// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
// Distributed under the MIT License (http://opensource.org/licenses/MIT)

#pragma once

#ifndef SPDLOG_HEADER_ONLY
#include <spdlog/pattern_formatter.h>
#endif

#include <spdlog/details/fmt_helper.h>
#include <spdlog/details/log_msg.h>
#include <spdlog/details/os.h>
#include <spdlog/fmt/fmt.h>
#include <spdlog/formatter.h>

#include <array>
#include <chrono>
#include <ctime>
#include <cctype>
#include <cstring>
#include <memory>
#include <mutex>
#include <string>
#include <thread>
#include <utility>
#include <vector>

namespace spdlog {
namespace details {

///////////////////////////////////////////////////////////////////////
// name & level pattern appender
///////////////////////////////////////////////////////////////////////

class scoped_padder
{
public:
    scoped_padder(size_t wrapped_size, const padding_info &padinfo, memory_buf_t &dest)
        : padinfo_(padinfo)
        , dest_(dest)
    {
        remaining_pad_ = static_cast<long>(padinfo.width_) - static_cast<long>(wrapped_size);
        if (remaining_pad_ <= 0)
        {
            return;
        }

        if (padinfo_.side_ == padding_info::pad_side::left)
        {
            pad_it(remaining_pad_);
            remaining_pad_ = 0;
        }
        else if (padinfo_.side_ == padding_info::pad_side::center)
        {
            auto half_pad = remaining_pad_ / 2;
            auto reminder = remaining_pad_ & 1;
            pad_it(half_pad);
            remaining_pad_ = half_pad + reminder; // for the right side
        }
    }

    template<typename T>
    static unsigned int count_digits(T n)
    {
        return fmt_helper::count_digits(n);
    }

    ~scoped_padder()
    {
        if (remaining_pad_ >= 0)
        {
            pad_it(remaining_pad_);
        }
        else if (padinfo_.truncate_)
        {
            long new_size = static_cast<long>(dest_.size()) + remaining_pad_;
            dest_.resize(static_cast<size_t>(new_size));
        }
    }

private:
    void pad_it(long count)
    {
        fmt_helper::append_string_view(string_view_t(spaces_.data(), static_cast<size_t>(count)), dest_);
    }

    const padding_info &padinfo_;
    memory_buf_t &dest_;
    long remaining_pad_;
    string_view_t spaces_{"                                                                ", 64};
};

struct null_scoped_padder
{
    null_scoped_padder(size_t /*wrapped_size*/, const padding_info & /*padinfo*/, memory_buf_t & /*dest*/) {}

    template<typename T>
    static unsigned int count_digits(T /* number */)
    {
        return 0;
    }
};

template<typename ScopedPadder>
class name_formatter final : public flag_formatter
{
public:
    explicit name_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &msg, const std::tm &, memory_buf_t &dest) override
    {
        ScopedPadder p(msg.logger_name.size(), padinfo_, dest);
        fmt_helper::append_string_view(msg.logger_name, dest);
    }
};

// log level appender
template<typename ScopedPadder>
class level_formatter final : public flag_formatter
{
public:
    explicit level_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &msg, const std::tm &, memory_buf_t &dest) override
    {
        string_view_t &level_name = level::to_string_view(msg.level);
        ScopedPadder p(level_name.size(), padinfo_, dest);
        fmt_helper::append_string_view(level_name, dest);
    }
};

// short log level appender
template<typename ScopedPadder>
class short_level_formatter final : public flag_formatter
{
public:
    explicit short_level_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &msg, const std::tm &, memory_buf_t &dest) override
    {
        string_view_t level_name{level::to_short_c_str(msg.level)};
        ScopedPadder p(level_name.size(), padinfo_, dest);
        fmt_helper::append_string_view(level_name, dest);
    }
};

///////////////////////////////////////////////////////////////////////
// Date time pattern appenders
///////////////////////////////////////////////////////////////////////

static const char *ampm(const tm &t)
{
    return t.tm_hour >= 12 ? "PM" : "AM";
}

static int to12h(const tm &t)
{
    return t.tm_hour > 12 ? t.tm_hour - 12 : t.tm_hour;
}

// Abbreviated weekday name
static std::array<const char *, 7> days{{"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"}};

template<typename ScopedPadder>
class a_formatter final : public flag_formatter
{
public:
    explicit a_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &, const std::tm &tm_time, memory_buf_t &dest) override
    {
        string_view_t field_value{days[static_cast<size_t>(tm_time.tm_wday)]};
        ScopedPadder p(field_value.size(), padinfo_, dest);
        fmt_helper::append_string_view(field_value, dest);
    }
};

