class Jekyll::SeoTag::AuthorDrop

for additional author metadata in ‘site.data.authors`
If the result from the name search is a string, we’ll also check
3. The ‘author` key in the site config
2. The first author in the page’s ‘authors` key
1. The page’s ‘author` key
Author name will be pulled from:
A drop representing the current page’s author

def author_hash

or an empty hash, if the author cannot be resolved
including site-wide metadata if the author is provided as a string,
Returns the normalized author hash representing the page author, 
def author_hash
  @author_hash ||= begin
    case resolved_author
    when Hash
      resolved_author
    when String
      { "name" => resolved_author }.merge!(site_data_hash)
    else
      {}
    end
  end
end

def initialize(page: nil, site: nil)

site - The Jekyll::Drops::SiteDrop
page - The page hash (e.g., Page#to_liquid)

Initialize a new AuthorDrop 
def initialize(page: nil, site: nil)
  raise ArgumentError unless page && site
  @mutations = {}
  @page = page
  @site = site
end

def name

replace `page.author`, if necessary, and remain backwards compatible
AuthorDrop#to_s should return name, allowing the author drop to safely 
def name
  author_hash["name"]
end

def resolved_author

Returns a string or hash representing the author

Finds the page author in the page.author, page.authors, or site.author 
def resolved_author
  return @resolved_author if defined? @resolved_author
  sources = [page["author"]]
  sources << page["authors"].first if page["authors"].is_a?(Array)
  sources << site["author"]
  @resolved_author = sources.find { |s| !s.to_s.empty? }
end

def site_data_hash

Returns a hash representing additional metadata or an empty hash

metadata in `site.data.authors`
If resolved_author is a string, attempts to find coresponding author 
def site_data_hash
  @site_data_hash ||= begin
    return {} unless resolved_author.is_a?(String)
    return {} unless site.data["authors"].is_a?(Hash)
    author_hash = site.data["authors"][resolved_author]
    author_hash.is_a?(Hash) ? author_hash : {}
  end
end

def twitter 

def twitter
  return @twitter if defined? @twitter
  twitter = author_hash["twitter"] || author_hash["name"]
  @twitter = twitter.is_a?(String) ? twitter.sub(%r!^@!, "") : nil
end