feat: Tighten types on Property class

app/models/Household.test.ts

@@ -38,7 +38,7 @@ beforeEach(() => {
     age: 10,
     size: 88,
     newBuildPricePerMetre: 2120,
-    averagePrice: 218091.58,
+    averageMarketPrice: 218091.58,
     itl3: "TLG24",
   });
 

app/models/Household.ts

@@ -86,7 +86,7 @@ export class Household {
     // calculate tenure market purchase
     this.tenure.marketPurchase = new MarketPurchase({
       incomeYearly: this.incomeYearly,
-      averagePrice: this.property.averagePrice,
+      averagePrice: this.property.averageMarketPrice,
       newBuildPrice: this.property.newBuildPrice,
       depreciatedBuildPrice: this.property.depreciatedBuildPrice,
       landPrice: this.property.landPrice,
@@ -104,7 +104,7 @@ export class Household {
     //calculate tenure market rent
     this.tenure.marketRent = new MarketRent({
       averageRentYearly: averageRentYearly,
-      averagePrice: this.property.averagePrice,
+      averagePrice: this.property.averageMarketPrice,
       newBuildPrice: this.property.newBuildPrice,
       depreciatedBuildPrice: this.property.depreciatedBuildPrice,
       landPrice: this.property.landPrice,
@@ -158,7 +158,7 @@ export class Household {
 
     this.tenure.fairholdLandRent = new FairholdLandRent({
       averageRentYearly: averageRentYearly,
-      averagePrice: this.property.averagePrice, // average price of the property
+      averagePrice: this.property.averageMarketPrice, // average price of the property
       newBuildPrice: this.property.newBuildPrice,
       depreciatedBuildPrice: this.property.depreciatedBuildPrice, // depreciated building price
       landPrice: this.property.landPrice, // land price

app/models/Property.test.ts

@@ -10,7 +10,7 @@ beforeEach(() => {
     age: 10,
     size: 88,
     newBuildPricePerMetre: 2120,
-    averagePrice: 218091.58,
+    averageMarketPrice: 218091.58,
     itl3: "TLG24",
   });
 });

app/models/Property.ts

@@ -1,124 +1,113 @@
 
 import * as math from "mathjs";
 
-export class Property {
-  postcode; // postcode of the property
-  houseType; // type of the house: D--> detached, S--> semidetached, T--> Terrace, F--> Flats
-  numberOfBedrooms; // number of bedrooms in the house
-  age; // age of the house
-  size; // size of the house in metre squares
-  newBuildPricePerMetre: number; // average build price per metre of a new house
-  averagePrice: number; // average market price
-  itl3: string; // ITL code
-  newBuildPrice?: number; // price of the house if it was new
-  depreciatedBuildPrice?: number; // price of the house according to the depreciation regression
-  bedWeightedAveragePrice?: number; // price of the house weigheted by the number of bedrooms
-  landPrice?: number; // price of the land
-  landToTotalRatio?: number; // ratio of the land price over the total
+/**
+ * Number of decimal places to use when rounding numerical values
+ */
+const PRECISION = 2
+const DEPRECIATION_FACTOR = -32938;
 
-  constructor({
-    postcode,
-    houseType,
-    numberOfBedrooms,
-    age,
-    size,
-    newBuildPricePerMetre,
-    averagePrice,
-    itl3,
-  }: {
-    postcode: any;
-    houseType: string;
-    numberOfBedrooms: number;
-    age: number;
-    size: number;
-    newBuildPricePerMetre: number;
-    averagePrice: number;
-    itl3: string;
-  }) {
-    this.postcode = postcode;
-    this.houseType = houseType;
-    this.numberOfBedrooms = numberOfBedrooms;
-    this.age = age;
-    this.size = size;
-    this.newBuildPricePerMetre = newBuildPricePerMetre;
-    this.averagePrice = averagePrice;
-    this.itl3 = itl3;
+type PropertyParams = Pick<
+  Property,
+  | "postcode"
+  | "houseType"
+  | "numberOfBedrooms"
+  | "age"
+  | "size"
+  | "newBuildPricePerMetre"
+  | "averageMarketPrice"
+  | "itl3"
+>;
 
