refactor: use simulation types throughout

Author: williamleven

src/lib/ForecastGraph.svelte

@@ -1,17 +1,13 @@
 <script lang="ts">
 	import * as d3 from 'd3';
 	import { afterUpdate } from 'svelte';
+	import type { YearState } from '$lib/simulation';
 
-	interface DataPoint {
-		year: number;
-		savings: number;
-		cashFlow: number;
-	}
-	export let forecast: Array<DataPoint>;
+	export let simulation: Array<YearState>;
 
-	$: data = forecast.map(({ savings, year, cashFlow }) => ({
+	$: data = simulation.map(({ iskSavings, year, cashFlow }) => ({
 		year: new Date(year, 1),
-		savings,
+		savings: iskSavings,
 		cashFlow
 	}));
 

src/lib/simulation.ts

@@ -32,6 +32,61 @@ export interface TimeBoundCashFlow {
 	//servicePensionContribution: number;
 }
 
+export interface Scenario {
+	parameters: Parameters;
+	startState: YearState;
+	endYear: number;
+}
+
+export function defaultScenario(): Scenario {
+	const currentYear = new Date().getFullYear();
+	return {
+		parameters: {
+			inflationRate: 0.025,
+			iskInterestRate: 0.08,
+			iskTax: 0.01086,
+			cashFlows: [
+				{
+					startYear: currentYear,
+					endYear: currentYear + 8,
+					yearlyNetCashFlow: 38500 * 12
+					// publicPensionContributing: true,
+					// servicePensionContribution: 4.5
+				},
+				{
+					startYear: currentYear,
+					endYear: currentYear + 8,
+					yearlyNetCashFlow: 2755 * 12
+					// publicPensionContributing: false,
+					// servicePensionContribution: 100
+				},
+				{
+					startYear: currentYear,
+					endYear: currentYear + 8,
+					yearlyNetCashFlow: -2755 * 12
+					// publicPensionContributing: false,
+					// servicePensionContribution: 0
+				},
+				{
+					startYear: currentYear,
+					endYear: currentYear + 50,
+					yearlyNetCashFlow: -15000 * 12
+					// pensionContributing: false,
+					// publicPensionContributing: false,
+					// servicePensionContribution: 0
+				}
+			]
+		},
+		startState: {
+			year: currentYear,
+			iskSavings: 1000000,
+			compoundedInflation: 1,
+			cashFlow: 0
+		},
+		endYear: 2100
+	};
+}
+
 function simulateYear(state: YearState, params: Parameters): YearState {
 	const newYear = state.year + 1;
 
@@ -66,10 +121,10 @@ function simulateYear(state: YearState, params: Parameters): YearState {
 	};
 }
 
-export function simulateYears(years: number, state: YearState, params: Parameters): YearState[] {
-	const results = [state];
-	for (let i = 0; i < years; i++) {
-		const newState = simulateYear(results[i], params);
+export function simulate({ endYear, startState, parameters }: Scenario): YearState[] {
+	const results = [startState];
+	for (let i = 0; i + startState.year < endYear; i++) {
+		const newState = simulateYear(results[i], parameters);
 		results.push(newState);
 	}
 	return results;

src/routes/+page.svelte

@@ -1,68 +1,20 @@
 <script lang="ts">
 	import ForecastGraph from '$lib/ForecastGraph.svelte';
-	import { type Parameters, simulateYears, type YearState } from '$lib/simulation';
+	import { defaultScenario, simulate } from '$lib/simulation';
 
-	const parameters: Parameters = {
-		inflationRate: 0.025,
-		iskInterestRate: 0.08,
-		iskTax: 0.01086,
-		cashFlows: [
-			{
-				startYear: 2024 + 0,
-				endYear: 2024 + 8,
-				yearlyNetCashFlow: 38500 * 12,
-				// publicPensionContributing: true,
-				// servicePensionContribution: 4.5
-			},
-			{
-				startYear: 2024 + 0,
-				endYear: 2024 + 8,
-				yearlyNetCashFlow: 2755 * 12,
-			  // publicPensionContributing: false,
-				// servicePensionContribution: 100
-			},
-			{
-				startYear: 2024 + 0,
-				endYear: 2024 + 8,
-				yearlyNetCashFlow: -2755 * 12,
-				// publicPensionContributing: false,
-				// servicePensionContribution: 0
-			},
-			{
-				startYear: 2024 + 0,
-				endYear: 2024 + 50,
-				yearlyNetCashFlow: -15000 * 12,
-				// pensionContributing: false,
-				// publicPensionContributing: false,
-				// servicePensionContribution: 0
-			}
-		]
-	};
-	const startState: YearState = {
-		year: 2024,
-		iskSavings: 1000000,
-		compoundedInflation: 1,
-		cashFlow: 0
-	};
+	let scenario = defaultScenario();
 
-	$: results = simulateYears(74, startState, parameters);
-	$: data = results.map((res) => {
-		return {
-			year: res.year,
-			savings: res.iskSavings,
-			cashFlow: res.cashFlow
-		};
-	});
+	$: simulation = simulate(scenario);
 </script>
 
 <section>TODO scenario drawer</section>
 <section>TODO scenario editor</section>
 <section>
-	<ForecastGraph forecast={data} />
+	<ForecastGraph {simulation} />
 </section>
 <section>
 	<h2>Results</h2>
-	<pre>{JSON.stringify(results, null, 2)}</pre>
+	<pre>{JSON.stringify(simulation, null, 2)}</pre>
 </section>
 
 <style lang="scss">