refactor: restructure fn and use better naming

Author: hhow09

Diff for: backend/src/command-service.ts

@@ -1,7 +1,7 @@
 import { Logger } from "pino";
 import { CommandAndResult } from "./entities/command-result.entity";
 import { IRepository } from "./repositories";
-import { isValidCommand, evaluate } from "./math/evaluate";
+import { evaluate } from "./math/evaluate";
 
 export interface ICommandService {
     evaluateAndSave(clientId: string, expression: string): Promise<string>;

Diff for: backend/src/math/evaluate.ts

@@ -1,33 +1,44 @@
 import { Summand } from './types';
 const operators = new Set(['+', '-', '*', '/']);
 
-// isValidCommand checks if the command is a allowed mathematical expression
-function isValidCommand(s: string): boolean {
-    s = s.replace(/ /g,''); // remove all spaces
-    if (s.length === 0) {
+// isValidOperation checks if the operation is a allowed mathematical expression
+function isValidOperation(operation: string): boolean {
+    const cleanedOperation = operation.replace(/ /g,''); // remove all spaces
+    if (cleanedOperation.length === 0) {
         return false;
     }
-    // allowed characters: 0-9, +, -, *, /, .
-    const regex = /^[\d+\-*/.]+$/;
-    if (!regex.test(s)) {
+    if (!allowedChars(cleanedOperation)) {
         return false;
     }
-    // operators cannot be adjacent to each other
-    for (let i = 0; i < s.length - 1; i++) {
-        if (operators.has(s[i]) && operators.has(s[i + 1])) {
-            return false;
-        }
+    if (!noAdjacentOperators(cleanedOperation)) {
+        return false;
     }
-    // operators cannot be at the end of the string
-    if (operators.has(s[s.length - 1])) {
+    if (noOperatorsAtTheEnd(cleanedOperation)) {
         return false;
     }
     return true;
 }
 
+function allowedChars(operation: string): boolean {
+    return /^[\d+\-*/.]+$/.test(operation);
+}
+
+function noAdjacentOperators(operation: string): boolean {
+    for (let i = 0; i < operation.length - 1; i++) {
+        if (operators.has(operation[i]) && operators.has(operation[i + 1])) {
+            return false;
+        }
+    }
+    return true;
+}
+
+function noOperatorsAtTheEnd(operation: string): boolean {
+    return operators.has(operation[operation.length - 1]);
+}
+
 // evaluate evaluate a mathematical expression
 function evaluate(s: string): string {
-    if (!isValidCommand(s)) {
+    if (!isValidOperation(s)) {
         throw new Error('Invalid command');
     }
     s = s.replace(/ /g,''); // remove all spaces
@@ -72,4 +83,4 @@ const parseExpression = (s: string): Summand[] => {
     return summands;
 }
 
-export { isValidCommand, evaluate };
+export { evaluate };

Diff for: backend/src/math/types.ts

@@ -79,7 +79,7 @@ export class Fraction {
     }
 
     public add(f: Fraction): Fraction {
-        const commonDenominator = getLcm(this.denominator, f.denominator);
+        const commonDenominator = getLowestCommonMultiple(this.denominator, f.denominator);
         const multiplyThis = commonDenominator.div(this.denominator);
         const multiplyF = commonDenominator.div(f.denominator);
         this.numerator = this.numerator.mul(multiplyThis);
@@ -95,16 +95,16 @@ export class Fraction {
     }
 }
 
-function getLcm(a: Decimal, b: Decimal): Decimal {
-    return a.mul(b).div(getGcd(a, b));
+function getLowestCommonMultiple(a: Decimal, b: Decimal): Decimal {
+    return a.mul(b).div(getGreatestCommonDivisor(a, b));
 }
 
-function getGcd(a: Decimal, b: Decimal): Decimal {
+function getGreatestCommonDivisor(a: Decimal, b: Decimal): Decimal {
     const max = Decimal.max(a, b);
     const min = Decimal.min(a, b);
     if (max.mod(min).eq(0)) {
         return min;
     } else {
-        return getGcd(max.mod(min), min);
+        return getGreatestCommonDivisor(max.mod(min), min);
     }
 }