feat: Impl help instruction display

Implement struct `ta_cli_argument_s` for saving information of instructions.
`ta_cli_arg_value_t` is an enum for recognising the commands.
And once calling the function `ta_usage()`, it will show all the currently available command.

accelerator/BUILD

@@ -68,3 +68,9 @@ cc_library(
     hdrs = ["errors.h"],
     visibility = ["//visibility:public"],
 )
+
+cc_library(
+    name = "message",
+    srcs = ["message.c"],
+    hdrs = ["message.h"],
+)

accelerator/message.c

@@ -0,0 +1,18 @@
+#include "message.h"
+#include "stdio.h"
+
+void ta_usage() {
+  printf("tangle-accelerator usage:\n");
+  for (int i = 0; i < cli_cmd_num; i++) {
+    printf("--%-34s ", ta_cli_arguments_g[i].name);
+    printf("     ");
+    if (ta_cli_arguments_g[i].has_arg == REQUIRED_ARG) {
+      printf(" arg ");
+    } else if (ta_cli_arguments_g[i].has_arg == OPTIONAL_ARG) {
+      printf("[arg]");
+    } else {
+      printf("     ");
+    }
+    printf(" %s \n", ta_cli_arguments_g[i].desc);
+  }
+}

accelerator/message.h

@@ -0,0 +1,52 @@
+#ifndef ACCELERATOR_MESSAGE_H_
+#define ACCELERATOR_MESSAGE_H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef enum ta_cli_arg_value_e {
+  HELP_CLI,
+
+  /** TA */
+  TA_HOST_CLI,
+  TA_PORT_CLI,
+  TA_THREAD_COUNT_CLI,
+  TA_VERSION_CLI,
+
+  /** IRI */
+  IRI_HOST_CLI,
+  IRI_PORT_CLI,
+
+  /** REDIS */
+  REDIS_HOST_CLI,
+  REDIS_PORT_CLI,
+
+  /** CONFIG */
+  MILESTONE_DEPTH_CLI,
+  MWM_CLI,
+  SEED_CLI,
+} ta_cli_arg_value_t;
+
+typedef enum ta_cli_arg_requirement_e {
+  NO_ARG,
+  REQUIRED_ARG,
+  OPTIONAL_ARG
+} ta_cli_arg_requirement_t;
+
+static struct ta_cli_argument_s {
+  char* name;
+  int val;
+  char* desc;
+  ta_cli_arg_requirement_t has_arg;
+} ta_cli_arguments_g[] = {
+    {"ta-help", HELP_CLI, "Show tangle-accelerator usage.", NO_ARG}};
+
+static const int cli_cmd_num =
+    sizeof(ta_cli_arguments_g) / sizeof(struct ta_cli_argument_s);
+void ta_usage();
+#ifdef __cplusplus
+}
+#endif
+
+#endif  // ACCELERATOR_MESSAGE_H_