From 03fc35e9d162a2ac0669681b9630645b04c9242f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9rgio=20Salgado?= <sergiodiassalgado@gmail.com>
Date: Fri, 15 Oct 2021 16:11:47 +0100
Subject: [PATCH] fix: edge cases on makeChangeDynamic

---
 lib/bill-math.js | 74 ++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 71 insertions(+), 3 deletions(-)

diff --git a/lib/bill-math.js b/lib/bill-math.js
index 960868ef..5ac9358b 100644
--- a/lib/bill-math.js
+++ b/lib/bill-math.js
@@ -17,7 +17,7 @@ exports.makeChange = function makeChange (cassettes, amount) {
   // Example: Denominations: [3, 5, 10] | User inputs 4 times the [3] button, resulting in a 12 fiat tx
   // This algorithm resolves for 1 x [10], and can't resolve the remainder of 2
 
-  return _.length(cassettes) > 2 ? makeChangeDynamic(cassettes, amount) : makeChangeDuo(cassettes, amount)
+  return _.size(cassettes) > 2 ? makeChangeDynamic(cassettes, amount) : makeChangeDuo(cassettes, amount)
 }
 
 function makeChangeDuo (cassettes, amount) {
@@ -61,6 +61,37 @@ function makeChangeDynamic (cassettes, amount) {
       amountNum;
       j++
     ) {
+      if (cassettes[1].denomination === 0) break
+      if (
+        i * cassettes[0].denomination +
+          j * cassettes[1].denomination ===
+          amountNum &&
+        i <= cassettes[0].count &&
+        j <= cassettes[1].count && i >= 0 && j >= 0
+      ) {
+        solutions.push([
+          {
+            provisioned: i,
+            denomination: cassettes[0].denomination,
+            id: uuid.v4()
+          },
+          {
+            provisioned: j,
+            denomination: cassettes[1].denomination,
+            id: uuid.v4()
+          },
+          {
+            provisioned: 0,
+            denomination: cassettes[2].denomination,
+            id: uuid.v4()
+          },
+          {
+            provisioned: 0,
+            denomination: cassettes[3].denomination,
+            id: uuid.v4()
+          }
+        ])
+      }
       for (
         let k = 0;
         i * cassettes[0].denomination +
@@ -69,6 +100,39 @@ function makeChangeDynamic (cassettes, amount) {
         amountNum;
         k++
       ) {
+        if (cassettes[2].denomination === 0) break
+        if (
+          i * cassettes[0].denomination +
+            j * cassettes[1].denomination +
+            k * cassettes[2].denomination ===
+            amountNum &&
+          i <= cassettes[0].count &&
+          j <= cassettes[1].count &&
+          k <= cassettes[2].count && i >= 0 && j >= 0 && k >= 0
+        ) {
+          solutions.push([
+            {
+              provisioned: i,
+              denomination: cassettes[0].denomination,
+              id: uuid.v4()
+            },
+            {
+              provisioned: j,
+              denomination: cassettes[1].denomination,
+              id: uuid.v4()
+            },
+            {
+              provisioned: k,
+              denomination: cassettes[2].denomination,
+              id: uuid.v4()
+            },
+            {
+              provisioned: 0,
+              denomination: cassettes[3].denomination,
+              id: uuid.v4()
+            }
+          ])
+        }
         for (
           let l = 0;
           i * cassettes[0].denomination +
@@ -78,6 +142,7 @@ function makeChangeDynamic (cassettes, amount) {
           amountNum;
           l++
         ) {
+          if (cassettes[3].denomination === 0) break
           if (
             i * cassettes[0].denomination +
               j * cassettes[1].denomination +
@@ -87,7 +152,7 @@ function makeChangeDynamic (cassettes, amount) {
             i <= cassettes[0].count &&
             j <= cassettes[1].count &&
             k <= cassettes[2].count &&
-            l <= cassettes[3].count && i > 0 && j > 0 && k > 0 && l > 0
+            l <= cassettes[3].count && i >= 0 && j >= 0 && k >= 0 && l >= 0
           ) {
             solutions.push([
               {
@@ -120,5 +185,8 @@ function makeChangeDynamic (cassettes, amount) {
   const sortedSolutions = _.sortBy(solutions, it => {
     _.reduce(it, (acc, value) => acc + value.provisioned, 0)
   })
-  return _.head(sortedSolutions)
+
+  const cleanSolution = _.filter(_.head(sortedSolutions), it => it.denomination > 0)
+
+  return cleanSolution
 }