-    this.calculateNewBuildPrice(); // calculate new building price
-    this.calculateDepreciatedBuildPrice(); // calculated the depreciated building price
-    this.calculateBedWeightedAveragePrice(); // calculate the bed weighted building price
-    this.calculateLandPrice(); // calculate the price of the land
-    if (
-      this.landPrice !== undefined &&
-      this.bedWeightedAveragePrice !== undefined
-    ) {
-      this.landToTotalRatio = this.landPrice / this.bedWeightedAveragePrice; // define the land to total ratio
-    }
-  }
+// TODO: Reuse HouseType enum
+type HouseType = "D" | "S" | "T" | "F";
 
-  // calculate new building price
-  calculateNewBuildPrice(precisionRounding: number = 2) {
-    if (!this.newBuildPricePerMetre) {
-      throw new Error(
-        "The Build Price cannot be calculated because pricePerMetre has not been set"
-      );
-    }
-    const newBuildPrice = this.newBuildPricePerMetre * this.size; // calculate the price of the new build
-    this.newBuildPrice = parseFloat(newBuildPrice.toFixed(precisionRounding)); // round the number
+export class Property {
+  postcode: string;
+  houseType: HouseType;
+  numberOfBedrooms: number;
+  age: number;
+  /**
+   * Size of the house in squares meters
+   */
+  size: number;
+  /**
+   * Average build price per metre of a new house
+   */
+  newBuildPricePerMetre: number;
+  averageMarketPrice: number;
+  itl3: string;
+  /**
+   *  Price of the house if it was new
+   */
+  newBuildPrice: number;
+  /**
+   * Price of the house according to the depreciation regression
+   */
+  depreciatedBuildPrice: number;
+  /**
+   * Price of the house weighted by the number of bedrooms
+   */
+  bedWeightedAveragePrice: number;
+  landPrice: number;
+  /**
+   * Ratio of the land price to the total price
+   */
+  landToTotalRatio: number;
+
+  constructor(params: PropertyParams) {
+    this.postcode = params.postcode;
+    this.houseType = params.houseType;
+    this.numberOfBedrooms = params.numberOfBedrooms;
+    this.age = params.age;
+    this.size = params.size;
+    this.newBuildPricePerMetre = params.newBuildPricePerMetre;
+    this.averageMarketPrice = params.averageMarketPrice;
+    this.itl3 = params.itl3;
 
-    return this.newBuildPrice;
+    // Computed properties, order is significant
+    this.newBuildPrice = this.calculateNewBuildPrice();
+    this.depreciatedBuildPrice = this.calculateDepreciatedBuildPrice();
+    this.bedWeightedAveragePrice = this.calculateBedWeightedAveragePrice();
+    this.landPrice = this.averageMarketPrice - this.newBuildPrice;
+    this.landToTotalRatio = this.landPrice / this.bedWeightedAveragePrice;
   }
 
-  // calculate nthe depraciated building price
-  calculateDepreciatedBuildPrice(
-    depreciationFactor: number = -32938,
-    precisionRounding: number = 2
-  ) {
-    if (!this.newBuildPrice) {
-      throw new Error(
-        "The Depreciated Price cannot be calculated because newBuildPrice has not been set"
-      );
-    }
+  private calculateNewBuildPrice() {
+    let newBuildPrice = this.newBuildPricePerMetre * this.size;
+    newBuildPrice = parseFloat(newBuildPrice.toFixed(PRECISION));
 
-    const depreciatedBuildPrice =
-      this.newBuildPrice + depreciationFactor * math.log(this.age); // depreciated building price
-    this.depreciatedBuildPrice = parseFloat(
-      depreciatedBuildPrice.toFixed(precisionRounding)
-    ); // round the number
+    return newBuildPrice;
+  }
 
