raise exception on unknown option

Rakefile

@@ -3,3 +3,5 @@ require "bundler/gem_tasks"
 require 'rspec/core/rake_task'
 
 RSpec::Core::RakeTask.new('spec')
+
+task :default => :spec

lib/yawpa.rb

@@ -1,8 +1,30 @@
 require "yawpa/version"
 
+# Example options configuration:
+# {
+#   version: {},
+#   verbose: {aliases: ['-v']},
+#   get: {nargs: 1},
+#   set: {nargs: 2},
+# }
 module Yawpa
+  class UnknownOptionException < Exception; end
+
   module_function
-  def parse(config, params)
-    return [[], params]
+  def parse(params, options)
+    opts = {}
+    args = []
+    i = 0
+    while i < params.length
+      param = params[i]
+      if param[0] != '-'
+        args << params[i]
+      else
+        opt_config = options[param] || options[param.to_sym]
+        raise UnknownOptionException.new("Unknown option '#{param}'") if opt_config.nil?
+      end
+      i += 1
+    end
+    return [opts, args]
   end
 end

spec/yawpa_spec.rb

@@ -3,11 +3,17 @@ require 'spec_helper'
 describe Yawpa do
   describe 'parse' do
     it "returns everything as arguments when no options present" do
-      config = { }
+      options = { }
       params = ['one', 'two', 'three', 'four']
-      opts, args = Yawpa.parse(config, params)
-      opts.should eq([])
+      opts, args = Yawpa.parse(params, options)
+      opts.should eq({})
       args.should eq(params)
     end
+
+    it "raises an exception when an invalid option is passed" do
+      options = { }
+      params = ['one', '--option', 'two']
+      expect { Yawpa.parse(params, options) }.to raise_error
+    end
   end
 end