Extract from Refile gem

.gitignore

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+/.bundle/
+/.yardoc
+/Gemfile.lock
+/_yardoc/
+/coverage/
+/doc/
+/pkg/
+/spec/reports/
+/tmp/
+*.bundle
+*.so
+*.o
+*.a
+mkmf.log
+s3.yml

Gemfile

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+source 'https://rubygems.org'
+
+# Specify your gem's dependencies in refile-s3.gemspec
+gemspec
+
+gem "refile", github: "refile/refile"

LICENSE.txt

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+Copyright (c) 2015 Jonas Nicklas
+
+MIT License
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

README.md

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+# Refile::S3
+
+Amazon S3 backend for the [Refile][gh] gem. See the Refile documentation for
+more details.
+
+## License
+
+[MIT](LICENSE.txt)
+
+[gh]: http://github.com/refile/refile

Rakefile

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+require "bundler/gem_tasks"
+

lib/refile/s3.rb

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+require "aws-sdk"
+require "open-uri"
+require "refile"
+require "refile/s3/version"
+
+module Refile
+  # A refile backend which stores files in Amazon S3
+  #
+  # @example
+  #   backend = Refile::Backend::S3.new(
+  #     access_key_id: "xyz",
+  #     secret_access_key: "abcd1234",
+  #     region: "sa-east-1",
+  #     bucket: "my-bucket",
+  #     prefix: "files"
+  #   )
+  #   file = backend.upload(StringIO.new("hello"))
+  #   backend.read(file.id) # => "hello"
+  class S3
+    extend Refile::BackendMacros
+
+    attr_reader :access_key_id, :max_size
+
+    # Sets up an S3 backend with the given credentials.
+    #
+    # @param [String] access_key_id
+    # @param [String] secret_access_key
+    # @param [String] region            The AWS region to connect to
+    # @param [String] bucket            The name of the bucket where files will be stored
+    # @param [String] prefix            A prefix to add to all files. Prefixes on S3 are kind of like folders.
+    # @param [Integer, nil] max_size    The maximum size of an uploaded file
+    # @param [#hash] hasher             A hasher which is used to generate ids from files
+    # @param [Hash] s3_options          Additional options to initialize S3 with
+    # @see http://docs.aws.amazon.com/AWSRubySDK/latest/AWS/Core/Configuration.html
+    # @see http://docs.aws.amazon.com/AWSRubySDK/latest/AWS/S3.html
+    def initialize(access_key_id:, secret_access_key:, region:, bucket:, max_size: nil, prefix: nil, hasher: Refile::RandomHasher.new, **s3_options)
+      @access_key_id = access_key_id
+      @secret_access_key = secret_access_key
+      @s3_options = { access_key_id: access_key_id, secret_access_key: secret_access_key, region: region }.merge s3_options
+      @s3 = Aws::S3::Resource.new @s3_options
+      @bucket_name = bucket
+      @bucket = @s3.bucket @bucket_name
+      @hasher = hasher
+      @prefix = prefix
+      @max_size = max_size
+    end
+
+    # Upload a file into this backend
+    #
+    # @param [IO] uploadable      An uploadable IO-like object.
+    # @return [Refile::File]      The uploaded file
+    verify_uploadable def upload(uploadable)
+      id = @hasher.hash(uploadable)
+
+      if uploadable.is_a?(Refile::File) and uploadable.backend.is_a?(S3) and uploadable.backend.access_key_id == access_key_id
+        object(id).copy_from(copy_source: [@bucket_name, uploadable.backend.object(uploadable.id).key].join("/"))
+      else
+        object(id).put(body: uploadable, content_length: uploadable.size)
+      end
+
+      Refile::File.new(self, id)
+    end
+
+    # Get a file from this backend.
+    #
+    # Note that this method will always return a {Refile::File} object, even
+    # if a file with the given id does not exist in this backend. Use
+    # {FileSystem#exists?} to check if the file actually exists.
+    #
+    # @param [Sring] id           The id of the file
+    # @return [Refile::File]      The retrieved file
+    verify_id def get(id)
+      Refile::File.new(self, id)
+    end
+
+    # Delete a file from this backend
+    #
+    # @param [Sring] id           The id of the file
+    # @return [void]
+    verify_id def delete(id)
+      object(id).delete
+    end
+
+    # Return an IO object for the uploaded file which can be used to read its
+    # content.
+    #
+    # @param [Sring] id           The id of the file
+    # @return [IO]                An IO object containing the file contents
+    verify_id def open(id)
+      Kernel.open(object(id).presigned_url(:get))
+    end
+
+    # Return the entire contents of the uploaded file as a String.
+    #
+    # @param [String] id           The id of the file
+    # @return [String]             The file's contents
+    verify_id def read(id)
+      object(id).get.body.read
+    rescue Aws::S3::Errors::NoSuchKey
+      nil
+    end
+
+    # Return the size in bytes of the uploaded file.
+    #
+    # @param [Sring] id           The id of the file
+    # @return [Integer]           The file's size
+    verify_id def size(id)
+      object(id).get.content_length
+    rescue Aws::S3::Errors::NoSuchKey
+      nil
+    end
+
+    # Return whether the file with the given id exists in this backend.
+    #
+    # @param [Sring] id           The id of the file
+    # @return [Boolean]
+    verify_id def exists?(id)
+      object(id).exists?
+    end
+
+    # Remove all files in this backend. You must confirm the deletion by
+    # passing the symbol `:confirm` as an argument to this method.
+    #
+    # @example
+    #   backend.clear!(:confirm)
+    # @raise [Refile::Confirm]     Unless the `:confirm` symbol has been passed.
+    # @param [:confirm] confirm    Pass the symbol `:confirm` to confirm deletion.
+    # @return [void]
+    def clear!(confirm = nil)
+      raise Refile::Confirm unless confirm == :confirm
+      @bucket.objects(prefix: @prefix).delete
+    end
+
+    # Return a presign signature which can be used to upload a file into this
+    # backend directly.
+    #
+    # @return [Refile::Signature]
+    def presign
+      id = RandomHasher.new.hash
+      signature = @bucket.presigned_post(key: [*@prefix, id].join("/"))
+      signature.content_length_range(0..@max_size) if @max_size
+      Signature.new(as: "file", id: id, url: signature.url.to_s, fields: signature.fields)
+    end
+
+    verify_id def object(id)
+      @bucket.object([*@prefix, id].join("/"))
+    end
+  end
+end

