From bd92c8b10aeb3bca6cdadd8d22b6385256b524f1 Mon Sep 17 00:00:00 2001
From: Stephen Paul Weber <singpolyma@singpolyma.net>
Date: Tue, 21 May 2019 20:12:17 -0500
Subject: [PATCH] Switch IntegrityCheck encoding to multihash

---
 dhall.gemspec        |  1 +
 lib/dhall/ast.rb     | 16 +++++-----------
 lib/dhall/binary.rb  | 19 ++++++++++++++-----
 lib/dhall/parser.rb  |  7 ++++++-
 test/test_resolve.rb |  5 +++--
 5 files changed, 29 insertions(+), 19 deletions(-)

diff --git a/dhall.gemspec b/dhall.gemspec
index 8507478..69912c6 100644
--- a/dhall.gemspec
+++ b/dhall.gemspec
@@ -27,6 +27,7 @@ Gem::Specification.new do |spec|
 
 	spec.add_dependency "cbor", "~> 0.5.9.3"
 	spec.add_dependency "citrus", "~> 3.0"
+	spec.add_dependency "multihashes", "~> 0.1.3"
 	spec.add_dependency "promise.rb", "~> 0.7.4"
 	spec.add_dependency "value_semantics", "~> 3.0"
 
diff --git a/lib/dhall/ast.rb b/lib/dhall/ast.rb
index b3d9689..22494b7 100644
--- a/lib/dhall/ast.rb
+++ b/lib/dhall/ast.rb
@@ -1,5 +1,6 @@
 # frozen_string_literal: true
 
+require "multihashes"
 require "uri"
 require "value_semantics"
 
@@ -1189,25 +1190,18 @@ module Dhall
 	class Import < Expression
 		class IntegrityCheck
 			include(ValueSemantics.for_attributes do
-				protocol "sha256"
-				data     Either(::String, nil)
+				code   ::Integer
+				digest ::String
 			end)
 
 			class FailureException < StandardError; end
 
-			def initialize(protocol, data=nil)
-				super(
-					protocol: protocol,
-					data:     data
-				)
-			end
-
 			def to_s
-				"#{@protocol}:#{hexdigest}"
+				"#{Multihashes::TABLE[code].sub(/\Asha2-/, "sha")}:#{hexdigest}"
 			end
 
 			def hexdigest
-				@data.unpack("H*").first.encode(Encoding::UTF_8)
+				digest.unpack("H*").first.encode(Encoding::UTF_8)
 			end
 
 			def check(expr)
diff --git a/lib/dhall/binary.rb b/lib/dhall/binary.rb
index a3a9d11..ba45005 100644
--- a/lib/dhall/binary.rb
+++ b/lib/dhall/binary.rb
@@ -2,6 +2,7 @@
 
 require "cbor"
 require "digest/sha2"
+require "multihashes"
 
 require "dhall/ast"
 require "dhall/builtins"
@@ -190,15 +191,23 @@ module Dhall
 	end
 
 	class Import
+		class IntegrityCheck
+			def self.decode(integrity_check)
+				return unless integrity_check
+
+				IntegrityCheck.new(
+					Multihashes.decode(integrity_check).select { |k, _|
+						[:code, :digest].include?(k)
+					}
+				)
+			end
+		end
+
 		def self.decode(integrity_check, import_type, path_type, *parts)
 			parts[0] = Dhall.decode(parts[0]) if path_type < 2 && !parts[0].nil?
 
-			check = if integrity_check
-				IntegrityCheck.new(integrity_check[0], [integrity_check[1]].pack("H*"))
-			end
-
 			new(
-				check,
+				IntegrityCheck.decode(integrity_check),
 				IMPORT_TYPES[import_type],
 				PATH_TYPES[path_type].new(*parts)
 			)
diff --git a/lib/dhall/parser.rb b/lib/dhall/parser.rb
index 5418e73..04dcaca 100644
--- a/lib/dhall/parser.rb
+++ b/lib/dhall/parser.rb
@@ -525,7 +525,12 @@ module Dhall
 		module Hash
 			def value
 				protocol, data = string.split(/:/, 2)
-				Dhall::Import::IntegrityCheck.new(protocol, [data].pack("H*"))
+				Dhall::Import::IntegrityCheck.new(
+					code:   Multihashes::TABLE.key(
+						protocol.sub(/\Asha(\d{3})/, "sha2-\\1")
+					),
+					digest: [data].pack("H*")
+				)
 			end
 		end
 
diff --git a/test/test_resolve.rb b/test/test_resolve.rb
index d7d4b93..b270932 100644
--- a/test/test_resolve.rb
+++ b/test/test_resolve.rb
@@ -167,7 +167,7 @@ class TestResolve < Minitest::Test
 
 	def test_integrity_check_failure
 		expr = Dhall::Import.new(
-			Dhall::Import::IntegrityCheck.new("sha256", "badhash"),
+			Dhall::Import::IntegrityCheck.new(code: 0x12, digest: "badhash".b),
 			Dhall::Import::Expression,
 			Dhall::Import::RelativePath.new("var")
 		)
@@ -260,7 +260,8 @@ class TestResolve < Minitest::Test
 
 		expr = Dhall::Import.new(
 			Dhall::Import::IntegrityCheck.new(
-				"sha256", Dhall::Variable["_"].digest.digest
+				code:   0x12,
+				digest: Dhall::Variable["_"].digest.digest
 			),
 			Dhall::Import::Expression,
 			Dhall::Import::Http.new(nil, "example.com", "thing.dhall", nil)
-- 
2.38.5