#ifndef READLINE_HPP
#define READLINE_HPP

#include <string>
#include <string_view>

using CodepointString = std::basic_string<char32_t>;

class ReadlineDevice {
public:
    using print_callback = void (*)(const CodepointString &text);

private:
    print_callback print_cb_;
    CodepointString desired_command_;
    CodepointString current_command_;
    CodepointString desired_prompt_;
    CodepointString current_prompt_;
    char32_t readline_lastc_;

    void erase_command();
    void echo_command();


public:
    ReadlineDevice();

    // The callback must be set before using the readline device.
    void set_print_callback(print_callback cb);
    
    // change the prompt.
    void set_prompt(const CodepointString &prompt);
    void set_prompt_utf8(const std::string &prompt);

    // Use this to print anything on the console.
    void print(const CodepointString &cps);

    // Whenever the user types a character, call 'putcode'. If the code is
    // newline, this returns the line of text that was entered, including the
    // newline.  Otherwise returns empty string. Backspace is handled here.
    CodepointString putcode(char32_t codepoint);

    // This can be used to convert a codepoint string into a
    // UTF8-string.
    static std::string to_utf8(const CodepointString &cps);

    // This can be used to convert UTF8 to a codepoint string.
    // Some of the bytes may not be consumed, if the source contains
    // a partial utf-8 sequence.  Returns the Codepoint string and the
    // number of bytes consumed.
    static CodepointString from_utf8(std::string_view source, int *consumed);
};


#endif // READLINE_HPP