Add number format function with 3 significant digits (#8135)

Author: szakarias

pkg/_pub_shared/lib/format/number_format.dart

@@ -18,3 +18,29 @@ String formatWithSuffix(int value) {
 String _toFixed(int value, int d) {
   return (((value * 10) ~/ d) / 10).toStringAsFixed(1);
 }
+
+/// Formats an int [value] to human readable chunk and suffix with at most 3
+/// significant digits.
+({String value, String suffix}) formatWith3SignificantDigits(int value) {
+  if (value >= 999500000) {
+    return (
+      value: (value / 1000000000).toStringAsPrecision(3),
+      suffix: 'B',
+    );
+  } else if (value >= 999500) {
+    return (
+      value: (value / 1000000).toStringAsPrecision(3),
+      suffix: 'M',
+    );
+  } else if (value >= 1000) {
+    return (
+      value: (value / 1000).toStringAsPrecision(3),
+      suffix: 'k',
+    );
+  } else {
+    return (
+      value: value.toString(),
+      suffix: '',
+    );
+  }
+}

pkg/_pub_shared/test/format/number_format_test.dart

@@ -29,4 +29,41 @@ void main() {
     expect(formatWithSuffix(999999 + 1), '1.0m');
     expect(formatWithSuffix(1234000), '1.2m');
   });
+
+  test('Significant digit 0-999', () {
+    expect(computeWith3SignificantDigits(0), (value: '0', suffix: ''));
+    expect(computeWith3SignificantDigits(1), (value: '1', suffix: ''));
+    expect(computeWith3SignificantDigits(23), (value: '23', suffix: ''));
+    expect(computeWith3SignificantDigits(999), (value: '999', suffix: ''));
+  });
+
+  test('Significant digit 1000-999499', () {
+    expect(computeWith3SignificantDigits(1000), (value: '1.00', suffix: 'k'));
+    expect(computeWith3SignificantDigits(1049), (value: '1.05', suffix: 'k'));
+    expect(computeWith3SignificantDigits(1051), (value: '1.05', suffix: 'k'));
+    expect(computeWith3SignificantDigits(1100), (value: '1.10', suffix: 'k'));
+    expect(computeWith3SignificantDigits(9500), (value: '9.50', suffix: 'k'));
+    expect(computeWith3SignificantDigits(99500), (value: '99.5', suffix: 'k'));
+    expect(computeWith3SignificantDigits(100490), (value: '100', suffix: 'k'));
+    expect(computeWith3SignificantDigits(100500), (value: '101', suffix: 'k'));
+    expect(computeWith3SignificantDigits(199500), (value: '200', suffix: 'k'));
+    expect(computeWith3SignificantDigits(999499), (value: '999', suffix: 'k'));
+  });
+
+  test('Significant digit 999500-100000000', () {
+    expect(computeWith3SignificantDigits(999500), (value: '1.00', suffix: 'M'));
+    expect(computeWith3SignificantDigits(999999), (value: '1.00', suffix: 'M'));
+    expect(
+        computeWith3SignificantDigits(900000000), (value: '900', suffix: 'M'));
+    expect(
+        computeWith3SignificantDigits(999500000), (value: '1.00', suffix: 'B'));
+    expect(computeWith3SignificantDigits(1009450000),
+        (value: '1.01', suffix: 'B'));
+    expect(computeWith3SignificantDigits(1094599999),
+        (value: '1.09', suffix: 'B'));
+    expect(computeWith3SignificantDigits(1095000001),
+        (value: '1.10', suffix: 'B'));
+    expect(computeWith3SignificantDigits(19000000000),
+        (value: '19.0', suffix: 'B'));
+  });
 }