roro9stack/lib/ui/src/input_history.h

#pragma once

#include <deque>
#include <string>

namespace roro {

// Lines already entered, browsed shell-style: up() goes back in time, down() forward, and past the
// newest line the draft being typed comes back.
class InputHistory {
   public:
    explicit InputHistory(size_t capacity) : capacity_(capacity) {}

    void add(const std::string& line) {
        browsing_ = -1;
        if (line.empty() || (!lines_.empty() && lines_.back() == line)) return;
        lines_.push_back(line);
        if (lines_.size() > capacity_) lines_.pop_front();
    }

    // `current` is what the editor holds now (kept as the draft when browsing starts).
    bool up(const std::string& current, std::string& out) {
        if (lines_.empty() || browsing_ == 0) return false;
        if (browsing_ < 0) {
            draft_ = current;
            browsing_ = static_cast<int>(lines_.size());
        }
        out = lines_[--browsing_];
        return true;
    }

    bool down(std::string& out) {
        if (browsing_ < 0) return false;
        if (++browsing_ >= static_cast<int>(lines_.size())) {
            browsing_ = -1;
            out = draft_;
        } else {
            out = lines_[browsing_];
        }
        return true;
    }

   private:
    size_t capacity_;
    std::deque<std::string> lines_;
    int browsing_ = -1;  // index being shown, -1 when editing the draft
    std::string draft_;
};

}  // namespace roro