Changeset: New API to simplify attribute processing

src/static/js/AttributeMap.js

@@ -0,0 +1,91 @@
+'use strict';
+
+const attributes = require('./attributes');
+
+/**
+ * A `[key, value]` pair of strings describing a text attribute.
+ *
+ * @typedef {[string, string]} Attribute
+ */
+
+/**
+ * A concatenated sequence of zero or more attribute identifiers, each one represented by an
+ * asterisk followed by a base-36 encoded attribute number.
+ *
+ * Examples: '', '*0', '*3*j*z*1q'
+ *
+ * @typedef {string} AttributeString
+ */
+
+/**
+ * Convenience class to convert an Op's attribute string to/from a Map of key, value pairs.
+ */
+class AttributeMap extends Map {
+  /**
+   * Converts an attribute string into an AttributeMap.
+   *
+   * @param {AttributeString} str - The attribute string to convert into an AttributeMap.
+   * @param {AttributePool} pool - Attribute pool.
+   * @returns {AttributeMap}
+   */
+  static fromString(str, pool) {
+    return new AttributeMap(pool).updateFromString(str);
+  }
+
+  /**
+   * @param {AttributePool} pool - Attribute pool.
+   */
+  constructor(pool) {
+    super();
+    /** @public */
+    this.pool = pool;
+  }
+
+  /**
+   * @param {string} k - Attribute name.
+   * @param {string} v - Attribute value.
+   * @returns {AttributeMap} `this` (for chaining).
+   */
+  set(k, v) {
+    k = k == null ? '' : String(k);
+    v = v == null ? '' : String(v);
+    this.pool.putAttrib([k, v]);
+    return super.set(k, v);
+  }
+
+  toString() {
+    return attributes.attribsToString(attributes.sort([...this]), this.pool);
+  }
+
+  /**
+   * @param {Iterable<Attribute>} entries - [key, value] pairs to insert into this map.
+   * @param {boolean} [emptyValueIsDelete] - If true and an entry's value is the empty string, the
+   *     key is removed from this map (if present).
+   * @returns {AttributeMap} `this` (for chaining).
+   */
+  update(entries, emptyValueIsDelete = false) {
+    for (let [k, v] of entries) {
+      k = k == null ? '' : String(k);
+      v = v == null ? '' : String(v);
+      if (!v && emptyValueIsDelete) {
+        this.delete(k);
+      } else {
+        this.set(k, v);
+      }
+    }
+    return this;
+  }
+
+  /**
+   * @param {AttributeString} str - The attribute string identifying the attributes to insert into
+   *     this map.
+   * @param {boolean} [emptyValueIsDelete] - If true and an entry's value is the empty string, the
+   *     key is removed from this map (if present).
+   * @returns {AttributeMap} `this` (for chaining).
+   */
+  updateFromString(str, emptyValueIsDelete = false) {
+    return this.update(attributes.attribsFromString(str, this.pool), emptyValueIsDelete);
+  }
+}
+
+module.exports = AttributeMap;