From 44dd279f93443414f29eaefb35140c9467f0fb80 Mon Sep 17 00:00:00 2001
From: Josh Holtrop <jholtrop@gmail.com>
Date: Sat, 5 Feb 2022 15:17:13 -0500
Subject: [PATCH] wip

---
 lib/rscons.rb        |  2 ++
 lib/rscons/script.rb | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/lib/rscons.rb b/lib/rscons.rb
index bfd14a1..28ea715 100644
--- a/lib/rscons.rb
+++ b/lib/rscons.rb
@@ -1,3 +1,5 @@
+require "net/http"
+require "digest"
 require_relative "rscons/ansi"
 require_relative "rscons/application"
 require_relative "rscons/basic_environment"
diff --git a/lib/rscons/script.rb b/lib/rscons/script.rb
index 799a264..a25c5b9 100644
--- a/lib/rscons/script.rb
+++ b/lib/rscons/script.rb
@@ -37,6 +37,39 @@ module Rscons
         end.sort
       end
 
+      # Download a file.
+      #
+      # @param url [String]
+      #   URL.
+      # @param dest [String]
+      #   Path to where to save the file.
+      # @param options [Hash]
+      #   Options.
+      # @option options [String] :sha256sum
+      #   Expected file checksum.
+      #
+      # @return [void]
+      def download(url, dest, options = {})
+        if File.exist?(dest) && options[:sha256sum]
+          if Digest::SHA2.hexdigest(File.binread(dest)) == options[:sha256sum]
+            # Destination file already exists and has the expected checksum.
+            return
+          end
+        end
+        uri = URI(url)
+        http = Net::HTTP.new(uri.host)
+        digest = Digest::SHA2.new
+        File.open(dest, "wb") do |fh|
+          http.get(uri.path) do |data|
+            fh.write(data)
+            digest << data
+          end
+        end
+        if options[:sha256sum] && options[:sha256sum] != digest.hexdigest
+          raise RsconsError.new("Unexpected checksum on #{dest}")
+        end
+      end
+
       # Construct a task parameter.
       #
       # @param name [String]