// Full weekday name
static std::array<const char *, 7> full_days{{"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"}};

template<typename ScopedPadder>
class A_formatter : public flag_formatter
{
public:
    explicit A_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &, const std::tm &tm_time, memory_buf_t &dest) override
    {
        string_view_t field_value{full_days[static_cast<size_t>(tm_time.tm_wday)]};
        ScopedPadder p(field_value.size(), padinfo_, dest);
        fmt_helper::append_string_view(field_value, dest);
    }
};

// Abbreviated month
static const std::array<const char *, 12> months{{"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sept", "Oct", "Nov", "Dec"}};

template<typename ScopedPadder>
class b_formatter final : public flag_formatter
{
public:
    explicit b_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &, const std::tm &tm_time, memory_buf_t &dest) override
    {
        string_view_t field_value{months[static_cast<size_t>(tm_time.tm_mon)]};
        ScopedPadder p(field_value.size(), padinfo_, dest);
        fmt_helper::append_string_view(field_value, dest);
    }
};

// Full month name
static const std::array<const char *, 12> full_months{
    {"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"}};

template<typename ScopedPadder>
class B_formatter final : public flag_formatter
{
public:
    explicit B_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &, const std::tm &tm_time, memory_buf_t &dest) override
    {
        string_view_t field_value{full_months[static_cast<size_t>(tm_time.tm_mon)]};
        ScopedPadder p(field_value.size(), padinfo_, dest);
        fmt_helper::append_string_view(field_value, dest);
    }
};

// Date and time representation (Thu Aug 23 15:35:46 2014)
template<typename ScopedPadder>
class c_formatter final : public flag_formatter
{
public:
    explicit c_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &, const std::tm &tm_time, memory_buf_t &dest) override
    {
        const size_t field_size = 24;
        ScopedPadder p(field_size, padinfo_, dest);

        fmt_helper::append_string_view(days[static_cast<size_t>(tm_time.tm_wday)], dest);
        dest.push_back(' ');
        fmt_helper::append_string_view(months[static_cast<size_t>(tm_time.tm_mon)], dest);
        dest.push_back(' ');
        fmt_helper::append_int(tm_time.tm_mday, dest);
        dest.push_back(' ');
        // time

        fmt_helper::pad2(tm_time.tm_hour, dest);
        dest.push_back(':');
        fmt_helper::pad2(tm_time.tm_min, dest);
        dest.push_back(':');
        fmt_helper::pad2(tm_time.tm_sec, dest);
        dest.push_back(' ');
        fmt_helper::append_int(tm_time.tm_year + 1900, dest);
    }
};

// year - 2 digit
template<typename ScopedPadder>
class C_formatter final : public flag_formatter
{
public:
    explicit C_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &, const std::tm &tm_time, memory_buf_t &dest) override
    {
        const size_t field_size = 2;
        ScopedPadder p(field_size, padinfo_, dest);
        fmt_helper::pad2(tm_time.tm_year % 100, dest);
    }
};

// Short MM/DD/YY date, equivalent to %m/%d/%y 08/23/01
template<typename ScopedPadder>
class D_formatter final : public flag_formatter
{
public:
    explicit D_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &, const std::tm &tm_time, memory_buf_t &dest) override
    {
        const size_t field_size = 10;
        ScopedPadder p(field_size, padinfo_, dest);

        fmt_helper::pad2(tm_time.tm_mon + 1, dest);
        dest.push_back('/');
        fmt_helper::pad2(tm_time.tm_mday, dest);
        dest.push_back('/');
        fmt_helper::pad2(tm_time.tm_year % 100, dest);
    }
};

// year - 4 digit
template<typename ScopedPadder>
class Y_formatter final : public flag_formatter
{
public:
    explicit Y_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &, const std::tm &tm_time, memory_buf_t &dest) override
    {
        const size_t field_size = 4;
        ScopedPadder p(field_size, padinfo_, dest);
        fmt_helper::append_int(tm_time.tm_year + 1900, dest);
    }
};

// month 1-12
template<typename ScopedPadder>
class m_formatter final : public flag_formatter
{
public:
    explicit m_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &, const std::tm &tm_time, memory_buf_t &dest) override
    {
        const size_t field_size = 2;
        ScopedPadder p(field_size, padinfo_, dest);
        fmt_helper::pad2(tm_time.tm_mon + 1, dest);
    }
};

// day of month 1-31
template<typename ScopedPadder>
class d_formatter final : public flag_formatter
{
public:
    explicit d_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &, const std::tm &tm_time, memory_buf_t &dest) override
    {
        const size_t field_size = 2;
        ScopedPadder p(field_size, padinfo_, dest);
        fmt_helper::pad2(tm_time.tm_mday, dest);
    }
};

