clear.hpp

#pragma once

#include <all.hpp>

class ClearCommand : public liteshell::BaseCommand
{
public:
    ClearCommand()
        : liteshell::BaseCommand(
              "clear",
              "Clear the console screen",
              "",
              {"cls"},
              liteshell::CommandConstraint()) {}

    DWORD run(const liteshell::Context &context)
    {
        // Example 2 in https://learn.microsoft.com/en-us/windows/console/clearing-the-screen

        auto hConsole = GetStdHandle(STD_OUTPUT_HANDLE);
        CONSOLE_SCREEN_BUFFER_INFO csbi;
        SMALL_RECT scrollRect;
        COORD scrollTarget;
        CHAR_INFO fill;

        // Get the number of character cells in the current buffer.
        if (!GetConsoleScreenBufferInfo(hConsole, &csbi))
        {
            throw std::runtime_error(utils::last_error("GetConsoleScreenBufferInfo ERROR"));
        }

        // Scroll the rectangle of the entire buffer.
        scrollRect.Left = 0;
        scrollRect.Top = 0;
        scrollRect.Right = csbi.dwSize.X;
        scrollRect.Bottom = csbi.dwSize.Y;

        // Scroll it upwards off the top of the buffer with a magnitude of the entire height.
        scrollTarget.X = 0;
        scrollTarget.Y = (SHORT)(0 - csbi.dwSize.Y);

        // Fill with empty spaces with the buffer's default text attribute.
        fill.Char.UnicodeChar = TEXT(' ');
        fill.Attributes = csbi.wAttributes;

        // Do the scroll
        ScrollConsoleScreenBuffer(hConsole, &scrollRect, NULL, scrollTarget, &fill);

        // Move the cursor to the top left corner too.
        csbi.dwCursorPosition.X = 0;
        csbi.dwCursorPosition.Y = 0;

        SetConsoleCursorPosition(hConsole, csbi.dwCursorPosition);

        return 0;
    }
};