#include "bencode.hpp"
#include <cstdlib>
#include <cinttypes>
#include <cstdio>

bool
bencode_read_integer(struct llarp_buffer_t* buffer, uint64_t* result)
{
  size_t len;
  if (*buffer->cur != 'i')
    return false;

  char numbuf[32];

  buffer->cur++;

  len = buffer->read_until('e', (byte_t*)numbuf, sizeof(numbuf) - 1);
  if (!len)
  {
    return false;
  }

  buffer->cur++;

  numbuf[len] = '\0';
  if (result)
    *result = std::strtoull(numbuf, nullptr, 10);
  return true;
}

bool
bencode_read_string(llarp_buffer_t* buffer, llarp_buffer_t* result)
{
  char numbuf[10];

  size_t len = buffer->read_until(':', (byte_t*)numbuf, sizeof(numbuf) - 1);
  if (!len)
    return false;

  numbuf[len] = '\0';
  const int num = atoi(numbuf);
  if (num < 0)
  {
    return false;
  }

  const size_t slen = num;

  buffer->cur++;

  len = buffer->size_left();
  if (len < slen)
  {
    return false;
  }
  if (result)
  {
    result->base = buffer->cur;
    result->cur = buffer->cur;
    result->sz = slen;
  }
  buffer->cur += slen;
  return true;
}

bool
bencode_write_bytestring(llarp_buffer_t* buff, const void* data, size_t sz)
{
  if (!buff->writef("%zu:", sz))
  {
    return false;
  }
  return buff->write(reinterpret_cast<const char*>(data), reinterpret_cast<const char*>(data) + sz);
}

bool
bencode_write_uint64(llarp_buffer_t* buff, uint64_t i)
{
  if (!buff->writef("i%" PRIu64, i))
  {
    return false;
  }

  static const char letter[1] = {'e'};
  assert(std::distance(std::begin(letter), std::end(letter)) == 1);
  return buff->write(std::begin(letter), std::end(letter));
}

bool
bencode_discard(llarp_buffer_t* buf)
{
  if (buf->size_left() == 0)
    return true;
  switch (*buf->cur)
  {
    case 'l':
      return llarp::bencode_read_list(
          [](llarp_buffer_t* buffer, bool more) -> bool {
            if (more)
            {
              return bencode_discard(buffer);
            }
            return true;
          },
          buf);
    case 'i':
      return bencode_read_integer(buf, nullptr);
    case 'd':
      return llarp::bencode_read_dict(
          [](llarp_buffer_t* buffer, llarp_buffer_t* key) -> bool {
            if (key)
              return bencode_discard(buffer);
            return true;
          },
          buf);
    case '0':
    case '1':
    case '2':
    case '3':
    case '4':
    case '5':
    case '6':
    case '7':
    case '8':
    case '9':
      return bencode_read_string(buf, nullptr);
    default:
      return false;
  }
}

bool
bencode_write_uint64_entry(llarp_buffer_t* buff, const void* name, size_t sz, uint64_t i)
{
  if (!bencode_write_bytestring(buff, name, sz))
    return false;

  return bencode_write_uint64(buff, i);
}

bool
bencode_start_list(llarp_buffer_t* buff)
{
  static const char letter[1] = {'l'};
  assert(std::distance(std::begin(letter), std::end(letter)) == 1);
  return buff->write(std::begin(letter), std::end(letter));
}

bool
bencode_start_dict(llarp_buffer_t* buff)
{
  static const char letter[1] = {'d'};
  assert(std::distance(std::begin(letter), std::end(letter)) == 1);
  return buff->write(std::begin(letter), std::end(letter));
}

bool
bencode_end(llarp_buffer_t* buff)
{
  static const char letter[1] = {'e'};
  assert(std::distance(std::begin(letter), std::end(letter)) == 1);
  return buff->write(std::begin(letter), std::end(letter));
}