file_grabber.rb

# FileGrabber
# Designed for downloading, unzipping, saving, and tidying of affiliate window product feeds.
# -------------------------------------------------------------------------------------------
# Usage: @foo = FileGrabber.new(url: "product-feed-url")
# Optional agrs:
# 	folder_name (sets the name of the folder which contains the downloaded files)
# 	folder_path (sets where to store the downloaded files)
# 	trim (how many downloads do you want to keep saved? The rest will be deleted)

class FileGrabber

	def initialize(args={})
		load_settings
		
		@url 			= args[:url] # url of the product feed
		@extension		= args[:extension] ||= @default_extension # should be .csv.gz for affiliate window product feeds
		@folder_name 	= args[:folder_name] ||= @default_folder_name # name of the local folder in which to store the file
		@folder_path 	= args[:folder_path] ||= @default_folder_path # pathway leading to the folder
		@name 			= args[:name] ||= @default_name # name of the file not including any time stamps
		@trim 			= args[:trim] ||= @default_trim # how many files allowed in the folder before we delete old ones
		
		@path 			= make_path # /app/assets/filegrabs
		@full_path		= make_full_path # /app/assets/filegrabs/grab001.csv
		@timestamp 		= make_timestamp # unix timestamp to be appended to file name
		@filename 		= make_filename

		validate_args
		validate_path

		if valid?
			download_file
			unzip_and_save
			delete_old_files
		else
			puts "FileGrabber didn't start because of a validation error."
			
		end
	end

	def valid?
		if has_errors?
			false
		else
			true
		end
	end

	def display_errors
		# Prints out each error
		# - See errors if you just want an array of the errors instead.
		@errors.each do |e|
			puts "FileGrabber error: #{e}"
		end
	end

	def errors
		# Returns an array of errors
		# - See display_errors if you're too lazy to puts them out.
		@errors
	end

	private

	def make_filename
		# => 10510987-grabbedfile
		"#{@timestamp}-#{@name}"
	end

	def make_full_path
		# = /home/al/sites/app/filegrabber/assorted/10510987-grabbedfile.csv
		"#{@path}#{@filename}"
	end

	def delete_old_files
		# Deletes old files from the path
		# - Hopefully it doesn't become self aware and delete all of the files ._.
		delete_count = list_files.count - @trim
		list_files.first(delete_count).each do |f|
			if f.include?(@name) # just to prevent accidentally deleting files that are not grabbed files
				File.delete("#{@path}#{f}")
				puts "Deleted #{@path}#{f}"
			end
		end
	end

	def list_files
		# Looks in the path and returns a list of file names, newest files first
		files = Dir.glob("#{@path}*")
		results = []
		files.each do |f|
			results << f.split("/").last
		end
		results.sort
	end

	def make_timestamp
		# Unix timestamp for appending to the file name
		Time.now.to_i
	end

	def validate_path
		# Makes sure there is a folder to save files to
		# - Not strictly speaking a validation as it won't return a boolean
		unless File.directory?(@path)
			create_folder
		end
	end

	def create_folder
		# Creates a folder for saving files to if one doesn't already exist.
		require 'fileutils'
		FileUtils::mkdir_p @path
	end

	def download_file
		# Not sure what will happen if the file is not downloaded correctly?
		# - maybe something to add in the future.
		require 'open-uri'
		@download = open(@url)
	end

	def save_file
		# Not any use for Affiliate window feeds as they are all zipped up
		# - use unzip_and_save instead.
		IO.copy_stream(@download, "#{@path}#{@filename}")
	end

	def unzip_and_save
		gz = Zlib::GzipReader.new(@download)
		csv = gz.read
		File.write("#{@path}/#{@filename}.csv", csv)
		gz.close
	end

	def load_settings
		@errors = [] # Empty array for filling up with error messages
		@default_folder_name 	= "assorted"
		@default_folder_path 	= "filegrabber"
		@file_name 				= "worksmate.png"
		@default_name 			= "grabbedfile"
		@default_trim 		 	= 3
		@default_extension 		= ".csv.gz"
	end

	def validate_args
		# validate args
		validate_url
	end

	def validate_url
		# FileGrabber needs at least a URL to kick things off
		# - foo = FileGrabber.new(url: "www.my-product-feed.com")
		if @url.blank?
			@errors << "URL was left blank."
		end
	end

	def has_errors?
		# Because we can't use the built in rails validations we shall roll our own.
		@errors.any?
	end

	def make_path
		# make path
		"#{Rails.root}/#{@folder_path}/#{@folder_name}/"
	end

end