// -*- mode: c++; c-basic-offset: 2; -*-

#include "common.hh"

#include "paths.hh"

// static
std::string Paths::join(std::string const& base, std::string const& path) {
  if (path.empty()) {
    return cleanup(base);
  } else if (path.front() == '/') {
    return cleanup(path);
  }
  std::string ret(cleanup(base));
  if (ret == ".") {
    return cleanup(path);
  }
  if (ret.empty() || ret.back() != '/') {
    ret.push_back('/');
  }
  ret.append(cleanup(path));
  return ret;
}

namespace {

std::string do_cleanup(std::string const& path) {
  size_t i = 0, j = 0;
  std::string ret;
  bool add_slash = false;
  if (path.front() == '/') {
    ret.push_back('/');
    i = j = 1;
  }
  while (true) {
    if (j == path.size() || path[j] == '/') {
      auto len = j - i;
      if (len > 0) {
        if (len == 1 && path[i] == '.') {
          i = ++j;
          continue;
        }
        if (add_slash && len == 2 && path[i] == '.' && path[i + 1] == '.') {
          auto x = ret.find_last_of('/');
          if (x == std::string::npos) x = 0;
          ret.erase(x);
          add_slash = !(ret.empty() || ret == "/");
          i = ++j;
          continue;
        }
        if (add_slash) {
          ret.push_back('/');
        } else {
          add_slash = true;
        }
        ret.append(path.substr(i, len));
      }
      if (j == path.size()) {
        return ret;
      }
      i = ++j;
    } else {
      ++j;
    }
  }
}

}  // namespace

// static
std::string Paths::cleanup(std::string const& path) {
  if (path.empty()) return ".";
  if (path[0] == '.') {
    if (path.size() == 1) return path;
    if (path[1] == '/') return do_cleanup(path);  // found ./ at beginning
  }
  for (size_t pos = 0; pos < path.size(); ++pos) {
    if (path[pos] == '/') {
      if (pos > 0 && pos + 1 == path.size()) {
        // found slash at end
        return path.substr(0, path.size() - 1);
      }
      if (path[pos + 1] == '/') return do_cleanup(path);  // found double slash
      if (path[pos + 1] == '.') {
        if (pos + 2 == path.size()) return do_cleanup(path);  // found /. at end
        if (path[pos + 2] == '/') return do_cleanup(path);  // found /./
        if (path[pos + 2] == '.') {
          if (pos + 3 == path.size()) {
            // found /.. at end
            return do_cleanup(path);
          }
          if (path[pos + 3] == '/') do_cleanup(path);  // found /../
        }
      }
    }
  }
  return path;
}