feat(core): add config prefixer

Ovidiu Barabula · Ovidiu Barabula · commit c0261f44b1b9 · 2018-03-26T11:18:10.000+03:00
Adds a custom prefix to config object keys
diff --git a/src/config-manager/prefixer.spec.ts b/src/config-manager/prefixer.spec.ts
@@ -0,0 +1,88 @@
+import { assert, expect } from 'chai';
+import 'mocha';
+import Prefixer, { ConfigPrefixer, ERRORS } from './prefixer';
+
+
+describe('ConfigPrefixer', () => {
+  let prefixer: ConfigPrefixer;
+  const prefix = 'prefix:';
+  const unprefixedConfig = {
+    anOption: 'aValue',
+    anotherOption: 'anotherValue',
+  };
+  const prefixedConfig = {
+    [`${prefix}anOption`]: 'aValue',
+    [`${prefix}anotherOption`]: 'anotherValue',
+  };
+
+  before(() => prefixer = Prefixer(prefix));
+
+  it('instantiates', () => {
+    expect(Prefixer(prefix)).to.be.an('object')
+      .to.contain.keys('apply', 'remove');
+  });
+
+
+  it('adds prefix to object keys', () => {
+    expect(prefixer.apply(unprefixedConfig)).to.deep.equal(prefixedConfig);
+  });
+
+
+  it('removes prefix from object keys', () => {
+    expect(prefixer.remove(prefixedConfig)).to.deep.equal(unprefixedConfig);
+  });
+
+
+  it('doesn\'t prefix already prefixed keys', () => {
+    expect(prefixer.apply(prefixedConfig)).to.deep.equal(prefixedConfig);
+  });
+
+
+  it('returns same object if it\'s not prefixed', () => {
+    expect(prefixer.remove(unprefixedConfig)).to.deep.equal(unprefixedConfig);
+  });
+
+
+  it('adds prefix only to non-prefixed keys', () => {
+    const config = {
+      anOption: 'aValue',
+      [`${prefix}anotherOption`]: 'anotherValue',
+    };
+    expect(prefixer.apply(config)).to.deep.equal({
+      [`${prefix}anOption`]: 'aValue',
+      [`${prefix}anotherOption`]: 'anotherValue',
+    });
+  });
+
+
+  it('removes prefix only from prefixed keys', () => {
+    const config = {
+      anOption: 'aValue',
+      [`${prefix}anotherOption`]: 'anotherValue',
+    };
+    expect(prefixer.remove(config)).to.deep.equal({
+      anOption: 'aValue',
+      anotherOption: 'anotherValue',
+    });
+  });
+
+
+  it('throws if <prefix> parameter is not passed', () => {
+    assert.throws(() => Prefixer(), ERRORS.PREFIX_REQUIRED);
+  });
+
+
+  it('throws if apply() method is called without parameter', () => {
+    assert.throws(() => prefixer.apply(), ERRORS.CONFIG_REQUIRED);
+  });
+
+
+  it('throws if remove() method is called without parameter', () => {
+    assert.throws(() => prefixer.remove(), ERRORS.CONFIG_REQUIRED);
+  });
+
+
+  it('throws if performOperation() method receives unknown operation', () => {
+    assert.throws(() => prefixer.performOperation(100, unprefixedConfig), ERRORS.UNKNOWN_OPERATION);
+  });
+});
diff --git a/src/config-manager/prefixer.ts b/src/config-manager/prefixer.ts
@@ -0,0 +1,125 @@
+/**
+ * Name: prefixer.ts
+ * Description: Configuration object key prefixer
+ * Author: Ovidiu Barabula <lectii2008@gmail.com>
+ * @since 0.1.0
+ */
+
+import { Config } from '../config-manager';
+import { required } from '../util/utility-functions';
+
+
+export enum PrefixOperation {
+  Remove,
+  Add,
+}
+
+export interface ConfigPrefixer {
+  apply(config: Config): Config;
+  remove(config: Config): Config;
+  performOperation?(type: PrefixOperation, config: Config): Config;
+}
+
+
+// Custom error messages
+export const ERRORS = {
+  CONFIG_REQUIRED: 'ConfigPrefixer> apply() and remove() methods require first parameter <config> of type \'object\'',
+  PREFIX_REQUIRED: 'ConfigPrefixer() requires first parameter <prefix> of type \'string\'',
+  UNKNOWN_OPERATION: 'ConfigPrefixer> An unknonw operation was passed to performOperation() method',
+};
+
+
+/**
+ * Prefix config keys with custom string
+ * @param prefix Prefix string to be added to each key
+ */
+function ConfigPrefixer(
+  prefix: string = required(ERRORS.PREFIX_REQUIRED),
+): ConfigPrefixer {
+  /**
+   * Check if key already has prefix applied
+   * @param key Key string
+   */
+  function hasPrefix(key: string): boolean {
+    return key.includes(prefix) && key.indexOf(prefix) === 0;
+  }
+
+
+  /**
+   * Add prefix to key
+   * @param key Object key string
+   */
+  function addPrefix(key: string): string {
+    return !hasPrefix(key) ? `${prefix}${key}` : key;
+  }
+
+
+  /**
+   * Remove prefix from key
+   * @param key Object key string
+   */
+  function removePrefix(key: string): string {
+    return hasPrefix(key) ? key.substring(prefix.length) : key;
+  }
+
+
+  /**
+   * Perform an operation on passed in configuration object
+   * @param type Type of the operation
+   * @param config Configuration object
+   */
+  function performOperation(type: PrefixOperation, config: Config): Config {
+    let operation: (key: string) => string;
+
+    if (type === PrefixOperation.Add) {
+      operation = (key: string) => addPrefix(key);
+    } else if (type === PrefixOperation.Remove) {
+      operation = (key: string) => removePrefix(key);
+    } else {
+      throw new Error(ERRORS.UNKNOWN_OPERATION);
+    }
+
+    return Object.keys(config)
+      .reduce((newConfig, key) => ({
+        ...newConfig,
+        ...{ [operation(key)]: config[key] },
+      }), {});
+  }
+
+
+  /**
+   * Apply prefix to object keys
+   * @param config Configuration object
+   */
+  function apply(config: Config = required(ERRORS.CONFIG_REQUIRED)): Config {
+    return performOperation(PrefixOperation.Add, config);
+  }
+
+
+  /**
+   * Remove prefix from object keys
+   * @param config Prefixed configuration object
+   */
+  function remove(config: Config = required(ERRORS.CONFIG_REQUIRED)): Config {
+    return performOperation(PrefixOperation.Remove, config);
+  }
+
+
+  // Creating the public API object
+  let publicApi: ConfigPrefixer = {
+    apply,
+    remove,
+  };
+
+  // Adding private methods to public API in test environment
+  /* test:start */
+  publicApi = {...publicApi,
+    performOperation,
+  };
+  /* test:end */
+
+  // Returning config wizard public API
+  return Object.freeze(publicApi);
+}
+
+export default ConfigPrefixer;
