#include "fgc/ui/Scroll.h"

#include <algorithm>

namespace fgc {

int scrollMax(int content_h, int view_h) {
    // An unmeasured view (first frame after an overlay opens or the terminal
    // resizes) pins to the top rather than guessing: the next repaint is 100ms
    // away and a guess would visibly jump.
    if (view_h <= 0) return 0;
    return std::max(0, content_h - view_h);
}

int scrollClamp(int top, int content_h, int view_h) {
    return std::clamp(top, 0, scrollMax(content_h, view_h));
}

int scrollBy(int top, int delta, int content_h, int view_h) {
    return scrollClamp(top + delta, content_h, view_h);
}

int scrollPage(int top, int dir, int content_h, int view_h) {
    const int step = std::max(1, view_h - 2);
    return scrollClamp(top + dir * step, content_h, view_h);
}

std::size_t gridRowsPerColumn(std::size_t item_count, std::size_t max_cols, std::size_t min_rows) {
    max_cols = std::max<std::size_t>(max_cols, 1);
    min_rows = std::max<std::size_t>(min_rows, 1);
    const std::size_t needed = (item_count + max_cols - 1) / max_cols;  // ceil
    return std::max(min_rows, needed);
}

}  // namespace fgc