#include "Command.h"

#include <iostream>


namespace Command {
    Command readCommand() {
        if (!std::cin)
            return {Exit{}};
        std::string line;
        if (!std::getline(std::cin, line))
            return {Exit{}};

        // Trim leading and trailing whitespaces
        constexpr std::string_view TO_TRIM = " \t\n\r";
        const size_t start = line.find_first_not_of(TO_TRIM);
        const size_t end = line.find_last_not_of(TO_TRIM);
        if (start == std::string::npos) return None{};
        const std::string_view line_trimmed(line.data() + start, end - start + 1);

        using namespace std::string_view_literals;
        if (line_trimmed == "r"sv || line_trimmed == "refresh"sv)
            return Refresh{};
        if (line_trimmed == "n"sv || line_trimmed == ">"sv || line_trimmed == "next"sv)
            return Next{};
        if (line_trimmed == "p"sv || line_trimmed == "<"sv || line_trimmed == "previous"sv)
            return Previous{};
        if (line_trimmed == "x"sv || line_trimmed == "exit"sv || line_trimmed == "q"sv || line_trimmed == "quit"sv)
            return Exit{};
        if (line_trimmed == "help"sv || line_trimmed == "?"sv || line_trimmed == "?"sv)
            return Help{};

        if (line_trimmed.starts_with("seek") || line.starts_with("s ")) {
            const size_t space = line_trimmed.find(' ');
            if (space == std::string::npos)
                throw NoNumberException();
            int number = 0;
            const size_t size = line.size();
            for (size_t i = space + 1; i < size; ++i) {
                const char c = line_trimmed[i];
                if (!std::isdigit(c))
                    throw NoNumberException();
                number = number * 10 + (c - '0');
            }

            return {Seek{number}};
        }

        return {None{}};
    }
}