require "pathname"
require "digest/sha1"
require "yaml"
require 'trollop'

module DirScan

  class Scanner

    def initialize dir=Dir.pwd, options={:verbose => false}
      @dir = Pathname.new(dir).expand_path
      @file = Pathname.new('dirscan.yml').expand_path
      @verbose = options[:verbose]
    end

    def scan
      puts "Scanning '#{@dir}'..."
      @contents = {}.tap do |contents|
        @dir.find do |f|
          contents[f.to_s] = sha1 f if f.file?
        end
      end
    end

    def sha1 file
      Digest::SHA1.new.tap do |hash|
        File.open(file, 'r') do |fh|
          while buffer = fh.read(1024) do
            hash << buffer
          end
        end
      end.to_s
    end

    def save
      puts "Saving '#{@file}'..."
      File.open(@file, 'w+') do |f|
        h = {
          :directory => @dir,
          :timestamp => Time.now,
          :contents => @contents
        }
        f.write h.to_yaml
      end
    end

    def compare
      @snapshot = YAML.load_file @file
      a_hash = @snapshot[:contents]
      b_hash = scan
      a_hash.delete_if {|k, v| k =~ /[\/\\]dirscan.yml$/}
      b_hash.delete_if {|k, v| k =~ /[\/\\]dirscan.yml$/}
      @result = {:created => [], :updated => [], :deleted => [], :unchanged => []}
      a_hash.each do |a_key, a_value|
        b_value = b_hash.delete a_key
        case
        when !b_value then
          @result[:deleted] << a_key
        when b_value != a_value then
          @result[:updated] << a_key
        else
          @result[:unchanged] << a_key
        end
      end
      @result[:created] = b_hash.keys
    end

    def report
      total = @result.values.map{|v| v.size}.inject :'+'
      puts "="*50
      puts "Total files: #{total}"
      puts "- Unchanged: #{@result[:unchanged].size}"
      puts
      puts "Differences since #{@snapshot[:timestamp]}:"
      puts "- Updated: #{@result[:updated].size}"
      show_files :updated
      puts "- Deleted: #{@result[:deleted].size}"
      show_files :deleted
      puts "- Created: #{@result[:created].size}"
      show_files :created
      puts "="*50
    end

    protected

    def show_files key
      return unless @verbose
      @result[key].each do |file|
        puts "\t#{file.gsub /^#{Regexp.escape @dir.to_s}/, ''}"
      end
    end
  end
end

options = Trollop::options do
  opt :scan, "Scan directory", :default => Dir.pwd
  opt :compare, "Compare files", :default => false
  opt :write, "Save snapshot file", :default => false
  opt :verbose, "Display file names as well", :default => false
end

scanner = DirScan::Scanner.new(options[:scan], :verbose => options[:verbose])

if options[:compare] then
  scanner.compare
  scanner.save if options[:write]
  scanner.report
else
  scanner.scan
  scanner.save
end