#ifndef BUFFERVIEW_H
#define BUFFERVIEW_H

#include "Buffer.h"
#include "CharacterWidthDeterminer.h"
#include <functional>
#include "BufferLineWalker.h"

/**
 * Tracks a "view" of a buffer, which is a two-dimensional grid of characters
 * that displays a section of a buffer's contents.
 */
class BufferView
{
public:
    class Iterator
    {
    public:
        Iterator(BufferView & bv) : m_buffer_view(bv)
        {
            if (bv.m_iterator->valid())
            {
                m_iterator = std::make_shared<Buffer::Iterator>(*m_buffer_view.m_first_line);
                m_row_offset = m_buffer_view.m_first_line_row_offset;
            }
        }
        void operator++()
        {
            (*this)++;
        }
        void operator++(int unused)
        {
            if (is_valid())
            {
                m_row_offset += m_buffer_view.calculate_rows_in_line(m_iterator);
                if ((m_row_offset >= m_buffer_view.m_height) || (!m_iterator->go_next_line()))
                {
                    m_iterator.reset();
                }
            }
        }
        bool is_valid()
        {
            return (bool)m_iterator;
        }
        int row_offset() const
        {
            return m_row_offset;
        }
        std::shared_ptr<Buffer::Iterator> iterator() const
        {
            return m_iterator;
        }

    protected:
        BufferView & m_buffer_view;
        std::shared_ptr<Buffer::Iterator> m_iterator;
        int m_row_offset;
    };

    BufferView(std::shared_ptr<Buffer> buffer,
            std::shared_ptr<Buffer::Iterator> iterator,
            CharacterWidthDeterminer & character_width_determiner);
    void resize(int width, int height);
    void set_scroll_offset(int scroll_offset);
    Iterator vert_iter();
    BufferLineWalker horiz_iter(std::shared_ptr<Buffer::Iterator> start_of_line)
    {
        return BufferLineWalker(m_buffer, start_of_line, m_width, m_character_width_determiner);
    }
    int cursor_screen_row() const { return m_cursor_screen_row; }
    int cursor_screen_column() const { return m_cursor_screen_column; }
    int cursor_virtual_column() const { return m_cursor_virtual_column; }

protected:
    std::shared_ptr<Buffer> m_buffer;
    std::shared_ptr<Buffer::Iterator> m_iterator;
    std::shared_ptr<Buffer::Iterator> m_first_line;
    int m_first_line_row_offset;
    int m_width;
    int m_height;
    int m_scroll_offset;
    int m_cursor_screen_row;
    int m_cursor_screen_column;
    int m_cursor_virtual_column;
    int m_cursor_row_offset;
    CharacterWidthDeterminer & m_character_width_determiner;

    int effective_scroll_offset()
    {
        return std::min(m_scroll_offset, (m_height - 1) / 2);
    }
    void update();
    int calculate_rows_in_line(std::shared_ptr<Buffer::Iterator> start_of_line);
    int calculate_rows_in_cursor_line(std::shared_ptr<Buffer::Iterator> start_of_line);
    int screen_rows_below_line(std::shared_ptr<Buffer::Iterator> line);
    int screen_rows_above_line(
            std::shared_ptr<Buffer::Iterator> line,
            std::list<std::pair<int, std::shared_ptr<Buffer::Iterator>>> & backward_lines);
};

#endif