#include "BufferPane.h"

BufferPane::BufferPane(Window * window, std::shared_ptr<Buffer> buffer)
    : m_window(window), m_buffer(buffer)
{
    m_cursor_screen_row = 0;
    m_scroll_offset = 5;
    m_iterator = buffer->add_iterator();
    m_target_column = 0;
    m_cursor_virtual_column = 0;
}

void BufferPane::resize(int width, int height)
{
    Pane::resize(width, height);
    m_columns = std::max(1, m_width / m_window->font()->get_advance());
    m_rows = std::max(1, m_height / m_window->font()->get_line_height());
}

void BufferPane::walk_line(const Buffer::Iterator & start_of_line, std::function<void(int, int, int, int, const Buffer::Iterator &)> callback)
{
    int row_offset = 0;
    int screen_column = 0;
    int virtual_column = 0;
    Buffer::Iterator i = start_of_line;
    for (;;)
    {
        uint32_t code_point = *i;
        if ((code_point == '\n') || (!i.valid()))
        {
            callback(row_offset, screen_column, virtual_column, 0, i);
            break;
        }
        int c_width;
        if (code_point == '\t')
        {
            uint8_t tabstop = m_buffer->tabstop();
            c_width = tabstop - screen_column % tabstop;
        }
        else
        {
            c_width = character_width(code_point);
        }
        if (((screen_column + c_width) > m_columns) &&
                (screen_column > 0))
        {
            row_offset++;
            screen_column = 0;
        }
        callback(row_offset, screen_column, virtual_column, c_width, i);
        virtual_column += c_width;
        if (code_point == '\t')
        {
            screen_column += c_width;
            while (screen_column >= m_columns)
            {
                screen_column -= m_columns;
                row_offset++;
            }
        }
        else
        {
            if ((screen_column + c_width) >= m_columns)
            {
                row_offset++;
                screen_column = 0;
            }
            else
            {
                screen_column += c_width;
            }
        }
        i.go_forward();
    }
}

int BufferPane::rows_in_line(const Buffer::Iterator & start_of_line)
{
    int saved_row_offset = 0;
    walk_line(start_of_line, [&saved_row_offset](int row_offset, int screen_column, int virtual_column, int character_width, const Buffer::Iterator & i) {
        uint32_t code_point = *i;
        if ((code_point != '\n') && (code_point != 0xFFFFFFFFu))
        {
            saved_row_offset = row_offset;
        }
    });
    return saved_row_offset + 1;
}

int BufferPane::rows_in_line_with_iterator_offset(const Buffer::Iterator & start_of_line, const Buffer::Iterator & reference, int * iterator_row_offset)
{
    int saved_row_offset = 0;
    walk_line(start_of_line, [this, &saved_row_offset, &reference, &iterator_row_offset](int row_offset, int screen_column, int virtual_column, int character_width, const Buffer::Iterator & i) {
        uint32_t code_point = *i;
        if (i == reference)
        {
            m_cursor_virtual_column = virtual_column;
            *iterator_row_offset = row_offset;
        }
        if ((code_point != '\n') && (code_point != 0xFFFFFFFFu))
        {
            saved_row_offset = row_offset;
        }
    });
    return saved_row_offset + 1;
}

int BufferPane::screen_rows_below_line(const Buffer::Iterator & line)
{
    Buffer::Iterator i = line;
    int rows = 0;
    while ((rows < m_rows) && i.go_next_line())
    {
        rows += rows_in_line(i);
    }
    return rows;
}

int BufferPane::screen_rows_above_line(const Buffer::Iterator & line, std::list<std::pair<int, Buffer::Iterator>> & backward_lines)
{
    Buffer::Iterator i = line;
    int rows = 0;
    while ((rows < m_rows) && i.go_previous_line())
    {
        int rows_in_this_line = rows_in_line(i);
        rows += rows_in_this_line;
        backward_lines.push_back(std::pair<int, Buffer::Iterator>(rows_in_this_line, i));
    }
    return rows;
}

int BufferPane::update_cursor_row(std::list<std::pair<int, Buffer::Iterator>> & backward_lines)
{
    Buffer::Iterator start_of_line = *m_iterator;
    start_of_line.go_start_of_line();
    int cursor_row_offset;
    int rows_in_cursor_line = rows_in_line_with_iterator_offset(start_of_line, *m_iterator, &cursor_row_offset);
    int so = effective_scroll_offset();
    int rows_above = screen_rows_above_line(*m_iterator, backward_lines) + cursor_row_offset;
    int rows_below = screen_rows_below_line(*m_iterator) + std::max(0, rows_in_cursor_line - cursor_row_offset - 1);
    int min_rows_to_leave_above = std::min(rows_above, so);
    int min_rows_to_leave_below = std::min(rows_below, so);
    m_cursor_screen_row = std::min(m_rows - min_rows_to_leave_below - 1, m_cursor_screen_row);
    m_cursor_screen_row = std::max(min_rows_to_leave_above, m_cursor_screen_row);
    m_cursor_screen_row = std::max(m_rows - rows_below - 1, m_cursor_screen_row);
    m_cursor_screen_row = std::min(rows_above, m_cursor_screen_row);
    return cursor_row_offset;
}

