Implement help command for dicttoolkit.

Bug: 10059681
Change-Id: I0cadf1f80103136cdac5c00b6fca4d81b4bf7384

native/dicttoolkit/src/command_executors/diff_executor.cpp

@@ -28,5 +28,11 @@ const char *const DiffExecutor::COMMAND_NAME = "diff";
     return 0;
 }
 
+/* static */ void DiffExecutor::printUsage() {
+    printf("*** %s\n", COMMAND_NAME);
+    printf("Usage: %s\n", COMMAND_NAME);
+    printf("Shows differences between two dictionaries.\n\n");
+}
+
 } // namespace dicttoolkit
 } // namespace latinime

native/dicttoolkit/src/command_executors/diff_executor.h

@@ -27,6 +27,7 @@ class DiffExecutor final {
     static const char *const COMMAND_NAME;
 
     static int run(const int argc, char **argv);
+    static void printUsage();
 
  private:
     DISALLOW_IMPLICIT_CONSTRUCTORS(DiffExecutor);

native/dicttoolkit/src/command_executors/header_executor.cpp

@@ -28,5 +28,11 @@ const char *const HeaderExecutor::COMMAND_NAME = "header";
     return 0;
 }
 
+/* static */ void HeaderExecutor::printUsage() {
+    printf("*** %s\n", COMMAND_NAME);
+    printf("Usage: %s\n", COMMAND_NAME);
+    printf("Prints the header contents of a dictionary file.\n\n");
+}
+
 } // namespace dicttoolkit
 } // namespace latinime

native/dicttoolkit/src/command_executors/header_executor.h

@@ -27,6 +27,7 @@ class HeaderExecutor final {
     static const char *const COMMAND_NAME;
 
     static int run(const int argc, char **argv);
+    static void printUsage();
 
  private:
     DISALLOW_IMPLICIT_CONSTRUCTORS(HeaderExecutor);

native/dicttoolkit/src/command_executors/help_executor.cpp

@@ -17,6 +17,14 @@
 #include "command_executors/help_executor.h"
 
 #include <cstdio>
+#include <functional>
+#include <vector>
+
+#include "command_executors/diff_executor.h"
+#include "command_executors/header_executor.h"
+#include "command_executors/info_executor.h"
+#include "command_executors/makedict_executor.h"
+#include "utils/command_utils.h"
 
 namespace latinime {
 namespace dicttoolkit {
@@ -24,9 +32,21 @@ namespace dicttoolkit {
 const char *const HelpExecutor::COMMAND_NAME = "help";
 
 /* static */ int HelpExecutor::run(const int argc, char **argv) {
-    fprintf(stderr, "Command '%s' has not been implemented yet.\n", COMMAND_NAME);
+    printf("Available commands:\n\n");
+    const std::vector<std::function<void(void)>> printUsageMethods = {DiffExecutor::printUsage,
+            HeaderExecutor::printUsage, InfoExecutor::printUsage, MakedictExecutor::printUsage,
+            printUsage};
+    for (const auto &printUsageMethod : printUsageMethods) {
+        printUsageMethod();
+    }
     return 0;
 }
 
+/* static */ void HelpExecutor::printUsage() {
+    printf("*** %s\n", COMMAND_NAME);
+    printf("Usage: %s\n", COMMAND_NAME);
+    printf("Show this help list.\n\n");
+}
+
 } // namespace dicttoolkit
 } // namespace latinime

native/dicttoolkit/src/command_executors/help_executor.h

@@ -27,6 +27,7 @@ class HelpExecutor final {
     static const char *const COMMAND_NAME;
 
     static int run(const int argc, char **argv);
+    static void printUsage();
 
  private:
     DISALLOW_IMPLICIT_CONSTRUCTORS(HelpExecutor);

native/dicttoolkit/src/command_executors/info_executor.cpp

@@ -28,5 +28,11 @@ const char *const InfoExecutor::COMMAND_NAME = "info";
     return 0;
 }
 
+/* static */ void InfoExecutor::printUsage() {
+    printf("*** %s\n", COMMAND_NAME);
+    printf("Usage: %s\n", COMMAND_NAME);
+    printf("Prints various information about a dictionary file.\n\n");
+}
+
 } // namespace dicttoolkit
 } // namespace latinime

native/dicttoolkit/src/command_executors/info_executor.h

@@ -27,6 +27,7 @@ class InfoExecutor final {
     static const char *const COMMAND_NAME;
 
     static int run(const int argc, char **argv);
+    static void printUsage();
 
  private:
     DISALLOW_IMPLICIT_CONSTRUCTORS(InfoExecutor);

native/dicttoolkit/src/command_executors/makedict_executor.cpp

@@ -28,5 +28,13 @@ const char *const MakedictExecutor::COMMAND_NAME = "makedict";
     return 0;
 }
 
+/* static */ void MakedictExecutor::printUsage() {
+    printf("*** %s\n", COMMAND_NAME);
+    printf("Usage: %s\n", COMMAND_NAME);
+    printf("Converts a source dictionary file to one or several outputs.\n"
+            "Source can be a binary dictionary file or a combined format file.\n"
+            "Binary version 2 (Jelly Bean), 4, and combined format outputs are supported.\n\n");
+}
+
 } // namespace dicttoolkit
 } // namespace latinime

native/dicttoolkit/src/command_executors/makedict_executor.h

@@ -27,6 +27,7 @@ class MakedictExecutor final {
     static const char *const COMMAND_NAME;
 
     static int run(const int argc, char **argv);
+    static void printUsage();
 
  private:
     DISALLOW_IMPLICIT_CONSTRUCTORS(MakedictExecutor);