#include "xmlencodinghandler.h"

bool XmlEncodingHandler::hasDeclaration(const std::string& utf8)
{
  size_t len = utf8.size();
  if (len < 6 ||
    utf8[0] != '<' ||
    utf8[1] != '?' ||
    utf8[2] != 'x' ||
    utf8[3] != 'm' ||
    utf8[4] != 'l')
    return false;
  return true;
}

std::string XmlEncodingHandler::get(
  const std::string& utf8)
{
  if (!hasDeclaration(utf8))
    return "UTF-8";

  size_t len = utf8.size();
  std::string s;
  for (size_t i = 0; i < len; ++i)
  {
    s += utf8[i];
    if (utf8[i] == '>')
      break;
  }

  if (s.find(">") == std::string::npos)
    return "";

  s = CaseHandler::lowerCase(s);
  
  if (s.find("encoding=") == std::string::npos ||
    s.find("utf-8") != std::string::npos)
    return "UTF-8";
  else if (s.find("utf-16le") != std::string::npos)
    return "UTF-16LE";
  else if (s.find("utf-16be") != std::string::npos)
    return "UTF-16BE";
  else if (s.find("utf-16") != std::string::npos)
    return "UTF-16";
  else if (s.find("iso-8859-1") != std::string::npos)
    return "ISO-8859-1";
  else if (s.find("us-ascii") != std::string::npos)
    return "US-ASCII";
  else
    return "";
}

bool XmlEncodingHandler::setUtf8(std::string& utf8, bool ignoreCurrentEncoding)
{
  if (!hasDeclaration(utf8))
    return true;
  
  if (get(utf8).empty() && !ignoreCurrentEncoding)
    return false;

  std::pair<int, int> p = getEncodingValueLimits(utf8);
  if (p.first == -1 || p.second == -1)
    return true; // attribute missing

  utf8.replace(p.first, p.second, "UTF-8");

  return true;
}

bool XmlEncodingHandler::set(std::string& buffer, std::string& encoding)
{
  std::pair<int, int> p = getEncodingValueLimits(buffer);
  if (p.first == -1 || p.second == -1)
    return false; // attribute missing
  buffer.replace(p.first, p.second, encoding.c_str());
  return true;
}

std::pair<int, int>
XmlEncodingHandler::getEncodingValueLimits(const std::string& utf8)
{
  if (!hasDeclaration(utf8))
    return make_pair(-1, -1);
  char *buffer, *start, *end;
  char delimit;
  char anchor[] = "encoding=";
  buffer = (char *)utf8.c_str();
  start = strstr(buffer, anchor);
  if (!start)
    return make_pair(-1, -1);
  start = start + strlen(anchor);
  if (*start != '\'' && *start != '\"')
    return make_pair(-1, -1);
  delimit = *start;
  if (strlen(start) < 2)
    return make_pair(-1, -1);
  ++start;
  for (end = start; *end && *end != delimit; ++end)
  {
    if (
      *end == '?' || *end == '>' || *end == '<' ||
      *end == ' ' || *end == '\t' || *end == '\n') { return make_pair(-1, -1); }
  }
  if (!*end)
    return make_pair(-1, -1);
  return make_pair(start - buffer, end - start);
}