#include <cstdio>
#include <cstring>
#include <stdexcept>
#include <utility>

struct SimpleString {
  SimpleString(size_t max_size)
      : max_size{ max_size }
      , length{} {
    if(max_size == 0) {
      throw std::runtime_error{ "Max size must be at least 1." };
    }
    buffer = new char[max_size];
    buffer[0] = 0;
  }
  ~SimpleString() {
    delete[] buffer;
  }
  SimpleString(const SimpleString& other)
      : max_size{ other.max_size }
      , buffer{ new char[other.max_size] }
      , length{ other.length } {
    std::strncpy(buffer, other.buffer, max_size);
  }
  SimpleString(SimpleString&& other) noexcept
      : max_size(other.max_size)
      , buffer(other.buffer)
      , length(other.length) {
    other.length = 0;
    other.buffer = nullptr;
    other.max_size = 0;
  }
  SimpleString& operator=(const SimpleString& other) {
    if(this == &other)
      return *this;
    const auto new_buffer = new char[other.max_size];
    delete[] buffer;
    buffer = new_buffer;
    length = other.length;
    max_size = other.max_size;
    std::strncpy(buffer, other.buffer, max_size);
    return *this;
  }
  SimpleString& operator=(SimpleString&& other) noexcept {
      if (this == &other)
          return *this;
      delete[] buffer;
      max_size = other.max_size;
      buffer = other.buffer;
      length = other.length;

      max_size = 0;
      buffer = nullptr;
      length = 0;
      return *this;
  }
  void print(const char* tag) const {
    printf("%s: %s", tag, buffer);
  }
  bool append_line(const char* x) {
    const auto x_len = strlen(x);
    if(x_len + length + 2 > max_size)
      return false;
    std::strncpy(buffer + length, x, max_size - length);
    length += x_len;
    buffer[length++] = '\n';
    buffer[length] = 0;
    return true;
  }

  private:
  size_t max_size;
  char* buffer;
  size_t length;
};

int main() {
  SimpleString a{ 50 };
  a.append_line("We apologise for the");
  SimpleString b{ 50 };
  b.append_line("Last message");
  a.print("a");
  b.print("b");
  b = std::move(a);
  // a is "moved-from"
  b.print("b");
}