add currency precision config, fix withdraw precision

app/models/withdraw.rb

@@ -23,6 +23,7 @@ class Withdraw < ActiveRecord::Base
   delegate :name, to: :member, prefix: true
   delegate :coin?, :fiat?, to: :currency_obj
 
+  before_validation :fix_precision
   before_validation :calc_fee
   before_validation :set_account
   after_create :generate_sn
@@ -207,6 +208,12 @@ def ensure_account_balance
     end
   end
 
+  def fix_precision
+    if sum && currency_obj.precision
+      self.sum = sum.round(currency_obj.precision, BigDecimal::ROUND_DOWN)
+    end
+  end
+
   def calc_fee
     if respond_to?(:set_fee)
       set_fee

config/currencies.yml.example

@@ -3,6 +3,7 @@
   code: cny
   symbol: "¥"
   coin: false
+  precision: 2
   assets:
     accounts:
       -

spec/fixtures/currencies.yml

@@ -7,6 +7,7 @@
   key: satoshi
   code: btc
   coin: true
+  precision: 8
   rpc: http://bitcoinrpc:[email protected]:18332
   blockchain: http://testnet.btclook.com/txn/#{txid}
   address_url: https://blockchain.info/address/#{address}

spec/models/withdraw_spec.rb

@@ -2,6 +2,13 @@
 
 describe Withdraw do
 
+  context '#fix_precision' do
+    it "should round down to max precision" do
+      withdraw = create(:satoshi_withdraw, sum: '0.123456789')
+      withdraw.sum.should == '0.12345678'.to_d
+    end
+  end
+
   context 'fund source' do
     it "should strip trailing spaces in fund_uid" do
       fund_source = create(:btc_fund_source, uid: 'test   ')