/* <!-- copyright */
/*
 * aria2 - The high speed download utility
 *
 * Copyright (C) 2011 Tatsuhiro Tsujikawa
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 *
 * In addition, as a special exception, the copyright holders give
 * permission to link the code of portions of this program with the
 * OpenSSL library under certain conditions as described in each
 * individual source file, and distribute linked combinations
 * including the two.
 * You must obey the GNU General Public License in all respects
 * for all of the code used other than OpenSSL.  If you modify
 * file(s) with this exception, you may extend this exception to your
 * version of the file(s), but you are not obligated to do so.  If you
 * do not wish to do so, delete this exception statement from your
 * version.  If you delete this exception statement from all source
 * files in the program, then also delete it here.
 */
/* copyright --> */
#include "json.h"

#include <sstream>

#include "array_fun.h"
#include "DlAbortEx.h"
#include "error_code.h"
#include "a2functional.h"
#include "util.h"
#include "fmt.h"
#include "Base64.h"

namespace aria2 {

namespace json {

// Function prototype declaration
namespace {
std::pair<SharedHandle<ValueBase>, std::string::const_iterator>
decode
(std::string::const_iterator first,
 std::string::const_iterator last,
 size_t depth);
} // namespace

namespace {
const char WS[] = { 0x20, 0x09, 0x0a, 0x0d };
const char ESCAPE_CHARS[] = { '"', '\\', '/', '\b', '\f', '\n', '\r', '\t' };
const size_t MAX_STRUCTURE_DEPTH = 100;
} // namespace

namespace {
std::string::const_iterator skipWs
(std::string::const_iterator first,
 std::string::const_iterator last)
{
  while(first != last && std::find(vbegin(WS), vend(WS), *first) != vend(WS)) {
    ++first;
  }
  return first;
}
} // namespace

namespace {
void checkEof
(std::string::const_iterator first,
 std::string::const_iterator last)
{
  if(first == last) {
    throw DL_ABORT_EX2("JSON decoding failed: unexpected EOF",
                       error_code::JSON_PARSE_ERROR);
  }
}
} // namespace

namespace {
std::string::const_iterator
decodeKeyword
(std::string::const_iterator first,
 std::string::const_iterator last,
 const std::string& keyword)
{
  size_t len = keyword.size();
  for(size_t i = 0; i < len; ++i) {
    checkEof(first, last);
    if(*first != keyword[i]) {
      throw DL_ABORT_EX2(fmt("JSON decoding failed: %s not found.",
                             keyword.c_str()),
                         error_code::JSON_PARSE_ERROR);
    }
    ++first;
  }
  return first;
}
} // namespace

namespace {
std::pair<SharedHandle<ValueBase>, std::string::const_iterator>
decodeTrue
(std::string::const_iterator first,
 std::string::const_iterator last)
{
  first = decodeKeyword(first, last, "true");
  return std::make_pair(Bool::gTrue(), first);
}
} // namespace

namespace {
std::pair<SharedHandle<ValueBase>, std::string::const_iterator>
decodeFalse
(std::string::const_iterator first,
 std::string::const_iterator last)
{
  first = decodeKeyword(first, last, "false");
  return std::make_pair(Bool::gFalse(), first);
}
} // namespace

namespace {
std::pair<SharedHandle<ValueBase>, std::string::const_iterator>
decodeNull
(std::string::const_iterator first,
 std::string::const_iterator last)
{
  first = decodeKeyword(first, last, "null");
  return std::make_pair(Null::g(), first);
}
} // namespace

