Add helper method for finding icons

closes #3

lib/manifique/metadata.rb

@@ -1,3 +1,4 @@
+require "pry"
 module Manifique
   class Metadata
 
@@ -22,9 +23,56 @@ module Manifique
       end
     end
 
+    def select_icon(options={})
+      if options[:type].nil? && options[:sizes].nil? && options[:purpose].nil?
+        raise ArgumentError, "Tell me what to do!"
+      end
+
+      results = icons
+
+      if options[:purpose]
+        results.reject! { |r| r["purpose"] != options[:purpose] }
+      else
+        # Do not return special icons by default
+        results.reject! { |r| r["purpose"] }
+      end
+
+      if options[:type]
+        results.reject! { |r| r["type"] != options[:type] }
+      end
+
+      if options[:sizes]
+        results.reject! { |r| r["sizes"].nil? }
+        results.sort!   { |a, b| sizes_to_i(b["sizes"]) <=> sizes_to_i(a["sizes"]) }
+
+        if icon = select_exact_size(results, options[:sizes])
+          return icon
+        else
+          return select_best_size(results, options[:sizes])
+        end
+      end
+
+      results.first
+    end
+
     def to_json
       # TODO serialize into JSON
     end
 
+    private
+
+    def sizes_to_i(str)
+      str.match(/(\d+)x/)[1].to_i
+    end
+
+    def select_exact_size(results, sizes)
+      results.select{|r| r["sizes"] == sizes}[0]
+    end
+
+    def select_best_size(results, sizes)
+      results.reject! { |r| sizes_to_i(r["sizes"]) < sizes_to_i(sizes) }
+      results.last
+    end
+
   end
 end

spec/manifique/metadata_spec.rb

@@ -38,4 +38,68 @@ RSpec.describe Manifique::Metadata do
     end
   end
 
+  describe "#select_icon" do
+    let(:metadata) { Manifique::Metadata.new }
+
+    before do
+      metadata.icons = icon_fixtures
+    end
+
+    it "expects at least one filter option" do
+      expect { metadata.select_icon }.to raise_error(ArgumentError)
+    end
+
+    describe "by purpose" do
+      it "returns the correct icon" do
+        icon = metadata.select_icon(purpose: "mask-icon")
+        expect(icon["src"]).to eq("/mask-icon.svg")
+      end
+    end
+
+    describe "by type" do
+      it "returns the largest image of the type" do
+        icon = metadata.select_icon(type: "image/png")
+        expect(icon["sizes"]).to eq("512x512")
+      end
+    end
+
+    describe "by size" do
+      it "returns the exact size when available" do
+        icon = metadata.select_icon(sizes: "256x256")
+        expect(icon["sizes"]).to eq("256x256")
+      end
+
+      it "returns the icon with the closest (but larger) size" do
+        icon = metadata.select_icon(sizes: "180x180")
+        expect(icon["sizes"]).to eq("192x192")
+      end
+    end
+
+    describe "special purpose by size" do
+      it "returns the exact size when available" do
+        icon = metadata.select_icon(purpose: "apple-touch-icon", sizes: "180x180")
+        expect(icon["sizes"]).to eq("180x180")
+      end
+
+      it "returns the icon with the closest (but larger) size" do
+        icon = metadata.select_icon(purpose: "apple-touch-icon", sizes: "44x44")
+        expect(icon["sizes"]).to eq("57x57")
+      end
+    end
+  end
+
+end
+
+def icon_fixtures
+  [
+    {"src"=>"/favicon.ico", "sizes"=>nil, "type"=>"image/x-icon"},
+    {"src"=>"/application_icon_x512.png", "sizes"=>"512x512", "type"=>"image/png"},
+    {"src"=>"/application_icon_x256.png", "sizes"=>"256x256", "type"=>"image/png"},
+    {"src"=>"/application_icon_x228.png", "sizes"=>"228x228", "type"=>"image/png"},
+    {"src"=>"/application_icon_x196.png", "sizes"=>"196x196", "type"=>"image/png"},
+    {"src"=>"/application_icon_x192.png", "sizes"=>"192x192", "type"=>"image/png"},
+    {"purpose"=>"apple-touch-icon", "src"=>"/apple-touch-icon.png", "sizes"=>"180x180", "type"=>"image/png" },
+    {"purpose"=>"apple-touch-icon", "src"=>"/apple-touch-icon-57px.png", "sizes"=>"57x57", "type"=>"image/png"},
+    {"purpose"=>"mask-icon", "src"=>"/mask-icon.svg", "type"=>"image/svg", "color"=>"#2b90d9"}
+  ]
 end