feat: migrate fake (#79)

Co-authored-by: Honza Machala <[email protected]>

2 files changed, 112 insertions, 1 deletions

diff --git a/src/fake.ts b/src/fake.ts
new file mode 100644
index 00000000..e435ce89
--- /dev/null
+++ b/src/fake.ts
@@ -0,0 +1,110 @@
+import type { Faker } from '.';
+
+/**
+ * Generator method for combining faker methods based on string input
+ */
+export class Fake {
+  constructor(private readonly faker: Faker) {
+    // Bind `this` so namespaced is working correctly
+    for (const name of Object.getOwnPropertyNames(Fake.prototype)) {
+      if (name === 'constructor' || typeof this[name] !== 'function') {
+        continue;
+      }
+      this[name] = this[name].bind(this);
+    }
+  }
+
+  /**
+   * Generator method for combining faker methods based on string input
+   *
+   * __Example:__
+   *
+   * ```
+   * console.log(faker.fake('{{name.lastName}}, {{name.firstName}} {{name.suffix}}'));
+   * // outputs: "Marks, Dean Sr."
+   * ```
+   *
+   * This will interpolate the format string with the value of methods
+   * [name.lastName]{@link faker.name.lastName}, [name.firstName]{@link faker.name.firstName},
+   * and [name.suffix]{@link faker.name.suffix}
+   *
+   * @method faker.fake
+   * @param str
+   */
+  fake(str: string): string {
+    // setup default response as empty string
+    let res = '';
+
+    // if incoming str parameter is not provided, return error message
+    if (typeof str !== 'string' || str.length === 0) {
+      throw new Error('string parameter is required!');
+    }
+
+    // find first matching {{ and }}
+    const start = str.search('{{');
+    const end = str.search('}}');
+
+    // if no {{ and }} is found, we are done
+    if (start === -1 || end === -1) {
+      return str;
+    }
+
+    // console.log('attempting to parse', str);
+
+    // extract method name from between the {{ }} that we found
+    // for example: {{name.firstName}}
+    const token = str.substr(start + 2, end - start - 2);
+    let method = token.replace('}}', '').replace('{{', '');
+
+    // console.log('method', method)
+
+    // extract method parameters
+    const regExp = /\(([^)]+)\)/;
+    const matches = regExp.exec(method);
+    let parameters = '';
+    if (matches) {
+      method = method.replace(regExp, '');
+      parameters = matches[1];
+    }
+
+    // split the method into module and function
+    const parts = method.split('.');
+
+    if (typeof this.faker[parts[0]] === 'undefined') {
+      throw new Error('Invalid module: ' + parts[0]);
+    }
+
+    if (typeof this.faker[parts[0]][parts[1]] === 'undefined') {
+      throw new Error('Invalid method: ' + parts[0] + '.' + parts[1]);
+    }
+
+    // assign the function from the module.function namespace
+    const fn = this.faker[parts[0]][parts[1]];
+
+    // If parameters are populated here, they are always going to be of string type
+    // since we might actually be dealing with an object or array,
+    // we always attempt to the parse the incoming parameters into JSON
+    let params: any;
+    // Note: we experience a small performance hit here due to JSON.parse try / catch
+    // If anyone actually needs to optimize this specific code path, please open a support issue on github
+    try {
+      params = JSON.parse(parameters);
+    } catch (err) {
+      // since JSON.parse threw an error, assume parameters was actually a string
+      params = parameters;
+    }
+
+    let result: string;
+    if (typeof params === 'string' && params.length === 0) {
+      result = fn.call(this);
+    } else {
+      result = fn.call(this, params);
+    }
+
+    // replace the found tag with the returned fake value
+    res = str.replace('{{' + token + '}}', result);
+
+    // return the response recursively until we are done finding all tags
+    return this.fake(res);
+  }
+}
diff --git a/src/index.ts b/src/index.ts
index 768ea2ef..b8fef5e8 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,5 +1,6 @@
 import { Datatype } from './datatype';
 import { _Date } from './date';
+import { Fake } from './fake';
 import { Git } from './git';
 import { Hacker } from './hacker';
 import { Helpers } from './helpers';
@@ -155,7 +156,7 @@ export class Faker {
 
   seedValue?: any[] | any;
 
-  readonly fake = new (require('./fake'))(this).fake;
+  readonly fake: Fake['fake'] = new Fake(this).fake;
   readonly unique = new (require('./unique'))(this).unique;
 
   readonly mersenne: Mersenne = new Mersenne();