// Buffer.h

#include <fstream>
#include <iomanip>
#include <iostream>
#include <string>
#include <vector>

class Buffer
{
public:
    void display() const;
    void erase();
    const std::string & get_file_name() const { return file_name_; }
    void insert(const std::string & new_line);
    void move_to_next_line();
    void move_to_previous_line();
    bool open(const std::string & new_file_name);
    bool save(const std::string & new_file_name);
    void set_window_height(int h) { window_height_ = h; }

private:
    std::vector<std::string> v_lines_;
    int ix_current_line_ = 0;
    int ix_top_line_ = 0;
    std::string file_name_;
    int window_height_;
};

inline void Buffer::erase()
{
    if (ix_current_line_ < v_lines_.size())
        v_lines_.erase(v_lines_.begin() + ix_current_line_);
}

inline void Buffer::insert(const std::string & new_line)
{
    v_lines_.insert(v_lines_.begin() + ix_current_line_, new_line);
    move_to_next_line();
}

inline void Buffer::move_to_next_line()
{
    if (ix_current_line_ < v_lines_.size()) {
        ++ix_current_line_;
        // check if window needs to be scrolled down
        if (ix_current_line_ >= ix_top_line_ + window_height_)
            ++ix_top_line_;
    }
}

inline void Buffer::move_to_previous_line()
{
    if (ix_current_line_ > 0) {
        --ix_current_line_;
        // check if window needs to be scrolled up
        if (ix_current_line_ < ix_top_line_)
            --ix_top_line_;
    }
}