text_editor.cpp

#include <list>
#include <iostream>
#include <string>
#include <iterator>
#include "test_runner.h"

using namespace std;

class Editor {
    list<char> text;
    list<char>::iterator cursor;
    list<char> buffer;
    auto shift(int64_t positions) const {
        auto result = cursor;
        while (result != text.end() && positions > 0) {
            positions--;
            result++;
        }
        while (result != text.begin() && positions < 0) {
            positions++;
            result--;
        }
        return result;
    }
public:
    Editor() : text(), buffer() {
        cursor = text.begin();
    }
    void Left() {
        cursor = shift(-1);
    }
    void Right() {
        cursor = shift(1);
    }
    void Insert(char token) {
        text.insert(cursor, token);
    }
    void Copy(size_t tokens) {
        buffer.clear();
        buffer = {cursor, shift(tokens)};
    }
    void Cut(size_t tokens) {
        Copy(tokens);
        cursor = text.erase(cursor, shift(tokens));
    }
    void Paste() {
        text.insert(cursor, buffer.begin(), buffer.end());
    }
    string GetText() const {
        return {text.begin(), text.end()};
    }
};

void TypeText(Editor& editor, const string& text) {
    for(char c : text) {
        editor.Insert(c);
    }
}

void TestEditing() {
    {
        Editor editor;

        const size_t text_len = 12;
        const size_t first_part_len = 7;
        TypeText(editor, "hello, world");
        for(size_t i = 0; i < text_len; ++i) {
            editor.Left();
        }
        editor.Cut(first_part_len);
        for(size_t i = 0; i < text_len - first_part_len; ++i) {
            editor.Right();
        }
        TypeText(editor, ", ");
        editor.Paste();
        editor.Left();
        editor.Left();
        editor.Cut(3);

        ASSERT_EQUAL(editor.GetText(), "world, hello");
    }
    {
        Editor editor;

        TypeText(editor, "misprnit");
        editor.Left();
        editor.Left();
        editor.Left();
        editor.Cut(1);
        editor.Right();
        editor.Paste();

        ASSERT_EQUAL(editor.GetText(), "misprint");
    }
}

void TestReverse() {
    Editor editor;

    const string text = "esreveR";
    for(char c : text) {
        editor.Insert(c);
        editor.Left();
    }

    ASSERT_EQUAL(editor.GetText(), "Reverse");
}

void TestNoText() {
    Editor editor;
    ASSERT_EQUAL(editor.GetText(), "");

    editor.Left();
    editor.Left();
    editor.Right();
    editor.Right();
    editor.Copy(0);
    editor.Cut(0);
    editor.Paste();

    ASSERT_EQUAL(editor.GetText(), "");
}

void TestEmptyBuffer() {
    Editor editor;

    editor.Paste();
    TypeText(editor, "example");
    editor.Left();
    editor.Left();
    editor.Paste();
    editor.Right();
    editor.Paste();
    editor.Copy(0);
    editor.Paste();
    editor.Left();
    editor.Cut(0);
    editor.Paste();

    ASSERT_EQUAL(editor.GetText(), "example");
}

int main() {
    TestRunner tr;
    RUN_TEST(tr, TestEditing);
    RUN_TEST(tr, TestReverse);
    RUN_TEST(tr, TestNoText);
    RUN_TEST(tr, TestEmptyBuffer);
    return 0;
}