feat: new functions to cast values to correct type

In many application repositories, we have an environmental variable
validation engine. It is typical for this engine to have code that needs
to transform incoming environmental variable values to values of a
specific type. These tasks are repeatable in many projects:
lidofinance/ethereum-validators-monitoring#224
lidofinance/node-operators-widget-backend-ts#41
lidofinance/lido-keys-api#216

It makes sense to move this repeated code from many projects to some
common place.

The new "transform" module introduced in this PR collects these common
transformation functions.

packages/utils/src/index.ts

@@ -5,3 +5,4 @@ export * from './partition';
 export * from './memoize-in-flight-promise';
 export * from './sleep';
 export * from './chunk';
+export * from './transform';

packages/utils/src/transform.ts

@@ -0,0 +1,45 @@
+export const toNumber =
+  ({ defaultValue }: { defaultValue: number }) =>
+  ({ value }: { value: unknown }) => {
+    if (value === '' || value == null) {
+      return defaultValue;
+    }
+    return Number(value);
+  };
+
+export const toBoolean = ({ defaultValue }: { defaultValue: boolean }) => {
+  return function ({ value }: { value: unknown }) {
+    if (value == null || value === '') {
+      return defaultValue;
+    }
+
+    if (typeof value === 'boolean') {
+      return value;
+    }
+
+    const str = String(value).toLowerCase().trim();
+
+    switch (str) {
+      case 'true':
+      case 'yes':
+      case '1':
+        return true;
+
+      case 'false':
+      case 'no':
+      case '0':
+        return false;
+
+      default:
+        return value;
+    }
+  };
+};
+
+export const toArrayOfUrls = (url: string | null | undefined): string[] => {
+  if (url == null || url === '') {
+    return [];
+  }
+
+  return url.split(',').map((str) => str.trim().replace(/\/$/, ''));
+};

packages/utils/test/transform.spec.ts

@@ -0,0 +1,120 @@
+import { toNumber, toBoolean, toArrayOfUrls } from '../src';
+
+describe('toNumber', () => {
+  test('should return a default value if value is null or undefined', () => {
+    expect(toNumber({ defaultValue: 3000 })({ value: undefined })).toEqual(
+      3000,
+    );
+    expect(toNumber({ defaultValue: 3000 })({ value: null })).toEqual(3000);
+  });
+
+  test('should return a default value if value is an empty string', () => {
+    expect(toNumber({ defaultValue: 3000 })({ value: '' })).toEqual(3000);
+  });
+
+  test('should convert a passed value to the number', () => {
+    expect(toNumber({ defaultValue: 3000 })({ value: '5000' })).toEqual(5000);
+  });
+});
+
+describe('toBoolean', () => {
+  test('should return a default value if value is null or undefined', () => {
+    expect(toBoolean({ defaultValue: true })({ value: undefined })).toEqual(
+      true,
+    );
+    expect(toBoolean({ defaultValue: true })({ value: null })).toEqual(true);
+  });
+
+  test('should return a default value if value is an empty string', () => {
+    expect(toBoolean({ defaultValue: true })({ value: '' })).toEqual(true);
+  });
+
+  test('should return the passed boolean value if it has a boolean type', () => {
+    expect(toBoolean({ defaultValue: true })({ value: false })).toEqual(false);
+    expect(toBoolean({ defaultValue: false })({ value: true })).toEqual(true);
+  });
+
+  test('should return true if the passed value is the word "true" in any case', () => {
+    expect(toBoolean({ defaultValue: false })({ value: 'true' })).toEqual(true);
+    expect(toBoolean({ defaultValue: false })({ value: 'True' })).toEqual(true);
+    expect(toBoolean({ defaultValue: false })({ value: 'TRUE' })).toEqual(true);
+  });
+
+  test('should return true if the passed value is the word "yes" in any case', () => {
+    expect(toBoolean({ defaultValue: false })({ value: 'yes' })).toEqual(true);
+    expect(toBoolean({ defaultValue: false })({ value: 'Yes' })).toEqual(true);
+    expect(toBoolean({ defaultValue: false })({ value: 'YES' })).toEqual(true);
+  });
+
+  test('should return true if the passed value is 1', () => {
+    expect(toBoolean({ defaultValue: false })({ value: '1' })).toEqual(true);
+    expect(toBoolean({ defaultValue: false })({ value: 1 })).toEqual(true);
+  });
+
+  test('should return false if the passed value is the word "false" in any case', () => {
+    expect(toBoolean({ defaultValue: true })({ value: 'false' })).toEqual(
+      false,
+    );
+    expect(toBoolean({ defaultValue: true })({ value: 'False' })).toEqual(
+      false,
+    );
+    expect(toBoolean({ defaultValue: true })({ value: 'FALSE' })).toEqual(
+      false,
+    );
+  });
+
+  test('should return false if the passed value is the word "no" in any case', () => {
+    expect(toBoolean({ defaultValue: true })({ value: 'no' })).toEqual(false);
+    expect(toBoolean({ defaultValue: true })({ value: 'No' })).toEqual(false);
+    expect(toBoolean({ defaultValue: true })({ value: 'NO' })).toEqual(false);
+  });
+
+  test('should return false if the passed value is 0', () => {
+    expect(toBoolean({ defaultValue: true })({ value: '0' })).toEqual(false);
+    expect(toBoolean({ defaultValue: true })({ value: 0 })).toEqual(false);
+  });
+
+  test('should return the passed value if it is not equal to any of the above-listed strings', () => {
+    expect(toBoolean({ defaultValue: true })({ value: 'abc' })).toEqual('abc');
+    expect(toBoolean({ defaultValue: true })({ value: '123' })).toEqual('123');
+    expect(toBoolean({ defaultValue: true })({ value: 123 })).toEqual(123);
+    expect(toBoolean({ defaultValue: true })({ value: 2 })).toEqual(2);
+    expect(toBoolean({ defaultValue: true })({ value: -1 })).toEqual(-1);
+
+    expect(toBoolean({ defaultValue: false })({ value: 'abc' })).toEqual('abc');
+    expect(toBoolean({ defaultValue: false })({ value: '123' })).toEqual('123');
+    expect(toBoolean({ defaultValue: false })({ value: 123 })).toEqual(123);
+    expect(toBoolean({ defaultValue: false })({ value: 2 })).toEqual(2);
+    expect(toBoolean({ defaultValue: false })({ value: -1 })).toEqual(-1);
+  });
+});
+
+describe('toArrayOfUrls', () => {
+  test('should return an empty array if passed URL is null or undefined', () => {
+    expect(toArrayOfUrls(undefined)).toEqual([]);
+    expect(toArrayOfUrls(null)).toEqual([]);
+  });
+
+  test('should return an empty array if passed URL is an empty string', () => {
+    expect(toArrayOfUrls('')).toEqual([]);
+  });
+
+  test('should split a string of comma-separated URLs into array of URLs', () => {
+    expect(toArrayOfUrls('https://google.com,https://microsoft.com')).toEqual([
+      'https://google.com',
+      'https://microsoft.com',
+    ]);
+  });
+
+  test('should remove leading and trailing whitespaces from the URLs in the resulting list', () => {
+    expect(
+      toArrayOfUrls('  https://google.com   , https://microsoft.com  '),
+    ).toEqual(['https://google.com', 'https://microsoft.com']);
+  });
+
+  test('should remove trailing slash from the URLs in the resulting list', () => {
+    expect(
+      toArrayOfUrls('  https://google.com/   , https://microsoft.com/  '),
+    ).toEqual(['https://google.com', 'https://microsoft.com']);
+  });
+});