-    if (this.depreciatedBuildPrice == undefined) {
-      throw new Error("depreciatedBuildPrice is undefined");
-    }
+  private calculateDepreciatedBuildPrice() {
+    let depreciatedBuildPrice =
+      this.newBuildPrice + DEPRECIATION_FACTOR * math.log(this.age);
+    depreciatedBuildPrice = parseFloat(
+      depreciatedBuildPrice.toFixed(PRECISION)
+    );
 
-    return this.depreciatedBuildPrice;
+    return depreciatedBuildPrice;
   }
 
-  // calculate the average property price based on the  number of bedrooms
-  calculateBedWeightedAveragePrice(
-    numberOfBeds: number = this.numberOfBedrooms,
+  private calculateBedWeightedAveragePrice(
     beds: number[] = [0, 1, 2, 3, 4, 5, 6],
     bedWeights: number[] = [0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4],
-    precisionRounding: number = 2
   ) {
-    let bedWeight; // initialize the variable
+    let bedWeight;
 
-    if (numberOfBeds < beds[beds.length - 1]) {
-      bedWeight = bedWeights[numberOfBeds]; // assign the weight based on the number of beds
+    if (this.numberOfBedrooms < beds[beds.length - 1]) {
+      // assign the weight based on the number of beds
+      bedWeight = bedWeights[this.numberOfBedrooms];
     } else {
-      bedWeight = bedWeights[bedWeights.length - 1]; // assign the last value if out of scale
+      // assign the last value if out of scale
+      bedWeight = bedWeights[bedWeights.length - 1];
     }
 
-    if (bedWeight == undefined) {
-      throw new Error("bedWeight is undefined.");
-    }
+    bedWeight = parseFloat(
+      (bedWeight * this.averageMarketPrice).toFixed(PRECISION)
+    );
 
-    return (this.bedWeightedAveragePrice = parseFloat(
-      (bedWeight * this.averagePrice).toFixed(precisionRounding)
-    )); // calculate the bed weighted average price
-  }
-  calculateLandPrice() {
-    if (this.newBuildPrice == undefined)
-      throw new Error("newBuildPrice is undefined");
-    return (this.landPrice = this.averagePrice - this.newBuildPrice); // calculate the price of the land
+    return bedWeight;
   }
 }

app/models/tenure/FairholdLandPurchase.test.ts

@@ -14,7 +14,7 @@ beforeEach(() => {
     age: 10,
     size: 88,
     newBuildPricePerMetre: 2120,
-    averagePrice: 218091.58,
+    averageMarketPrice: 218091.58,
     itl3: "TLG24",
   });
 

app/models/tenure/FairholdLandRent.test.ts

@@ -15,7 +15,7 @@ beforeEach(() => {
     age: 10,
     size: 88,
     newBuildPricePerMetre: 2120,
-    averagePrice: 218091.58,
+    averageMarketPrice: 218091.58,
     itl3: "TLG24",
   });
 

app/models/tenure/MarketPurchase.test.ts

@@ -21,7 +21,7 @@ beforeEach(() => {
     age: 10,
     size: 88,
     newBuildPricePerMetre: 2120,
-    averagePrice: 218091.58,
+    averageMarketPrice: 218091.58,
     itl3: "TLG24",
   });
 

app/models/tenure/MarketRent.test.ts

@@ -21,7 +21,7 @@ beforeEach(() => {
     age: 10,
     size: 88,
     newBuildPricePerMetre: 2120,
-    averagePrice: 218091.58,
+    averageMarketPrice: 218091.58,
     itl3: "TLG24",
   });
 

app/models/tenure/SocialRent.test.ts

@@ -21,7 +21,7 @@ beforeEach(() => {
     age: 10,
     size: 88,
     newBuildPricePerMetre: 2120,
-    averagePrice: 218091.58,
+    averageMarketPrice: 218091.58,
     itl3: "TLG24",
   });
 

app/models/testClasses.ts

@@ -18,7 +18,7 @@ function calculateFairhold(responseData: any) {
     age: responseData.houseAge,
     size: responseData.houseSize,
     newBuildPricePerMetre: responseData.buildPrice,
-    averagePrice: responseData.averagePrice,
+    averageMarketPrice: responseData.averagePrice,
     itl3: responseData.itl3,
   });