// hours in 24 format 0-23
template<typename ScopedPadder>
class H_formatter final : public flag_formatter
{
public:
    explicit H_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &, const std::tm &tm_time, memory_buf_t &dest) override
    {
        const size_t field_size = 2;
        ScopedPadder p(field_size, padinfo_, dest);
        fmt_helper::pad2(tm_time.tm_hour, dest);
    }
};

// hours in 12 format 1-12
template<typename ScopedPadder>
class I_formatter final : public flag_formatter
{
public:
    explicit I_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &, const std::tm &tm_time, memory_buf_t &dest) override
    {
        const size_t field_size = 2;
        ScopedPadder p(field_size, padinfo_, dest);
        fmt_helper::pad2(to12h(tm_time), dest);
    }
};

// minutes 0-59
template<typename ScopedPadder>
class M_formatter final : public flag_formatter
{
public:
    explicit M_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &, const std::tm &tm_time, memory_buf_t &dest) override
    {
        const size_t field_size = 2;
        ScopedPadder p(field_size, padinfo_, dest);
        fmt_helper::pad2(tm_time.tm_min, dest);
    }
};

// seconds 0-59
template<typename ScopedPadder>
class S_formatter final : public flag_formatter
{
public:
    explicit S_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &, const std::tm &tm_time, memory_buf_t &dest) override
    {
        const size_t field_size = 2;
        ScopedPadder p(field_size, padinfo_, dest);
        fmt_helper::pad2(tm_time.tm_sec, dest);
    }
};

// milliseconds
template<typename ScopedPadder>
class e_formatter final : public flag_formatter
{
public:
    explicit e_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &msg, const std::tm &, memory_buf_t &dest) override
    {
        auto millis = fmt_helper::time_fraction<std::chrono::milliseconds>(msg.time);
        const size_t field_size = 3;
        ScopedPadder p(field_size, padinfo_, dest);
        fmt_helper::pad3(static_cast<uint32_t>(millis.count()), dest);
    }
};

// microseconds
template<typename ScopedPadder>
class f_formatter final : public flag_formatter
{
public:
    explicit f_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &msg, const std::tm &, memory_buf_t &dest) override
    {
        auto micros = fmt_helper::time_fraction<std::chrono::microseconds>(msg.time);

        const size_t field_size = 6;
        ScopedPadder p(field_size, padinfo_, dest);
        fmt_helper::pad6(static_cast<size_t>(micros.count()), dest);
    }
};

// nanoseconds
template<typename ScopedPadder>
class F_formatter final : public flag_formatter
{
public:
    explicit F_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &msg, const std::tm &, memory_buf_t &dest) override
    {
        auto ns = fmt_helper::time_fraction<std::chrono::nanoseconds>(msg.time);
        const size_t field_size = 9;
        ScopedPadder p(field_size, padinfo_, dest);
        fmt_helper::pad9(static_cast<size_t>(ns.count()), dest);
    }
};

// seconds since epoch
template<typename ScopedPadder>
class E_formatter final : public flag_formatter
{
public:
    explicit E_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &msg, const std::tm &, memory_buf_t &dest) override
    {
        const size_t field_size = 10;
        ScopedPadder p(field_size, padinfo_, dest);
        auto duration = msg.time.time_since_epoch();
        auto seconds = std::chrono::duration_cast<std::chrono::seconds>(duration).count();
        fmt_helper::append_int(seconds, dest);
    }
};

// AM/PM
template<typename ScopedPadder>
class p_formatter final : public flag_formatter
{
public:
    explicit p_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &, const std::tm &tm_time, memory_buf_t &dest) override
    {
        const size_t field_size = 2;
        ScopedPadder p(field_size, padinfo_, dest);
        fmt_helper::append_string_view(ampm(tm_time), dest);
    }
};

// 12 hour clock 02:55:02 pm
template<typename ScopedPadder>
class r_formatter final : public flag_formatter
{
public:
    explicit r_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &, const std::tm &tm_time, memory_buf_t &dest) override
    {
        const size_t field_size = 11;
        ScopedPadder p(field_size, padinfo_, dest);

        fmt_helper::pad2(to12h(tm_time), dest);
        dest.push_back(':');
        fmt_helper::pad2(tm_time.tm_min, dest);
        dest.push_back(':');
        fmt_helper::pad2(tm_time.tm_sec, dest);
        dest.push_back(' ');
        fmt_helper::append_string_view(ampm(tm_time), dest);
    }
};

// 24-hour HH:MM time, equivalent to %H:%M
template<typename ScopedPadder>
class R_formatter final : public flag_formatter
{
public:
    explicit R_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &, const std::tm &tm_time, memory_buf_t &dest) override
    {
        const size_t field_size = 5;
        ScopedPadder p(field_size, padinfo_, dest);

        fmt_helper::pad2(tm_time.tm_hour, dest);
        dest.push_back(':');
        fmt_helper::pad2(tm_time.tm_min, dest);
    }
};

