Merge pull request #5 from hmrc/feature/HMA-2552-first-bonus-period-c…

…alculator

HMA-2552: Added HTS calculation for first bonus calculator

.gitignore

@@ -27,4 +27,5 @@ yarn-error.log
 /.idea/
 /.gradle/
 credentials.properties
-gradlew.bat
+gradlew.bat
+local.properties

README.md

@@ -46,6 +46,31 @@ This will returns an object of type `CalculatorResponse`.  This provide headline
 * `endOfPeriod2Savings: Double`
 * `endOfPeriod2Total: Double`
 
+### For existing accounts in first term
+```kotlin
+FirstBonusTermCalculator.runFirstBonusCalculator(input)
+```
+Where `input` have the following object:
+```
+regularPayment: Double, // 25.0
+currentBalance: Double, // 25.0
+paidInThisMonth: Double, // 50.0
+accountStartDate: YearMonthDayInput, // YearMonthDayInput(2020, 3)
+firstTermEndDate: YearMonthDayInput, // YearMonthDayInput(2022, 2, 28)
+secondTermEndDate: YearMonthDayInput, // YearMonthDayInput(2024, 2, 28)
+balanceMustBeMoreThanForBonus: Double // 50.0
+```
+
+## Response
+This will returns an object of type `FirstBonusCalculatorResponse`. 
+* `totalProjectedSavingsIncludingBonuses: Double`
+* `totalProjectedSavings: Double`
+* `totalProjectedBonuses: Double`
+* `projectedSavingsFirstBonusPeriod: Double`
+* `projectedFirstBonus: Double`
+* `projectedAdditionalSavingsFinalBonusPeriod: Double`
+* `projectedFinalBonus: Double`
+
 ## Validation
 
 To validate the monthly contributions:

src/commonMain/kotlin/uk/gov/hmrc/helptosavecalculator/FirstBonusTermCalculation.kt

@@ -0,0 +1,97 @@
+/*
+ * Copyright 2020 HM Revenue & Customs
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package uk.gov.hmrc.helptosavecalculator
+
+import uk.gov.hmrc.helptosavecalculator.models.FirstBonusInput
+import uk.gov.hmrc.helptosavecalculator.utils.monthsSince
+
+internal class FirstBonusTermCalculation {
+
+    fun calculateTotalProjectedSavingsIncludeBonuses(
+        totalProjectedSavings: Double,
+        totalProjectedBonuses: Double
+    ): Double {
+        return totalProjectedSavings + totalProjectedBonuses
+    }
+
+    fun calculateAdditionalSavingsThisMonth(input: FirstBonusInput): Double {
+        return if (input.regularPayment > input.paidInThisMonth) {
+            input.regularPayment - input.paidInThisMonth
+        } else {
+            0.0
+        }
+    }
+
+    fun calculateTotalProjectedSavings(
+        input: FirstBonusInput,
+        additionalSavingsThisMonth: Double,
+        monthsLeftInScheme: Int
+    ): Double {
+        return input.currentBalance + additionalSavingsThisMonth + (input.regularPayment * monthsLeftInScheme)
+    }
+
+    fun calculateTotalProjectedBonuses(
+        projectedFirstBonus: Double,
+        projectedFinalBonus: Double
+    ): Double {
+        return projectedFirstBonus + projectedFinalBonus
+    }
+
+    fun calculateProjectedSavingsFirstBonusPeriod(
+        input: FirstBonusInput,
+        additionalSavingsThisMonth: Double,
+        monthsLeftInFirstTerm: Int
+    ): Double {
+        return input.currentBalance + additionalSavingsThisMonth + (input.regularPayment * monthsLeftInFirstTerm)
+    }
+
+    fun calculateHighestBalanceFirstBonusPeriod(
+        input: FirstBonusInput,
+        projectedSavingsFirstBonusPeriod: Double
+    ): Double {
+        return input.balanceMustBeMoreThanForBonus.takeIf {
+            it > projectedSavingsFirstBonusPeriod
+        } ?: projectedSavingsFirstBonusPeriod
+    }
+
+    fun calculateProjectedFirstBonus(highestBalanceFirstBonusPeriod: Double): Double {
+        return highestBalanceFirstBonusPeriod / 2
+    }
+
+    fun calculateProjectedAdditionalSavingsFinalBonusPeriod(input: FirstBonusInput): Double {
+        return input.regularPayment * 24
+    }
+
+    fun calculateProjectedFinalBonus(
+        highestBalanceFinalBonusPeriod: Double,
+        highestBalanceFirstBonusPeriod: Double
+    ): Double {
+        return if (highestBalanceFinalBonusPeriod > highestBalanceFirstBonusPeriod) {
+            (highestBalanceFinalBonusPeriod - highestBalanceFirstBonusPeriod) / 2
+        } else {
+            0.0
+        }
+    }
+
+    fun calculateMonthsLeftInScheme(input: FirstBonusInput): Pair<Int, Int> {
+        val startDate = input.accountStartDate.convertToDateTime()
+        val secondTermEndDate = input.secondTermEndDate.convertToDateTime()
+        val firstTermEndDate = input.firstTermEndDate.convertToDateTime()
+        val monthsLeftInScheme = startDate.monthsSince(secondTermEndDate)
+        val monthsLeftInFirstTerm = startDate.monthsSince(firstTermEndDate)
+        return Pair(monthsLeftInScheme, monthsLeftInFirstTerm)
+    }
+}

src/commonMain/kotlin/uk/gov/hmrc/helptosavecalculator/FirstBonusTermCalculator.kt

