From f7b089d954cb028ee3c46ad45f0f81ae2e5386cf Mon Sep 17 00:00:00 2001
From: Matthew Hall <hallmatthew314@gmail.com>
Date: Wed, 8 Mar 2023 20:11:24 +1300
Subject: Implement Phrase

---
 spec/parcom_spec.cr | 25 ++++++++++++++++++++++++-
 src/parcom.cr       | 14 +++++++++++++-
 2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/spec/parcom_spec.cr b/spec/parcom_spec.cr
index f35465c..c395636 100644
--- a/spec/parcom_spec.cr
+++ b/spec/parcom_spec.cr
@@ -310,7 +310,30 @@ describe Plus do
   end
 end
 
-pending Phrase do
+describe Phrase do
+  p = Phrase.new(Token.new('t'))
+
+  describe "#parse" do
+    it "fails if the wrapped parser fails" do
+      tokens = TokenStream.from_string("_")
+
+      expect_raises(ParserException) { p.parse(tokens) }
+    end
+
+    it "fails if not all of the input tokens are parsed" do
+      tokens = TokenStream.from_string("tt")
+
+      expect_raises(ParserException) { p.parse(tokens) }
+    end
+
+    it "succeeds if the wrapped parser successfully parses all of the input" do
+      tokens = TokenStream.from_string("t")
+      result = p.parse(tokens)
+
+      result.tokens.empty?.should be_true
+      result.value.should eq('t')
+    end
+  end
 end
 
 pending Recover do
diff --git a/src/parcom.cr b/src/parcom.cr
index 8d1d47b..4d49a97 100644
--- a/src/parcom.cr
+++ b/src/parcom.cr
@@ -166,7 +166,19 @@ module Parcom
     end
   end
 
-  class Phrase
+  class Phrase(T, V)
+    def initialize(@p : Parser(T, V))
+    end
+
+    def parse(tokens : TokenStream(T)) : Result(T, V)
+      r = @p.parse(tokens)
+
+      unless r.tokens.empty?
+        raise ParserException.new("Phrase: some of the input was not parsed")
+      end
+
+      r
+    end
   end
 
   class Plus(T, V, U) < Parser(T, {V, U})
-- 
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