namespace {
std::pair<SharedHandle<ValueBase>, std::string::const_iterator>
decodeString
(std::string::const_iterator first,
 std::string::const_iterator last)
{
  // Consume first char, assuming it is '"'.
  ++first;
  std::string s;
  std::string::const_iterator offset = first;
  while(first != last) {
    if(*first == '"') {
      break;
    }
    if(*first == '\\') {
      s += std::string(offset, first);
      ++first;
      checkEof(first, last);
      if(*first == 'u') {
        ++first;
        std::string uchars;
        for(int i = 0; i < 4; ++i, ++first) {
          checkEof(first, last);
          uchars += *first;
        }
        checkEof(first, last);
        uint16_t codepoint = util::parseUInt(uchars, 16);
        if(codepoint <= 0x007fu) {
          s += static_cast<char>(codepoint);
        } else if(codepoint <= 0x07ffu) {
          unsigned char c2 = 0x80u | (codepoint & 0x003fu);
          unsigned char c1 = 0xC0u | (codepoint >> 6);
          s += c1;
          s += c2;
        } else if(in(codepoint, 0xD800u, 0xDBFFu)) {
          // surrogate pair
          if(*first != '\\' || first+1 == last ||
             *(first+1) != 'u') {
            throw DL_ABORT_EX2("JSON decoding failed: bad UTF-8 sequence.",
                               error_code::JSON_PARSE_ERROR);
          }
          first += 2;
          std::string uchars;
          for(int i = 0; i < 4; ++i, ++first) {
            checkEof(first, last);
            uchars += *first;
          }
          checkEof(first, last);
          uint16_t codepoint2 = util::parseUInt(uchars, 16);
          if(!in(codepoint2, 0xDC00u, 0xDFFFu)) {
            throw DL_ABORT_EX2("JSON decoding failed: bad UTF-8 sequence.",
                               error_code::JSON_PARSE_ERROR);
          }
          uint32_t fullcodepoint = 0x010000u;
          fullcodepoint += (codepoint & 0x03FFu) << 10;
          fullcodepoint += (codepoint2 & 0x03FFu);
          unsigned char c4 = 0x80u | (fullcodepoint & 0x003Fu);
          unsigned char c3 = 0x80u | ((fullcodepoint >> 6) & 0x003Fu);
          unsigned char c2 = 0x80u | ((fullcodepoint >> 12) & 0x003Fu);
          unsigned char c1 = 0xf0u | (fullcodepoint >> 18);
          s += c1;
          s += c2;
          s += c3;
          s += c4;
        } else {
          unsigned char c3 = 0x80u | (codepoint & 0x003Fu);
          unsigned char c2 = 0x80u | ((codepoint >> 6) & 0x003Fu);
          unsigned char c1 = 0xE0u | (codepoint >> 12);
          s += c1;
          s += c2;
          s += c3;
        }
        offset = first;
      } else {
        if(*first == 'b') {
          s += '\b';
        } else if(*first == 'f') {
          s += '\f';
        } else if(*first == 'n') {
          s += '\n';
        } else if(*first == 'r') {
          s += '\r';
        } else if(*first == 't') {
          s += '\t';
        } else {
          s += *first;
        }
        ++first;
        offset = first;
      }
    } else {
      ++first;
    }
  }
  checkEof(first, last);
  if(std::distance(offset, first) > 0) {
    s += std::string(offset, first);
  }
  if(!util::isUtf8(s)) {
    throw DL_ABORT_EX2("JSON decoding failed: Non UTF-8 string.",
                       error_code::JSON_PARSE_ERROR);
  }
  ++first;
  return std::make_pair(String::g(s), first);
}
} // namespace

namespace {
void checkEmptyDigit
(std::string::const_iterator first,
 std::string::const_iterator last)
{
  if(std::distance(first, last) == 0) {
    throw DL_ABORT_EX2("JSON decoding failed: zero DIGIT.",
                       error_code::JSON_PARSE_ERROR);
  }
}
} // namespace

namespace {
void checkLeadingZero
(std::string::const_iterator first,
 std::string::const_iterator last)
{
  if(std::distance(first, last) > 2 && *first == '0') {
    throw DL_ABORT_EX2("JSON decoding failed: leading zero.",
                       error_code::JSON_PARSE_ERROR);
  }
}
} // namespace

namespace {
std::pair<SharedHandle<ValueBase>, std::string::const_iterator>
decodeNumber
(std::string::const_iterator first,
 std::string::const_iterator last)
{
  std::string s;
  if(*first == '-') {
    s += *first;
    ++first;
  }
  std::string::const_iterator offset = first;
  while(first != last && in(*first, '0', '9')) {
    ++first;
  }
  checkEof(first, last);
  checkEmptyDigit(offset, first);
  checkLeadingZero(offset, first);
  s += std::string(offset, first);
  bool fp = false;
  if(*first == '.') {
    fp = true;
    s += *first;
    ++first;
    offset = first;
    while(first != last && in(*first, '0', '9')) {
      ++first;
    }
    checkEof(first, last);
    checkEmptyDigit(offset, first);
    s += std::string(offset, first);
  }
  if(*first == 'e') {
    fp = true;
    s += *first;
    ++first;
    checkEof(first, last);
    if(*first == '+' || *first == '-') {
      s += *first;
      ++first;
    }
    offset = first;
    while(first != last && in(*first, '0', '9')) {
      ++first;
    }
    checkEof(first, last);
    checkEmptyDigit(offset, first);
    s += std::string(offset, first);
  }
  if(fp) {
    // Since we don't have floating point coutner part in ValueBase,
    // we just treat it as string.
    return std::make_pair(String::g(s), first);
  } else {
    Integer::ValueType val = util::parseLLInt(s);
    return std::make_pair(Integer::g(val), first);
  }
}
} // namespace

