Implement argument parser

lib/kangaru/input_parsers/argument_parser.rb

@@ -0,0 +1,30 @@
+module Kangaru
+  module InputParsers
+    class ArgumentParser < InputParser
+      using Patches::Inflections
+
+      def parse
+        grouped_argument_tokens.to_h do |tokens|
+          key   = parse_key(tokens.shift || raise)
+          value = parse_value(tokens)
+
+          [key, value]
+        end
+      end
+
+      private
+
+      def grouped_argument_tokens
+        argument_tokens.slice_before(ARGUMENT_TOKEN).to_a
+      end
+
+      def parse_key(key)
+        key.gsub(/^-+/, "").to_snakecase.to_sym
+      end
+
+      def parse_value(tokens)
+        tokens.empty? || tokens.join(" ")
+      end
+    end
+  end
+end

sig/kangaru/input_parsers/argument_parser.rbs

@@ -0,0 +1,15 @@
+module Kangaru
+  module InputParsers
+    class ArgumentParser < InputParser
+      def parse: -> Hash[Symbol, untyped]
+
+      private
+
+      def grouped_argument_tokens: -> Array[InputParser::tokens]
+
+      def parse_key: (String) -> Symbol
+
+      def parse_value: (Array[untyped]) -> untyped
+    end
+  end
+end

spec/kangaru/input_parsers/argument_parser_spec.rb

@@ -0,0 +1,111 @@
+RSpec.describe Kangaru::InputParsers::ArgumentParser do
+  subject(:argument_parser) { described_class.new(tokens) }
+
+  let(:tokens) { [command_tokens, argument_tokens].flatten.compact }
+
+  describe "#parse" do
+    subject(:arguments) { argument_parser.parse }
+
+    shared_examples :parses_arguments_hash do |options|
+      let(:expected_hash) { options[:to] }
+
+      it "returns a hash" do
+        expect(arguments).to be_a(Hash)
+      end
+
+      it "has symbol keys" do
+        expect(arguments.keys).to all be_a(Symbol)
+      end
+
+      it "is the expected hash" do
+        expect(arguments).to eq(expected_hash)
+      end
+    end
+
+    context "when input does not contain command tokens" do
+      let(:command_tokens) { nil }
+
+      context "and single unary argument is passed" do
+        context "and terse flag form given" do
+          let(:argument_tokens) { ["-f"] }
+
+          include_examples :parses_arguments_hash, to: { f: true }
+        end
+
+        context "and verbose flag form given" do
+          let(:argument_tokens) { ["--foo-bar"] }
+
+          include_examples :parses_arguments_hash, to: { foo_bar: true }
+        end
+      end
+
+      context "and single binary argument is passed" do
+        context "and terse flag form given" do
+          let(:argument_tokens) { %w[-t Hello world] }
+
+          include_examples :parses_arguments_hash, to: { t: "Hello world" }
+        end
+
+        context "and verbose flag form given" do
+          let(:argument_tokens) { %w[--full-title Hello world] }
+
+          include_examples :parses_arguments_hash,
+                           to: { full_title: "Hello world" }
+        end
+      end
+
+      context "and multiple arguments are passed" do
+        let(:argument_tokens) do
+          %w[--title This is the title -d Foobar --cleanup -f]
+        end
+
+        include_examples :parses_arguments_hash, to: {
+          title: "This is the title", d: "Foobar", cleanup: true, f: true
+        }
+      end
+    end
+
+    context "when input contains command tokens" do
+      let(:command_tokens) { %w[foo bar baz] }
+
+      context "and single unary argument is passed" do
+        context "and terse flag form given" do
+          let(:argument_tokens) { ["-f"] }
+
+          include_examples :parses_arguments_hash, to: { f: true }
+        end
+
+        context "and verbose flag form given" do
+          let(:argument_tokens) { ["--foo-bar"] }
+
+          include_examples :parses_arguments_hash, to: { foo_bar: true }
+        end
+      end
+
+      context "and single binary argument is passed" do
+        context "and terse flag form given" do
+          let(:argument_tokens) { %w[-t Hello world] }
+
+          include_examples :parses_arguments_hash, to: { t: "Hello world" }
+        end
+
+        context "and verbose flag form given" do
+          let(:argument_tokens) { %w[--full-title Hello world] }
+
+          include_examples :parses_arguments_hash,
+                           to: { full_title: "Hello world" }
+        end
+      end
+
+      context "and multiple arguments are passed" do
+        let(:argument_tokens) do
+          %w[--title This is the title -d Foobar --cleanup -f]
+        end
+
+        include_examples :parses_arguments_hash, to: {
+          title: "This is the title", d: "Foobar", cleanup: true, f: true
+        }
+      end
+    end
+  end
+end