Add 'activestorage/' from commit '3f4a7218a4a4923a0e7ce1b2eb0d2888ce30da58'

git-subtree-dir: activestorage
git-subtree-mainline: 0d58e7e478e79c2d6b2a39a4444d2a17a903b2a6
git-subtree-split: 3f4a7218a4a4923a0e7ce1b2eb0d2888ce30da58

5 files changed, 406 insertions, 0 deletions

diff --git a/activestorage/app/models/active_storage/attachment.rb b/activestorage/app/models/active_storage/attachment.rb
new file mode 100644
index 0000000000..2c8b7a9cf2
--- /dev/null
+++ b/activestorage/app/models/active_storage/attachment.rb
@@ -0,0 +1,29 @@
+require "active_storage/blob"
+require "active_support/core_ext/module/delegation"
+
+# Attachments associate records with blobs. Usually that's a one record-many blobs relationship, 
+# but it is possible to associate many different records with the same blob. If you're doing that,
+# you'll want to declare with `has_one/many_attached :thingy, dependent: false`, so that destroying
+# any one record won't destroy the blob as well. (Then you'll need to do your own garbage collecting, though).
+class ActiveStorage::Attachment < ActiveRecord::Base
+  self.table_name = "active_storage_attachments"
+
+  belongs_to :record, polymorphic: true
+  belongs_to :blob, class_name: "ActiveStorage::Blob"
+
+  delegate_missing_to :blob
+
+  # Purging an attachment will purge the blob (delete the file on the service, then destroy the record)
+  # and then destroy the attachment itself.
+  def purge
+    blob.purge
+    destroy
+  end
+
+  # Purging an attachment means purging the blob, which means talking to the service, which means
+  # talking over the internet. Whenever you're doing that, it's a good idea to put that work in a job,
+  # so it doesn't hold up other operations. That's what #purge_later provides.
+  def purge_later
+    ActiveStorage::PurgeJob.perform_later(self)
+  end
+end
diff --git a/activestorage/app/models/active_storage/blob.rb b/activestorage/app/models/active_storage/blob.rb
new file mode 100644
index 0000000000..9208d36ee3
--- /dev/null
+++ b/activestorage/app/models/active_storage/blob.rb
@@ -0,0 +1,193 @@
+require "active_storage/service"
+require "active_storage/filename"
+require "active_storage/purge_job"
+require "active_storage/variant"
+require "active_storage/variation"
+
+# 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 #create_after_upload!
+# 2) Ahead of the file being directly uploaded client-side to the service via #create_before_direct_upload!
+#
+# 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.
+class ActiveStorage::Blob < ActiveRecord::Base
+  self.table_name = "active_storage_blobs"
+
+  has_secure_token :key
+  store :metadata, coder: JSON
+
+  class_attribute :service
+
+  class << self
+    # You can used 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.
+    def build_after_upload(io:, filename:, content_type: nil, metadata: nil)
+      new.tap do |blob|
+        blob.filename     = filename
+        blob.content_type = content_type
+        blob.metadata     = metadata
+
+        blob.upload io
+      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 doing to avoid opening a transaction and talking to
+    # the service during that (which is a bad idea and leads to deadlocks).
+    def create_after_upload!(io:, filename:, content_type: nil, metadata: nil)
+      build_after_upload(io: io, filename: filename, content_type: content_type, metadata: metadata).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 `ActiveStorage.verifier`, 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 a `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 =~ /^image/ end
+
+  # Returns true if the content_type of this blob is in the audio range, like audio/mpeg.
+  def audio?() content_type =~ /^audio/ end
+
+  # Returns true if the content_type of this blob is in the video range, like video/mp4.
+  def video?() content_type =~ /^video/ end
+
+  # Returns true if the content_type of this blob is in the text range, like text/plain.
+  def text?()  content_type =~ /^text/  end
+
+  # Returns a `ActiveStorage::Variant` instance with the set of `transformations` passed in. This is only relevant
+  # for image files, and it allows any image to be transformed for size, colors, and the like. Example:
+  #
+  #   avatar.variant(resize: "100x100").processed.service_url
+  #
+  # This will create and process a variant of the avatar blob that's constrained to a height and width of 100.
+  # Then it'll upload said variant to the service according to a derivative key of the blob and the transformations.
