
	@Override
	public HandshakeResult handshake(@NonNull HandshakeRequest handshakeRequest)
	throws IOException {
	if (!connected) {
	throw new RuntimeException("Not connected to Cmake server.");
	}
	writeMessage(new GsonBuilder().setPrettyPrinting().create().toJson(handshakeRequest));
	return decodeResponse(HandshakeResult.class);
	}

	@NonNull
	@Override
	public ConfigureCommandResult configure(@NonNull String... cacheArguments) throws IOException {
	if (!connected) {
	throw new RuntimeException("Not connected to Cmake server.");
	}

	ConfigureRequest configureRequest = new ConfigureRequest();

	// Insert a blank element to work around a bug in Cmake 3.7.1 where the first element is
	// ignored.
	configureRequest.cacheArguments = new String[cacheArguments.length + 1];
	configureRequest.cacheArguments[0] = "";
	System.arraycopy(
	cacheArguments, 0, configureRequest.cacheArguments, 1, cacheArguments.length);

	writeMessage(new GsonBuilder().setPrettyPrinting().create().toJson(configureRequest));
	configureMessages = new ArrayList<>();
	ConfigureResult configureResult = decodeResponse(ConfigureResult.class, configureMessages);
	configured = ServerUtils.isConfigureResultValid(configureResult);

	return new ConfigureCommandResult(
	configureResult,
	!configureMessages.isEmpty()
	? getInteractiveMessagesAsString(configureMessages)
	: "");
	}

	@NonNull
	@Override
	public ComputeResult compute() throws IOException {
	if (!connected) {
	throw new RuntimeException("Not connected to Cmake server.");
	}

	if (!configured) {
	throw new RuntimeException(
	"Cmake server has not been configured successfully, unable to compute.");
	}

	writeMessage("{\"type\":\"compute\"}");
	ComputeResult computeResult = decodeResponse(ComputeResult.class);
	computed = ServerUtils.isComputedResultValid(computeResult);
	return computeResult;
	}

	@NonNull
	@Override
	public CodeModel codemodel() throws IOException {
	if (!connected) {
	throw new RuntimeException("Not connected to Cmake server.");
	}

	if (!computed) {
	throw new RuntimeException("Need to compute before requesting for codemodel.");
	}

	writeMessage("{\"type\":\"codemodel\"}");
	return decodeResponse(CodeModel.class);
	}

	@NonNull
	@Override
	public CacheResult cache() throws IOException {
	if (!connected) {
	throw new RuntimeException("Not connected to Cmake server.");
	}

	CacheRequest request = new CacheRequest();
	writeMessage(new GsonBuilder().setPrettyPrinting().create().toJson(request));
	return decodeResponse(CacheResult.class);
	}

	@NonNull
	@Override
	public GlobalSettings globalSettings() throws IOException {
	if (!connected) {
	throw new RuntimeException("Not connected to Cmake server.");
	}

	writeMessage("{\"type\":\"globalSettings\"}");
	return decodeResponse(GlobalSettings.class);
	}

	@NonNull
	@Override
	public String getCCompilerExecutable() {
	final String prefixMessage = "Check for working C compiler: ";
	final String suffixMessage = " -- works";

	return hackyGetLangExecutable(prefixMessage, suffixMessage);
	}

	@NonNull
	@Override
	public String getCppCompilerExecutable() {
	final String prefixMessage = "Check for working CXX compiler: ";
	final String suffixMessage = " -- works";

	return hackyGetLangExecutable(prefixMessage, suffixMessage);
	}

	@NonNull
	@Override
	public String getCmakePath() {
	return cmakeInstallPath.getAbsolutePath();
	}

