readline.cpp

#include <readline/history.h>
#include <readline/readline.h>
#include <iostream>
#include <vector>

std::vector<std::string> commandList =
{
    "start",
    "status",
    "stop",
    "restart",
    "kill",
    "quit",
    "show",
};

char * generate(char const * text, int state)
{
    static size_t index{0};

    if (state == 0)
    {
        index = 0;
    }

    std::cerr << "\033[36mCALL:\033[0m generate(text=\033[35m\"" << text << "\"\033[0m, state=\033[35m" << state << "\033[0m)" << std::endl;

    auto const input = std::string(text);

    char * possibleMatch{nullptr};

    while (index < commandList.size() and possibleMatch == nullptr)
    {
        auto const& command = commandList[index];

        if (command.size() >= input.size() and command.compare(0, input.size(), input) == 0)
        {
            possibleMatch = strdup(commandList[index].c_str());
        }

        index++;
    }

    return possibleMatch;
}

char * generate2(const char *text, int state)
{
  static std::vector<std::string> matches;
  static size_t match_index = 0;

  if (state == 0) {
    matches.clear();
    match_index = 0;

    std::string textstr(text);
    for (auto word : commandList) {
      if (word.size() >= textstr.size() &&
          word.compare(0, textstr.size(), textstr) == 0) {
        matches.push_back(word);
      }
    }
  }

  if (match_index >= matches.size()) {
    return nullptr;
  } else {
    return strdup(matches[match_index++].c_str());
  }
}

char ** complete(char const * text, int start, int end)
{
    rl_attempted_completion_over = 1;
    std::cerr << "\033[36mCALL:\033[0m complete(text=\033[35m\"" << text << "\"\033[0m, start=\033[35m" << start << "\033[0m, end=\033[35m" << end << "\033[0m)" << std::endl;

    if (start > 0)
    {
        return nullptr;
    }

    return rl_completion_matches(text, generate);
}

int main(int argc, char *argv[])
{
    std::cerr << "\033[34mSTART\033[0m" << std::endl;
    rl_attempted_completion_function = complete;

    while (true)
    {
        char * line = readline("> ");

        if (line == nullptr)
        {
            std::cerr << "\033[31mNULL\033[0m" << std::endl;
            break;
        }
        else if (*line)
        {
            add_history(line);
            std::cerr << "\033[32mRECEIVED:\033[0m " << line << std::endl;
        }
        else
        {
            std::cerr << "\033[33mEMPTY\033[0m" << std::endl;
        }

        free(line);
    }

    std::cerr << "\033[34mSTOP\033[0m" << std::endl;
    return 0;
}