D2 string

#include <algorithm>
#include <functional>
#include <iostream>
#include <numeric>
#include <queue>
#include <stack>
#include <string>
#include <vector>

using namespace std;

string substring(const string& s, string::size_type begin, string::size_type end) {
  return s.substr(begin, (end == string::npos ? s.size() : end) - begin);
}

string joined(const vector<string>& stringList, const char* joiner = "\n")
{
    assert(!stringList.empty());
    return accumulate(next(stringList.cbegin()), stringList.cend(), stringList.front(), [&](const string& s1, const string& s2) {
        return s1 + joiner + s2;
    });
}

vector<string> split(const string& s, const string& separator = "\n", const function<string(string)>& lineTransform = [](string&& s){ return s; })
{
  vector<string> lines;
  assert(!separator.empty());
  string::size_type findPos = 0;
  for (;;) {
    auto separatorPos = s.find(separator, findPos);
    lines.emplace_back(lineTransform(substring(s, findPos, separatorPos)));
    if (separatorPos == string::npos)
      break;
    findPos = separatorPos + separator.size();
  }
  return lines;
}

string buildColoredString(const string& s, const string& color)
{
  return "<span style='color: " + color + "'>" + s + "</span>";
}

struct ColoredEntry {
  string text;
  string color;
  bool addLineBreak;
};

int main(int argc, char const *argv[])
{
  for (int i = 1; i < argc; ++i) {
    string text = argv[i];
    string::size_type findPos = 0;
    string color = "white";
    vector<pair<string, string>> coloredParts;
    for (;;) {
      auto colorStartPos = text.find('\\', findPos);
      coloredParts.emplace_back(color, substring(text, findPos, colorStartPos));

      if (colorStartPos == string::npos) {
        break;
      }

      // TODO: handle npos
      auto colorEndPos = text.find(';', ++colorStartPos);
      // if (colorEndPos == string::npos) {
      //   continue;
      // }
      findPos = colorEndPos + 1;

      color = substring(text, colorStartPos, colorEndPos);
    }
    assert(!coloredParts.empty());

    stack<queue<ColoredEntry>> entries;
    decltype(entries)::value_type* lastEntry = nullptr;
    for (const auto& it : coloredParts) {
      auto color = it.first;
      auto lines = split(it.second);
      for (const auto& line : lines) {
        ColoredEntry e;
        e.text = line;
        e.color = color;
        auto moveToQueue = [&](decltype(entries)::value_type& queue) {
          queue.emplace(std::move(e));
        };

        if (lastEntry) {
          assert(!lastEntry->empty());
          // prevents adding useless items with empty text that won't have line break
          if (lastEntry->front().text.empty())
            lastEntry->pop();
          moveToQueue(*lastEntry);
          lastEntry = nullptr;
        } else {
          decltype(entries)::value_type q;
          moveToQueue(q);
          entries.emplace(std::move(q));
        }
      }
      lastEntry = &entries.top();
    }
    assert(!entries.empty());

    vector<ColoredEntry> output;
    do {
      auto& q = entries.top();
      do {
        auto& e = q.front();
        e.addLineBreak = false;
        output.emplace_back(std::move(e));
        q.pop();
      } while (!q.empty());
      output.back().addLineBreak = true;
      entries.pop();
    } while (!entries.empty());
    assert(!output.empty());
    output.back().addLineBreak = false;

    // JSON
    cout << "[\n";
    for (const auto& it : output) {
      cout << "\t{\n";
      cout << "\t\t\"text\": " << "\"" << it.text << "\",\n";
      cout << "\t\t\"color\": " << "\"" << it.color << "\",\n";
      cout << "\t\t\"addLineBreak\": " << (it.addLineBreak ? "true" : "false") << "\n";
      cout << "\t},\n";
    }
    cout << "]\n\n";

    /*
    // HTML
    cout << "&lt;<br />\n";
    for (const auto& it : output) {
      if (!it.text.empty())
        cout << buildColoredString(it.text, it.color);
      if (it.addLineBreak)
        cout << "<br />\n";
    }
    cout << "\n<br />&gt;<br /><br /><br />\n\n";

    // plain text
    for (const auto& it : output) {
      cout << it.text;
      if (it.addLineBreak)
        cout << "\n";
    }
    cout << "\n";
    */
  }
  return 0;
}