// ISO 8601 time format (HH:MM:SS), equivalent to %H:%M:%S
template<typename ScopedPadder>
class T_formatter final : public flag_formatter
{
public:
    explicit T_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &, const std::tm &tm_time, memory_buf_t &dest) override
    {
        const size_t field_size = 8;
        ScopedPadder p(field_size, padinfo_, dest);

        fmt_helper::pad2(tm_time.tm_hour, dest);
        dest.push_back(':');
        fmt_helper::pad2(tm_time.tm_min, dest);
        dest.push_back(':');
        fmt_helper::pad2(tm_time.tm_sec, dest);
    }
};

// ISO 8601 offset from UTC in timezone (+-HH:MM)
template<typename ScopedPadder>
class z_formatter final : public flag_formatter
{
public:
    explicit z_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    z_formatter() = default;
    z_formatter(const z_formatter &) = delete;
    z_formatter &operator=(const z_formatter &) = delete;

    void format(const details::log_msg &msg, const std::tm &tm_time, memory_buf_t &dest) override
    {
        const size_t field_size = 6;
        ScopedPadder p(field_size, padinfo_, dest);

        auto total_minutes = get_cached_offset(msg, tm_time);
        bool is_negative = total_minutes < 0;
        if (is_negative)
        {
            total_minutes = -total_minutes;
            dest.push_back('-');
        }
        else
        {
            dest.push_back('+');
        }

        fmt_helper::pad2(total_minutes / 60, dest); // hours
        dest.push_back(':');
        fmt_helper::pad2(total_minutes % 60, dest); // minutes
    }

private:
    log_clock::time_point last_update_{std::chrono::seconds(0)};
    int offset_minutes_{0};

    int get_cached_offset(const log_msg &msg, const std::tm &tm_time)
    {
        // refresh every 10 seconds
        if (msg.time - last_update_ >= std::chrono::seconds(10))
        {
            offset_minutes_ = os::utc_minutes_offset(tm_time);
            last_update_ = msg.time;
        }
        return offset_minutes_;
    }
};

// Thread id
template<typename ScopedPadder>
class t_formatter final : public flag_formatter
{
public:
    explicit t_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &msg, const std::tm &, memory_buf_t &dest) override
    {
        const auto field_size = ScopedPadder::count_digits(msg.thread_id);
        ScopedPadder p(field_size, padinfo_, dest);
        fmt_helper::append_int(msg.thread_id, dest);
    }
};

// Current pid
template<typename ScopedPadder>
class pid_formatter final : public flag_formatter
{
public:
    explicit pid_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &, const std::tm &, memory_buf_t &dest) override
    {
        const auto pid = static_cast<uint32_t>(details::os::pid());
        auto field_size = ScopedPadder::count_digits(pid);
        ScopedPadder p(field_size, padinfo_, dest);
        fmt_helper::append_int(pid, dest);
    }
};

template<typename ScopedPadder>
class v_formatter final : public flag_formatter
{
public:
    explicit v_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &msg, const std::tm &, memory_buf_t &dest) override
    {
        ScopedPadder p(msg.payload.size(), padinfo_, dest);
        fmt_helper::append_string_view(msg.payload, dest);
    }
};

class ch_formatter final : public flag_formatter
{
public:
    explicit ch_formatter(char ch)
        : ch_(ch)
    {}

    void format(const details::log_msg &, const std::tm &, memory_buf_t &dest) override
    {
        dest.push_back(ch_);
    }

private:
    char ch_;
};

// aggregate user chars to display as is
class aggregate_formatter final : public flag_formatter
{
public:
    aggregate_formatter() = default;

    void add_ch(char ch)
    {
        str_ += ch;
    }
    void format(const details::log_msg &, const std::tm &, memory_buf_t &dest) override
    {
        fmt_helper::append_string_view(str_, dest);
    }

private:
    std::string str_;
};

// mark the color range. expect it to be in the form of "%^colored text%$"
class color_start_formatter final : public flag_formatter
{
public:
    explicit color_start_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &msg, const std::tm &, memory_buf_t &dest) override
    {
        msg.color_range_start = dest.size();
    }
};

class color_stop_formatter final : public flag_formatter
{
public:
    explicit color_stop_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &msg, const std::tm &, memory_buf_t &dest) override
    {
        msg.color_range_end = dest.size();
    }
};

