Class: APNS::Truncate

Inherits:
Object
  • Object
show all
Defined in:
lib/apns/truncate.rb

Constant Summary collapse

TRUNCATE_METHOD_SOFT = 
'soft'
TRUNCATE_METHOD_HARD = 
'hard'
NOTIFICATION_MAX_BYTE_SIZE = 
256

Class Method Summary collapse

Class Method Details

.truncate_notification(notification, clean_whitespace = true, truncate_mode = TRUNCATE_METHOD_SOFT, truncate_soft_max_chopped = 10, ellipsis = "\u2026") ⇒ Object

forces a notification to fit within Apple’s payload limits by truncating the message as required

Raises:

  • (ArgumentError) 


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# File 'lib/apns/truncate.rb', line 34

def self.truncate_notification(notification, clean_whitespace = true, truncate_mode = TRUNCATE_METHOD_SOFT, truncate_soft_max_chopped = 10, ellipsis = "\u2026")
  
  raise ArgumentError, "notification is not a hash" unless notification.is_a?(Hash)
  raise ArgumentError, "notification hash should contain :aps key" unless notification[:aps]
  
  return notification if !notification[:aps][:alert] || notification[:aps][:alert] == ""
  
  # cleans up whitespace
  notification[:aps][:alert].gsub!(/([\s])+/, " ") if clean_whitespace
            
  # wd: trims the notification payload to fit in 255 bytes
  if ApnsJSON.apns_json_size(notification) > NOTIFICATION_MAX_BYTE_SIZE

    oversize_by = ApnsJSON.apns_json_size(notification) - NOTIFICATION_MAX_BYTE_SIZE
    message_target_byte_size = ApnsJSON.apns_json_size(notification[:aps][:alert]) - oversize_by

    if message_target_byte_size < 0
      raise TrucateException, "notification does not fit within 256 byte limit even by if the message was completely truncated"
    end
    if message_target_byte_size == 0
      raise TrucateException, "notification would only fit within 256 byte limit by completely truncating the message which changes the presentation in iOS"
    end

    notification[:aps][:alert] = truncate_string(notification[:aps][:alert], message_target_byte_size, truncate_mode, truncate_soft_max_chopped, ellipsis)
  end
  
  return notification
end

.truncate_string(input_string, target_byte_size, truncate_mode = TRUNCATE_METHOD_SOFT, truncate_soft_max_chopped = 10, ellipsis = "\u2026", truncate_soft_regex = /\s/) ⇒ Object

truncates a string to a given byte size

Raises:

  • (ArgumentError) 


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# File 'lib/apns/truncate.rb', line 64

def self.truncate_string(input_string, target_byte_size, truncate_mode = TRUNCATE_METHOD_SOFT, truncate_soft_max_chopped = 10, ellipsis = "\u2026", truncate_soft_regex = /\s/)

  raise ArgumentError, "Cannot truncate string to a negative number" if target_byte_size < 0 
  
  return input_string if ApnsJSON.apns_json_size(input_string) <= target_byte_size
  
  # if the target size is below the size of the ellipsis, reverts to a hard-truncate with no ellipsis
  if target_byte_size < ApnsJSON.apns_json_size(ellipsis)
    truncate_mode = TRUNCATE_METHOD_HARD
    ellipsis = ''
  end

  # reduces target-size by the ellipsis size
  target_byte_size -= ApnsJSON.apns_json_size(ellipsis)

  # starts with a string length equal to the target number bytes (which for an ASCII-only string is the final string)
  string = input_string[0,target_byte_size]
  
  # chops off characters one at a time until the byte-size is within our target size, to handle variable-byte char strings
  while ApnsJSON.apns_json_size(string) > target_byte_size
    string = string[0,string.length-1]
  end
  
  # further truncates string on whitespace boundaries
  if truncate_mode == TRUNCATE_METHOD_SOFT
  
    string = input_string[0, string.length+1] # elongates string by 1 character in case it happens to be whitespace
    trim_to_index = string.rindex(/\s/) # sets trim index to be last whitespace character
    if !trim_to_index || (string.length - trim_to_index) > truncate_soft_max_chopped
      trim_to_index = string.length-1 # cancels soft-truncate if no whitespace, or too much would be chopped
    end
    
    string = string[0,trim_to_index]
  end

  string = '' if string.nil?  # if string is nil, it was entirely truncated
  
  return string + ellipsis
end