[HMA-1837] - Limit taxToPay to 50% of wages if taxToPay is over 50% o…

…f their wages (#24)

README.md

@@ -3,8 +3,8 @@
 
 [![Build Status](https://app.bitrise.io/app/cd7fb52c258b9273/status.svg?token=lntO8o4xz5AUEvLwVzbo3A&branch=master)](https://app.bitrise.io/app/cd7fb52c258b9273)
 ![LINE](https://img.shields.io/badge/line--coverage-98%25-brightgreen.svg)
-![BRANCH](https://img.shields.io/badge/branch--coverage-94%25-brightgreen.svg)
-![COMPLEXITY](https://img.shields.io/badge/complexity-1.48-brightgreen.svg)
+![BRANCH](https://img.shields.io/badge/branch--coverage-92%25-brightgreen.svg)
+![COMPLEXITY](https://img.shields.io/badge/complexity-1.52-brightgreen.svg)
 [ ![Download](https://api.bintray.com/packages/hmrc/mobile-releases/tax-kalculator/images/download.svg) ](https://bintray.com/hmrc/mobile-releases/tax-kalculator/_latestVersion)
 
 ## Calculate take-home pay
@@ -32,7 +32,8 @@ val response = calculator.run()
 
 This will returns an object of type `CalculatorResponse`. This class is broken up into weekly, four_weekly, monthly and yearly. Each of these members is of type `CalculatorResponsePayPeriod` and the members of this class are what will return the values (relative to their PayPeriod) needed for the app, they are:
 
-- `taxToPay: Double`
+- `taxToPay: Double` -> This will capped at a maximum of 50% of their wages
+- `maxTaxAmountExceeded: Boolean` -> This will always be false unless taxToPay is adjusted for 50%
 - `employeesNI: Double`
 - `employersNI: Double`
 - `wages: Double`
@@ -48,7 +49,7 @@ This will returns an object of type `CalculatorResponse`. This class is broken u
 To validate a tax code:
 
 ```kotlin
-val isValid = Calculator.isValidTaxCode("1250L") // true
+val isValid = Validator.isValidTaxCode("1250L") // true
 ```
 
 To validate wages:

src/commonMain/kotlin/uk/gov/hmrc/calculator/Calculator.kt

@@ -15,6 +15,7 @@
  */
 package uk.gov.hmrc.calculator
 
+import kotlin.jvm.JvmOverloads
 import uk.gov.hmrc.calculator.annotations.Throws
 import uk.gov.hmrc.calculator.exception.InvalidHoursException
 import uk.gov.hmrc.calculator.exception.InvalidPayPeriodException
@@ -51,7 +52,7 @@ import uk.gov.hmrc.calculator.utils.convertListOfBandBreakdownForPayPeriod
 import uk.gov.hmrc.calculator.utils.convertWageToYearly
 import uk.gov.hmrc.calculator.utils.toTaxCode
 
