feat: Add regex parser

lib/parsby/combinators.rb

@@ -408,5 +408,22 @@ def splicer
         block.call(parse)
       end
     end
+
+    # Matches a regular expression
+    define_combinator :regex do |regex|
+      Parsby.new :regex do |target|
+        position = target.bio.pos
+        target_string = target.bio.read
+
+        unless target_string.match?(regex)
+          raise ExpectationFailed.new target
+        end
+
+        match = target_string.match(regex).to_s
+        target.bio.restore_to(position + match.length)
+
+        match
+      end
+    end
   end
 end

spec/parsby/combinators_spec.rb

@@ -505,4 +505,12 @@ def self.parenthesis
       expect { test_parser.parse("ad") }.to raise_error Parsby::ExpectationFailed
     end
   end
+
+  describe "#regex" do
+    it "matches a regex to a string" do
+      expect(regex(/[A-Z][a-z] ./).parse("Hi !")).to eq "Hi !"
+      expect(regex(/\w+@\w+\.\w+/).parse("[email protected] extra")).to eq "[email protected]"
+      expect {regex(/\w+@\w+\.\w+/).parse("user@gmail")}.to raise_error Parsby::ExpectationFailed
+    end
+  end
 end