server: exclude thinking tokens when finding the slot (#1079)

refactor find slot

enable by default

Fix load prompt

rename variables

Co-authored-by: firecoperana <firecoperana>

examples/server/server-common.cpp

@@ -1773,6 +1773,84 @@ server_tokens::server_tokens(const llama_tokens& tokens, bool has_mtmd) : has_mt
         return max_idx; // all tokens are equal
     }
 
+    llama_tokens server_tokens::get_text_tokens_exclude_think(const llama_context* ctx, const thinking_tokens& think_token) const {
+        if (!think_token.exclude) {
+            return get_text_tokens();
+        }
+        GGML_ASSERT((think_token.begin != "" && think_token.end != "") && "think tokens cannot be empty");
+        std::string startStr = think_token.begin;
+        std::string endStr = think_token.end;
+
+        llama_tokens tokens = get_text_tokens();
+        std::string str = llama_detokenize(ctx, tokens, true);
+
+        std::vector<std::pair<size_t, size_t>> results;
+        // Find all positions of start and end
+        std::vector<size_t> startPositions;
+        std::vector<size_t> endPositions;
+
+        size_t pos = 0;
+        // Find all start positions
+        while ((pos = str.find(startStr, pos)) != std::string::npos) {
+            startPositions.push_back(pos);
+            pos += startStr.length();
+        }
+
+        pos = 0;
+        // Find all end positions
+        while ((pos = str.find(endStr, pos)) != std::string::npos) {
+            endPositions.push_back(pos + endStr.length());
+            pos += endStr.length();
+        }
+
+        // For each start position, pair with all end positions that come after it
+        for (size_t i = 0; i < startPositions.size(); i++) {
+            for (size_t j = 0; j < endPositions.size(); j++) {
+                if (results.size()) {
+                    // start must be after last end
+                    if (startPositions[i] > results[results.size() - 1].second && endPositions[j] > startPositions[i]) {
+                        results.push_back({ startPositions[i], endPositions[j] });
+                        break;
+                    }
+                }
+                else {
+                    if (endPositions[j] > startPositions[i]) {
+                        results.push_back({ startPositions[i], endPositions[j] });
+                        break;
+                    }
+                }
+
+            }
+        }
+        if (!results.size()) {
+            return tokens;
+        }
+
+        // Exclude tokens
+        pos = 0;
+        size_t n = 0;
+        size_t string_len = 0;
+        llama_tokens tokens_new;
+        auto model = llama_get_model(ctx);
+        for (n = 0; n < tokens.size(); ++n) {
+            str = llama_token_to_piece(model, tokens[n], true);
+            string_len = string_len + str.size();
+            if (string_len <= results[pos].first) {
+                tokens_new.push_back(tokens[n]);
+            }
+            else if (string_len <= results[pos].second) {
+                continue;
+            }
+            else {
+                tokens_new.push_back(tokens[n]);
+                if (pos+1 < results.size()) {
+                    pos++;
+                }
+            }            
+        }
+        return tokens_new;
+    }
+
 
     common_prefix server_tokens::get_common_prefix(const llama_context* ctx, const server_tokens& b, bool exact) const {
         common_prefix token_prefix;