motd-witty

motd-witty

#!/usr/bin/ruby

GREETINGS_FILE = '/etc/motd-witty.json'


#
# motd-witty
# 
# Version 1.1
# Talus Baddley, 2013.
# Copyright; GNU GPL v2.
# 
# 
# (I really should come up with a better name for this.)
# 
# motd-witty provides a simple mechanism for both important
# announcements and (as the name implies) witty quips and pro-tips
# randomly selected for each user. The former we call Messages and
# the latter we simply refer to as Protips. Additionally, any of
# these may be limited to a particular time-frame.
# 
# This script is intended to work as a part of Ubuntu's update-motd.d
# system. It reads greetings the administrator places in the
# GREETINGS_FILE as specified above, and writes them out to the
# message of the day as any user logs in. (Read man update-motd for
# more info on the larger system in which this operates.)
# 
# The format for the greetings file is a JSON array of records.
# A 'record' is a dictionary defining a date range, and either
# a message or a set of protips.
# 
# An example file:
# [
#   {
#      "startDate": "2013-09-20T17:18:05-0600",
#      "lifetime": 1.75,
#      "message": "Updates are done for this week.\nYou may safely carry on.\n\n"
#   },
#   {
#      "startDate": "2013-09-23T06:00:00-0600",
#      "lifetime": 7,
#      "protips": [
#        "Because three heads are better than four cores.",
#        "This week's shell brought to you by Jason Bourne."
#      ]
#   },
#   {
#      "default": true,
#      "protips": [
#        "Protip: run `cowsay Moo!` periodically.",
#        "Don't try and sudo. The terrier reviews all such incidents."
#      ]
#   }
# ]
# 
# We see the outer array [] and its dictionary records {}, {}, {}
# In a record, we see a message string or a protips array of string.
# The record's startDate should be expressed according to ISO 8601.
# That is, yyyy-mm-ddThh:mm:ss-timezone.
# The lifetime of a record after its startDate is expressed in days.
# Note that Salt Lake is in timezone -0600 in daylight savings and
# -0700 otherwise.
# 
# At the moment a user logs in, all messages applicable to that
# moment (according to their date ranges) are collected and displayed
# to the user, in the order they appear in the file. If there are no
# applicable messages, all the applicable protips are pooled, and one
# of them is randomly shown to the user.
# 
# We also see the special default record at the end.
# Its contents are always considered applicable.
# 


# Protip: for a message to be seen, end it in \n\n
#         as in the example.


# Update for 1.1: Now uses JSON rather than XML Property List,
# as Ruby's plist interpreter is nonconformant.



require 'time'
require 'yaml'

RIGHT_NOW = Time.now
TERM_W = 69   # Assume a 70-char terminal.

SECONDS_IN_DAY = 86400  # = 24 * 60 * 60

START_DATE_KEY = 'startDate'
LIFETIME_KEY = 'lifetime'
MAND_MESSAGE_KEY = 'message'
OPT_MESSAGES_KEY = 'protips'
DEFAULT_KEY = 'default'


def do_greet
    
    #
    # 1.
    # Start by reading in the greetings data.
    #
    greetingInfo = extract_greeting_info GREETINGS_FILE
    return unless greetingInfo
    
    
    #
    # 2.
    # Filter out the records which are inapplicable to the current date.
    #
    relevantRecords = greetingInfo.select do |record|
        startDate = record[START_DATE_KEY]
        lifetime = record[LIFETIME_KEY]
        next true if startDate.nil? || lifetime.nil?
        
        relevant_date?(startDate, lifetime)  ? true : false
    end
    
    
    #
    # 3.
    # We would grab the default record, but the 'default' key is
    # really just commenting: Its not having a date range
    # automatically includes it in the output.
    # If there are no applicable records at all, return having done nothing.
    #
    return if relevantRecords.empty?
    
    
    #
    # 4.
    # Puts the mandatory messages.
    #
    mandatoryMessages = relevantRecords.lazymap_nonnil {|record| record[MAND_MESSAGE_KEY] }
    mandatoryMessages.each {|msg| puts msg }
    
    return if mandatoryMessages.first  # If there were any messages, exit now.
    
    
    #
    # 5.
    # Puts the random protip!
    #
    protipBucket = relevantRecords.flat_map do |record|
        msgs = record[OPT_MESSAGES_KEY]
        msgs ? msgs : []  # Yields the list of protips if they exist,
                          # otherwise the empty list.
    end
    puts protipBucket.sample.center_each_line(TERM_W)  unless protipBucket.empty?
    
end




class String
    def center_each_line width
        self.each_line.map {|line| line.chomp.center width }.join($/)
    end
end





def extract_greeting_info inFile
    resultat = nil
    File.open(inFile) do |fpipe|
        resultat = YAML.load( fpipe.set_encoding('UTF-8').read )
    end
    return resultat
    
rescue StandardError
    return nil
end



def relevant_date? dateString, lifetime
    date = Time.iso8601(dateString)  rescue Time.parse(dateString)
    endDate = date + (lifetime * SECONDS_IN_DAY)
    date <= RIGHT_NOW  &&  endDate > RIGHT_NOW  ?  true : false
end



# lazymap_nonnil for Enumerables by Talus Baddley
module Enumerable
    # Maps all values on the receiver through the provided block,
    # omitting nil values on output.
    def lazymap_nonnil
        Enumerator.new do |yielder|
            self.each do |enumeritem|
                resultat = yield enumeritem
                yielder << resultat  unless resultat.nil?
            end
        end
    end
end



do_greet

Okay, so it's actually a YAML parser, not a JSON one. Makes for cleaner files.