// print source location
template<typename ScopedPadder>
class source_location_formatter final : public flag_formatter
{
public:
    explicit source_location_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &msg, const std::tm &, memory_buf_t &dest) override
    {
        if (msg.source.empty())
        {
            return;
        }

        size_t text_size;
        if (padinfo_.enabled())
        {
            // calc text size for padding based on "filename:line"
            text_size = std::char_traits<char>::length(msg.source.filename) + ScopedPadder::count_digits(msg.source.line) + 1;
        }
        else
        {
            text_size = 0;
        }

        ScopedPadder p(text_size, padinfo_, dest);
        fmt_helper::append_string_view(msg.source.filename, dest);
        dest.push_back(':');
        fmt_helper::append_int(msg.source.line, dest);
    }
};

// print source filename
template<typename ScopedPadder>
class source_filename_formatter final : public flag_formatter
{
public:
    explicit source_filename_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &msg, const std::tm &, memory_buf_t &dest) override
    {
        if (msg.source.empty())
        {
            return;
        }
        size_t text_size = padinfo_.enabled() ? std::char_traits<char>::length(msg.source.filename) : 0;
        ScopedPadder p(text_size, padinfo_, dest);
        fmt_helper::append_string_view(msg.source.filename, dest);
    }
};

template<typename ScopedPadder>
class short_filename_formatter final : public flag_formatter
{
public:
    explicit short_filename_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    static const char *basename(const char *filename)
    {
        const char *rv = std::strrchr(filename, os::folder_sep);
        return rv != nullptr ? rv + 1 : filename;
    }

    void format(const details::log_msg &msg, const std::tm &, memory_buf_t &dest) override
    {
        if (msg.source.empty())
        {
            return;
        }
        auto filename = basename(msg.source.filename);
        size_t text_size = padinfo_.enabled() ? std::char_traits<char>::length(filename) : 0;
        ScopedPadder p(text_size, padinfo_, dest);
        fmt_helper::append_string_view(filename, dest);
    }
};

template<typename ScopedPadder>
class source_linenum_formatter final : public flag_formatter
{
public:
    explicit source_linenum_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &msg, const std::tm &, memory_buf_t &dest) override
    {
        if (msg.source.empty())
        {
            return;
        }

        auto field_size = ScopedPadder::count_digits(msg.source.line);
        ScopedPadder p(field_size, padinfo_, dest);
        fmt_helper::append_int(msg.source.line, dest);
    }
};

// print source funcname
template<typename ScopedPadder>
class source_funcname_formatter final : public flag_formatter
{
public:
    explicit source_funcname_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &msg, const std::tm &, memory_buf_t &dest) override
    {
        if (msg.source.empty())
        {
            return;
        }
        size_t text_size = padinfo_.enabled() ? std::char_traits<char>::length(msg.source.funcname) : 0;
        ScopedPadder p(text_size, padinfo_, dest);
        fmt_helper::append_string_view(msg.source.funcname, dest);
    }
};

// print elapsed time since last message
template<typename ScopedPadder, typename Units>
class elapsed_formatter final : public flag_formatter
{
public:
    using DurationUnits = Units;

    explicit elapsed_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
        , last_message_time_(log_clock::now())
    {}

    void format(const details::log_msg &msg, const std::tm &, memory_buf_t &dest) override
    {
        auto delta = (std::max)(msg.time - last_message_time_, log_clock::duration::zero());
        auto delta_units = std::chrono::duration_cast<DurationUnits>(delta);
        last_message_time_ = msg.time;
        auto delta_count = static_cast<size_t>(delta_units.count());
        auto n_digits = static_cast<size_t>(ScopedPadder::count_digits(delta_count));
        ScopedPadder p(n_digits, padinfo_, dest);
        fmt_helper::append_int(delta_count, dest);
    }

private:
    log_clock::time_point last_message_time_;
};

// Full info formatter
// pattern: [%Y-%m-%d %H:%M:%S.%e] [%n] [%l] %v
class full_formatter final : public flag_formatter
{
public:
    explicit full_formatter(padding_info padinfo)
        : flag_formatter(padinfo)
    {}

    void format(const details::log_msg &msg, const std::tm &tm_time, memory_buf_t &dest) override
    {
        using std::chrono::duration_cast;
        using std::chrono::milliseconds;
        using std::chrono::seconds;

