wip(js): add head.html and assets/js

assets/js/modules/theme.js

@@ -0,0 +1,138 @@
+/**
+ * Theme management class
+ *
+ * To reduce flickering during page load, this script should be loaded synchronously.
+ */
+class Theme {
+  static #modeKey = 'mode';
+  static #modeAttr = 'data-mode';
+  static #darkMedia = window.matchMedia('(prefers-color-scheme: dark)');
+  static switchable = !document.documentElement.hasAttribute(this.#modeAttr);
+
+  static get DARK() {
+    return 'dark';
+  }
+
+  static get LIGHT() {
+    return 'light';
+  }
+
+  /**
+   * @returns {string} Theme mode identifier
+   */
+  static get ID() {
+    return 'theme-mode';
+  }
+
+  /**
+   * Gets the current visual state of the theme.
+   *
+   * @returns {string} The current visual state, either the mode if it exists,
+   *                   or the system dark mode state ('dark' or 'light').
+   */
+  static get visualState() {
+    if (this.#hasMode) {
+      return this.#mode;
+    } else {
+      return this.#sysDark ? this.DARK : this.LIGHT;
+    }
+  }
+
+  static get #mode() {
+    return (
+      sessionStorage.getItem(this.#modeKey) ||
+      document.documentElement.getAttribute(this.#modeAttr)
+    );
+  }
+
+  static get #isDarkMode() {
+    return this.#mode === this.DARK;
+  }
+
+  static get #hasMode() {
+    return this.#mode !== null;
+  }
+
+  static get #sysDark() {
+    return this.#darkMedia.matches;
+  }
+
+  /**
+   * Maps theme modes to provided values
+   * @param {string} light Value for light mode
+   * @param {string} dark Value for dark mode
+   * @returns {Object} Mapped values
+   */
+  static getThemeMapper(light, dark) {
+    return {
+      [this.LIGHT]: light,
+      [this.DARK]: dark
+    };
+  }
+
+  /**
+   * Initializes the theme based on system preferences or stored mode
+   */
+  static init() {
+    if (!this.switchable) {
+      return;
+    }
+
+    this.#darkMedia.addEventListener('change', () => {
+      const lastMode = this.#mode;
+      this.#clearMode();
+
+      if (lastMode !== this.visualState) {
+        this.#notify();
+      }
+    });
+
+    if (!this.#hasMode) {
+      return;
+    }
+
+    if (this.#isDarkMode) {
+      this.#setDark();
+    } else {
+      this.#setLight();
+    }
+  }
+
+  /**
+   * Flips the current theme mode
+   */
+  static flip() {
+    if (this.#hasMode) {
+      this.#clearMode();
+    } else {
+      this.#sysDark ? this.#setLight() : this.#setDark();
+    }
+    this.#notify();
+  }
+
+  static #setDark() {
+    document.documentElement.setAttribute(this.#modeAttr, this.DARK);
+    sessionStorage.setItem(this.#modeKey, this.DARK);
+  }
+
+  static #setLight() {
+    document.documentElement.setAttribute(this.#modeAttr, this.LIGHT);
+    sessionStorage.setItem(this.#modeKey, this.LIGHT);
+  }
+
+  static #clearMode() {
+    document.documentElement.removeAttribute(this.#modeAttr);
+    sessionStorage.removeItem(this.#modeKey);
+  }
+
+  /**
+   * Notifies other plugins that the theme mode has changed
+   */
+  static #notify() {
+    window.postMessage({ id: this.ID }, '*');
+  }
+}
+
+Theme.init();
+
+export default Theme;