	@NonNull
	public HelloResult getHelloResult() {
	return helloResult;
	}

	// Helper functions

	/**
	* Ideally, we should use compile_commands.json generated by Cmake to get C and Cxx compiler
	* information. If for whatever reason the file is not present (or not generated), we fall back
	* to check the progress messages generated Cmake server when configuring, to get the desired
	* information.
	*
	* @param prefixMessage - prefix string to search
	* @param suffixMessage - suffix string to search
	* @return C/CXX compiler
	*/
	private String hackyGetLangExecutable(
	@NonNull String prefixMessage, @NonNull String suffixMessage) {
	if (configureMessages == null \|\| configureMessages.isEmpty()) {
	return null;
	}

	for (InteractiveMessage message : configureMessages) {
	if (message.message == null
	\|\| !message.message.startsWith(prefixMessage)
	\|\| !message.message.endsWith(suffixMessage)) {
	continue;
	}
	return message.message.substring(
	prefixMessage.length(), message.message.length() - suffixMessage.length());
	}

	return null;
	}

	/**
	* Initializes the server.
	*
	* @throws IOException I/O failure
	*/
	private void init() throws IOException {
	if (process == null) {
	ProcessBuilder processBuilder = getCmakeServerProcessBuilder();
	processBuilder.environment().putAll(new ProcessBuilder().environment());
	process = processBuilder.start();
	}

	if (input == null) {
	input = new BufferedReader(new InputStreamReader(process.getInputStream()));
	}
	if (output == null) {
	output = new BufferedWriter(new OutputStreamWriter(process.getOutputStream()));
	}
	}

	/**
	* Prints diagnostic messages.
	*
	* @param format - diagnostic message format
	* @param args - diagnostic message arguments
	*/
	private void diagnostic(String format, Object... args) {
	if (serverReceiver.getDiagnosticReceiver() != null) {
	serverReceiver.getDiagnosticReceiver().receive(String.format(format, args));
	}
	}

	/**
	* Constructs a Cmake server process builder.
	*
	* @return process builder
	*/
	private ProcessBuilder getCmakeServerProcessBuilder() {
	final String cmakeBinPath = new File(this.cmakeInstallPath, "cmake").getPath();
	return new ProcessBuilder(cmakeBinPath, "-E", "server", "--experimental", "--debug");
	}

	/**
	* Decodes the responses received during Cmake server interactions for a given request.
	*
	* @param clazz Class object that represents the response class
	* @return decoded response
	* @throws IOException I/O failure
	*/
	private <T> T decodeResponse(Class<T> clazz) throws IOException {
	return decodeResponse(clazz, null);
	}

	private <T> T decodeResponse(Class<T> clazz, List<InteractiveMessage> interactiveMessages)
	throws IOException {
	Gson gson = new GsonBuilder().create();
	String message = readMessage();
	String messageType = gson.fromJson(message, TypeOfMessage.class).type;

	final List supportedTypes = Arrays.asList("message", "progress", "signal");
	// Process supported interactive messages.
	// For a given command, the CMake server would respond with message types
	// 0 or more of (message \| progress \| signal)
	// and finally terminates with a message with message types
	// (hello \| reply \| error)
	// More info:
	// https://cmake.org/cmake/help/v3.7/manual/cmake-server.7.html#general-message-layout
	while (supportedTypes.contains(messageType)) {
	switch (messageType) {
	case "message":
	if (serverReceiver.getMessageReceiver() != null) {
	InteractiveMessage interactiveMessage =
	gson.fromJson(message, InteractiveMessage.class);
	serverReceiver.getMessageReceiver().receive(interactiveMessage);
	// Record the interactive messages only if need be.
	if (interactiveMessages != null) {
	serverReceiver.getMessageReceiver().receive(interactiveMessage);
	interactiveMessages.add(interactiveMessage);
	}
	}
	break;
	case "progress":
	if (serverReceiver.getProgressReceiver() != null) {
	serverReceiver
	.getProgressReceiver()
	.receive(gson.fromJson(message, InteractiveProgress.class));
	break;
	}
	break;
	case "signal":
	if (serverReceiver.getProgressReceiver() != null) {
	serverReceiver
	.getProgressReceiver()
	.receive(gson.fromJson(message, InteractiveProgress.class));
	break;
	}
	}
	message = readMessage();
	messageType = gson.fromJson(message, TypeOfMessage.class).type;
	}

