module AWS::S3::ACLOptions

def acl_options acl
  case acl
  when Symbol
    { :acl => acl.to_s.tr('_', '-') }
  when String
    # Strings are either access control policies (xml strings)
    # or they are canned acls
    xml?(acl) ?
      { :access_control_policy => acl } :
      { :acl => acl }
  when AccessControlList
      { :access_control_policy => acl.to_xml }
  when Hash
    # Hashes are either grant hashes or constructor args for an
    # access control list (deprecated)
    grant_hash?(acl) ?
      format_grants(acl) :
      { :access_control_policy => AccessControlList.new(acl).to_xml }
  else
    # failed to parse the acl option
    msg = "expected a canned ACL, AccessControlList object, ACL "
          "XML string or a grants hash"
    raise ArgumentError, msg
  end
end

def format_grantee grantee
  case grantee
  when String then grantee
  when Hash
    if grantee.keys.count != 1
      msg = "grantee hashes must have exactly 1 key"
      raise ArgumentError, msg
    end
    # A granee hash looks like:
    #   { :id => 'abc...fec' }
    #   { :uri => 'http://abc.com/foo' }
    #   { :email_address => 'xyz@amazon.com }
    #
    # It needs to look like
    #   'id="abc...fec"'
    #   'uri="http://abc.com/foo"'
    #   'emailAddress="xyz@amazon.com"'
    type, token = grantee.to_a.flatten
    type = type.to_s.split('_').map{|part| ucfirst(part) }.join
    "#{type[0,1].downcase}#{type[1..-1]}=\"#{token}\""
  else
    raise ArgumentError, "grantees must be a string or a hash"
  end
end

def format_grants acl_hash
  grants = {}
  acl_hash.each_pair do |grant,grantees|
    grantees = [grantees] unless grantees.is_a?(Array)
    grants[grant] = grantees.map{|g| format_grantee(g) }.join(', ')
  end
  grants
end

def grant_hash? acl_hash
  grant_keys = [
    :grant_read,
    :grant_write,
    :grant_read_acp,
    :grant_write_acp,
    :grant_full_control,
  ]
  acl_hash.keys.all?{|key| grant_keys.include?(key) }
end

def ucfirst str
  str[0,1].upcase + str[1..-1]
end

def xml? acl_string
  begin
    REXML::Document.new(acl_string).has_elements?
  rescue
    false
  end
end