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2020 HM Revenue & Customs
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package uk.gov.hmrc.helptosavecalculator
+
+import uk.gov.hmrc.helptosavecalculator.exceptions.InvalidRegularPaymentException
+import uk.gov.hmrc.helptosavecalculator.models.FirstBonusCalculatorResponse
+import uk.gov.hmrc.helptosavecalculator.models.FirstBonusInput
+import uk.gov.hmrc.helptosavecalculator.validation.RegularPaymentValidators
+
+object FirstBonusTermCalculator {
+
+    private val calculation = FirstBonusTermCalculation()
+
+    fun runFirstBonusCalculator(input: FirstBonusInput): FirstBonusCalculatorResponse {
+        return calculateFirstBonus(input)
+    }
+
+    private fun calculateFirstBonus(input: FirstBonusInput): FirstBonusCalculatorResponse {
+        validateUserInput(input.regularPayment)
+
+        val (monthLeftInScheme, monthLeftInFirstTerm) = calculation.calculateMonthsLeftInScheme(input)
+        val additionalSavingsThisMonth = calculation.calculateAdditionalSavingsThisMonth(input)
+        val totalProjectedSavings = calculation.calculateTotalProjectedSavings(input,
+                additionalSavingsThisMonth,
+                monthLeftInScheme)
+        val projectedSavingsFirstBonusPeriod = calculation.calculateProjectedSavingsFirstBonusPeriod(input,
+                additionalSavingsThisMonth,
+                monthLeftInFirstTerm)
+        val highestBalanceFirstBonusPeriod = calculation.calculateHighestBalanceFirstBonusPeriod(input,
+                projectedSavingsFirstBonusPeriod)
+        val projectedFirstBonus = calculation.calculateProjectedFirstBonus(highestBalanceFirstBonusPeriod)
+        val projectedAdditionalSavingsFinalBonusPeriod =
+                calculation.calculateProjectedAdditionalSavingsFinalBonusPeriod(input)
+        val projectedFinalBonus = calculation.calculateProjectedFinalBonus(totalProjectedSavings,
+                highestBalanceFirstBonusPeriod)
+        val totalProjectedBonuses = calculation.calculateTotalProjectedBonuses(projectedFirstBonus,
+                projectedFinalBonus)
+        val totalProjectedSavingsIncludingBonuses =
+                calculation.calculateTotalProjectedSavingsIncludeBonuses(totalProjectedSavings,
+                totalProjectedBonuses)
+
+        return FirstBonusCalculatorResponse(
+                totalProjectedSavingsIncludingBonuses,
+                totalProjectedSavings,
+                totalProjectedBonuses,
+                projectedSavingsFirstBonusPeriod,
+                projectedFirstBonus,
+                projectedAdditionalSavingsFinalBonusPeriod,
+                projectedFinalBonus
+        )
+    }
+
+    private fun validateUserInput(regularPayment: Double) {
+        if (!RegularPaymentValidators.isValidRegularPayments(regularPayment)) {
+            throw InvalidRegularPaymentException(regularPayment)
+        }
+    }
+}

src/commonMain/kotlin/uk/gov/hmrc/helptosavecalculator/models/CalculatorResponse.kt

@@ -38,3 +38,13 @@ data class MonthlyBreakdown(
 ) {
     val bonusToDate: Double = period1Bonus + period2Bonus
 }
+
+data class FirstBonusCalculatorResponse(
+    val totalProjectedSavingsIncludingBonuses: Double,
+    val totalProjectedSavings: Double,
+    val totalProjectedBonuses: Double,
+    val projectedSavingsFirstBonusPeriod: Double,
+    val projectedFirstBonus: Double,
+    val projectedAdditionalSavingsFinalBonusPeriod: Double,
+    val projectedFinalBonus: Double
+)

src/commonMain/kotlin/uk/gov/hmrc/helptosavecalculator/models/FirstBonusInput.kt

@@ -0,0 +1,26 @@
+/*
+ * Copyright 2020 HM Revenue & Customs
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package uk.gov.hmrc.helptosavecalculator.models
+
+data class FirstBonusInput(
+    val regularPayment: Double,
+    val currentBalance: Double,
+    val paidInThisMonth: Double,
+    val accountStartDate: YearMonthDayInput,
+    val firstTermEndDate: YearMonthDayInput,
+    val secondTermEndDate: YearMonthDayInput,
+    val balanceMustBeMoreThanForBonus: Double
+)

src/commonMain/kotlin/uk/gov/hmrc/helptosavecalculator/models/YearMonthDayInput.kt

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2020 HM Revenue & Customs
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package uk.gov.hmrc.helptosavecalculator.models
+
+import com.soywiz.klock.DateTime
+
+data class YearMonthDayInput(
+    val year: Int,
+    val month: Int,
+    val day: Int = 1
+) {
+    internal fun convertToDateTime(): DateTime {
+        return DateTime(year, month, day)
+    }
+}