require "cognac/version"
require 'active_support/core_ext/numeric/time'
require "erb"

module Cognac
  
  class CloudFile
    def self.generate(file_name)
      "#{SecureRandom.hex(4).to_s}_#{file_name}"
    end
    
    def self.resource_end_point(bucket, file_name)
      "http://#{bucket}.s3.amazonaws.com/#{file_name}"
    end
  end
  
  # AWS Signature Version 2 : http://docs.aws.amazon.com/AmazonS3/latest/dev/RESTAuthentication.html
  class Signature
    NEW_LINE = "\n"
    
    def self.build_string_to_sign(options = {})
      options = {
        http_verb:     "PUT",
        content_md5:   nil,
        content_type:  nil,
        date:          an_hour_from_now,
        amz_headers:   [],
        resource:      ""
      }.merge(options)

      add_new_line(options[:http_verb]) +
      add_new_line(options[:content_md5]) +
      add_new_line(options[:content_type]) +
      add_new_line(options[:date]) +
      (options[:amz_headers].any? ? (options[:amz_headers].join(NEW_LINE) + NEW_LINE) : "") +
      options[:resource]
   end
   
   def self.build_s3_rest_signature(secret_access_key, options = {})
      s = build_string_to_sign(options).force_encoding("UTF-8")
      Base64.encode64(OpenSSL::HMAC.digest("sha1", secret_access_key, s)).strip
   end
   
   def self.build_s3_upload_url(end_point, aws_access_key, secret_access_key, signature_options = {})
     signature = encoded_signature(secret_access_key, signature_options)
     expires = expiration(signature_options)
     "#{end_point}?AWSAccessKeyId=#{aws_access_key}&Expires=#{expires}&Signature=#{signature}"     
   end
   
   def self.generate_options_for_build_s3_upload_url(bucket, file_name, content_type)
      {
         http_verb:    "PUT", 
         date:         1.hours.from_now.to_i, 
         resource:     "/#{bucket}/#{file_name}",
         content_type: content_type
      }
   end
   
   private
   
   def self.add_new_line(option)
     option.to_s + NEW_LINE
   end
   
   def self.an_hour_from_now
     1.hours.from_now.rfc822
   end
   
   def self.encoded_signature(secret_access_key, signature_options)
     ERB::Util.url_encode(build_s3_rest_signature(secret_access_key, signature_options))
   end
   
   def self.expiration(signature_options)
     signature_options[:date] || an_hour_from_now
   end
   
  end
end