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feat: Improve types in Mortgage and FairholdLandPurchase
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,95 +1,115 @@ | ||
| import { MONTHS_PER_YEAR } from "./constants"; | ||
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| const DEFAULT_INTEREST_RATE = 0.06; | ||
| const DEFAULT_MORTGAGE_TERM = 30; | ||
| const DEFAULT_INITIAL_DEPOSIT = 0.15; | ||
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| type MortgageBreakdown = { | ||
| yearlyPayment: number; | ||
| cumulativePaid: number; | ||
| remainingBalance: number; | ||
| }[]; | ||
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| export class Mortgage { | ||
| propertyValue: number; //value of the property for the mortgage | ||
| interestRate: number; // interest rate of the mortgage in percentage e.r, 0.05=5% | ||
| termYears: number; // number of years of the mortgage | ||
| initialDeposit: number; // initial deposit of the value of the mortgage in percentage e.g. 0.15 =15% deposit | ||
| principal?: number; // amount of the morgage requested | ||
| monthlyPayment?: number; // monthly rate of the mortgage | ||
| totalMortgageCost?: number; // total cost of the mortgage | ||
| yearlyPaymentBreakdown?: { | ||
| yearlyPayment: number; | ||
| cumulativePaid: number; | ||
| remainingBalance: number; | ||
| }[]; // yearly breakdown of the mortgage | ||
| propertyValue: number; | ||
| /** | ||
| * This value is given as a percentage. For example, 0.05 represents a 5% rate | ||
| */ | ||
| interestRate: number; | ||
| termYears: number; | ||
| /** | ||
| * This value is given as a percentage. For example, 0.15 represents a 15% deposit | ||
| */ | ||
| initialDeposit: number; | ||
| /** | ||
| * The principle is the value of the property, minus the deposit | ||
| */ | ||
| principal: number; | ||
| monthlyPayment: number; | ||
| totalMortgageCost: number; | ||
| yearlyPaymentBreakdown: MortgageBreakdown; | ||
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| constructor({ | ||
| propertyValue, | ||
| interestRate = 0.06, | ||
| termOfTheMortgage = 30, | ||
| initialDeposit = 0.15, | ||
| interestRate = DEFAULT_INTEREST_RATE, | ||
| mortgageTerm = DEFAULT_MORTGAGE_TERM, | ||
| initialDeposit = DEFAULT_INITIAL_DEPOSIT, | ||
| }: { | ||
| propertyValue: number; | ||
| interestRate?: number; | ||
| termOfTheMortgage?: number; | ||
| mortgageTerm?: number; | ||
| initialDeposit?: number; | ||
| }) { | ||
| this.propertyValue = propertyValue; | ||
| this.initialDeposit = initialDeposit; | ||
| this.interestRate = interestRate; | ||
| this.termYears = termOfTheMortgage; | ||
| this.calculateAmountOfTheMortgage(); // calculate the amount of the mortgage | ||
| this.calculateMonthlyMortgagePayment(); // calculate the montly payment | ||
| this.calculateYearlyPaymentBreakdown(); // calculate the yearly breakdown; | ||
| this.termYears = mortgageTerm; | ||
| this.principal = this.calculateMortgagePrinciple(); | ||
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| const { monthlyPayment, totalMortgageCost } = | ||
| this.calculateMonthlyMortgagePayment(); | ||
| this.monthlyPayment = monthlyPayment; | ||
| this.totalMortgageCost = totalMortgageCost; | ||
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| this.yearlyPaymentBreakdown = this.calculateYearlyPaymentBreakdown(); | ||
| } | ||
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| calculateAmountOfTheMortgage() { | ||
| this.principal = this.propertyValue * (1 - this.initialDeposit); // calculate the amount of the mortgage by removing the deposit | ||
| return this.principal; | ||
| calculateMortgagePrinciple() { | ||
| const principal = this.propertyValue * (1 - this.initialDeposit); | ||
| return principal; | ||
| } | ||
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| calculateMonthlyMortgagePayment() { | ||
| const monthlyInterestRate = this.interestRate / 12; // Convert annual interest rate to monthly rate | ||
| const numberOfPayments = this.termYears * 12; // Convert term in years to total number of payments | ||
| if (this.principal !== undefined) { | ||
| const monthlyPayment = | ||
