Refactoring and added common utils

SiaDrive.Api/SiaCommon.cpp

@@ -2,4 +2,35 @@
 #include "SiaCommon.h"
 #include <ttmath/ttmath.h>
 
-using namespace Sia::Api;
+using namespace Sia::Api;
+
+
+/*
+// avgHostMetric computes the average of the metric given by `metric` on the
+// list of `hosts`.
+const avgHostMetric = (hosts, metric) = >
+hosts.reduce((sum, host) = > sum.add(host[metric]), new BigNumber(0))
+.dividedBy(hosts.size)
+
+// avgStorageCost returns the average storage cost from a list of hosts given a
+// period (blocks) and redundancy.
+const avgStorageCost = (hosts, period, redundancy) = >
+avgHostMetric(hosts, 'storageprice')
+.times(period)
+.plus(avgHostMetric(hosts, 'uploadbandwidthprice'))
+.times(redundancy)
+.plus(avgHostMetric(hosts, 'downloadbandwidthprice'))
+
+// Compute an estimated amount of storage from an amount of funds (Hastings)
+// and a list of hosts.
+export const estimatedStorage = (funds, hosts) = > {
+	const validHosts = List(hosts).take(28)
+		const avgStorage = avgStorageCost(validHosts, allowancePeriod, baseRedundancy)
+
+		let fee = SiaAPI.siacoinsToHastings(baseFee)
+		fee = fee.plus(avgHostMetric(validHosts, 'contractprice').times(ncontracts))
+		fee = fee.plus(funds.minus(fee).times(siafundRate))
+
+		return '~' + readableFilesize(Math.max(0, funds.minus(fee).dividedBy(avgStorage).toNumber().toPrecision(1)))
+}
+*/