+  #
+  # Frequently, though, you don't actually want to transform the variant right away. But rather simply refer to a
+  # specific variant that can be created by a controller on-demand. Like so:
+  #
+  #   <%= image_tag url_for(Current.user.avatar.variant(resize: "100x100")) %>
+  #
+  # This will create a URL for that specific blob with that specific variant, which the `ActiveStorage::VariantsController`
+  # can then produce on-demand.
+  def variant(transformations)
+    ActiveStorage::Variant.new(self, ActiveStorage::Variation.new(transformations))
+  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: 5.minutes, disposition: :inline)
+    service.url key, expires_in: expires_in, disposition: disposition, filename: filename, content_type: content_type
+  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: 5.minutes)
+    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.
+  #
+  # 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)
+    self.checksum  = compute_checksum_in_chunks(io)
+    self.byte_size = io.size
+
+    service.upload(key, io, checksum: checksum)
+  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
+
+
+  # Deletes the file on the service that's associated with this 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 the `#purge` and `#purge_later`
+  # methods in most circumstances.
+  def delete
+    service.delete key
+  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
+    delete
+    destroy
+  end
+
+  # Enqueues a `ActiveStorage::PurgeJob` job that'll call `#purge`. This is the recommended way to purge blobs when the call
+  # needs to be made from a transaction, a callback, or 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
+end
diff --git a/activestorage/app/models/active_storage/filename.rb b/activestorage/app/models/active_storage/filename.rb
new file mode 100644
index 0000000000..35f4a8ac59
--- /dev/null
+++ b/activestorage/app/models/active_storage/filename.rb
@@ -0,0 +1,49 @@
+# Encapsulates a string representing a filename to provide convenience access to parts of it and a sanitized version.
+# This is what's returned by `ActiveStorage::Blob#filename`. A Filename instance is comparable so it can be used for sorting.
+class ActiveStorage::Filename
+  include Comparable
+
+  def initialize(filename)
+    @filename = filename
+  end
+
+  # Filename.new("racecar.jpg").extname # => ".jpg"
+  def extname
+    File.extname(@filename)
+  end
+
+  # Filename.new("racecar.jpg").extension # => "jpg"
+  def extension
+    extname.from(1)
+  end
+
+  # Filename.new("racecar.jpg").base # => "racecar"
+  def base
+    File.basename(@filename, extname)
+  end
+
+  # Filename.new("foo:bar.jpg").sanitized # => "foo-bar.jpg"
+  # Filename.new("foo/bar.jpg").sanitized # => "foo-bar.jpg"
+  #
+  # ...and any other character unsafe for URLs or storage is converted or stripped.
+  def sanitized
+    @filename.encode(Encoding::UTF_8, invalid: :replace, undef: :replace, replace: "�").strip.tr("\u{202E}%$|:;/\t\r\n\\", "-")
+  end
+
+  # Returns the sanitized version of the filename.
+  def to_s
+    sanitized.to_s
+  end
+
+  def as_json(*)
+    to_s
+  end
+
+  def to_json
+    to_s
+  end
+
+  def <=>(other)
+    to_s.downcase <=> other.to_s.downcase
+  end
+end
diff --git a/activestorage/app/models/active_storage/variant.rb b/activestorage/app/models/active_storage/variant.rb
new file mode 100644
index 0000000000..a8e64f781e
--- /dev/null
+++ b/activestorage/app/models/active_storage/variant.rb
@@ -0,0 +1,82 @@
+require "active_storage/blob"
+
+# Image blobs can have variants that are the result of a set of transformations applied to the original.
+# These variants are used to create thumbnails, fixed-size avatars, or any other derivative image from the
+# original.
+#
+# Variants rely on `MiniMagick` for the actual transformations of the file, so you must add `gem "mini_magick"`
+# to your Gemfile if you wish to use variants.
+#
+# Note that to create a variant it's necessary to download the entire blob file from the service and load it
+# into memory. The larger the image, the more memory is used. Because of this process, you also want to be
+# considerate about when the variant is actually processed. You shouldn't be processing variants inline in a
+# template, for example. Delay the processing to an on-demand controller, like the one provided in
+# `ActiveStorage::VariantsController`.
+#
+# To refer to such a delayed on-demand variant, simply link to the variant through the resolved route provided
+# by Active Storage like so:
+#
+#   <%= image_tag url_for(Current.user.avatar.variant(resize: "100x100")) %>
+#
+# This will create a URL for that specific blob with that specific variant, which the `ActiveStorage::VariantsController`
+# can then produce on-demand.
