require "fileutils"
require "find"

module AmazonAssociate
  module CachingStrategy
    class Filesystem < AmazonAssociate::CachingStrategy::Base
      #disk quota in megabytes
      DEFAULT_DISK_QUOTA = 200
    
      #frequency of sweeping in hours
      DEFAULT_SWEEP_FREQUENCY = 2
    
      def self.cache(request, response)
        path = self.cache_path
        cached_filename = Digest::SHA1.hexdigest(response.request_url)
        cached_folder = cached_filename[0..2]
      
        FileUtils.mkdir_p(File.join(path, cached_folder, cached_folder))
      
        cached_file = File.open(File.join(path, cached_folder, cached_filename), "w")
        cached_file.puts response.doc.to_s
        cached_file.close
      end
    
      def self.get(request)
        path = self.cache_path
        cached_filename = Digest::SHA1.hexdigest(request)
        file_path = File.join(path, cached_filename[0..2], cached_filename)
        if FileTest.exists?(file_path)
          File.read(file_path).chomp
        else
          nil
        end
      end
    
      def self.initialize_options(options)      
        #check for required options
        if options[:caching_options].nil?
          raise AmazonAssociate::ConfigurationError, "You must specify caching options for filesystem caching: :cache_path is required"
        end
      
        #default disk quota to 200MB
        @@disk_quota = options[:caching_options][:disk_quota] || DEFAULT_DISK_QUOTA
      
        @@sweep_frequency = options[:caching_options][:sweep_frequency] || DEFAULT_SWEEP_FREQUENCY
      
        @@cache_path = options[:caching_options][:cache_path]
      
        if @@cache_path.nil? || !File.directory?(@@cache_path)
          raise AmazonAssociate::ConfigurationError, "You must specify a cache path for filesystem caching"
        end
      
        return options
      end
    
      def self.sweep
        self.perform_sweep if must_sweep?
      end
    
      def self.disk_quota
        @@disk_quota
      end
    
      def self.sweep_frequency
        @@sweep_frequency
      end
    
      def self.cache_path
        @@cache_path
      end
    
      private
      def self.perform_sweep
        FileUtils.rm_rf(Dir.glob("#{@@cache_path}/*"))
      
        self.timestamp_sweep_performance
      end
    
      def self.timestamp_sweep_performance
        #remove the timestamp
        FileUtils.rm_rf(self.timestamp_filename)
      
        #create a new one its place
        timestamp = File.open(self.timestamp_filename, "w")
        timestamp.puts(Time.now)
        timestamp.close
      end
    
      def self.must_sweep?
        sweep_time_expired? || disk_quota_exceeded?
      end
    
      def self.sweep_time_expired?
        FileTest.exists?(timestamp_filename) && Time.parse(File.read(timestamp_filename).chomp) < Time.now - (sweep_frequency * 3600)
      end
    
      def self.disk_quota_exceeded?
        cache_size > @@disk_quota
      end
    
      def self.timestamp_filename
        File.join(self.cache_path, ".amz_timestamp")
      end
    
      def self.cache_size
        size = 0
        Find.find(@@cache_path) do|f|
           size += File.size(f) if File.file?(f)
        end
        size / 1000000
      end
    end
  end
end