        // cache the date/time part for the next second.
        auto duration = msg.time.time_since_epoch();
        auto secs = duration_cast<seconds>(duration);

        if (cache_timestamp_ != secs || cached_datetime_.size() == 0)
        {
            cached_datetime_.clear();
            cached_datetime_.push_back('[');
            fmt_helper::append_int(tm_time.tm_year + 1900, cached_datetime_);
            cached_datetime_.push_back('-');

            fmt_helper::pad2(tm_time.tm_mon + 1, cached_datetime_);
            cached_datetime_.push_back('-');

            fmt_helper::pad2(tm_time.tm_mday, cached_datetime_);
            cached_datetime_.push_back(' ');

            fmt_helper::pad2(tm_time.tm_hour, cached_datetime_);
            cached_datetime_.push_back(':');

            fmt_helper::pad2(tm_time.tm_min, cached_datetime_);
            cached_datetime_.push_back(':');

            fmt_helper::pad2(tm_time.tm_sec, cached_datetime_);
            cached_datetime_.push_back('.');

            cache_timestamp_ = secs;
        }
        dest.append(cached_datetime_.begin(), cached_datetime_.end());

        auto millis = fmt_helper::time_fraction<milliseconds>(msg.time);
        fmt_helper::pad3(static_cast<uint32_t>(millis.count()), dest);
        dest.push_back(']');
        dest.push_back(' ');

        // append logger name if exists
        if (msg.logger_name.size() > 0)
        {
            dest.push_back('[');
            fmt_helper::append_string_view(msg.logger_name, dest);
            dest.push_back(']');
            dest.push_back(' ');
        }

        dest.push_back('[');
        // wrap the level name with color
        msg.color_range_start = dest.size();
        // fmt_helper::append_string_view(level::to_c_str(msg.level), dest);
        fmt_helper::append_string_view(level::to_string_view(msg.level), dest);
        msg.color_range_end = dest.size();
        dest.push_back(']');
        dest.push_back(' ');

        // add source location if present
        if (!msg.source.empty())
        {
            dest.push_back('[');
            const char *filename = details::short_filename_formatter<details::null_scoped_padder>::basename(msg.source.filename);
            fmt_helper::append_string_view(filename, dest);
            dest.push_back(':');
            fmt_helper::append_int(msg.source.line, dest);
            dest.push_back(']');
            dest.push_back(' ');
        }
        // fmt_helper::append_string_view(msg.msg(), dest);
        fmt_helper::append_string_view(msg.payload, dest);
    }

private:
    std::chrono::seconds cache_timestamp_{0};
    memory_buf_t cached_datetime_;
};

} // namespace details

SPDLOG_INLINE pattern_formatter::pattern_formatter(
    std::string pattern, pattern_time_type time_type, std::string eol, custom_flags custom_user_flags)
    : pattern_(std::move(pattern))
    , eol_(std::move(eol))
    , pattern_time_type_(time_type)
    , last_log_secs_(0)
    , custom_handlers_(std::move(custom_user_flags))
{
    std::memset(&cached_tm_, 0, sizeof(cached_tm_));
    compile_pattern_(pattern_);
}

// use by default full formatter for if pattern is not given
SPDLOG_INLINE pattern_formatter::pattern_formatter(pattern_time_type time_type, std::string eol)
    : pattern_("%+")
    , eol_(std::move(eol))
    , pattern_time_type_(time_type)
    , last_log_secs_(0)
{
    std::memset(&cached_tm_, 0, sizeof(cached_tm_));
    formatters_.push_back(details::make_unique<details::full_formatter>(details::padding_info{}));
}

SPDLOG_INLINE std::unique_ptr<formatter> pattern_formatter::clone() const
{
    custom_flags cloned_custom_formatters;
    for (auto &it : custom_handlers_)
    {
        cloned_custom_formatters[it.first] = it.second->clone();
    }
    return details::make_unique<pattern_formatter>(pattern_, pattern_time_type_, eol_, std::move(cloned_custom_formatters));
}

SPDLOG_INLINE void pattern_formatter::format(const details::log_msg &msg, memory_buf_t &dest)
{
    auto secs = std::chrono::duration_cast<std::chrono::seconds>(msg.time.time_since_epoch());
    if (secs != last_log_secs_)
    {
        cached_tm_ = get_time_(msg);
        last_log_secs_ = secs;
    }

    for (auto &f : formatters_)
    {
        f->format(msg, cached_tm_, dest);
    }
    // write eol
    details::fmt_helper::append_string_view(eol_, dest);
}

SPDLOG_INLINE void pattern_formatter::set_pattern(std::string pattern)
{
    pattern_ = std::move(pattern);
    compile_pattern_(pattern_);
}

SPDLOG_INLINE std::tm pattern_formatter::get_time_(const details::log_msg &msg)
{
    if (pattern_time_type_ == pattern_time_type::local)
    {
        return details::os::localtime(log_clock::to_time_t(msg.time));
    }
    return details::os::gmtime(log_clock::to_time_t(msg.time));
}

template<typename Padder>
SPDLOG_INLINE void pattern_formatter::handle_flag_(char flag, details::padding_info padding)
{
    // process custom flags
    auto it = custom_handlers_.find(flag);
    if (it != custom_handlers_.end())
    {
        auto custom_handler = it->second->clone();
        custom_handler->set_padding_info(padding);
        formatters_.push_back(std::move(custom_handler));
        return;
    }

