From 44ce154e375081b7c0a339aa77a6d0fd0888870a Mon Sep 17 00:00:00 2001
From: TapTap <taptap.programming@gmail.com>
Date: Thu, 3 Sep 2026 16:42:29 +0200
Subject: [PATCH] feat: add checksum choice alias

---
 src/client/client_cli.c |  7 +++++++
 src/client/usage.c      |  2 ++
 tests/test_client_cli.c | 32 ++++++++++++++++++++++++++++++++
 3 files changed, 41 insertions(+)

diff --git a/src/client/client_cli.c b/src/client/client_cli.c
index 191cc07..3d54efc 100644
--- a/src/client/client_cli.c
+++ b/src/client/client_cli.c
@@ -361,6 +361,13 @@ int parse_args(Config* config, int argc, char* argv[], int* positional_args,
         log_message(LOG_LEVEL_ERROR, "--compress-level must be between 1 and 22");
         return -1;
       }
+    } else if (opt_is(argv[i], "--checksum-choice", "--cc")) {
+      if (i + 1 >= argc) {
+        log_message(LOG_LEVEL_ERROR, "missing argument for %s", argv[i]);
+        return -1;
+      }
+      log_message(LOG_LEVEL_ERROR, "%s is not supported yet (xxHash64 is used)", argv[i]);
+      return -1;
     } else if (argv[i][0] == '-') {
       fprintf(stderr, "Unknown option: %s\n", argv[i]);
       print_usage();
diff --git a/src/client/usage.c b/src/client/usage.c
index 2f800af..1d09f8b 100644
--- a/src/client/usage.c
+++ b/src/client/usage.c
@@ -28,6 +28,8 @@ void print_usage(void) {
   printf("  --max-size <n>      Skip files larger than n bytes\n");
   printf("  --min-size <n>      Skip files smaller than n bytes\n");
   printf("  --incremental       Skip files unchanged since last transfer\n");
+  printf("  --checksum-choice, --cc <alg>  Checksum algorithm (not supported yet; xxHash64 is "
+         "used)\n");
   printf("  --delta             Delta transfer for changed files (requires --incremental)\n");
   printf("  --delta-block <n>   Delta block size in bytes (default: %d)\n",
          DELTA_BLOCK_SIZE_DEFAULT);
diff --git a/tests/test_client_cli.c b/tests/test_client_cli.c
index 656fd40..98d1f6f 100644
--- a/tests/test_client_cli.c
+++ b/tests/test_client_cli.c
@@ -339,6 +339,36 @@ static void test_parse_args_archive() {
   config_delete(cfg);
 }
 
+/* Checksum-choice spellings are recognized and rejected until algorithms are implemented. */
+static void test_parse_args_checksum_choice_aliases() {
+  static const char* const options[] = {"--checksum-choice", "--cc"};
+
+  for (size_t i = 0; i < sizeof(options) / sizeof(options[0]); i++) {
+    Config* cfg = config_create();
+    char* argv[] = {"fastsync", (char*)options[i], "xxh64", "/src", "/dst"};
+    int positional_args[2];
+    int positional_count = 0;
+
+    EXPECT_EQ_INT(parse_args(cfg, 5, argv, positional_args, &positional_count), -1);
+    config_delete(cfg);
+  }
+}
+
+/* Both checksum-choice spellings require a value. */
+static void test_parse_args_checksum_choice_requires_value() {
+  static const char* const options[] = {"--checksum-choice", "--cc"};
+
+  for (size_t i = 0; i < sizeof(options) / sizeof(options[0]); i++) {
+    Config* cfg = config_create();
+    char* argv[] = {"fastsync", (char*)options[i]};
+    int positional_args[2];
+    int positional_count = 0;
+
+    EXPECT_EQ_INT(parse_args(cfg, 2, argv, positional_args, &positional_count), -1);
+    config_delete(cfg);
+  }
+}
+
 void test_client_cli() {
   test_validate_config_required_paths();
   test_validate_config_incompatible_options();
@@ -360,4 +390,6 @@ void test_client_cli() {
   test_parse_args_unknown_option();
   test_parse_args_rejects_unimplemented_options();
   test_parse_args_archive();
+  test_parse_args_checksum_choice_aliases();
+  test_parse_args_checksum_choice_requires_value();
 }