-class Calculator(
+class Calculator @JvmOverloads constructor(
     private val taxCode: String,
     private val wages: Double,
     private val payPeriod: PayPeriod,
@@ -100,41 +101,41 @@ class Calculator(
             isKCode = taxCode is KTaxCode,
             weekly = CalculatorResponsePayPeriod(
                 payPeriod = WEEKLY,
-                taxToPay = taxPayable.convertAmountFromYearlyToPayPeriod(WEEKLY),
+                taxToPayForPayPeriod = taxPayable.convertAmountFromYearlyToPayPeriod(WEEKLY),
                 employeesNI = employeesNI.convertAmountFromYearlyToPayPeriod(WEEKLY),
                 employersNI = employersNI.convertAmountFromYearlyToPayPeriod(WEEKLY),
                 wages = yearlyWages.convertAmountFromYearlyToPayPeriod(WEEKLY),
-                taxBreakdown = bandBreakdown.convertListOfBandBreakdownForPayPeriod(WEEKLY),
+                taxBreakdownForPayPeriod = bandBreakdown.convertListOfBandBreakdownForPayPeriod(WEEKLY),
                 taxFree = taxFreeAmount.convertAmountFromYearlyToPayPeriod(WEEKLY),
                 kCodeAdjustment = amountToAddToWages?.convertAmountFromYearlyToPayPeriod(WEEKLY)
             ),
             fourWeekly = CalculatorResponsePayPeriod(
                 payPeriod = FOUR_WEEKLY,
-                taxToPay = taxPayable.convertAmountFromYearlyToPayPeriod(FOUR_WEEKLY),
+                taxToPayForPayPeriod = taxPayable.convertAmountFromYearlyToPayPeriod(FOUR_WEEKLY),
                 employeesNI = employeesNI.convertAmountFromYearlyToPayPeriod(FOUR_WEEKLY),
                 employersNI = employersNI.convertAmountFromYearlyToPayPeriod(FOUR_WEEKLY),
                 wages = yearlyWages.convertAmountFromYearlyToPayPeriod(FOUR_WEEKLY),
-                taxBreakdown = bandBreakdown.convertListOfBandBreakdownForPayPeriod(FOUR_WEEKLY),
+                taxBreakdownForPayPeriod = bandBreakdown.convertListOfBandBreakdownForPayPeriod(FOUR_WEEKLY),
                 taxFree = taxFreeAmount.convertAmountFromYearlyToPayPeriod(FOUR_WEEKLY),
                 kCodeAdjustment = amountToAddToWages?.convertAmountFromYearlyToPayPeriod(FOUR_WEEKLY)
             ),
             monthly = CalculatorResponsePayPeriod(
                 payPeriod = MONTHLY,
-                taxToPay = taxPayable.convertAmountFromYearlyToPayPeriod(MONTHLY),
+                taxToPayForPayPeriod = taxPayable.convertAmountFromYearlyToPayPeriod(MONTHLY),
                 employeesNI = employeesNI.convertAmountFromYearlyToPayPeriod(MONTHLY),
                 employersNI = employersNI.convertAmountFromYearlyToPayPeriod(MONTHLY),
                 wages = yearlyWages.convertAmountFromYearlyToPayPeriod(MONTHLY),
-                taxBreakdown = bandBreakdown.convertListOfBandBreakdownForPayPeriod(MONTHLY),
+                taxBreakdownForPayPeriod = bandBreakdown.convertListOfBandBreakdownForPayPeriod(MONTHLY),
                 taxFree = taxFreeAmount.convertAmountFromYearlyToPayPeriod(MONTHLY),
                 kCodeAdjustment = amountToAddToWages?.convertAmountFromYearlyToPayPeriod(MONTHLY)
             ),
             yearly = CalculatorResponsePayPeriod(
                 payPeriod = YEARLY,
-                taxToPay = taxPayable.convertAmountFromYearlyToPayPeriod(YEARLY),
+                taxToPayForPayPeriod = taxPayable.convertAmountFromYearlyToPayPeriod(YEARLY),
                 employeesNI = employeesNI.convertAmountFromYearlyToPayPeriod(YEARLY),
                 employersNI = employersNI.convertAmountFromYearlyToPayPeriod(YEARLY),
                 wages = yearlyWages.convertAmountFromYearlyToPayPeriod(YEARLY),
-                taxBreakdown = bandBreakdown,
+                taxBreakdownForPayPeriod = bandBreakdown,
                 taxFree = taxFreeAmount,
                 kCodeAdjustment = amountToAddToWages
             )

src/commonMain/kotlin/uk/gov/hmrc/calculator/model/CalculatorResponse.kt

@@ -21,18 +21,22 @@ data class BandBreakdown(val percentage: Double, val amount: Double) {
     val bandDescription: String = "Income taxed at $percentageFormatted%"
 }
 
-data class CalculatorResponsePayPeriod(
+class CalculatorResponsePayPeriod(
     val payPeriod: PayPeriod,
-    val taxToPay: Double,
+    taxToPayForPayPeriod: Double,
     val employeesNI: Double,
     val employersNI: Double,
     val wages: Double,
-    val taxBreakdown: List<BandBreakdown>,
+    taxBreakdownForPayPeriod: List<BandBreakdown>?,
     val taxFree: Double,
     val kCodeAdjustment: Double? = null
 ) {
+    private val maxTaxAmount = wages / 2
+    val taxToPay = if (taxToPayForPayPeriod > maxTaxAmount) maxTaxAmount else taxToPayForPayPeriod
+    val maxTaxAmountExceeded = (taxToPayForPayPeriod > maxTaxAmount)
     val totalDeductions = taxToPay + employeesNI
     val takeHome = wages - totalDeductions
+    val taxBreakdown = if (maxTaxAmountExceeded) null else taxBreakdownForPayPeriod
 }
 
