Support extension priorities

lib/mime/type.rb

@@ -102,7 +102,7 @@ def to_s
   # :stopdoc:
   # TODO verify mime-type character restrictions; I am pretty sure that this is
   # too wide open.
-  MEDIA_TYPE_RE = %r{([-\w.+]+)/([-\w.+]*)}.freeze
+  MEDIA_TYPE_RE = %r{([a-zA-Z][-a-zA-Z0-9+_.]*)/([a-zA-Z0-9][-a-zA-Z0-9+_.]*)}.freeze
   I18N_RE = /[^[:alnum:]]/.freeze
   BINARY_ENCODINGS = %w[base64 8bit].freeze
   ASCII_ENCODINGS = %w[7bit quoted-printable].freeze
@@ -131,6 +131,7 @@ def initialize(content_type) # :yields: self
     @friendly = {}
     @obsolete = @registered = @provisional = false
     @preferred_extension = @docs = @use_instead = @__sort_priority = nil
+    self.__extension_priorities
 
     self.extensions = []
 
@@ -302,7 +303,7 @@ def add_extensions(*extensions)
   # exceptions defined, the first extension will be used.
   #
   # When setting #preferred_extensions, if #extensions does not contain this
-  # extension, this will be added to #xtensions.
+  # extension, this will be added to #extensions.
   #
   # :attr_accessor: preferred_extension
 
@@ -313,10 +314,31 @@ def preferred_extension
 
   ##
   def preferred_extension=(value) # :nodoc:
-    add_extensions(value) if value
+    if value
+      add_extensions(value)
+      set_preferred_extension_priority(value)
+    else
+      clear_extension_priority(@preferred_extension)
+    end
     @preferred_extension = value
   end
 
+  ##
+  # Optional extension priorities for this MIME type. This is a relative value
+  # similar to nice(1). An explicitly set `preferred_extension` is automatically
+  # given a relative priority of `-10`.
+  #
+  # :attr_reader: extension_priorities
+  attr_accessor :extension_priorities
+
+  ##
+  # Returns the priority for the provided extension or extensions. If a priority
+  # is not set, the default priority is 0. The range for priorities is -20..20,
+  # inclusive.
+  def extension_priority(*exts)
+    exts.map { |ext| get_extension_priority(ext) }.min
+  end
+
   ##
   # The encoding (+7bit+, +8bit+, <tt>quoted-printable</tt>, or +base64+)
   # required to transport the data of this content type safely across a
@@ -537,7 +559,8 @@ def encode_with(coder)
     coder["registered"] = registered?
     coder["provisional"] = provisional? if provisional?
     coder["signature"] = signature? if signature?
-    coder["__sort_priority"] = __sort_priority
+    coder["sort-priority"] = __sort_priority
+    coder["extension-priorities"] = __extension_priorities unless __extension_priorities.empty?
     coder
   end
 
@@ -546,6 +569,7 @@ def encode_with(coder)
   #
   # This method should be considered a private implementation detail.
   def init_with(coder)
+    @__sort_priority = 0
     self.content_type = coder["content-type"]
     self.docs = coder["docs"] || ""
     self.encoding = coder["encoding"]
@@ -557,9 +581,11 @@ def init_with(coder)
     self.signature = coder["signature"]
     self.xrefs = coder["xrefs"] || {}
     self.use_instead = coder["use-instead"]
-    @__sort_priority = coder["__sort_priority"]
+    self.extension_priorities = coder["extension-priorities"]
 
     friendly(coder["friendly"] || {})
+
+    update_sort_priority
   end
 
   def inspect # :nodoc:
@@ -615,6 +641,22 @@ def simplify_matchdata(matchdata, remove_x = false, joiner: "/")
 
   private
 
+  def __extension_priorities
+    @extension_priorities ||= {}
+  end
+
+  def clear_extension_priority(ext)
+    __extension_priorities.delete(ext) if ext
+  end
+
+  def get_extension_priority(ext)
+    [[-20, __extension_priorities[ext] || 0].max, 20].min
+  end
+
+  def set_preferred_extension_priority(ext)
+    __extension_priorities[ext] = -10 unless __extension_priorities.has_key?(ext)
+  end
+
   def clear_sort_priority
     @__sort_priority = nil
   end

lib/mime/type/columnar.rb

@@ -39,6 +39,7 @@ def self.column(*methods, file: nil) # :nodoc:
     :signature?, :provisional, :provisional=, :provisional?, file: "flags"
   column :xrefs, :xrefs=, :xref_urls
   column :use_instead, :use_instead=
+  column :extension_priorities, :extension_priorities=
 
   def encode_with(coder) # :nodoc:
     @container.send(:load_friendly)
@@ -48,6 +49,7 @@ def encode_with(coder) # :nodoc:
     @container.send(:load_use_instead)
     @container.send(:load_xrefs)
     @container.send(:load_preferred_extension)
+    @container.send(:load_extension_priorities)
     super
   end
 

lib/mime/types.rb

@@ -151,10 +151,18 @@ def [](type_id, complete: false, registered: false)
   #   puts MIME::Types.type_for(%w(citydesk.xml citydesk.gif))
   #     => [application/xml, image/gif, text/xml]
   def type_for(filename)
-    Array(filename).flat_map { |fn|
-      @extension_index[fn.chomp.downcase[/\.?([^.]*?)$/, 1]]
+    extensions = Array(filename).map { |fn| fn.chomp.downcase[/\.?([^.]*?)$/, 1] }
+
+    extensions.flat_map { |ext|
+      @extension_index[ext]
     }.compact.inject(Set.new, :+).sort { |a, b|
-      a.priority_compare(b)
+      by_ext = a.extension_priority(*extensions) <=> b.extension_priority(*extensions)
+
+      if by_ext.zero?
+        a.priority_compare(b)
+      else
+        by_ext
+      end
     }
   end
   alias_method :of, :type_for

lib/mime/types/_columnar.rb

@@ -91,7 +91,7 @@ def load_flags
 
   def load_xrefs
     each_file_line("xrefs") { |type, line|
-      type.instance_variable_set(:@xrefs, dict(line, array: true))
+      type.instance_variable_set(:@xrefs, dict(line, transform: :array))
     }
   end
 
@@ -107,18 +107,47 @@ def load_use_instead
     end
   end
 
-  def dict(line, array: false)
+  def load_extension_priorities
+    each_file_line("extpri") do |type, line|
+      type.instance_variable_set(:@extension_priorities, dict(line, transform: :extension_priority))
+    end
+  rescue
+    # This path preserves backwards compatibility.
+  end
+
+  def dict(line, transform: nil)
     if line == "-"
       {}
     else
       line.split("|").each_with_object({}) { |l, h|
         k, v = l.split("^")
         v = nil if v.empty?
-        h[k] = array ? Array(v) : v
+
+        if transform
+          send(:"dict_#{transform}", h, k, v)
+        else
+          h[k] = v
+        end
       }
     end
   end
 
+  def dict_extension_priority(h, k, v)
+    return if v.nil?
+
+    v = v.to_i if v.kind_of?(String)
+    v = v.trunc if v.kind_of?(Float)
+    v =  [[-20, v].max, 20].min
+
+    return if v.zero?
+
+    h[k] = v
+  end
+
+  def dict_array(h, k, v)
+    h[k] = Array(v)
+  end
+
   def arr(line)
     if line == "-"
       []