#pragma once

#include <vector>

#include <sstream>

/**

* Terminal pager that displays output written to stdout one page at a time, allowing the user to

* interactively scroll up and down. If cout is not a tty or the output is shorter than a single

* terminal page it does nothing.

*

* It expects all of cout to be written before the first page is displayed, so it does not pipe from

* cout which would be a more complicated implementation allowing the first page to be displayed

* before all of the output is written. This may need to be reconsidered if we need more performant

* handling of slow subcommands such as `git2cpp log` of repos with long histories.

*

* Keys handled:

* d, space scroll down a page

* u scroll up a page

* q quit pager

* down arrow, enter, return scroll down a line

* up arrow scroll up a line

*

* Emits a BEL (ASCII 7) for unrecognised keys or attempts to scroll too far, which is used by some

* terminals for visual and/or audible feedback.

*

* Does not respond to a change of terminal size whilst it is waiting for input, but it will the

* next time the output is scrolled.

*/

class terminal_pager

{

public:

terminal_pager();

~terminal_pager();

void show();

private:

std::string get_input() const;

void maybe_grab_cout();

// Return true if should stop pager.

bool process_input(std::string input);

void release_cout();

void render_terminal() const;

void scroll(bool up, bool page);

void split_input_at_newlines(std::string_view str);

void update_terminal_size();

std::stringbuf m_stringbuf;

std::streambuf* m_cout_rdbuf;

std::vector<std::string> m_lines;

size_t m_rows, m_columns;

size_t m_start_row_index;

};