// Copyright (c) 2017-2020, University of Cincinnati, developed by Henry Schreiner
// under NSF AWARD 1414736 and by the respective contributors.
// All rights reserved.
//
// SPDX-License-Identifier: BSD-3-Clause

#pragma once

// On GCC < 4.8, the following define is often missing. Due to the
// fact that this library only uses sleep_for, this should be safe
#if defined(__GNUC__) && !defined(__clang__) && __GNUC__ < 5 && __GNUC_MINOR__ < 8
#define _GLIBCXX_USE_NANOSLEEP
#endif

#include <array>
#include <chrono>
#include <functional>
#include <iostream>
#include <string>
#include <utility>

namespace CLI {

/// This is a simple timer with pretty printing. Creating the timer starts counting.
class Timer {
  protected:
    /// This is a typedef to make clocks easier to use
    using clock = std::chrono::steady_clock;

    /// This typedef is for points in time
    using time_point = std::chrono::time_point<clock>;

    /// This is the type of a printing function, you can make your own
    using time_print_t = std::function<std::string(std::string, std::string)>;

    /// This is the title of the timer
    std::string title_;

    /// This is the function that is used to format most of the timing message
    time_print_t time_print_;

    /// This is the starting point (when the timer was created)
    time_point start_;

    /// This is the number of times cycles (print divides by this number)
    std::size_t cycles{1};

  public:
    /// Standard print function, this one is set by default
    static std::string Simple(std::string title, std::string time) { return title + ": " + time; }

    /// This is a fancy print function with --- headers
    static std::string Big(std::string title, std::string time) {
        return std::string("-----------------------------------------\n") + "| " + title + " | Time = " + time + "\n" +
               "-----------------------------------------";
    }

  public:
    /// Standard constructor, can set title and print function
    explicit Timer(std::string title = "Timer", time_print_t time_print = Simple)
        : title_(std::move(title)), time_print_(std::move(time_print)), start_(clock::now()) {}

    /// Time a function by running it multiple times. Target time is the len to target.
    std::string time_it(std::function<void()> f, double target_time = 1) {
        time_point start = start_;
        double total_time;

        start_ = clock::now();
        std::size_t n = 0;
        do {
            f();
            std::chrono::duration<double> elapsed = clock::now() - start_;
            total_time = elapsed.count();
        } while(n++ < 100u && total_time < target_time);

        std::string out = make_time_str(total_time / static_cast<double>(n)) + " for " + std::to_string(n) + " tries";
        start_ = start;
        return out;
    }

    /// This formats the numerical value for the time string
    std::string make_time_str() const {
        time_point stop = clock::now();
        std::chrono::duration<double> elapsed = stop - start_;
        double time = elapsed.count() / static_cast<double>(cycles);
        return make_time_str(time);
    }

    // LCOV_EXCL_START
    /// This prints out a time string from a time
    std::string make_time_str(double time) const {
        auto print_it = [](double x, std::string unit) {
            const unsigned int buffer_length = 50;
            std::array<char, buffer_length> buffer;
            std::snprintf(buffer.data(), buffer_length, "%.5g", x);
            return buffer.data() + std::string(" ") + unit;
        };

        if(time < .000001)
            return print_it(time * 1000000000, "ns");
        else if(time < .001)
            return print_it(time * 1000000, "us");
        else if(time < 1)
            return print_it(time * 1000, "ms");
        else
            return print_it(time, "s");
    }
    // LCOV_EXCL_STOP

    /// This is the main function, it creates a string
    std::string to_string() const { return time_print_(title_, make_time_str()); }

    /// Division sets the number of cycles to divide by (no graphical change)
    Timer &operator/(std::size_t val) {
        cycles = val;
        return *this;
    }
};

/// This class prints out the time upon destruction
class AutoTimer : public Timer {
  public:
    /// Reimplementing the constructor is required in GCC 4.7
    explicit AutoTimer(std::string title = "Timer", time_print_t time_print = Simple) : Timer(title, time_print) {}
    // GCC 4.7 does not support using inheriting constructors.

    /// This destructor prints the string
    ~AutoTimer() { std::cout << to_string() << std::endl; }
};

}  // namespace CLI

/// This prints out the time if shifted into a std::cout like stream.
inline std::ostream &operator<<(std::ostream &in, const CLI::Timer &timer) { return in << timer.to_string(); }
