refactoring the find_first_substring function

Author: matteoserva

tools/server/server.cpp

@@ -2217,11 +2217,11 @@ struct server_context {
                 search_pos = slot.generated_text.size() - search_len;
             }
 
-            std::pair<size_t, int> search_result = find_first_substring(slot.generated_text,slot.params.start_strings, search_pos);
+            std::pair<size_t, std::string> search_result = find_first_substring(slot.generated_text,slot.params.start_strings, search_pos);
             bool start_string_found = search_result.first != std::string::npos;
             if (start_string_found) {
                 auto found_pos = search_result.first;
-                std::string found_string = slot.params.start_strings[search_result.second];
+                std::string found_string = search_result.second;
                 slot.generated_text.erase(
                     slot.generated_text.begin(),
                     slot.generated_text.begin() + found_pos + found_string.size());

tools/server/utils.hpp

@@ -491,21 +491,21 @@ static size_t find_partial_stop_string(const std::string &stop, const std::strin
 
 /* returns a pair containing the position and index of first element found.
    returns npos and -1 if not found */
-static std::pair<size_t, int> find_first_substring(const std::string &haystack, const std::vector<std::string> & needles, size_t search_pos = 0)
+static std::pair<size_t, std::string> find_first_substring(const std::string &haystack, const std::vector<std::string> & needles, size_t search_pos = 0)
 {
     size_t found_pos  = std::string::npos;
-    int    found_idx = -1;
+    std::string    found_str = "";
 
     for (unsigned int i = 0; i < needles.size(); ++i) {
         const std::string & start_string = needles[i];
         auto needle_pos = haystack.find(start_string,search_pos);
         if (needle_pos != std::string::npos && (found_pos == std::string::npos || needle_pos < found_pos) ) {
             found_pos = needle_pos;
-            found_idx = i;
+            found_str = start_string;
         }
     }
 
-    return std::pair<size_t, int>(found_pos,found_idx);
+    return std::pair<size_t, std::string>(found_pos,found_str);
 }
 
 // TODO: reuse llama_detokenize