int BufferPane::determine_new_cursor_screen_row()
{
    if (m_screen_lines.size() > 0)
    {
        if (m_iterator->line() < m_screen_lines.begin()->second.line())
        {
            return 0;
        }
        if (m_iterator->line() > m_screen_lines.rbegin()->second.line())
        {
            return m_rows;
        }
        for (auto screen_line : m_screen_lines)
        {
            if (screen_line.second.line() == m_iterator->line())
            {
                int row_offset;
                rows_in_line_with_iterator_offset(screen_line.second, *m_iterator, &row_offset);
                return screen_line.first + row_offset;
            }
        }
    }
    return 0;
}

void BufferPane::draw()
{
    m_screen_lines.clear();
    if (m_iterator->valid())
    {
        std::list<std::pair<int, Buffer::Iterator>> backward_lines;
        int cursor_row_offset_in_current_line = update_cursor_row(backward_lines);
        int screen_row = m_cursor_screen_row - cursor_row_offset_in_current_line;
        Buffer::Iterator i = *m_iterator;
        if (screen_row <= 0)
        {
            i.go_start_of_line();
        }
        else for (auto rows_iterator_pair : backward_lines)
        {
            screen_row -= rows_iterator_pair.first;
            i = rows_iterator_pair.second;
            if (screen_row <= 0)
            {
                break;
            }
        }
        while (screen_row <= m_rows)
        {
            m_screen_lines.push_back(std::pair<int, Buffer::Iterator>(screen_row, i));
            screen_row += draw_buffer_line(screen_row, i);
            if (!i.go_next_line())
            {
                break;
            }
        }
    }
    else
    {
        draw_cursor(col_x(0), row_y(0), m_buffer->insert_mode());
    }
}

int BufferPane::draw_buffer_line(int screen_row, const Buffer::Iterator & start_of_line)
{
    int saved_row_offset = 0;
    walk_line(start_of_line, [this, &saved_row_offset, &screen_row](int row_offset, int screen_column, int virtual_column, int character_width, const Buffer::Iterator & i) {
        uint32_t code_point = *i;
        int draw_row = screen_row + row_offset;
        int x = col_x(screen_column);
        int y = row_y(draw_row);
        if ((draw_row >= 0) && (draw_row <= m_rows))
        {
            if (i == *m_iterator)
            {
                /* TODO: highlight multi-column characters */
                draw_cursor(x, y, m_buffer->insert_mode());
            }
            if ((code_point == '\n') || (code_point == 0xFFFFFFFFu))
            {
            }
            else
            {
                saved_row_offset = row_offset;
                if ((code_point != '\t') && (code_point != ' '))
                {
                    m_window->gl()->draw_character(win_x(x), win_y(y), code_point, *m_window->font());
                }
            }
        }
    });
    return saved_row_offset + 1;
}

int BufferPane::character_width(uint32_t character)
{
    if (character < 0x20u)
    {
        return 2;
    }
    else if (character < 0x80u)
    {
        return 1u;
    }
    else
    {
        return std::max(1, m_window->font()->get_glyph(character)->get_advance() / m_window->font()->get_advance());
    }
}

void BufferPane::draw_buffer_character(int screen_column, int screen_row, uint32_t character)
{
    if (character < 0x20u)
    {
        m_window->gl()->draw_character(win_x(col_x(screen_column)), win_y(row_y(screen_row)),
                '^', *m_window->font());
        m_window->gl()->draw_character(win_x(col_x(screen_column + 1)), win_y(row_y(screen_row)),
                (character - 0x20u + 'A'), *m_window->font());
    }
    else
    {
        m_window->gl()->draw_character(win_x(col_x(screen_column)), win_y(row_y(screen_row)),
                character, *m_window->font());
    }
}

void BufferPane::draw_cursor(int x, int y, bool insert_mode)
{
    int width = m_window->font()->get_advance();
    int height = m_window->font()->get_line_height();
    if (insert_mode)
    {
        m_window->gl()->draw_rect(win_x(x), win_y(y), 1, height, 1.0, 0.2, 1.0, 1.0);
        m_window->gl()->draw_rect(win_x(x + 1), win_y(y + height - 1), 2, 1, 1.0, 0.2, 1.0, 1.0);
        m_window->gl()->draw_rect(win_x(x + 1), win_y(y), 2, 1, 1.0, 0.2, 1.0, 1.0);
    }
    else
    {
        m_window->gl()->draw_rect(win_x(x), win_y(y), width, height, 1.0, 0.2, 1.0, 1.0);
    }
}

