Added download manager, added excon dependency

cyberarm_engine.gemspec

@@ -28,6 +28,7 @@ Gem::Specification.new do |spec|
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ["lib", "assets"]
 
+  spec.add_dependency "excon", "~> 0.76.0"
   spec.add_dependency "gosu", "~> 0.15.0"
   spec.add_dependency "gosu_more_drawables", "~> 0.3"
   spec.add_dependency "clipboard", "~> 1.3.4"

lib/cyberarm_engine.rb

@@ -7,6 +7,7 @@ rescue LoadError => e
   require "gosu"
 end
 require "json"
+require "excon"
 require "gosu_more_drawables"
 require "clipboard"
 

lib/cyberarm_engine/cache.rb

@@ -0,0 +1,4 @@
+module CyberarmEngine
+  module Cache
+  end
+end

lib/cyberarm_engine/cache/download_manager.rb

@@ -0,0 +1,119 @@
+module CyberarmEngine
+  module Cache
+    class DownloadManager
+      attr_reader :downloads
+
+      def initialize(max_parallel_downloads: 4)
+        @max_parallel_downloads = max_parallel_downloads
+        @downloads = []
+      end
+
+      def download(url:, save_as: nil, &callback)
+        uri = URI(url)
+        save_as ||= "filename_path" # TODO: if no save_as path is provided, then get one from the Cache controller
+
+        @downloads << Download.new(uri: uri, save_as: save_as, callback: callback)
+      end
+
+      def status
+        if active_downloads > 0
+          :busy
+        else
+          :idle
+        end
+      end
+
+      def progress
+        remaining_bytes = @downloads.map { |d| d.remaining_bytes }.sum
+        total_bytes = @downloads.map { |d| d.total_bytes }.sum
+
+        v = 1.0 - (remaining_bytes.to_f / total_bytes.to_f)
+        return 0.0 if v.nan?
+        return v
+      end
+
+      def active_downloads
+        @downloads.select { |d| [:pending, :downloading].include?(d.status) }
+      end
+
+      def update
+        @downloads.each do |download|
+          if download.status == :pending && active_downloads.size <= @max_parallel_downloads
+            download.status = :downloading
+            Thread.start { download.download }
+          end
+        end
+      end
+
+      def prune
+        @downloads.delete_if { |d| d.status == :finished || d.status == :failed }
+      end
+
+      class Download
+        attr_accessor :status
+        attr_reader :uri, :save_as, :callback, :remaining_bytes, :total_downloaded_bytes, :total_bytes,
+                    :error_message, :started_at, :finished_at
+        def initialize(uri:, save_as:, callback: nil)
+          @uri = uri
+          @save_as = save_as
+          @callback = callback
+
+          @status = :pending
+
+          @remaining_bytes = 0.0
+          @total_downloaded_bytes = 0.0
+          @total_bytes = 0.0
+
+          @error_message = ""
+        end
+
+        def progress
+          v = 1.0 - (@remaining_bytes.to_f / total_bytes.to_f)
+          return 0.0 if v.nan?
+          return v
+        end
+
+        def download
+          @status = :downloading
+          @started_at = Time.now # TODO: monotonic time
+
+          io = File.open(@save_as, "w")
+          streamer = lambda do |chunk, remaining_bytes, total_bytes|
+            io.write(chunk)
+
+            @remaining_bytes = remaining_bytes.to_f
+            @total_downloaded_bytes += chunk.size
+            @total_bytes = total_bytes.to_f
+          end
+
+          begin
+            response = Excon.get(
+              @uri.to_s,
+              middlewares: Excon.defaults[:middlewares] + [Excon::Middleware::RedirectFollower],
+              response_block: streamer
+            )
+
+            if response.status == 200
+              @status = :finished
+              @finished_at = Time.now # TODO: monotonic time
+              @callback.call(self) if @callback
+            else
+              @error_message = "Got a non 200 HTTP status of #{response.status}"
+              @status = :failed
+              @finished_at = Time.now # TODO: monotonic time
+              @callback.call(self) if @callback
+            end
+          rescue => e # TODO: cherrypick errors to cature
+            @status = :failed
+            @finished_at = Time.now # TODO: monotonic time
+            @error_message = e.message
+            @callback.call(self) if @callback
+          end
+
+          ensure
+            io.close if io
+        end
+      end
+    end
+  end
+end