Cater for negative values in number formats (#415)

* Cater for negative values in number formats

* Handle edge-case where -text is provided

packages/util/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@polkadot/util",
-  "version": "0.92.0-beta.3",
+  "version": "0.92.0",
   "description": "A collection of useful utilities for @polkadot",
   "main": "index.js",
   "keywords": [

packages/util/src/format/formatBalance.spec.ts

@@ -68,6 +68,20 @@ describe('formatBalance', () => {
     ).toEqual('123.456 Unit');
   });
 
+  it('formats -123,456,789,000 (decimals=15)', () => {
+    expect(
+      formatBalance(new BN('-123456789000'), true, 15)
+    ).toEqual('-123.456µ Unit');
+  });
+
+  describe('calcSi', () => {
+    it('exposes calcSi on formatBalance', () => {
+      expect(
+        formatBalance.calcSi('12345').value
+      ).toEqual('k');
+    });
+  });
+
   describe('findSi', () => {
     it('finds the SI value', () => {
       expect(

packages/util/src/format/formatBalance.ts

@@ -31,12 +31,20 @@ let defaultUnit = DEFAULT_UNIT;
 
 // Formats a string/number with <prefix>.<postfix><type> notation
 function _formatBalance (input?: number | string | BN, withSi: boolean = true, decimals: number = defaultDecimals): string {
-  const text = (input || '').toString();
+  let text = (input || '').toString();
 
   if (text.length === 0 || text === '0') {
     return '0';
   }
 
+  // strip the negative sign so we can work with clean groupings, re-add this in the
+  // end when we return the result (from here on we work with positive numbers)
+  const isNegative = text[0] === '-';
+
+  if (isNegative) {
+    text = text.substr(1);
+  }
+
   assert(/^\d+$/.test(text), `Non-integer input value '${text}' supplied to balanceFormat`);
 
   // NOTE We start at midpoint (8) minus 1 - this means that values display as
@@ -54,7 +62,7 @@ function _formatBalance (input?: number | string | BN, withSi: boolean = true, d
     )
     : '';
 
-  return `${formatDecimal(prefix || '0')}.${postfix}${units}`;
+  return `${isNegative ? '-' : ''}${formatDecimal(prefix || '0')}.${postfix}${units}`;
 }
 
 const formatBalance = _formatBalance as BalanceFormatter;

packages/util/src/format/formatDecimal.spec.ts

@@ -16,4 +16,12 @@ describe('formatDecimal', () => {
   it('returns input for non-decimal', () => {
     expect(formatDecimal('test')).toEqual('test');
   });
+
+  it('returns non-sensical negative text', () => {
+    expect(formatDecimal('-test')).toEqual('-test');
+  });
+
+  it('formats negative numbers', () => {
+    expect(formatDecimal('-123456')).toEqual('-123,456');
+  });
 });

packages/util/src/format/formatDecimal.ts

@@ -5,9 +5,14 @@
 const NUMBER_REGEX = new RegExp('(\\d+?)(?=(\\d{3})+(?!\\d)|$)', 'g');
 
 export default function formatDecimal (value: string): string {
-  const matched = value.match(NUMBER_REGEX);
+  // We can do this by adjusting the regx, however for the sake of clarity
+  // we rather strip and re-add the negative sign in the output
+  const isNegative = value[0] === '-';
+  const matched = isNegative
+    ? value.substr(1).match(NUMBER_REGEX)
+    : value.match(NUMBER_REGEX);
 
   return matched
-    ? matched.join(',')
+    ? `${isNegative ? '-' : ''}${matched.join(',')}`
     : value;
 }

packages/util/src/format/formatNumber.spec.ts

@@ -0,0 +1,35 @@
+// Copyright 2017-2019 @polkadot/util authors & contributors
+// This software may be modified and distributed under the terms
+// of the Apache-2.0 license. See the LICENSE file for details.
+
+import { Compact } from './types';
+
+import BN from 'bn.js';
+
+import formatNumber from './formatNumber';
+
+describe('formatNumber', () => {
+  it('formats empty', () => {
+    expect(
+      formatNumber()
+    ).toEqual('0');
+  });
+
+  it('formats negative numbers', () => {
+    expect(
+      formatNumber(-123456)
+    ).toEqual('-123,456');
+  });
+
+  it('formats BN numbers', () => {
+    expect(
+      formatNumber(new BN(12345))
+    ).toEqual('12,345');
+  });
+
+  it('formats Compact<BN>', () => {
+    expect(
+      formatNumber({ toBn: () => new BN(12345) } as Compact)
+    ).toEqual('12,345');
+  });
+});