Send an email to subscribers notifying of a new post

This query sends an email to all users, notifying of the creation of a new post on the site.

It includes the ability to select users who subscribed to an email list, however this portion of the query is commented out. (Please uncomment if needed.) The subscribed users are those with meta email_list with value new_posts.

This query requires the endpoint to have Nested Mutations enabled.

query GetPostAndExportData($postId: ID!) {
  post(by: { id: $postId }) {
    content @export(as: "postContent")
    title @export(as: "postTitle")
    url @export(as: "postURL")
  }
 
  hasPost: _notNull(value: $__post)
    @export(as: "doSendEmail")
}
 
query GetEmailData
  @depends(on: "GetPostAndExportData")
  @include(if: $doSendEmail)
{ 
  siteName: optionValue(name: "blogname")
    @export(as: "siteName")
 
  emailSubject: _sprintf(
    string: "There is a new post: \"%s\"",
    values: [$postTitle]
  )
    @export(as: "emailSubject")
}
 
mutation SendEmailToUsersAboutNewPost
  @depends(on: "GetEmailData")
  @include(if: $doSendEmail)
{
  users
  # # Retrieve only users subscribed to an email list (uncomment if needed)
  # (
  #   filter: {
  #     metaQuery: {
  #       key: "email_list",
  #       compareBy: {
  #         arrayValue: {
  #           value: "new_posts",
  #           operator: IN
  #         }
  #       }
  #     }
  #   }
  # )
  {
    displayName
    email
 
    emailMessageTemplate: _strConvertMarkdownToHTML(
      text: """
 
Hi {$userDisplayName},
 
There is a new post on the **{$siteName}** website:
 
[**{$postTitle}**]({$postURL})
 
{$postContent}
  
      """
    )
      @remove
    emailMessage: _strReplaceMultiple(
      search: ["{$userDisplayName}", "{$siteName}", "{$postTitle}", "{$postContent}", "{$postURL}"],
      replaceWith: [$__displayName, $siteName, $postTitle, $postContent, $postURL],
      in: $__emailMessageTemplate
    )
      @remove
 
    _sendEmail(
      input: {
        to: $__email
        subject: $emailSubject
        messageAs: {
          html: $__emailMessage
        }
      }
    ) {
      status
      errors {
        __typename
        ...on ErrorPayload {
          message
        }
      }
    }
  }
}