feat: makeChange function supporting multiple cassettes

lib/bill-math.js

@@ -1,4 +1,5 @@
 const uuid = require('uuid')
+const _ = require('lodash')
 
 // Custom algorith for two cassettes. For three or more denominations, we'll need
 // to rethink this. Greedy algorithm fails to find *any* solution in some cases.
@@ -10,28 +11,37 @@ exports.makeChange = function makeChange (cassettes, amount) {
   // Note: Everything here is converted to primitive numbers,
   // since they're all integers, well within JS number range,
   // and this is way more efficient in a tight loop.
-
-  const small = cassettes[0]
-  const large = cassettes[1]
-
-  const largeDenom = large.denomination
-  const smallDenom = small.denomination
-  const largeBills = Math.min(large.count, Math.floor(amount / largeDenom))
+  const cassetteMap = _.map(cassettes, it => ({
+    denomination: it.denomination
+  }))
   const amountNum = amount.toNumber()
 
-  for (let i = largeBills; i >= 0; i--) {
-    const remainder = amountNum - largeDenom * i
+  const sortedCassettes = _.orderBy(cassetteMap, ['denomination'], ['desc'])
 
-    if (remainder % smallDenom !== 0) continue
+  const finalDist = []
 
-    const smallCount = remainder / smallDenom
-    if (smallCount > small.count) continue
+  let mutableAmount = _.clone(amountNum)
 
-    return [
-      {provisioned: smallCount, denomination: small.denomination, id: uuid.v4()},
-      {provisioned: i, denomination: largeDenom, id: uuid.v4()}
-    ]
+  while(mutableAmount >= 0) {
+    _.each(sortedCassettes, it => {
+      if (mutableAmount === 0) {
+        finalDist.push({provisioned: 0, denomination: it.denomination, id: uuid.v4()})
+        return
       }
 
-  return null
+      const remainder = mutableAmount % it.denomination
+      const amountToSub = mutableAmount - remainder
+      const numberOfBills = amountToSub / it.denomination
+      mutableAmount -= amountToSub
+
+      finalDist.push({provisioned: numberOfBills, denomination: it.denomination, id: uuid.v4()})
+      return
+    })
+
+    if (mutableAmount === 0) {
+      break
+    }
+  }
+
+  return finalDist
 }

lib/cash-out/cash-out-helper.js

@@ -42,8 +42,12 @@ function addDbBills (tx) {
   return _.assign(tx, {
     provisioned1: bills[0].provisioned,
     provisioned2: bills[1].provisioned,
+    provisioned3: bills[2].provisioned,
+    provisioned4: bills[3].provisioned,
     denomination1: bills[0].denomination,
-    denomination2: bills[1].denomination
+    denomination2: bills[1].denomination,
+    denomination3: bills[2].denomination,
+    denomination4: bills[3].denomination
   })
 }
 
@@ -76,7 +80,7 @@ function toObj (row) {
 
   newObj.direction = 'cashOut'
 
-  const billFields = ['denomination1', 'denomination2', 'provisioned1', 'provisioned2']
+  const billFields = ['denomination1', 'denomination2', 'denomination3', 'denomination4', 'provisioned1', 'provisioned2', 'provisioned3', 'provisioned4']
 
   if (_.every(_.isNil, _.at(billFields, newObj))) return newObj
   if (_.some(_.isNil, _.at(billFields, newObj))) throw new Error('Missing cassette values')
@@ -89,6 +93,14 @@ function toObj (row) {
     {
       denomination: newObj.denomination2,
       provisioned: newObj.provisioned2
+    },
+    {
+      denomination: newObj.denomination3,
+      provisioned: newObj.provisioned3
+    },
+    {
+      denomination: newObj.denomination4,
+      provisioned: newObj.provisioned4
     }
   ]
 

lib/plugins.js

@@ -105,19 +105,18 @@ function plugins (settings, deviceId) {
   }
 
   function computeAvailableCassettes (cassettes, redeemableTxs) {
-    if (_.isEmpty(redeemableTxs)) return cassettes
+    const orderedCassettes = _.orderBy(['denomination'], ['desc'], cassettes)
+    if (_.isEmpty(redeemableTxs)) return orderedCassettes
 
     const sumTxs = (sum, tx) => {
       const bills = tx.bills
       const sameDenominations = a => a[0].denomination === a[1].denomination
 
-      console.log('tx', tx)
-      console.log('cassettes', cassettes)
-      console.log('bills', bills)
-      const doDenominationsMatch = _.every(it => {
-        console.log('it', it)
-        return sameDenominations(it)
-      }, _.zip(cassettes, bills))
+      // Order cassettes and bills to make sure they match
+      const orderedBills = _.orderBy(['denomination'], ['desc'], bills)
+      console.log('orderedBills', orderedBills)
+
+      const doDenominationsMatch = _.every(sameDenominations, _.zip(orderedCassettes, orderedBills))
 
       if (!doDenominationsMatch) {
         throw new Error('Denominations don\'t add up, cassettes were changed.')
@@ -126,8 +125,8 @@ function plugins (settings, deviceId) {
       return _.map(r => r[0] + r[1].provisioned, _.zip(sum, tx.bills))
     }
 
-    const provisioned = _.reduce(sumTxs, Array(_.size(cassettes)).fill(0), redeemableTxs)
-    const zipped = _.zip(_.map('count', cassettes), provisioned)
+    const provisioned = _.reduce(sumTxs, Array(_.size(orderedCassettes)).fill(0), redeemableTxs)
+    const zipped = _.zip(_.map('count', orderedCassettes), provisioned)
     const counts = _.map(r => r[0] - r[1], zipped)
 
     if (_.some(_.lt(_, 0), counts)) {
@@ -136,12 +135,20 @@ function plugins (settings, deviceId) {
 
     return [
       {
-        denomination: cassettes[0].denomination,
+        denomination: orderedCassettes[0].denomination,
         count: counts[0]
       },
       {
-        denomination: cassettes[1].denomination,
+        denomination: orderedCassettes[1].denomination,
         count: counts[1]
+      },
+      {
+        denomination: orderedCassettes[2].denomination,
+        count: counts[2]
+      },
+      {
+        denomination: orderedCassettes[3].denomination,
+        count: counts[3]
       }
     ]
   }