| (this.principal * | ||
| monthlyInterestRate * | ||
| Math.pow(1 + monthlyInterestRate, numberOfPayments)) / | ||
| (Math.pow(1 + monthlyInterestRate, numberOfPayments) - 1); // Calculate the monthly payment | ||
| this.monthlyPayment = parseFloat(monthlyPayment.toFixed(2)); // Store monthly payment rounded to 2 decimal places in class property | ||
| this.totalMortgageCost = this.monthlyPayment * numberOfPayments; // total cost of the mortgage | ||
| return this.monthlyPayment; | ||
| } else { | ||
| throw new Error("amountOfTheMortgage is undefined"); | ||
| } | ||
| const monthlyInterestRate = this.interestRate / MONTHS_PER_YEAR; | ||
| const numberOfPayments = this.termYears * MONTHS_PER_YEAR; | ||
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| let monthlyPayment = | ||
| (this.principal * | ||
| monthlyInterestRate * | ||
| Math.pow(1 + monthlyInterestRate, numberOfPayments)) / | ||
| (Math.pow(1 + monthlyInterestRate, numberOfPayments) - 1); | ||
| monthlyPayment = parseFloat(monthlyPayment.toFixed(2)); | ||
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| const totalMortgageCost = monthlyPayment * numberOfPayments; | ||
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| return { monthlyPayment, totalMortgageCost }; | ||
| } | ||
| calculateYearlyPaymentBreakdown() { | ||
| if (this.monthlyPayment == undefined || this.totalMortgageCost == undefined) | ||
| throw new Error("monthlyPayment or totalMortgageCost is undefined"); | ||
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| let yearlyPayment = | ||
| this.initialDeposit * this.propertyValue + this.monthlyPayment * 12; | ||
| this.initialDeposit * this.propertyValue + | ||
| this.monthlyPayment * MONTHS_PER_YEAR; | ||
| let cumulativePaid = | ||
| this.initialDeposit * this.propertyValue + this.monthlyPayment * 12; | ||
| let remainingBalance = this.totalMortgageCost - this.monthlyPayment * 12; | ||
| this.initialDeposit * this.propertyValue + | ||
| this.monthlyPayment * MONTHS_PER_YEAR; | ||
| let remainingBalance = | ||
| this.totalMortgageCost - this.monthlyPayment * MONTHS_PER_YEAR; | ||
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| interface mortgageBreakdownTypes { | ||
| yearlyPayment: number; | ||
| cumulativePaid: number; | ||
| remainingBalance: number; | ||
| } | ||
| let yearlyPaymentBreakdown: mortgageBreakdownTypes[] = [ | ||
| let yearlyPaymentBreakdown: MortgageBreakdown = [ | ||
| { | ||
| yearlyPayment: yearlyPayment, | ||
| cumulativePaid: cumulativePaid, | ||
| remainingBalance: remainingBalance, | ||
| }, | ||
| ]; // initialize the yearlyPaymentBreakdown | ||
| ]; | ||
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| for (let i = 0; i < this.termYears - 1; i++) { | ||
| if (i != this.termYears - 1) { | ||
| yearlyPayment = this.monthlyPayment * 12; // calculate the yearly payment | ||
| yearlyPayment = this.monthlyPayment * MONTHS_PER_YEAR; | ||
| } else { | ||
| yearlyPayment = remainingBalance; // last year just pay the remaining balance | ||
| // last year just pay the remaining balance | ||
| yearlyPayment = remainingBalance; | ||
| } | ||
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| cumulativePaid = cumulativePaid + yearlyPayment; // calculate the updated cumulative paid | ||
| remainingBalance = remainingBalance - yearlyPayment; // calculate the updated remaining balance | ||
| cumulativePaid = cumulativePaid + yearlyPayment; | ||
| remainingBalance = remainingBalance - yearlyPayment; | ||
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| yearlyPaymentBreakdown.push({ | ||
| yearlyPayment: yearlyPayment, | ||
| cumulativePaid: cumulativePaid, | ||
| remainingBalance: remainingBalance, | ||
| }); // add the current yearly payment to the yearlyPaymentBreakdown | ||
| }); | ||
| } | ||
| this.yearlyPaymentBreakdown = yearlyPaymentBreakdown; // set the yearlyPaymentBreakdown | ||
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| return yearlyPaymentBreakdown; | ||
| } | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1 @@ | ||
| export const MONTHS_PER_YEAR = 12; |
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