aboutsummaryrefslogtreecommitdiffstats
path: root/activestorage/app/models/active_storage/blob.rb
blob: 04f9dbff9fb78e73b3b6cff360f457cec8290f58 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
# frozen_string_literal: true

require "active_storage/downloader"

# A blob is a record that contains the metadata about a file and a key for where that file resides on the service.
# Blobs can be created in two ways:
#
# 1. Subsequent to the file being uploaded server-side to the service via <tt>create_after_upload!</tt>.
# 2. Ahead of the file being directly uploaded client-side to the service via <tt>create_before_direct_upload!</tt>.
#
# The first option doesn't require any client-side JavaScript integration, and can be used by any other back-end
# service that deals with files. The second option is faster, since you're not using your own server as a staging
# point for uploads, and can work with deployments like Heroku that do not provide large amounts of disk space.
#
# Blobs are intended to be immutable in as-so-far as their reference to a specific file goes. You're allowed to
# update a blob's metadata on a subsequent pass, but you should not update the key or change the uploaded file.
# If you need to create a derivative or otherwise change the blob, simply create a new blob and purge the old one.
class ActiveStorage::Blob < ActiveRecord::Base
  require_dependency "active_storage/blob/analyzable"
  require_dependency "active_storage/blob/identifiable"
  require_dependency "active_storage/blob/representable"

  include Analyzable
  include Identifiable
  include Representable

  self.table_name = "active_storage_blobs"

  has_secure_token :key
  store :metadata, accessors: [ :analyzed, :identified ], coder: ActiveRecord::Coders::JSON

  class_attribute :service

  has_many :attachments

  scope :unattached, -> { left_joins(:attachments).where(ActiveStorage::Attachment.table_name => { blob_id: nil }) }

  before_destroy(prepend: true) do
    raise ActiveRecord::InvalidForeignKey if attachments.exists?
  end

  class << self
    # You can use the signed ID of a blob to refer to it on the client side without fear of tampering.
    # This is particularly helpful for direct uploads where the client-side needs to refer to the blob
    # that was created ahead of the upload itself on form submission.
    #
    # The signed ID is also used to create stable URLs for the blob through the BlobsController.
    def find_signed(id)
      find ActiveStorage.verifier.verify(id, purpose: :blob_id)
    end

    # Returns a new, unsaved blob instance after the +io+ has been uploaded to the service.
    # When providing a content type, pass <tt>identify: false</tt> to bypass automatic content type inference.
    def build_after_upload(io:, filename:, content_type: nil, metadata: nil, identify: true)
      new(filename: filename, content_type: content_type, metadata: metadata).tap do |blob|
        blob.upload(io, identify: identify)
      end
    end

    def build_after_unfurling(io:, filename:, content_type: nil, metadata: nil, identify: true) #:nodoc:
      new(filename: filename, content_type: content_type, metadata: metadata).tap do |blob|
        blob.unfurl(io, identify: identify)
      end
    end

    # Returns a saved blob instance after the +io+ has been uploaded to the service. Note, the blob is first built,
    # then the +io+ is uploaded, then the blob is saved. This is done this way to avoid uploading (which may take
    # time), while having an open database transaction.
    # When providing a content type, pass <tt>identify: false</tt> to bypass automatic content type inference.
    def create_after_upload!(io:, filename:, content_type: nil, metadata: nil, identify: true)
      build_after_upload(io: io, filename: filename, content_type: content_type, metadata: metadata, identify: identify).tap(&:save!)
    end

    # Returns a saved blob _without_ uploading a file to the service. This blob will point to a key where there is
    # no file yet. It's intended to be used together with a client-side upload, which will first create the blob
    # in order to produce the signed URL for uploading. This signed URL points to the key generated by the blob.
    # Once the form using the direct upload is submitted, the blob can be associated with the right record using
    # the signed ID.
    def create_before_direct_upload!(filename:, byte_size:, checksum:, content_type: nil, metadata: nil)
      create! filename: filename, byte_size: byte_size, checksum: checksum, content_type: content_type, metadata: metadata
    end
  end

  # Returns a signed ID for this blob that's suitable for reference on the client-side without fear of tampering.
  # It uses the framework-wide verifier on <tt>ActiveStorage.verifier</tt>, but with a dedicated purpose.
  def signed_id
    ActiveStorage.verifier.generate(id, purpose: :blob_id)
  end

  # Returns the key pointing to the file on the service that's associated with this blob. The key is in the
  # standard secure-token format from Rails. So it'll look like: XTAPjJCJiuDrLk3TmwyJGpUo. This key is not intended
  # to be revealed directly to the user. Always refer to blobs using the signed_id or a verified form of the key.
  def key
    # We can't wait until the record is first saved to have a key for it
    self[:key] ||= self.class.generate_unique_secure_token
  end

  # Returns an ActiveStorage::Filename instance of the filename that can be
  # queried for basename, extension, and a sanitized version of the filename
  # that's safe to use in URLs.
  def filename
    ActiveStorage::Filename.new(self[:filename])
  end

  # Returns true if the content_type of this blob is in the image range, like image/png.
  def image?
    content_type.start_with?("image")
  end

  # Returns true if the content_type of this blob is in the audio range, like audio/mpeg.
  def audio?
    content_type.start_with?("audio")
  end

  # Returns true if the content_type of this blob is in the video range, like video/mp4.
  def video?
    content_type.start_with?("video")
  end

  # Returns true if the content_type of this blob is in the text range, like text/plain.
  def text?
    content_type.start_with?("text")
  end