+#
+# When you do want to actually produce the variant needed, call `#processed`. This will check that the variant
+# has already been processed and uploaded to the service, and, if so, just return that. Otherwise it will perform
+# the transformations, upload the variant to the service, and return itself again. Example:
+#
+#   avatar.variant(resize: "100x100").processed.service_url
+#
+# This will create and process a variant of the avatar blob that's constrained to a height and width of 100.
+# Then it'll upload said variant to the service according to a derivative key of the blob and the transformations.
+#
+# A list of all possible transformations is available at https://www.imagemagick.org/script/mogrify.php. You can
+# combine as many as you like freely:
+#
+#   avatar.variant(resize: "100x100", monochrome: true, flip: "-90")
+class ActiveStorage::Variant
+  attr_reader :blob, :variation
+  delegate :service, to: :blob
+
+  def initialize(blob, variation)
+    @blob, @variation = blob, variation
+  end
+
+  # Returns the variant instance itself after it's been processed or an existing processing has been found on the service.
+  def processed
+    process unless processed?
+    self
+  end
+
+  # Returns a combination key of the blob and the variation that together identifies a specific variant.
+  def key
+    "variants/#{blob.key}/#{variation.key}"
+  end
+
+  # Returns the URL of the variant 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 redirec to the `service_url` to be cached in the view.
+  #
+  # Use `url_for(variant)` (or the implied form, like `link_to variant` or `redirect_to variant`) to get the stable URL
+  # for a variant that points to the `ActiveStorage::VariantsController`, which in turn will use this `#service_call` method
+  # for its redirection.
+  def service_url(expires_in: 5.minutes, disposition: :inline)
+    service.url key, expires_in: expires_in, disposition: disposition, filename: blob.filename, content_type: blob.content_type
+  end
+
+
+  private
+    def processed?
+      service.exist?(key)
+    end
+
+    def process
+      service.upload key, transform(service.download(blob.key))
+    end
+
+    def transform(io)
+      require "mini_magick"
+      File.open MiniMagick::Image.read(io).tap { |image| variation.transform(image) }.path
+    end
+end
diff --git a/activestorage/app/models/active_storage/variation.rb b/activestorage/app/models/active_storage/variation.rb
new file mode 100644
index 0000000000..34b854fd9f
--- /dev/null
+++ b/activestorage/app/models/active_storage/variation.rb
@@ -0,0 +1,53 @@
+require "active_support/core_ext/object/inclusion"
+
+# A set of transformations that can be applied to a blob to create a variant. This class is exposed via 
+# the `ActiveStorage::Blob#variant` method and should rarely be used directly.
+#
+# In case you do need to use this directly, it's instantiated using a hash of transformations where
+# the key is the command and the value is the arguments. Example:
+#
+#   ActiveStorage::Variation.new(resize: "100x100", monochrome: true, trim: true, rotate: "-90")
+#
+# A list of all possible transformations is available at https://www.imagemagick.org/script/mogrify.php.
+class ActiveStorage::Variation
+  attr_reader :transformations
+
+  class << self
+    # Returns a variation instance with the transformations that were encoded by `#encode`.
+    def decode(key)
+      new ActiveStorage.verifier.verify(key, purpose: :variation)
+    end
+
+    # Returns a signed key for the `transformations`, which can be used to refer to a specific
+    # variation in a URL or combined key (like `ActiveStorage::Variant#key`).
+    def encode(transformations)
+      ActiveStorage.verifier.generate(transformations, purpose: :variation)
+    end
+  end
+
+  def initialize(transformations)
+    @transformations = transformations
+  end
+
+  # Accepts an open MiniMagick image instance, like what's return by `MiniMagick::Image.read(io)`,
+  # and performs the `transformations` against it. The transformed image instance is then returned.
+  def transform(image)
+    transformations.each do |(method, argument)|
+      if eligible_argument?(argument)
+        image.public_send(method, argument)
+      else
+        image.public_send(method)
+      end
+    end
+  end
+
+  # Returns a signed key for all the `transformations` that this variation was instantiated with.
+  def key
+    self.class.encode(transformations)
+  end
+
+  private
+    def eligible_argument?(argument)
+      argument.present? && argument != true
+    end
+end