    // process built-in flags
    switch (flag)
    {
    case ('+'): // default formatter
        formatters_.push_back(details::make_unique<details::full_formatter>(padding));
        break;

    case 'n': // logger name
        formatters_.push_back(details::make_unique<details::name_formatter<Padder>>(padding));
        break;

    case 'l': // level
        formatters_.push_back(details::make_unique<details::level_formatter<Padder>>(padding));
        break;

    case 'L': // short level
        formatters_.push_back(details::make_unique<details::short_level_formatter<Padder>>(padding));
        break;

    case ('t'): // thread id
        formatters_.push_back(details::make_unique<details::t_formatter<Padder>>(padding));
        break;

    case ('v'): // the message text
        formatters_.push_back(details::make_unique<details::v_formatter<Padder>>(padding));
        break;

    case ('a'): // weekday
        formatters_.push_back(details::make_unique<details::a_formatter<Padder>>(padding));
        break;

    case ('A'): // short weekday
        formatters_.push_back(details::make_unique<details::A_formatter<Padder>>(padding));
        break;

    case ('b'):
    case ('h'): // month
        formatters_.push_back(details::make_unique<details::b_formatter<Padder>>(padding));
        break;

    case ('B'): // short month
        formatters_.push_back(details::make_unique<details::B_formatter<Padder>>(padding));
        break;

    case ('c'): // datetime
        formatters_.push_back(details::make_unique<details::c_formatter<Padder>>(padding));
        break;

    case ('C'): // year 2 digits
        formatters_.push_back(details::make_unique<details::C_formatter<Padder>>(padding));
        break;

    case ('Y'): // year 4 digits
        formatters_.push_back(details::make_unique<details::Y_formatter<Padder>>(padding));
        break;

    case ('D'):
    case ('x'): // datetime MM/DD/YY
        formatters_.push_back(details::make_unique<details::D_formatter<Padder>>(padding));
        break;

    case ('m'): // month 1-12
        formatters_.push_back(details::make_unique<details::m_formatter<Padder>>(padding));
        break;

    case ('d'): // day of month 1-31
        formatters_.push_back(details::make_unique<details::d_formatter<Padder>>(padding));
        break;

    case ('H'): // hours 24
        formatters_.push_back(details::make_unique<details::H_formatter<Padder>>(padding));
        break;

    case ('I'): // hours 12
        formatters_.push_back(details::make_unique<details::I_formatter<Padder>>(padding));
        break;

    case ('M'): // minutes
        formatters_.push_back(details::make_unique<details::M_formatter<Padder>>(padding));
        break;

    case ('S'): // seconds
        formatters_.push_back(details::make_unique<details::S_formatter<Padder>>(padding));
        break;

    case ('e'): // milliseconds
        formatters_.push_back(details::make_unique<details::e_formatter<Padder>>(padding));
        break;

    case ('f'): // microseconds
        formatters_.push_back(details::make_unique<details::f_formatter<Padder>>(padding));
        break;

    case ('F'): // nanoseconds
        formatters_.push_back(details::make_unique<details::F_formatter<Padder>>(padding));
        break;

    case ('E'): // seconds since epoch
        formatters_.push_back(details::make_unique<details::E_formatter<Padder>>(padding));
        break;

    case ('p'): // am/pm
        formatters_.push_back(details::make_unique<details::p_formatter<Padder>>(padding));
        break;

    case ('r'): // 12 hour clock 02:55:02 pm
        formatters_.push_back(details::make_unique<details::r_formatter<Padder>>(padding));
        break;

    case ('R'): // 24-hour HH:MM time
        formatters_.push_back(details::make_unique<details::R_formatter<Padder>>(padding));
        break;

    case ('T'):
    case ('X'): // ISO 8601 time format (HH:MM:SS)
        formatters_.push_back(details::make_unique<details::T_formatter<Padder>>(padding));
        break;

    case ('z'): // timezone
        formatters_.push_back(details::make_unique<details::z_formatter<Padder>>(padding));
        break;

    case ('P'): // pid
        formatters_.push_back(details::make_unique<details::pid_formatter<Padder>>(padding));
        break;

    case ('^'): // color range start
        formatters_.push_back(details::make_unique<details::color_start_formatter>(padding));
        break;

    case ('$'): // color range end
        formatters_.push_back(details::make_unique<details::color_stop_formatter>(padding));
        break;

    case ('@'): // source location (filename:filenumber)
        formatters_.push_back(details::make_unique<details::source_location_formatter<Padder>>(padding));
        break;

    case ('s'): // short source filename - without directory name
        formatters_.push_back(details::make_unique<details::short_filename_formatter<Padder>>(padding));
        break;

