Function format_time

smallthinker/common/chat.cpp:20–27

#include <vector>

static std::string format_time(const std::chrono::system_clock::time_point & now, const std::string & format) {
    auto time = std::chrono::system_clock::to_time_t(now);
    auto local_time = *std::localtime(&time);
    std::ostringstream ss;
    ss << std::put_time(&local_time, format.c_str());
    auto res = ss.str();
    return res;
}

static std::string string_diff(const std::string & last, const std::string & current) {
    if (last.empty()) {