Спринт 8. Эффективный список.

#include <list>
#include <algorithm>
#include <iostream>
#include <string>

using namespace std;

class Editor {
public:
    Editor(){
        it_=line_.begin();
    }

    void Left(){
        if (it_ ==line_.begin()) {
            return;
        }
        --it_;
    }

    void Right(){
        if (it_ ==line_.end()) {
            return;
        }
        ++it_;
    }

    void Insert(char token){
        line_.insert(it_, token);
    }

    void Cut(size_t tokens = 1){
        buffer_.clear();
        if (tokens > (size_t)(distance(it_, line_.end()))){
            tokens = (size_t)(distance(it_, line_.end()));
        }
        auto helper = std::next(it_, tokens);
        buffer_.assign(it_, helper);
        it_ = line_.erase(it_, helper);
    }

    void Copy(size_t tokens = 1){
        buffer_.clear();
        if (tokens > (size_t)(distance(it_, line_.end()))){
            tokens = (size_t)(distance(it_, line_.end()));
        }
        auto helper = std::next(it_, tokens);
        buffer_.assign(it_, helper);
    }

    void Paste(){
        for (char helper :buffer_) {
            it_ = line_.insert(it_, helper);
            ++it_;
        }
    }

    string GetText() const{
        return {line_.begin(), line_.end()};
    }
private:
    list<char> buffer_;
    list<char> line_;
    list<char>::iterator it_;
};

int main() {
    Editor editor;
    const string text = "hello, world"s;
    for (char c : text) {
        editor.Insert(c);
    }

    for (size_t i = 0; i < text.size(); ++i) {
        editor.Left();
    }

    editor.Cut(7);

    for (size_t i = 0; i < 5; ++i) {
        editor.Right();
    }

    editor.Insert(',');
    editor.Insert(' ');

    editor.Paste();

    editor.Left();
    editor.Left();

    editor.Cut(3);

    cout << editor.GetText();

    return 0;
}