upstream-tiptap/packages/extension-subscript/src/subscript.ts

import { Mark, mergeAttributes } from '@tiptap/core'
import type { StyleParseRule } from '@tiptap/pm/model'

export interface SubscriptExtensionOptions {
  /**
   * HTML attributes to add to the subscript element.
   * @default {}
   * @example { class: 'foo' }
   */
  HTMLAttributes: Record<string, any>
}

declare module '@tiptap/core' {
  interface Commands<ReturnType> {
    subscript: {
      /**
       * Set a subscript mark
       * @example editor.commands.setSubscript()
       */
      setSubscript: () => ReturnType
      /**
       * Toggle a subscript mark
       * @example editor.commands.toggleSubscript()
       */
      toggleSubscript: () => ReturnType
      /**
       * Unset a subscript mark
       * @example editor.commands.unsetSubscript()
       */
      unsetSubscript: () => ReturnType
    }
  }
}

/**
 * This extension allows you to create subscript text.
 * @see https://www.tiptap.dev/api/marks/subscript
 */
export const Subscript = Mark.create<SubscriptExtensionOptions>({
  name: 'subscript',

  addOptions() {
    return {
      HTMLAttributes: {},
    }
  },

  parseHTML() {
    return [
      {
        tag: 'sub',
      },
      {
        style: 'vertical-align',
        getAttrs(value) {
          // Don’t match this rule if the vertical align isn’t sub.
          if (value !== 'sub') {
            return false
          }

          // If it falls through we’ll match, and this mark will be applied.
          return null
        },
      } as StyleParseRule,
    ]
  },

  renderHTML({ HTMLAttributes }) {
    return ['sub', mergeAttributes(this.options.HTMLAttributes, HTMLAttributes), 0]
  },

  addCommands() {
    return {
      setSubscript:
        () =>
        ({ commands }) => {
          return commands.setMark(this.name)
        },
      toggleSubscript:
        () =>
        ({ commands }) => {
          return commands.toggleMark(this.name)
        },
      unsetSubscript:
        () =>
        ({ commands }) => {
          return commands.unsetMark(this.name)
        },
    }
  },

  addKeyboardShortcuts() {
    return {
      'Mod-,': () => this.editor.commands.toggleSubscript(),
    }
  },
})