namespace {
void checkDepth(size_t depth)
{
  if(depth >= MAX_STRUCTURE_DEPTH) {
    throw DL_ABORT_EX2("JSON decoding failed: Structure is too deep.",
                       error_code::JSON_PARSE_ERROR);
  }
}
} // namespace

namespace {
std::pair<SharedHandle<ValueBase>, std::string::const_iterator>
decodeArray
(std::string::const_iterator first,
 std::string::const_iterator last,
 size_t depth)
{
  checkDepth(depth);
  SharedHandle<List> list = List::g();
  // Consume first char, assuming it is '['.
  ++first;
  first = skipWs(first, last);
  checkEof(first, last);
  if(*first != ']') {
    while(1) {
      std::pair<SharedHandle<ValueBase>, std::string::const_iterator>
        r = decode(first, last, depth);
      list->append(r.first);
      first = r.second;
      first = skipWs(first, last);
      if(first == last || (*first != ',' && *first != ']')) {
        throw DL_ABORT_EX2("JSON decoding failed:"
                           " value-separator ',' or ']' is not found.",
                           error_code::JSON_PARSE_ERROR);
      }
      if(*first == ']') {
        break;
      }
      ++first;
    }
  }
  ++first;
  return std::make_pair(list, first);
}
} // namespace

namespace {
std::pair<SharedHandle<ValueBase>, std::string::const_iterator>
decodeObject
(std::string::const_iterator first,
 std::string::const_iterator last,
 size_t depth)
{
  checkDepth(depth);
  SharedHandle<Dict> dict = Dict::g();
  // Consume first char, assuming it is '{'
  ++first;
  first = skipWs(first, last);
  checkEof(first, last);
  if(*first != '}') {
    while(1) {
      std::pair<SharedHandle<ValueBase>, std::string::const_iterator>
        keyRet = decodeString(first, last);
      first = keyRet.second;
      first = skipWs(first, last);
      if(first == last || *first != ':') {
        throw DL_ABORT_EX2("JSON decoding failed:"
                           " name-separator ':' is not found.",
                           error_code::JSON_PARSE_ERROR);
      }
      ++first;
      std::pair<SharedHandle<ValueBase>, std::string::const_iterator>
        valueRet = decode(first, last, depth);
      dict->put(downcast<String>(keyRet.first)->s(), valueRet.first);
      first = valueRet.second;
      first = skipWs(first, last);
      if(first == last || (*first != ',' && *first != '}')) {
        throw DL_ABORT_EX2("JSON decoding failed:"
                           " value-separator ',' or '}' is not found.",
                           error_code::JSON_PARSE_ERROR);
      }
      if(*first == '}') {
        break;
      }
      ++first;
      first = skipWs(first, last);
      checkEof(first, last);
    }
  }
  ++first;
  return std::make_pair(dict, first);
}
} // namespace

namespace {
std::pair<SharedHandle<ValueBase>, std::string::const_iterator>
decode
(std::string::const_iterator first,
 std::string::const_iterator last,
 size_t depth)
{
  first = skipWs(first, last);
  if(first == last) {
    throw DL_ABORT_EX2("JSON decoding failed:"
                       " Unexpected EOF in term context.",
                       error_code::JSON_PARSE_ERROR);
  }
  if(*first == '[') {
    return decodeArray(first, last, depth+1);
  } else if(*first == '{') {
    return decodeObject(first, last, depth+1);
  } else if(*first == '"') {
    return decodeString(first, last);
  } else if(*first == '-' || in(*first, '0', '9')) {
    return decodeNumber(first, last);
  } else if(*first == 't') {
    return decodeTrue(first, last);
  } else if(*first == 'f') {
    return decodeFalse(first, last);
  } else if(*first == 'n') {
    return decodeNull(first, last);
  } else {
    throw DL_ABORT_EX2("JSON decoding failed:"
                       " Unexpected character in term context.",
                       error_code::JSON_PARSE_ERROR);
  }
}
} // namespace

SharedHandle<ValueBase> decode(const std::string& json)
{
  std::string::const_iterator first = json.begin();
  std::string::const_iterator last = json.end();
  first = skipWs(first, last);
  if(first == last) {
    throw DL_ABORT_EX2("JSON decoding failed:"
                       " Unexpected EOF in term context.",
                       error_code::JSON_PARSE_ERROR);
  }
  std::pair<SharedHandle<ValueBase>, std::string::const_iterator> r;
  if(*first == '[') {
    r = decodeArray(first, last, 1);
  } else if(*first == '{') {
    r = decodeObject(first, last, 1);
  } else {
    throw DL_ABORT_EX2("JSON decoding failed:"
                       " Unexpected EOF in term context.",
                       error_code::JSON_PARSE_ERROR);
  }
  return r.first;
}

