common, server : report model input/output modalities in GET /models (#29987)

Signed-off-by: Adrien Gallouët <angt@huggingface.co>

common/common.cpp

@@ -1,4 +1,5 @@
 #include "ggml.h"
+#include "ggml-cpp.h"
 #include "gguf.h"
 
 #include "build-info.h"
@@ -1191,6 +1192,41 @@ common_decision_type common_get_decision_type(const struct llama_model * model)
     return common_decision_type_from_string(buf);
 }
 
+common_decision_type common_get_decision_type(const std::string & fname) {
+    struct gguf_init_params gguf_params = {
+        /* .no_alloc = */ true,
+        /* .ctx      = */ nullptr,
+    };
+
+    gguf_context_ptr gguf_ctx(gguf_init_from_file(fname.c_str(), gguf_params));
+    if (!gguf_ctx) {
+        return COMMON_DECISION_TYPE_UNKNOWN; // missing or unreadable file
+    }
+
+    std::string arch;
+    const int64_t arch_id = gguf_find_key(gguf_ctx.get(), "general.architecture");
+    if (arch_id < 0) {
+        return COMMON_DECISION_TYPE_UNKNOWN; // no architecture in the metadata
+    }
+    if (gguf_get_kv_type(gguf_ctx.get(), arch_id) != GGUF_TYPE_STRING) {
+        return COMMON_DECISION_TYPE_UNKNOWN; // malformed metadata
+    }
+    arch = gguf_get_val_str(gguf_ctx.get(), arch_id);
+    if (arch.empty()) {
+        return COMMON_DECISION_TYPE_UNKNOWN;
+    }
+
+    const std::string key = arch + ".decision.type";
+    const int64_t type_id = gguf_find_key(gguf_ctx.get(), key.c_str());
+    if (type_id < 0) {
+        return COMMON_DECISION_TYPE_NONE;
+    }
+    if (gguf_get_kv_type(gguf_ctx.get(), type_id) != GGUF_TYPE_STRING) {
+        return COMMON_DECISION_TYPE_UNKNOWN; // malformed metadata
+    }
+    return common_decision_type_from_string(gguf_get_val_str(gguf_ctx.get(), type_id));
+}
+
 common_init_result::common_init_result(common_params & params, bool model_only) :
     pimpl(new impl{}) {
     auto mparams = common_model_params_to_llama(params);