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// @ts-check
import { createElement as h, Fragment } from "react";
/** Document head tag manager {@linkcode Fragment}. */export default class HeadManager extends EventTarget {  constructor() {    super();
    /**     * @type {Map<     *   import("react").ReactNode,     *   { key: string, priority: number }     * >}     */    this.managed = new Map();  }
  /**   * Gets the managed document head tag content.   *   * If multiple entries have the same head tag fragment key, higher priority or   * later added ones override.   *   * The final head tag fragments are ordered by key, ensuring:   *   * - The project author can control the order.   * - Adding or removing managed document head tags causes minimal React   *   rendering DOM mutations that can cause FOUC.   */  getHeadContent() {    /**     * @type {Map<     *   string,     *   { priority: number, content: import("react").ReactNode }     * >}     */    const deduped = new Map();
    for (const [content, { key, priority }] of [...this.managed].reverse()) {      const existing = deduped.get(key);
      if (!existing || existing.priority < priority) {        deduped.set(key, { priority, content });      }    }
    const sorted = new Map([...deduped].sort(([a], [b]) => a.localeCompare(b)));    const content = [];
    for (const [key, value] of sorted) {      content.push(h(Fragment, { key }, value.content));    }
    return content;  }
  /**   * Adds document head tags.   * @param {string} key Head tag fragment key.   * @param {import("react").ReactNode} content Memoized React content   *   containing head tags.   * @param {number} [priority=0] Priority. Higher priority managed head tags   *   override lower priority ones with the same head tag fragment key.   */  add(key, content, priority = 0) {    if (typeof key !== "string") {      throw new TypeError("Argument 1 `key` must be a string.");    }
    if (arguments.length < 2) {      throw new TypeError("Argument 2 `content` must be specified.");    }
    if (typeof priority !== "number") {      throw new TypeError("Argument 3 `priority` must be a number.");    }
    const preexisting = this.managed.get(content);
    if (!preexisting) {      this.managed.set(content, { key, priority });      this.dispatchEvent(new CustomEvent("update"));    } else {      if (key !== preexisting.key) {        throw new TypeError(          `Argument 2 \`content\` already added with a different \`key\` of \`${preexisting.key}\`.`,        );      }
      if (priority !== preexisting.priority) {        throw new TypeError(          `Argument 2 \`content\` already added with a different \`priority\` of \`${preexisting.priority}\`.`,        );      }
      // Do nothing as this exact combination of arguments has already been      // added.    }  }
  /**   * Removes document head tags.   * @param {import("react").ReactNode} content Memoized React content   *   containing head tags to remove.   */  remove(content) {    if (this.managed.has(content)) {      this.managed.delete(content);      this.dispatchEvent(new CustomEvent("update"));    }  }}