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/*************************************************************************
> File Name: Calendar.cpp
> Author: Netcan
> Blog: https://netcan.github.io/
> Mail: netcan1996@gmail.com
> Created Time: 2021-07-25 11:47
************************************************************************/
// g++-11 -std=c++2a Calendar.cpp
#include <chrono>
#include <algorithm>
#include <cstdio>
#include <iostream>
#include <iterator>
#include <string>
#include <fmt/core.h> // <format>
#include "Views.h"
namespace chrono = std::chrono;
///////////////////////////////////////////////////////////////////////////////
// Date
struct Date {
using difference_type = std::ptrdiff_t;
Date() = default;
Date(uint16_t year, uint16_t month, uint16_t day):
days_{ chrono::year(year) / chrono::month(month) / chrono::day(day) } { }
bool operator==(const Date&) const = default;
Date& operator++() { ++days_; return *this; }
Date operator++(int) { Date tmp(*this); ++*this; return tmp; }
uint16_t day() const { return static_cast<unsigned>(chrono::year_month_day(days_).day()); }
uint16_t month() const { return static_cast<unsigned>(chrono::year_month_day(days_).month()); }
uint16_t year() const { return static_cast<int>(chrono::year_month_day(days_).year()); }
uint16_t dayOfWeek() const { // 得到当前日期星期数，值域[0,7)，0表示星期天
return chrono::weekday(days_).c_encoding();
}
bool weekdaylessThan(const Date& rhs) {
return dayOfWeek() < rhs.dayOfWeek();
}
const char* monthName() const { return MONTH_NAME[month()]; }
friend std::ostream& operator<<(std::ostream& out, const Date& d) {
out << d.year() << "-" << d.month() << "-" << d.day();
return out;
}
private:
static constexpr const char* MONTH_NAME[] = {
"", "January", "February", "March",
"April", "May", "June", "July",
"August", "September", "October",
"November", "December",
};
chrono::sys_days days_;
};
static_assert(std::weakly_incrementable<Date>);
auto dates_between(uint16_t start, uint16_t stop) {
return views::iota(Date{start, 1, 1}, Date{stop, 1, 1});
}
auto by_month() {
return group_by([](Date a, Date b) { return a.month() == b.month(); });
}
auto by_week() {
return group_by([](Date a, Date b) { return a.weekdaylessThan(b); });
}
// TODO: c++20 std::format
std::string month_title(const Date& d) {
return fmt::format("{:^22}", d.monthName());
}
// TODO: c++20 std::format
std::string format_day(const Date& d) {
return fmt::format("{:>3}", d.day());
}
// in: range<range<Date>>
// out: range<std::string>
auto format_weeks() {
return views::transform([](/*range<Date>*/ auto&& week) {
auto ws = week | views::transform(format_day) | views::join | views::common;
std::string weeks(ws.begin(), ws.end());
auto align_size = (*ranges::begin(week)).dayOfWeek() * 3;
return fmt::format("{}{:<{}}",
std::string(align_size, ' '),
weeks, 22 - align_size);
});
}
// in: range<range<Date>>
// out: range<range<std::string>>
auto layout_months() {
return views::transform([](/*range<Date>*/ auto&& month) {
auto week_count = ranges::distance(month | by_week());
return concat(
views::single(month_title(*ranges::begin(month))),
views::single(std::string(" Su Mo Tu We Th Fr Sa ")),
month | by_week() | format_weeks(),
repeat_n(std::string(22, ' '), 6 - week_count)
);
});
}
// In: range<range<range<string>>>
// Out: range<range<range<string>>>, transposing months.
auto transpose_months() {
return views::transform([](/*range<range<string>>*/ auto&& rng) {
return rng | transpose;
});
}
// In: range<range<string>>
// Out: range<join_view<char>>, joining the strings of the inner ranges
auto join_months() {
return views::transform([](/*range<string>*/ auto&& rng) {
return views::join(rng);
});
}
int main(int argc, char** argv) {
auto formattedCalendar
= dates_between(2022, 2023) // range<Date>: 356
| by_month() // range<range<Date>>: 12 x month
| layout_months() // range<range<std::string>>: 12 x 8 x 22
| chunk(4) // range<range<range<std::string>>>: 3 x 4 x 8 x 22
| transpose_months() // range<range<range<std::string>>>: 3 x 8 x 4 x 22
| views::join // range<range<std::string>>: 24 x 4 x 22
| join_months() // range<join_view<char>>: 24 x 88
;
// print_range(formattedCalendar);
for (auto&& line: formattedCalendar) {
ranges::copy(line, std::ostream_iterator<char>(std::cout));
std::cout << std::endl;
}
return 0;
}