import time
import hashlib

import bencode
import resumablehashlib

from app import app


ANNOUNCE_URL = app.config.get('TORRENT_ANNOUNCE_URL')
NAMING_SALT = app.config.get('TORRENT_NAMING_SALT')
REGISTRY_TITLE = app.config.get('REGISTRY_TITLE')

def public_torrent_filename(blob_uuid):
  return hashlib.sha256(blob_uuid).hexdigest()

def per_user_torrent_filename(user_uuid, blob_uuid):
  return hashlib.sha256(blob_uuid + user_uuid + NAMING_SALT).hexdigest()


def make_torrent(name, webseed, length, piece_length, pieces):
  return bencode.bencode({
    'announce': ANNOUNCE_URL,
    'url-list': webseed,
    'encoding': 'UTF-8',
    'created by': REGISTRY_TITLE,
    'creation date': int(time.time()),
    'info': {
      'name': name,
      'length': length,
      'piece length': piece_length,
      'pieces': pieces,
    },
  })


class PieceHasher(object):
  def __init__(self, piece_size, starting_offset, starting_piece_hash_bytes, hash_fragment_to_resume):
    if not isinstance(starting_offset, (int, long)):
      raise TypeError('starting_offset must be an integer')
    elif not isinstance(piece_size, (int, long)):
      raise TypeError('piece_size must be an integer')

    self._current_offset = starting_offset
    self._piece_size = piece_size
    self._hash_fragment = hash_fragment_to_resume
    self._piece_hashes = bytearray(starting_piece_hash_bytes)

  def update(self, buf):
    buf_offset = 0
    while buf_offset < len(buf):
      buf_bytes_to_hash = buf[0:self._piece_length_remaining()]
      to_hash_len = len(buf_bytes_to_hash)

      if self._piece_offset() == 0 and to_hash_len > 0 and self._current_offset > 0:
        # We are opening a new piece
        self._piece_hashes.extend(self._hash_fragment.digest())
        self._hash_fragment = resumablehashlib.sha1()

      self._hash_fragment.update(buf_bytes_to_hash)
      self._current_offset += to_hash_len
      buf_offset += to_hash_len

  def _piece_length_remaining(self):
    return self._piece_size - (self._current_offset % self._piece_size)

  def _piece_offset(self):
    return self._current_offset % self._piece_size

  @property
  def piece_hashes(self):
    return self._piece_hashes

  @property
  def hash_fragment(self):
    return self._hash_fragment