.gitignore

.ruby-version

2.4.1

app.rb

#! /usr/bin/env ruby
require 'rest-client'
require 'json'
require 'active_record'
require 'sqlite3'
require 'sinatra'

URL = 'https://www.gaitameonline.com/rateaj/getrate'
@rates = JSON.parse(RestClient.get(URL))["quotes"]
ActiveRecord::Base.establish_connection(adapter: :sqlite3, database: "fx.sqlite3")

def create_positions_tbl
  ActiveRecord::Base.connection.execute(
    "create table positions(currency string, price float, final float, created_at datetime);"
  )
end

def create_table(tbl)
  ActiveRecord::Base.connection.execute "create table #{tbl}(price float, created_at datetime);"
end
#create_positions_tbl
#create_table "usd_jpies"
class Position < ActiveRecord::Base
  scope :price, -> (v) { where(currency: v) }
  def self.profit(cur)
    price(cur).all.inject(0) {|sum, pos|
      if pos.final
        sum + pos.final - pos.price
      else
        sum
      end
    }
  end
end
class UsdJpy < ActiveRecord::Base; end

def price(cur)
  @rates.select { |r|
    r["currencyPairCode"] == cur
  }.first["ask"]
end

def buy(cur, price)
  Position.create(cur: cur, price: price)
end

p Position.profit("USDJPY")

v = UsdJpy.create(created_at: Time.now, price: price("USDJPY"))
p v.created_at
p v.price

fx.sqlite3

Gemfile

# frozen_string_literal: true
source "https://rubygems.org"

gem "rest-client"
gem "sqlite3"
gem "activerecord"
gem "sinatra"

Gemfile.lock

GEM
  remote: https://rubygems.org/
  specs:
    activemodel (5.1.1)
      activesupport (= 5.1.1)
    activerecord (5.1.1)
      activemodel (= 5.1.1)
      activesupport (= 5.1.1)
      arel (~> 8.0)
    activesupport (5.1.1)
      concurrent-ruby (~> 1.0, >= 1.0.2)
      i18n (~> 0.7)
      minitest (~> 5.1)
      tzinfo (~> 1.1)
    arel (8.0.0)
    concurrent-ruby (1.0.5)
    domain_name (0.5.20170404)
      unf (>= 0.0.5, < 1.0.0)
    http-cookie (1.0.3)
      domain_name (~> 0.5)
    i18n (0.8.1)
    mime-types (3.1)
      mime-types-data (~> 3.2015)
    mime-types-data (3.2016.0521)
    minitest (5.10.2)
    mustermann (1.0.0)
    netrc (0.11.0)
    rack (2.0.3)
    rack-protection (2.0.0)
      rack
    rest-client (2.0.2)
      http-cookie (>= 1.0.2, < 2.0)
      mime-types (>= 1.16, < 4.0)
      netrc (~> 0.8)
    sinatra (2.0.0)
      mustermann (~> 1.0)
      rack (~> 2.0)
      rack-protection (= 2.0.0)
      tilt (~> 2.0)
    sqlite3 (1.3.13)
    thread_safe (0.3.6)
    tilt (2.0.7)
    tzinfo (1.2.3)
      thread_safe (~> 0.1)
    unf (0.1.4)
      unf_ext
    unf_ext (0.0.7.4)

PLATFORMS
  ruby

DEPENDENCIES
  activerecord
  rest-client
  sinatra
  sqlite3

BUNDLED WITH
   1.14.6