add hw2

node_modules/commander/lib/argument.js

@@ -0,0 +1,150 @@
+const { InvalidArgumentError } = require('./error.js');
+
+class Argument {
+  /**
+   * Initialize a new command argument with the given name and description.
+   * The default is that the argument is required, and you can explicitly
+   * indicate this with <> around the name. Put [] around the name for an optional argument.
+   *
+   * @param {string} name
+   * @param {string} [description]
+   */
+
+  constructor(name, description) {
+    this.description = description || '';
+    this.variadic = false;
+    this.parseArg = undefined;
+    this.defaultValue = undefined;
+    this.defaultValueDescription = undefined;
+    this.argChoices = undefined;
+
+    switch (name[0]) {
+      case '<': // e.g. <required>
+        this.required = true;
+        this._name = name.slice(1, -1);
+        break;
+      case '[': // e.g. [optional]
+        this.required = false;
+        this._name = name.slice(1, -1);
+        break;
+      default:
+        this.required = true;
+        this._name = name;
+        break;
+    }
+
+    if (this._name.endsWith('...')) {
+      this.variadic = true;
+      this._name = this._name.slice(0, -3);
+    }
+  }
+
+  /**
+   * Return argument name.
+   *
+   * @return {string}
+   */
+
+  name() {
+    return this._name;
+  }
+
+  /**
+   * @package
+   */
+
+  _collectValue(value, previous) {
+    if (previous === this.defaultValue || !Array.isArray(previous)) {
+      return [value];
+    }
+
+    previous.push(value);
+    return previous;
+  }
+
+  /**
+   * Set the default value, and optionally supply the description to be displayed in the help.
+   *
+   * @param {*} value
+   * @param {string} [description]
+   * @return {Argument}
+   */
+
+  default(value, description) {
+    this.defaultValue = value;
+    this.defaultValueDescription = description;
+    return this;
+  }
+
+  /**
+   * Set the custom handler for processing CLI command arguments into argument values.
+   *
+   * @param {Function} [fn]
+   * @return {Argument}
+   */
+
+  argParser(fn) {
+    this.parseArg = fn;
+    return this;
+  }
+
+  /**
+   * Only allow argument value to be one of choices.
+   *
+   * @param {string[]} values
+   * @return {Argument}
+   */
+
+  choices(values) {
+    this.argChoices = values.slice();
+    this.parseArg = (arg, previous) => {
+      if (!this.argChoices.includes(arg)) {
+        throw new InvalidArgumentError(
+          `Allowed choices are ${this.argChoices.join(', ')}.`,
+        );
+      }
+      if (this.variadic) {
+        return this._collectValue(arg, previous);
+      }
+      return arg;
+    };
+    return this;
+  }
+
+  /**
+   * Make argument required.
+   *
+   * @returns {Argument}
+   */
+  argRequired() {
+    this.required = true;
+    return this;
+  }
+
+  /**
+   * Make argument optional.
+   *
+   * @returns {Argument}
+   */
+  argOptional() {
+    this.required = false;
+    return this;
+  }
+}
+
+/**
+ * Takes an argument and returns its human readable equivalent for help usage.
+ *
+ * @param {Argument} arg
+ * @return {string}
+ * @private
+ */
+
+function humanReadableArgName(arg) {
+  const nameOutput = arg.name() + (arg.variadic === true ? '...' : '');
+
+  return arg.required ? '<' + nameOutput + '>' : '[' + nameOutput + ']';
+}
+
+exports.Argument = Argument;
+exports.humanReadableArgName = humanReadableArgName;