Initial commit

src/util/BitField.js

@@ -0,0 +1,170 @@
+'use strict';
+
+const { RangeError } = require('../errors');
+
+/**
+ * Data structure that makes it easy to interact with a bitfield.
+ */
+class BitField {
+  /**
+   * @param {BitFieldResolvable} [bits=this.constructor.defaultBit] Bit(s) to read from
+   */
+  constructor(bits = this.constructor.defaultBit) {
+    /**
+     * Bitfield of the packed bits
+     * @type {number|bigint}
+     */
+    this.bitfield = this.constructor.resolve(bits);
+  }
+
+  /**
+   * Checks whether the bitfield has a bit, or any of multiple bits.
+   * @param {BitFieldResolvable} bit Bit(s) to check for
+   * @returns {boolean}
+   */
+  any(bit) {
+    return (this.bitfield & this.constructor.resolve(bit)) !== this.constructor.defaultBit;
+  }
+
+  /**
+   * Checks if this bitfield equals another
+   * @param {BitFieldResolvable} bit Bit(s) to check for
+   * @returns {boolean}
+   */
+  equals(bit) {
+    return this.bitfield === this.constructor.resolve(bit);
+  }
+
+  /**
+   * Checks whether the bitfield has a bit, or multiple bits.
+   * @param {BitFieldResolvable} bit Bit(s) to check for
+   * @returns {boolean}
+   */
+  has(bit) {
+    bit = this.constructor.resolve(bit);
+    return (this.bitfield & bit) === bit;
+  }
+
+  /**
+   * Gets all given bits that are missing from the bitfield.
+   * @param {BitFieldResolvable} bits Bit(s) to check for
+   * @param {...*} hasParams Additional parameters for the has method, if any
+   * @returns {string[]}
+   */
+  missing(bits, ...hasParams) {
+    return new this.constructor(bits).remove(this).toArray(...hasParams);
+  }
+
+  /**
+   * Freezes these bits, making them immutable.
+   * @returns {Readonly<BitField>}
+   */
+  freeze() {
+    return Object.freeze(this);
+  }
+
+  /**
+   * Adds bits to these ones.
+   * @param {...BitFieldResolvable} [bits] Bits to add
+   * @returns {BitField} These bits or new BitField if the instance is frozen.
+   */
+  add(...bits) {
+    let total = this.constructor.defaultBit;
+    for (const bit of bits) {
+      total |= this.constructor.resolve(bit);
+    }
+    if (Object.isFrozen(this)) return new this.constructor(this.bitfield | total);
+    this.bitfield |= total;
+    return this;
+  }
+
+  /**
+   * Removes bits from these.
+   * @param {...BitFieldResolvable} [bits] Bits to remove
+   * @returns {BitField} These bits or new BitField if the instance is frozen.
+   */
+  remove(...bits) {
+    let total = this.constructor.defaultBit;
+    for (const bit of bits) {
+      total |= this.constructor.resolve(bit);
+    }
+    if (Object.isFrozen(this)) return new this.constructor(this.bitfield & ~total);
+    this.bitfield &= ~total;
+    return this;
+  }
+
+  /**
+   * Gets an object mapping field names to a {@link boolean} indicating whether the
+   * bit is available.
+   * @param {...*} hasParams Additional parameters for the has method, if any
+   * @returns {Object}
+   */
+  serialize(...hasParams) {
+    const serialized = {};
+    for (const [flag, bit] of Object.entries(this.constructor.Flags)) serialized[flag] = this.has(bit, ...hasParams);
+    return serialized;
+  }
+
+  /**
+   * Gets an {@link Array} of bitfield names based on the bits available.
+   * @param {...*} hasParams Additional parameters for the has method, if any
+   * @returns {string[]}
+   */
+  toArray(...hasParams) {
+    return Object.keys(this.constructor.Flags).filter(bit => this.has(bit, ...hasParams));
+  }
+
+  toJSON() {
+    return typeof this.bitfield === 'number' ? this.bitfield : this.bitfield.toString();
+  }
+
+  valueOf() {
+    return this.bitfield;
+  }
+
+  *[Symbol.iterator]() {
+    yield* this.toArray();
+  }
+
+  /**
+   * Data that can be resolved to give a bitfield. This can be:
+   * * A bit number (this can be a number literal or a value taken from {@link BitField.Flags})
+   * * A string bit number
+   * * An instance of BitField
+   * * An Array of BitFieldResolvable
+   * @typedef {number|string|bigint|BitField|BitFieldResolvable[]} BitFieldResolvable
+   */
+
+  /**
+   * Resolves bitfields to their numeric form.
+   * @param {BitFieldResolvable} [bit] bit(s) to resolve
+   * @returns {number|bigint}
+   */
+  static resolve(bit) {
+    const { defaultBit } = this;
+    if (typeof defaultBit === typeof bit && bit >= defaultBit) return bit;
+    if (bit instanceof BitField) return bit.bitfield;
+    if (Array.isArray(bit)) return bit.map(p => this.resolve(p)).reduce((prev, p) => prev | p, defaultBit);
+    if (typeof bit === 'string') {
+      if (typeof this.Flags[bit] !== 'undefined') return this.Flags[bit];
+      if (!isNaN(bit)) return typeof defaultBit === 'bigint' ? BigInt(bit) : Number(bit);
+    }
+    throw new RangeError('BITFIELD_INVALID', bit);
+  }
+}
+
+/**
+ * Numeric bitfield flags.
+ * <info>Defined in extension classes</info>
+ * @type {Object}
+ * @abstract
+ */
+BitField.Flags = {};
+
+/**
+ * @type {number|bigint}
+ * @private
+ */
+BitField.defaultBit = 0;
+
+module.exports = BitField;