lib/refile/s3/version.rb

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+module Refile
+  class S3
+    VERSION = "0.0.1"
+  end
+end

refile-s3.gemspec

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+# coding: utf-8
+lib = File.expand_path('../lib', __FILE__)
+$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
+require 'refile/s3/version'
+
+Gem::Specification.new do |spec|
+  spec.name          = "refile-s3"
+  spec.version       = Refile::S3::VERSION
+  spec.authors       = ["Jonas Nicklas"]
+  spec.email         = ["jonas.nicklas@gmail.com"]
+  spec.summary       = "Amazon S3 backend for the Refile gem"
+  spec.homepage      = ""
+  spec.license       = "MIT"
+
+  spec.files         = `git ls-files -z`.split("\x0")
+  spec.executables   = spec.files.grep(%r{^bin/}) { |f| File.basename(f) }
+  spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
+  spec.require_paths = ["lib"]
+
+  spec.add_dependency "refile", "~> 0.5.0"
+  spec.add_dependency "aws-sdk", "~> 2.0"
+  spec.add_development_dependency "bundler", "~> 1.7"
+  spec.add_development_dependency "rake", "~> 10.0"
+  spec.add_development_dependency "rspec", "~> 3.0"
+  spec.add_development_dependency "webmock"
+end

spec/refile/s3_spec.rb

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+require "refile/spec_helper"
+require "refile/s3"
+
+WebMock.allow_net_connect!
+
+config = YAML.load_file("s3.yml").map { |k, v| [k.to_sym, v] }.to_h
+
+RSpec.describe Refile::S3 do
+  let(:backend) { Refile::S3.new(max_size: 100, **config) }
+
+  it_behaves_like :backend
+end