1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
# frozen_string_literal: true
require "em-http"
require "em_promise"
require "em-synchrony/em-http" # For aget vs get
require "money/bank/open_exchange_rates_bank"
require "nokogiri"
require_relative "em"
class BTCSellPrices
def initialize(redis, oxr_app_id)
@redis = redis
@oxr = Money::Bank::OpenExchangeRatesBank.new(
Money::RatesStore::Memory.new
)
@oxr.app_id = oxr_app_id
end
def cad
fetch_canadianbitcoins.then do |http|
canadianbitcoins = Nokogiri::HTML.parse(http.response)
bitcoin_row = canadianbitcoins.at("#ticker > table > tbody > tr")
raise "Bitcoin row has moved" unless bitcoin_row.at("td").text == "Bitcoin"
BigDecimal(
bitcoin_row.at("td:nth-of-type(3)").text.match(/^\$(\d+\.\d+)/)[1]
)
end
end
def usd
EMPromise.all([cad, cad_to_usd]).then { |(a, b)| a * b }
end
protected
def fetch_canadianbitcoins
EM::HttpRequest.new(
"https://www.canadianbitcoins.com",
tls: { verify_peer: true }
).aget
end
def cad_to_usd
@redis.get("cad_to_usd").then do |rate|
next rate.to_f if rate
EM.promise_defer {
# OXR gem is not async, so defer to threadpool
@oxr.update_rates
@oxr.get_rate("CAD", "USD")
}.then do |orate|
@redis.set("cad_to_usd", orate, ex: 60 * 60).then { orate }
end
end
end
end