use integers to calculate formulas for evaluator (#214)

src/components/desktop/AmountInput.vue

@@ -79,7 +79,7 @@ import type { CurrencyPrependAndAppendText } from '@/core/currency.ts';
 import { DEFAULT_DECIMAL_NUMBER_COUNT } from '@/consts/numeral.ts';
 import { TRANSACTION_MIN_AMOUNT, TRANSACTION_MAX_AMOUNT } from '@/consts/transaction.ts';
 import { isNumber, replaceAll } from '@/lib/common.ts';
-import { evaluateExpression } from '@/lib/evaluator.ts';
+import { evaluateExpressionToAmount } from '@/lib/evaluator.ts';
 import type { ComponentDensity } from '@/lib/ui/desktop.ts';
 import logger from '@/lib/logger.ts';
 
@@ -116,7 +116,6 @@ const {
     getCurrentDecimalSeparator,
     parseAmountFromLocalizedNumerals,
     formatAmountToLocalizedNumeralsWithoutDigitGrouping,
-    formatNumberToLocalizedNumerals,
     getAmountPrependAndAppendText
 } = useI18n();
 
@@ -218,15 +217,24 @@ function calculateFormula(): void {
     }
 
     finalFormula = numeralSystem.value.replaceLocalizedDigitsToWesternArabicDigits(finalFormula);
-    const calculatedValue = evaluateExpression(finalFormula);
 
-    if (isNumber(calculatedValue)) {
-        const textualValue = formatNumberToLocalizedNumerals(calculatedValue, 2);
-        const hasDecimalSeparator = textualValue.indexOf(decimalSeparator) >= 0;
-        currentValue.value = getValidFormattedValue(calculatedValue * 100, textualValue, hasDecimalSeparator);
-        formulaMode.value = false;
-    } else {
-        snackbar.value?.showMessage('Formula is invalid');
+    try {
+        const calculatedAmount = evaluateExpressionToAmount(finalFormula);
+
+        if (isNumber(calculatedAmount)) {
+            const textualValue = getFormattedValue(calculatedAmount);
+            const hasDecimalSeparator = textualValue.indexOf(decimalSeparator) >= 0;
+            currentValue.value = getValidFormattedValue(calculatedAmount, textualValue, hasDecimalSeparator);
+            formulaMode.value = false;
+        } else {
+            snackbar.value?.showMessage('Formula is invalid');
+        }
+    } catch (ex) {
+        logger.error('cannot evaluate formula in amount input, original formula is ' + finalFormula, ex);
+
+        if (ex instanceof Error) {
+            snackbar.value?.showMessage(ex.message);
+        }
     }
 }
 

src/lib/evaluator.ts

@@ -1,7 +1,14 @@
+import { TRANSACTION_MIN_AMOUNT, TRANSACTION_MAX_AMOUNT } from '../consts/transaction.ts';
+
 import { replaceAll } from './common.ts';
 
 import logger from './logger.ts';
 
+const maxAllowedDecimalCount = 6;
+const normalizeFactor: number = 1000000;
+const normalizedDecimalsMaxZeroString: string = '000000';
+const normalizedNumberToAmountFactor: number = 10000; // 1000000 / 100
+
 const operatorPriority: Record<string, number> = {
     '+': 1,
     '-': 1,
@@ -9,6 +16,36 @@ const operatorPriority: Record<string, number> = {
     '/': 2,
 };
 
+function normalizeNumber(textualNumber: string): number {
+    const decimalSeparatorPos = textualNumber.indexOf('.');
+
+    if (decimalSeparatorPos < 0) {
+        return parseInt(textualNumber + normalizedDecimalsMaxZeroString);
+    }
+
+    const integer = textualNumber.substring(0, decimalSeparatorPos);
+    const decimals = textualNumber.substring(decimalSeparatorPos + 1);
+
+    if (decimals.length > maxAllowedDecimalCount) {
+        throw new Error('Numeric Overflow');
+    }
+
+    const paddedDecimals = (decimals + normalizedDecimalsMaxZeroString).substring(0, maxAllowedDecimalCount);
+    return parseInt(integer + paddedDecimals);
+}
+
+function denormalizeNumberToAmount(num: number): number {
+    return Math.floor(num / normalizedNumberToAmountFactor);
+}
+
+function checkNumberRange(num: number): void {
+    const amount = denormalizeNumberToAmount(num);
+
+    if (amount > TRANSACTION_MAX_AMOUNT || amount < TRANSACTION_MIN_AMOUNT) {
+        throw new Error('Numeric Overflow');
+    }
+}
+
 function toPostfixExprTokens(expr: string): string[] | null {
     const finalTokens: string[] = [];
     const operatorStack: string[] = [];
@@ -143,31 +180,28 @@ function evaluatePostfixExpr(tokens: string[]): number | null {
                         result = a - b;
                         break;
                     case '*':
-                        result = a * b;
+                        result = Math.floor(a * b / normalizeFactor);
                         break;
                     case '/':
                         if (b === 0) {
                             logger.warn(`cannot evaluate expression "${tokens.join(' ')}", because division by zero`);
                             return null;
                         }
-                        result = a / b;
+                        result = Math.floor(a * normalizeFactor / b);
                         break;
                     default:
                         return null;
                 }
 
+                checkNumberRange(result);
+
                 // push the result back to the stack
                 stack.push(result);
                 break;
             default: // operands
-                const num = parseFloat(token);
-
-                if (isNaN(num)) {
-                    logger.warn(`cannot evaluate expression "${tokens.join(' ')}", because containing invalid number`);
-                    return null;
-                }
-
-                stack.push(num);
+                const normalizedNum = normalizeNumber(token);
+                checkNumberRange(normalizedNum);
+                stack.push(normalizedNum);
                 break;
         }
     }
@@ -179,7 +213,7 @@ function evaluatePostfixExpr(tokens: string[]): number | null {
 
     return stack[0];
 }
-export function evaluateExpression(expr: string): number | undefined {
+export function evaluateExpressionToAmount(expr: string): number | undefined {
     if (!expr) {
         return undefined;
     }
@@ -196,5 +230,5 @@ export function evaluateExpression(expr: string): number | undefined {
         return undefined;
     }
 
-    return result;
+    return denormalizeNumberToAmount(result);
 }