 data class CalculatorResponse(

src/commonTest/kotlin/uk/gov/hmrc/calculator/model/CalculatorResponseTests.kt

@@ -29,11 +29,11 @@ class CalculatorResponseTests {
     fun `Check Summation Of Total Deductions`() {
         val response = CalculatorResponsePayPeriod(
             payPeriod = YEARLY,
-            taxToPay = 100.0,
+            taxToPayForPayPeriod = 100.0,
             employeesNI = 200.0,
             employersNI = 300.0,
             wages = 1000.0,
-            taxBreakdown = listOf(
+            taxBreakdownForPayPeriod = listOf(
                 BandBreakdown(0.0, 0.0),
                 BandBreakdown(0.2, 2000.0)
             ),
@@ -82,7 +82,7 @@ class CalculatorResponseTests {
                 )
             ), response.yearly.taxBreakdown
         )
-        assertEquals(response.yearly.taxBreakdown[0].bandDescription, "Income taxed at 20%")
+        assertEquals(response.yearly.taxBreakdown?.get(0)?.bandDescription, "Income taxed at 20%")
 
         assertEquals(191.51666666666668, response.monthly.taxToPay)
         assertEquals(153.67999999999998, response.monthly.employeesNI)
@@ -160,8 +160,8 @@ class CalculatorResponseTests {
                 BandBreakdown(percentage = 0.4, amount = 32000.00)
             ), response.yearly.taxBreakdown
         )
-        assertEquals(response.yearly.taxBreakdown[0].bandDescription, "Income taxed at 20%")
-        assertEquals(response.yearly.taxBreakdown[1].bandDescription, "Income taxed at 40%")
+        assertEquals(response.monthly.taxBreakdown?.get(0)?.bandDescription, "Income taxed at 20%")
+        assertEquals(response.monthly.taxBreakdown?.get(1)?.bandDescription, "Income taxed at 40%")
 
         assertEquals(3291.5166666666664, response.monthly.taxToPay)
         assertEquals(530.3466666666667, response.monthly.employeesNI)
@@ -249,10 +249,10 @@ class CalculatorResponseTests {
                 BandBreakdown(percentage = 0.41, amount = 35493.70)
             ), response.yearly.taxBreakdown
         )
-        assertEquals(response.yearly.taxBreakdown[0].bandDescription, "Income taxed at 19%")
-        assertEquals(response.yearly.taxBreakdown[1].bandDescription, "Income taxed at 20%")
-        assertEquals(response.yearly.taxBreakdown[2].bandDescription, "Income taxed at 21%")
-        assertEquals(response.yearly.taxBreakdown[3].bandDescription, "Income taxed at 41%")
+        assertEquals(response.monthly.taxBreakdown?.get(0)?.bandDescription, "Income taxed at 19%")
+        assertEquals(response.monthly.taxBreakdown?.get(1)?.bandDescription, "Income taxed at 20%")
+        assertEquals(response.monthly.taxBreakdown?.get(2)?.bandDescription, "Income taxed at 21%")
+        assertEquals(response.monthly.taxBreakdown?.get(3)?.bandDescription, "Income taxed at 41%")
 
         assertEquals(3486.8633333333332, response.monthly.taxToPay)
         assertEquals(530.3466666666667, response.monthly.employeesNI)
@@ -343,12 +343,13 @@ class CalculatorResponseTests {
             ), response.yearly.taxBreakdown
         )
     }
+
     @Test
-    fun `NT`() {
+    fun NT() {
         val taxCode = "NT"
         val wages = 130000.00
         val response = Calculator(taxCode, wages, payPeriod = YEARLY).run()
-
+        assertEquals(false, response.yearly.maxTaxAmountExceeded)
         assertEquals(6564.16, response.yearly.totalDeductions)
         assertEquals(
             listOf(
@@ -359,4 +360,27 @@ class CalculatorResponseTests {
             ), response.yearly.taxBreakdown
         )
     }
+
+    @Test
+    fun `Check K9999 (Ensure HMRC does not tax you more than 50%)`() {
+        val taxCode = "K9999"
+        val wages = 400.00
+        val response = Calculator(taxCode, wages, payPeriod = PayPeriod.WEEKLY).run()
+
+        assertEquals(ENGLAND, response.country)
+        assertEquals(true, response.isKCode)
+        assertEquals("K9999", response.taxCode)
+
+        // Year
+        assertEquals(YEARLY, response.yearly.payPeriod)
+        assertEquals(10400.0, response.yearly.taxToPay)
+        assertEquals(1460.1599999999999, response.yearly.employeesNI)
+        assertEquals(true, response.yearly.maxTaxAmountExceeded)
+        assertEquals(11860.16, response.yearly.totalDeductions)
+        assertEquals(8939.84, response.yearly.takeHome)
+        assertEquals(0.0, response.yearly.taxFree)
+        assertEquals(20800.0, response.yearly.wages)
+        assertEquals(99999.0, response.yearly.kCodeAdjustment)
+        assertEquals(null, response.yearly.taxBreakdown)
+    }
 }