first working number scaling

vue3/src/utils/number_utils.ts

@@ -0,0 +1,82 @@
+function getUserPreference(pref: string) {
+    return false // TODO only placeholder, add real function
+}
+
+
+/**
+ * round to the number of decimals specified in user preferences
+ * @param num number to round
+ */
+export function roundDecimals(num: number) {
+    let decimals = 2 //TODO get user preference
+    return num.toFixed(decimals)
+}
+
+/**
+ * calculates the amount of food, based on the factor and converts it to a fraction if that is the users preference
+ * @param amount food amount to calculate based upon
+ * @param factor factor to scale food amount by
+ */
+export function calculateFoodAmount(amount: number, factor: number) {
+    if (getUserPreference("use_fractions")) {
+        let return_string = ""
+        let fraction = frac(amount * factor, 16, true)
+
+        if (fraction[0] === 0 && fraction[1] === 0 && fraction[2] === 1) {
+            return roundDecimals(amount * factor)
+        }
+
+        if (fraction[0] > 0) {
+            return_string += fraction[0]
+        }
+
+        if (fraction[1] > 0) {
+            return_string += ` <sup>${fraction[1]}</sup>&frasl;<sub>${fraction[2]}</sub>`
+        }
+
+        return return_string
+    } else {
+        return roundDecimals(amount * factor)
+    }
+}
+
+
+/* frac.js (C) 2012-present SheetJS -- http://sheetjs.com */
+
+/* https://www.npmjs.com/package/frac Apache license*/
+/**
+ * calculates the closest approximation of a fraction for a given decimal number
+ * @param x decimal number to convert into fraction
+ * @param D the maximum denominator to return
+ * @param mixed true to return mixed fractions (e.g. 2 1/2) or false to return improper fractions (e.g. 5/2)
+ * @returns [quot, num, den] array of numbers, quot is either 0 for improper fractions or the whole number, num is the numerator of the fraction and den the denominator
+ */
+export function frac(x, D, mixed) {
+    let n1 = Math.floor(x), d1 = 1;
+    let n2 = n1 + 1, d2 = 1;
+    if (x !== n1) while (d1 <= D && d2 <= D) {
+        let m = (n1 + n2) / (d1 + d2);
+        if (x === m) {
+            if (d1 + d2 <= D) {
+                d1 += d2;
+                n1 += n2;
+                d2 = D + 1;
+            } else if (d1 > d2) d2 = D + 1;
+            else d1 = D + 1;
+            break;
+        } else if (x < m) {
+            n2 = n1 + n2;
+            d2 = d1 + d2;
+        } else {
+            n1 = n1 + n2;
+            d1 = d1 + d2;
+        }
+    }
+    if (d1 > D) {
+        d1 = d2;
+        n1 = n2;
+    }
+    if (!mixed) return [0, n1, d1];
+    let q = Math.floor(n1 / d1);
+    return [q, n1 - q * d1, d1];
+}