    case ('g'): // full source filename
        formatters_.push_back(details::make_unique<details::source_filename_formatter<Padder>>(padding));
        break;

    case ('#'): // source line number
        formatters_.push_back(details::make_unique<details::source_linenum_formatter<Padder>>(padding));
        break;

    case ('!'): // source funcname
        formatters_.push_back(details::make_unique<details::source_funcname_formatter<Padder>>(padding));
        break;

    case ('%'): // % char
        formatters_.push_back(details::make_unique<details::ch_formatter>('%'));
        break;

    case ('u'): // elapsed time since last log message in nanos
        formatters_.push_back(details::make_unique<details::elapsed_formatter<Padder, std::chrono::nanoseconds>>(padding));
        break;

    case ('i'): // elapsed time since last log message in micros
        formatters_.push_back(details::make_unique<details::elapsed_formatter<Padder, std::chrono::microseconds>>(padding));
        break;

    case ('o'): // elapsed time since last log message in millis
        formatters_.push_back(details::make_unique<details::elapsed_formatter<Padder, std::chrono::milliseconds>>(padding));
        break;

    case ('O'): // elapsed time since last log message in seconds
        formatters_.push_back(details::make_unique<details::elapsed_formatter<Padder, std::chrono::seconds>>(padding));
        break;

    default: // Unknown flag appears as is
        auto unknown_flag = details::make_unique<details::aggregate_formatter>();

        if (!padding.truncate_)
        {
            unknown_flag->add_ch('%');
            unknown_flag->add_ch(flag);
            formatters_.push_back((std::move(unknown_flag)));
        }
        // fix issue #1617 (prev char was '!' and should have been treated as funcname flag instead of truncating flag)
        // spdlog::set_pattern("[%10!] %v") => "[      main] some message"
        // spdlog::set_pattern("[%3!!] %v") => "[mai] some message"
        else
        {
            padding.truncate_ = false;
            formatters_.push_back(details::make_unique<details::source_funcname_formatter<Padder>>(padding));
            unknown_flag->add_ch(flag);
            formatters_.push_back((std::move(unknown_flag)));
        }

        break;
    }
}

// Extract given pad spec (e.g. %8X, %=8X, %-8!X, %8!X, %=8!X, %-8!X, %+8!X)
// Advance the given it pass the end of the padding spec found (if any)
// Return padding.
SPDLOG_INLINE details::padding_info pattern_formatter::handle_padspec_(std::string::const_iterator &it, std::string::const_iterator end)
{
    using details::padding_info;
    using details::scoped_padder;
    const size_t max_width = 64;
    if (it == end)
    {
        return padding_info{};
    }

    padding_info::pad_side side;
    switch (*it)
    {
    case '-':
        side = padding_info::pad_side::right;
        ++it;
        break;
    case '=':
        side = padding_info::pad_side::center;
        ++it;
        break;
    default:
        side = details::padding_info::pad_side::left;
        break;
    }

    if (it == end || !std::isdigit(static_cast<unsigned char>(*it)))
    {
        return padding_info{}; // no padding if no digit found here
    }

    auto width = static_cast<size_t>(*it) - '0';
    for (++it; it != end && std::isdigit(static_cast<unsigned char>(*it)); ++it)
    {
        auto digit = static_cast<size_t>(*it) - '0';
        width = width * 10 + digit;
    }

    // search for the optional truncate marker '!'
    bool truncate;
    if (it != end && *it == '!')
    {
        truncate = true;
        ++it;
    }
    else
    {
        truncate = false;
    }

    return details::padding_info{std::min<size_t>(width, max_width), side, truncate};
}

SPDLOG_INLINE void pattern_formatter::compile_pattern_(const std::string &pattern)
{
    auto end = pattern.end();
    std::unique_ptr<details::aggregate_formatter> user_chars;
    formatters_.clear();
    for (auto it = pattern.begin(); it != end; ++it)
    {
        if (*it == '%')
        {
            if (user_chars) // append user chars found so far
            {
                formatters_.push_back(std::move(user_chars));
            }

            auto padding = handle_padspec_(++it, end);

            if (it != end)
            {
                if (padding.enabled())
                {
                    handle_flag_<details::scoped_padder>(*it, padding);
                }
                else
                {
                    handle_flag_<details::null_scoped_padder>(*it, padding);
                }
            }
            else
            {
                break;
            }
        }
        else // chars not following the % sign should be displayed as is
        {
            if (!user_chars)
            {
                user_chars = details::make_unique<details::aggregate_formatter>();
            }
            user_chars->add_ch(*it);
        }
    }
    if (user_chars) // append raw chars found so far
    {
        formatters_.push_back(std::move(user_chars));
    }
}
} // namespace spdlog
