use fixed tarifs and add additional costs

helpers/bill.ts

@@ -0,0 +1,65 @@
+import { MILAGE_TARIFS } from '../db/enums'
+import { AdditionalCost } from '../db/bill'
+
+function roundToCent(amount: number) {
+  return Math.round(amount * 100) / 100
+}
+
+export function getMilageCosts(tarif: MILAGE_TARIFS, km: number): number {
+  if (tarif === MILAGE_TARIFS.NOCHARGE) {
+    return 0
+  }
+
+  if (km <= 0) {
+    return 0
+  }
+
+  let rate: number
+
+  if (tarif === MILAGE_TARIFS.EXTERN) {
+    if (km <= 200) {
+      rate = 0.42
+    } else if (km <= 1000) {
+      rate = 0.25
+    } else if (km <= 2000) {
+      rate = 0.2
+    } else {
+      rate = 0.18
+    }
+  }
+
+  if (tarif === MILAGE_TARIFS.INTERN) {
+    if (km <= 200) {
+      rate = 0.37
+    } else if (km <= 1000) {
+      rate = 0.22
+    } else if (km <= 2000) {
+      rate = 0.15
+    } else {
+      rate = 0.13
+    }
+  }
+
+  if (rate === undefined) {
+    throw Error('Unable to determine rate')
+  }
+
+  return roundToCent(km * rate)
+}
+
+export function getBillTotal({
+  tarif,
+  milage,
+  additionalCosts,
+}: {
+  tarif: MILAGE_TARIFS
+  milage?: number
+  additionalCosts: AdditionalCost[]
+}): number {
+  const milageCosts = getMilageCosts(tarif, milage)
+  const additionalCostsSum = additionalCosts
+    .map(({ value }) => value)
+    .reduce((acc: number, value: number) => acc + value, 0)
+
+  return roundToCent(milageCosts + additionalCostsSum)
+}