asset.rb

# frozen_string_literal: true

require "digest/sha1"
require "digest/sha2"
require "action_dispatch/http/mime_type"

class Propshaft::Asset
  attr_reader :path, :logical_path, :load_path

  CONTENT_TYPES_WITH_UTF8_CHARSET = [ Mime::Type.lookup("text/html"), Mime::Type.lookup("text/css") ]

  class << self
    def extract_path_and_digest(digested_path)
      digest = digested_path[/-([0-9a-zA-Z]{7,128})\.(?!digested)([^.]|.map)+\z/, 1]
      path   = digest ? digested_path.sub("-#{digest}", "") : digested_path

      [ path, digest ]
    end
  end

  def initialize(path, logical_path:, load_path:)
    @path, @logical_path, @load_path = path, Pathname.new(logical_path), load_path
  end

  def compiled_content
    @compiled_content ||= load_path.compilers.compile(self)
  end

  def content(encoding: "ASCII-8BIT")
    File.read(path, encoding: encoding, mode: "rb")
  end

  def content_type
    @content_type ||= Mime::Type.lookup_by_extension(logical_path.extname.from(1))
  end

  def app?
    path.to_s.start_with?(*load_path.app_paths)
  end

  def content_type_with_charset
    if content_type.in? CONTENT_TYPES_WITH_UTF8_CHARSET
      "#{content_type}; charset=utf-8"
    else
      content_type
    end
  end

  def length
    content.size
  end

  def digest
    @digest ||= Digest::SHA1.hexdigest("#{content_with_compile_references}#{load_path.version}").first(8)
  end

  def integrity(hash_algorithm:)
    # Following the Subresource Integrity spec draft
    # https://w3c.github.io/webappsec-subresource-integrity/
    # allowing only sha256, sha384, and sha512
    bitlen = case hash_algorithm
    when "sha256"
        256
    when "sha384"
        384
    when "sha512"
        512
    else
        raise(StandardError.new("Subresource Integrity hash algorithm must be one of SHA2 family (sha256, sha384, sha512)"))
    end

    [ hash_algorithm, Digest::SHA2.new(bitlen).base64digest(compiled_content) ].join("-")
  end

  def digested_path
    if already_digested?
      logical_path
    else
      logical_path.sub(/\.(\w+(\.map)?)$/) { |ext| "-#{digest}#{ext}" }
    end
  end

  def fresh?(digest)
    self.digest == digest || already_digested?
  end

  def ==(other_asset)
    logical_path.hash == other_asset.logical_path.hash
  end

  private
    def content_with_compile_references
      content + load_path.find_referenced_by(self).collect(&:content).join
    end

    def already_digested?
      logical_path.to_s =~ /-([0-9a-zA-Z_-]{7,128})\.digested/
    end
end