main.cpp fixes, refactoring (#571)

- main: entering empty line passes back control without new input in interactive/instruct modes
- instruct mode: keep prompt fix
- instruct mode: duplicate instruct prompt fix
- refactor: move common console code from main->common

examples/common.h

@@ -63,3 +63,33 @@ std::string gpt_random_prompt(std::mt19937 & rng);
 //
 
 std::vector<llama_token> llama_tokenize(struct llama_context * ctx, const std::string & text, bool add_bos);
+
+//
+// Console utils
+//
+
+#define ANSI_COLOR_RED     "\x1b[31m"
+#define ANSI_COLOR_GREEN   "\x1b[32m"
+#define ANSI_COLOR_YELLOW  "\x1b[33m"
+#define ANSI_COLOR_BLUE    "\x1b[34m"
+#define ANSI_COLOR_MAGENTA "\x1b[35m"
+#define ANSI_COLOR_CYAN    "\x1b[36m"
+#define ANSI_COLOR_RESET   "\x1b[0m"
+#define ANSI_BOLD          "\x1b[1m"
+
+enum console_color_t {
+    CONSOLE_COLOR_DEFAULT=0,
+    CONSOLE_COLOR_PROMPT,
+    CONSOLE_COLOR_USER_INPUT
+};
+
+struct console_state {
+    bool use_color = false;
+    console_color_t color = CONSOLE_COLOR_DEFAULT;
+};
+
+void set_console_color(console_state & con_st, console_color_t color);
+
+#if defined (_WIN32)
+void win32_console_init(bool enable_color);
+#endif