	// Process the final message.
	switch (messageType) {
	case "hello":
	case "reply":
	if (serverReceiver.getDeserializationMonitor() != null) {
	serverReceiver.getDeserializationMonitor().receive(message, clazz);
	}
	return gson.fromJson(message, clazz);
	case "error":
	if (serverReceiver.getMessageReceiver() != null) {
	InteractiveMessage interactiveMessage =
	gson.fromJson(message, InteractiveMessage.class);
	serverReceiver.getMessageReceiver().receive(interactiveMessage);
	}
	return null;
	default:
	throw new RuntimeException(
	"Unsupported message type " + messageType + " received from CMake server.");
	}
	}

	/**
	* Appends the messages from the given list of InteractiveMessage to return it as a single
	* string.
	*
	* @param interactiveMessages - list of interactive messages received from Cmake server
	* @return A single string with all the messages from interactive messages.
	*/
	private static String getInteractiveMessagesAsString(
	List<InteractiveMessage> interactiveMessages) {
	StringBuilder result = new StringBuilder();
	for (InteractiveMessage interactiveMessage : interactiveMessages) {
	result.append(interactiveMessage.message).append("\n");
	}

	return result.toString();
	}

	/**
	* Reads a line from Cmake server
	*
	* @return a line read from Cmake servers response
	* @throws IOException I/O failure
	*/
	private String readLine() throws IOException {
	final String line = input.readLine();
	diagnostic(line + "\n");
	return line;
	}

	/**
	* Writes a string to Cmake server
	*
	* @throws IOException I/O failure
	*/
	private void writeLine(String message) throws IOException {
	diagnostic("%s\n", message);
	output.write(message);
	output.newLine();
	}

	/**
	* Reads until the expected string is found. Skip unexpected (or non-conforming) messages if
	* need be until the expected string is found. Note: The CMake server sometimes writes
	* non-conforming messages (by deviating from the general message layout: https://goo.gl/d4XMmB)
	* to stdout, these are harmless (i.e., they don't break the build) and hence need to be
	* ignored.
	*/
	private void readExpected(@NonNull String expectedString) throws IOException {
	String line = readLine();
	while (!line.equals(expectedString)) {
	// Skip a blank line if there is one.
	if (!line.isEmpty() && serverReceiver.getDiagnosticReceiver() != null) {
	serverReceiver.getDiagnosticReceiver().receive(line);
	}
	line = readLine();
	}
	}

	/**
	* Reads a message send by CMake server. CMake Server sends the messages wrapped within a
	* defined header and footer string, this function reads everything inbetween the header and
	* footer and returns it. General message layout we expect from CMake Server:
	*
	* <p>[non-conforming messages from CMake Server]
	*
	* <p>[== "CMake Server" ==[
	*
	* <p>InteractiveMessage
	*
	* <p>[non-conforming messages from CMake Server]
	*
	* <p>]== "CMake Server" ==]
	*
	* @return The string contained within the header and footer
	* @throws IOException I/O failure
	*/
	private String readMessage() throws IOException {
	readExpected(CMAKE_SERVER_HEADER_MSG);
	final String line = readLine();
	readExpected(CMAKE_SERVER_FOOTER_MSG);
	return line;
	}

	/**
	* Writes a message wrapped within the header and footer.
	*
	* @param message string to be sent to Cmake server
	* @throws IOException I/O failure
	*/
	private void writeMessage(String message) throws IOException {
	writeLine(CMAKE_SERVER_HEADER_MSG);
	writeLine(message);
	writeLine(CMAKE_SERVER_FOOTER_MSG);
	output.flush();
	}
	}