void BufferPane::handle_key(uint32_t keyval)
{
    if (m_buffer->insert_mode())
    {
        if (keyval == '\033')
        {
            m_buffer->exit_insert_mode();
            if (!m_iterator->is_start_of_line())
            {
                m_iterator->go_back();
            }
        }
        else if (keyval == SDLK_BACKSPACE)
        {
            Buffer::Iterator i = *m_iterator;
            i.go_back();
            if (i.valid())
            {
                m_buffer->erase_code_point(i);
                m_window->request_redraw();
            }
        }
        else if (keyval <= 0xFFu)
        {
            if (keyval == SDLK_RETURN)
            {
                keyval = '\n';
                m_cursor_screen_row++;
            }
            m_buffer->insert_code_point(keyval);
        }
        m_window->request_redraw();
    }
    else
    {
        switch (keyval)
        {
        case '0':
            cursor_move(CursorMovement::SOL);
            break;
        case '$':
            cursor_move(CursorMovement::EOL);
            break;
        case 'a':
            if (**m_iterator != '\n')
            {
                m_iterator->go_forward();
            }
            m_buffer->enter_insert_mode(*m_iterator);
            m_window->request_redraw();
            break;
        case 'h':
            cursor_move(CursorMovement::LEFT);
            break;
        case 'i':
            m_buffer->enter_insert_mode(*m_iterator);
            m_window->request_redraw();
            break;
        case 'j':
            cursor_move(CursorMovement::DOWN);
            break;
        case 'k':
            cursor_move(CursorMovement::UP);
            break;
        case 'l':
            cursor_move(CursorMovement::RIGHT);
            break;
        case 'x':
            if (**m_iterator != '\n')
            {
                m_buffer->erase_code_point(*m_iterator);
                if (**m_iterator == '\n')
                {
                    m_iterator->go_left_in_line();
                }
                m_window->request_redraw();
            }
            break;
        }
    }
}

size_t BufferPane::display_column() const
{
    if (!m_iterator->valid())
    {
        return 0u;
    }
    if ((**m_iterator == '\n') && (!m_buffer->insert_mode()))
    {
        Buffer::Iterator i = *m_iterator;
        if (!i.go_left_in_line())
        {
            return 0u;
        }
    }
    return m_cursor_virtual_column + 1u;
}

void BufferPane::cursor_move(CursorMovement which)
{
    bool moved = false;

    switch (which)
    {
    case CursorMovement::LEFT:
        moved = m_iterator->go_left_in_line();
        break;
    case CursorMovement::RIGHT:
        moved = m_iterator->go_right_in_line(m_buffer->insert_mode());
        break;
    case CursorMovement::UP:
        moved = m_iterator->go_previous_line();
        break;
    case CursorMovement::DOWN:
        moved = m_iterator->go_next_line();
        break;
    case CursorMovement::SOL:
        moved = m_iterator->go_start_of_line();
        break;
    case CursorMovement::EOL:
        moved = m_iterator->go_end_of_line(m_buffer->insert_mode());
        break;
    }
    if (moved)
    {
        switch (which)
        {
        case CursorMovement::LEFT:
        case CursorMovement::RIGHT:
            {
                int cursor_row_offset;
                Buffer::Iterator start_of_line = *m_iterator;
                start_of_line.go_start_of_line();
                rows_in_line_with_iterator_offset(start_of_line, *m_iterator, &cursor_row_offset);
                m_target_column = m_cursor_virtual_column;
            }
            break;
        case CursorMovement::UP:
            forward_to_column(m_target_column, m_buffer->insert_mode());
            break;
        case CursorMovement::DOWN:
            forward_to_column(m_target_column, m_buffer->insert_mode());
            break;
        case CursorMovement::SOL:
            m_target_column = 0;
            break;
        case CursorMovement::EOL:
            m_target_column = INT_MAX;
            break;
        }
        m_cursor_screen_row = determine_new_cursor_screen_row();
        m_window->request_redraw();
    }
}

void BufferPane::forward_to_column(int column, bool allow_eol)
{
    Buffer::Iterator start_of_line = *m_iterator;
    start_of_line.go_start_of_line();
    walk_line(start_of_line, [this, &column, &allow_eol](int row_offset, int screen_column, int virtual_column, int character_width, const Buffer::Iterator & i) {
        uint32_t code_point = *i;
        if ((code_point != '\n') || allow_eol)
        {
            if (virtual_column <= column)
            {
                *m_iterator = i;
            }
        }
    });
}