std::string jsonEscape(const std::string& s)
{
  std::string t;
  for(std::string::const_iterator i = s.begin(), eoi = s.end(); i != eoi;
      ++i) {
    if(*i == '"' || *i == '\\' || *i == '/') {
      t += '\\';
      t += *i;
    } else if(*i == '\b') {
      t += "\\b";
    } else if(*i == '\f') {
      t += "\\f";
    } else if(*i == '\n') {
      t += "\\n";
    } else if(*i == '\r') {
      t += "\\r";
    } else if(*i == '\t') {
      t += "\\t";
    } else if(in(static_cast<unsigned char>(*i), 0x00u, 0x1Fu)) {
      t += "\\u00";
      char temp[3];
      temp[2] = '\0';
      temp[0] = (*i >> 4);
      temp[1] = (*i)&0x0Fu;
      for(int j = 0; j < 2; ++j) {
        if(temp[j] < 10) {
          temp[j] += '0';
        } else {
          temp[j] += 'A'-10;
        }
      }
      t += temp;
    } else {
      t += *i;
    }
  }
  return t;
}

std::string encode(const ValueBase* vlb)
{
  class JsonValueBaseVisitor:public ValueBaseVisitor {
  private:
    std::ostringstream out_;
  public:
    virtual void visit(const String& string)
    {
      const std::string& s = string.s();
      std::string t = jsonEscape(s);
      out_ << '"';
      out_.write(t.data(), t.size());
      out_ << '"';
    }

    virtual void visit(const Integer& integer)
    {
      out_ << integer.i();
    }

    virtual void visit(const Bool& boolValue)
    {
      out_ << (boolValue.val() ? "true" : "false");
    }

    virtual void visit(const Null& nullValue)
    {
      out_ << "null";
    }

    virtual void visit(const List& list)
    {
      out_ << '[';
      List::ValueType::const_iterator i = list.begin();
      if(!list.empty()) {
        (*i)->accept(*this);
      }
      ++i;
      for(List::ValueType::const_iterator eoi = list.end(); i != eoi; ++i){
        out_ << ',';
        (*i)->accept(*this);
      }
      out_ << ']';
    }

    virtual void visit(const Dict& dict)
    {
      out_ << '{';
      Dict::ValueType::const_iterator i = dict.begin();
      if(!dict.empty()) {
        std::string key = jsonEscape((*i).first);
        out_ << '"';
        out_.write(key.data(), key.size());
        out_ << "\":";
        (*i).second->accept(*this);
      }
      ++i;
      for(Dict::ValueType::const_iterator eoi = dict.end(); i != eoi; ++i){
        out_ << ',';
        std::string key = jsonEscape((*i).first);
        out_ << '"';
        out_.write(key.data(), key.size());
        out_ << "\":";
        (*i).second->accept(*this);
      }
      out_ << '}';
    }

    std::string getResult() const
    {
      return out_.str();
    }
  };
  JsonValueBaseVisitor visitor;
  vlb->accept(visitor);
  return visitor.getResult();
}

// Serializes JSON object or array.
std::string encode(const SharedHandle<ValueBase>& json)
{
  std::ostringstream out;
  return encode(out, json.get()).str();
}

JsonGetParam::JsonGetParam
(const std::string& request, const std::string& callback)
  : request(request), callback(callback)
{}

JsonGetParam
decodeGetParams(const std::string& query)
{
  std::string jsonRequest;
  std::string callback;
  if(!query.empty() && query[0] == '?') {
    std::string method;
    std::string id;
    std::string params;
    std::vector<std::string> getParams;
    util::split(query.substr(1), std::back_inserter(getParams), "&");
    for(std::vector<std::string>::const_iterator i =
          getParams.begin(), eoi = getParams.end(); i != eoi; ++i) {
      if(util::startsWith(*i, "method=")) {
        method = (*i).substr(7);
      } else if(util::startsWith(*i, "id=")) {
        id = (*i).substr(3);
      } else if(util::startsWith(*i, "params=")) {
        params = (*i).substr(7);
      } else if(util::startsWith(*i, "jsoncallback=")) {
        callback = (*i).substr(13);
      }
    }
    std::string jsonParam =
      Base64::decode(util::percentDecode(params));
    if(method.empty() && id.empty()) {
      // Assume batch call.
      jsonRequest = jsonParam;
    } else {
      jsonRequest = '{';
      if(!method.empty()) {
        strappend(jsonRequest, "\"method\":\"", method, "\"");
      }
      if(!id.empty()) {
        strappend(jsonRequest, ",\"id\":\"", id, "\"");
      }
      if(!params.empty()) {
        strappend(jsonRequest, ",\"params\":", jsonParam);
      }
      jsonRequest += '}';
    }
  }
  return JsonGetParam(jsonRequest, callback);
}

} // namespace json

} // namespace aria2