Minor logger refactor, add documentation

packages/common/README.md

@@ -1,6 +1,9 @@
 # common
 
-Utilities commonly used by other packages.
+Utilities commonly used by other packages. Each common utility lives in its own folder together with its documentation.
+The implementation is re-exported by main entry of this package. The package consists of:
+
+- [logger](./src/logger) - Backend-only logger for Node.js packages based on Winston logger.
 
 ## Getting started
 

packages/common/src/index.test.ts

@@ -1,12 +1,13 @@
 import { readFileSync, readdirSync } from 'fs';
 import { join } from 'path';
 
-it('index file re-exports from all implementation files', () => {
-  const files = readdirSync(__dirname);
-  const ignoreList = ['index.ts'];
+it('index file re-exports from all implementation folders', () => {
+  const entries = readdirSync(__dirname, { withFileTypes: true });
 
-  const implementationFiles = files.filter((file) => !file.endsWith('.test.ts') && !ignoreList.includes(file));
-  const exports = [...readFileSync(join(__dirname, './index.ts'), 'utf8').matchAll(/export \* from/g)];
+  const subFolders = entries.filter((entry) => entry.isDirectory()).map((dir) => dir.name);
+  const mainExports = [
+    ...readFileSync(join(__dirname, './index.ts'), 'utf8').matchAll(/export \* from '\.\/(.+)'/g),
+  ].map((match) => match[1]);
 
-  expect(implementationFiles.length).toEqual(exports.length);
+  expect(subFolders).toEqual(mainExports);
 });

packages/common/src/logger/README.md

@@ -0,0 +1,38 @@
+# Logger
+
+Backend-only logger for Node.js packages based on Winston logger.
+
+## Configuration
+
+Logger configuration is essentially:
+
+```ts
+interface LogConfiguration {
+  type: 'hidden' | 'json' | 'pretty'; // Specifies the log format.
+  styling: 'on' | 'off'; // Toggles output colorization.
+  minLevel: 'debug' | 'info' | 'warn' | 'error'; // Specifies the minimum log level that is logged.
+}
+```
+
+### type
+
+- `hidden` - Silences all logs. This is suitable for test environment.
+- `json` - Specifies JSON log format. This is suitable when running in production and streaming logs to other services.
+- `pretty` - Logs are formatted in a human-friendly "pretty" way. Ideal, when running the service locally and in
+  development.
+
+### styling
+
+- `on` - Enables colors in the log output. The output has special color setting characters that are parseable by CLI.
+  Recommended when running locally and in development.
+- `off` - Disables colors in the log output. Recommended for production.
+
+### minLevel
+
+One of the following options:
+
+```ts
+'debug' | 'info' | 'warn' | 'error';
+```
+
+Logs with smaller level (severity) will be silenced.