  # Returns the URL of the blob on the service. This URL is intended to be short-lived for security and not used directly
  # with users. Instead, the +service_url+ should only be exposed as a redirect from a stable, possibly authenticated URL.
  # Hiding the +service_url+ behind a redirect also gives you the power to change services without updating all URLs. And
  # it allows permanent URLs that redirect to the +service_url+ to be cached in the view.
  def service_url(expires_in: ActiveStorage.service_urls_expire_in, disposition: :inline, filename: nil, **options)
    filename = ActiveStorage::Filename.wrap(filename || self.filename)

    service.url key, expires_in: expires_in, filename: filename, content_type: content_type_for_service_url,
      disposition: forced_disposition_for_service_url || disposition, **options
  end

  # Returns a URL that can be used to directly upload a file for this blob on the service. This URL is intended to be
  # short-lived for security and only generated on-demand by the client-side JavaScript responsible for doing the uploading.
  def service_url_for_direct_upload(expires_in: ActiveStorage.service_urls_expire_in)
    service.url_for_direct_upload key, expires_in: expires_in, content_type: content_type, content_length: byte_size, checksum: checksum
  end

  # Returns a Hash of headers for +service_url_for_direct_upload+ requests.
  def service_headers_for_direct_upload
    service.headers_for_direct_upload key, filename: filename, content_type: content_type, content_length: byte_size, checksum: checksum
  end


  # Uploads the +io+ to the service on the +key+ for this blob. Blobs are intended to be immutable, so you shouldn't be
  # using this method after a file has already been uploaded to fit with a blob. If you want to create a derivative blob,
  # you should instead simply create a new blob based on the old one.
  #
  # Prior to uploading, we compute the checksum, which is sent to the service for transit integrity validation. If the
  # checksum does not match what the service receives, an exception will be raised. We also measure the size of the +io+
  # and store that in +byte_size+ on the blob record. The content type is automatically extracted from the +io+ unless
  # you specify a +content_type+ and pass +identify+ as false.
  #
  # Normally, you do not have to call this method directly at all. Use the factory class methods of +build_after_upload+
  # and +create_after_upload!+.
  def upload(io, identify: true)
    unfurl io, identify: identify
    upload_without_unfurling io
  end

  def unfurl(io, identify: true) #:nodoc:
    self.checksum     = compute_checksum_in_chunks(io)
    self.content_type = extract_content_type(io) if content_type.nil? || identify
    self.byte_size    = io.size
    self.identified   = true
  end

  def upload_without_unfurling(io) #:nodoc:
    service.upload key, io, checksum: checksum, **service_metadata
  end

  # Downloads the file associated with this blob. If no block is given, the entire file is read into memory and returned.
  # That'll use a lot of RAM for very large files. If a block is given, then the download is streamed and yielded in chunks.
  def download(&block)
    service.download key, &block
  end

  # Downloads the blob to a tempfile on disk. Yields the tempfile.
  #
  # The tempfile's name is prefixed with +ActiveStorage-+ and the blob's ID. Its extension matches that of the blob.
  #
  # By default, the tempfile is created in <tt>Dir.tmpdir</tt>. Pass +tempdir:+ to create it in a different directory:
  #
  #   blob.open(tempdir: "/path/to/tmp") do |file|
  #     # ...
  #   end
  #
  # The tempfile is automatically closed and unlinked after the given block is executed.
  #
  # Raises ActiveStorage::IntegrityError if the downloaded data does not match the blob's checksum.
  def open(tempdir: nil, &block)
    ActiveStorage::Downloader.new(self, tempdir: tempdir).download_blob_to_tempfile(&block)
  end


  # Deletes the files on the service associated with the blob. This should only be done if the blob is going to be
  # deleted as well or you will essentially have a dead reference. It's recommended to use #purge and #purge_later
  # methods in most circumstances.
  def delete
    service.delete(key)
    service.delete_prefixed("variants/#{key}/") if image?
  end

  # Deletes the file on the service and then destroys the blob record. This is the recommended way to dispose of unwanted
  # blobs. Note, though, that deleting the file off the service will initiate a HTTP connection to the service, which may
  # be slow or prevented, so you should not use this method inside a transaction or in callbacks. Use #purge_later instead.
  def purge
    destroy
    delete
  rescue ActiveRecord::InvalidForeignKey
  end

  # Enqueues an ActiveStorage::PurgeJob to call #purge. This is the recommended way to purge blobs from a transaction,
  # an Active Record callback, or in any other real-time scenario.
  def purge_later
    ActiveStorage::PurgeJob.perform_later(self)
  end

  private
    def compute_checksum_in_chunks(io)
      Digest::MD5.new.tap do |checksum|
        while chunk = io.read(5.megabytes)
          checksum << chunk
        end

        io.rewind
      end.base64digest
    end

    def extract_content_type(io)
      Marcel::MimeType.for io, name: filename.to_s, declared_type: content_type
    end

    def forcibly_serve_as_binary?
      ActiveStorage.content_types_to_serve_as_binary.include?(content_type)
    end

    def allowed_inline?
      ActiveStorage.content_types_allowed_inline.include?(content_type)
    end

    def content_type_for_service_url
      forcibly_serve_as_binary? ? ActiveStorage.binary_content_type : content_type
    end

    def forced_disposition_for_service_url
      if forcibly_serve_as_binary? || !allowed_inline?
        :attachment
      end
    end

    def service_metadata
      if forcibly_serve_as_binary?
        { content_type: ActiveStorage.binary_content_type, disposition: :attachment, filename: filename }
      elsif !allowed_inline?
        { content_type: content_type, disposition: :attachment, filename: filename }
      else
        { content_type: content_type }
      end
    end

    ActiveSupport.run_load_hooks(:active_storage_blob, self)
end