class Eth::OpenSsl

def BN_num_bytes(ptr)
  (BN_num_bits(ptr) + 7) / 8
end

def bn_free_each(*list)
  list.each{|j| BN_free(j) }
end

def init_ffi_ssl
  return if @ssl_loaded
  SSL_library_init()
  ERR_load_crypto_strings()
  SSL_load_error_strings()
  RAND_poll()
  @ssl_loaded = true
end

def recover_compact(hash, signature)
  return false if signature.bytesize != 65
  version = signature.unpack('C')[0]
  v_base = Eth.replayable_v?(version) ? Eth.replayable_chain_id : Eth.v_base
  return false if version < v_base
  recover_public_key_from_signature(hash, signature, (version - v_base), false)
end

def recover_public_hex(eckey)
  length = i2o_ECPublicKey(eckey, nil)
  buf = FFI::MemoryPointer.new(:uint8, length)
  ptr = FFI::MemoryPointer.new(:pointer).put_pointer(0, buf)
  pub_hex = if i2o_ECPublicKey(eckey, ptr) == length
    buf.read_string(length).unpack("H*")[0]
  end
  EC_KEY_free(eckey)
  pub_hex
end

def recover_public_key_from_signature(message_hash, signature, rec_id, is_compressed)
  return nil if rec_id < 0 or signature.bytesize != 65
  init_ffi_ssl
  signature = FFI::MemoryPointer.from_string(signature)
  r = BN_bin2bn(signature[1], 32, BN_new())
  s = BN_bin2bn(signature[33], 32, BN_new())
  _n, i = 0, rec_id / 2
  eckey = EC_KEY_new_by_curve_name(NID_secp256k1)
  EC_KEY_set_conv_form(eckey, POINT_CONVERSION_COMPRESSED) if is_compressed
  group = EC_KEY_get0_group(eckey)
  order = BN_new()
  EC_GROUP_get_order(group, order, nil)
  x = BN_dup(order)
  BN_mul_word(x, i)
  BN_add(x, x, r)
  field = BN_new()
  EC_GROUP_get_curve_GFp(group, field, nil, nil, nil)
  if BN_cmp(x, field) >= 0
    bn_free_each r, s, order, x, field
    EC_KEY_free(eckey)
    return nil
  end
  big_r = EC_POINT_new(group)
  EC_POINT_set_compressed_coordinates_GFp(group, big_r, x, rec_id % 2, nil)
  big_q = EC_POINT_new(group)
  n = EC_GROUP_get_degree(group)
  e = BN_bin2bn(message_hash, message_hash.bytesize, BN_new())
  BN_rshift(e, e, 8 - (n & 7)) if 8 * message_hash.bytesize > n
  ctx = BN_CTX_new()
  zero, rr, sor, eor = BN_new(), BN_new(), BN_new(), BN_new()
  BN_set_word(zero, 0)
  BN_mod_sub(e, zero, e, order, ctx)
  BN_mod_inverse(rr, r, order, ctx)
  BN_mod_mul(sor, s, rr, order, ctx)
  BN_mod_mul(eor, e, rr, order, ctx)
  EC_POINT_mul(group, big_q, eor, big_r, sor, ctx)
  EC_KEY_set_public_key(eckey, big_q)
  BN_CTX_free(ctx)
  bn_free_each r, s, order, x, field, e, zero, rr, sor, eor
  [big_r, big_q].each{|j| EC_POINT_free(j) }
  recover_public_hex eckey
end

def sign_compact(hash, private_key, public_key_hex)
  private_key = [private_key].pack("H*") if private_key.bytesize >= 64
  pubkey_compressed = false
  init_ffi_ssl
  eckey = EC_KEY_new_by_curve_name(NID_secp256k1)
  priv_key = BN_bin2bn(private_key, private_key.bytesize, BN_new())
  group, order, ctx = EC_KEY_get0_group(eckey), BN_new(), BN_CTX_new()
  EC_GROUP_get_order(group, order, ctx)
  pub_key = EC_POINT_new(group)
  EC_POINT_mul(group, pub_key, priv_key, nil, nil, ctx)
  EC_KEY_set_private_key(eckey, priv_key)
  EC_KEY_set_public_key(eckey, pub_key)
  signature = ECDSA_do_sign(hash, hash.bytesize, eckey)
  BN_free(order)
  BN_CTX_free(ctx)
  EC_POINT_free(pub_key)
  BN_free(priv_key)
  EC_KEY_free(eckey)
  buf, rec_id, head = FFI::MemoryPointer.new(:uint8, 32), nil, nil
  r, s = signature.get_array_of_pointer(0, 2).map{|i| BN_bn2bin(i, buf); buf.read_string(BN_num_bytes(i)).rjust(32, "\x00") }
  if signature.get_array_of_pointer(0, 2).all?{|i| BN_num_bits(i) <= 256 }
    4.times{|i|
      head = [ Eth.v_base + i ].pack("C")
      if public_key_hex == recover_public_key_from_signature(hash, [head, r, s].join, i, pubkey_compressed)
        rec_id = i; break
      end
    }
  end
  ECDSA_SIG_free(signature)
  [ head, [r,s] ].join if rec_id
end