#!/usr/bin/env ruby

require 'yaml'
require 'tempfile'

# Used to compare the output of the `cratus` command across multiple runs

input1 = ARGV[0]
input2 = ARGV[1]

# Find our diff command and break if we don't have one
diff_path = `which diff`.chomp
raise "Missing diff command in PATH!" unless $?.success?

# The command we'll use later to see what has changed
diff_cmd = "#{diff_path} -U 999999"

## Methods / Functions
def validate_input(input)
  # Make sure the input is set
  raise "Missing First Input!" unless input
  # Make sure the input is a valid file that we can read
  raise "Invalid Input File #{input}" unless File.readable?(input)
  # TODO: make sure the input file is valid YAML
end

# Read in some input
def read_input(input)
  begin
    YAML.load_file(input)
  rescue => e
    raise "Unable to open #{input}: #{e.message}"
  end
end

## Execution
validate_input(input1)
validate_input(input2)

data1 = read_input(input1)
data2 = read_input(input2)

if data1 == data2
  exit 0
else
  STDERR.puts "Looks like things have changed!"

  # Calculate what has actually changed
  additions_and_differences = (data2.to_a - data1.to_a)
  removals = (data1.to_a - data2.to_a)
  results = {}
  additions_and_differences.each do |user|
    results[user[0]] = user[1]
  end

  # Temporary files for a call to `diff`
  newdata = Tempfile.new('new')
  olddata = Tempfile.new('old')

  # Add the results from our comparison to the first temp file
  newdata.write(results.to_yaml)

  # Grab the old data for just our changed users and put it into a new hash
  oldhash = {}
  results.each do |user,data|
    oldhash[user] = data1[user] if data1.key?(user)
  end
  # Add things that were removed from the old data (removed users)
  removals.each do |removed_user|
    oldhash[removed_user[0]] = removed_user[1]
  end

  # Write out the old data
  olddata.write(oldhash.to_yaml)

  # Close and flush our temp files
  newdata.close
  olddata.close

  # The actual call to the `diff` command
  system("#{diff_cmd} #{olddata.path} #{newdata.path}")

  # Destroy the temp files after the diff command finishes
  newdata.unlink
  olddata.unlink
end