Binary to run govspeak from CLI

Introduces a `govspeak` bin which can take input in three ways:

1. As an argument: `govspeak "render me"`
2. From a file: `govspeak --file render-me.md`
3. From stdin: `echo "render-me" | govspeak`

All output to stdout

Govspeak options can be passed in as JSON as a string through
`--options` or as a file through `--options-file options.json`

bin/govspeak

@@ -0,0 +1,8 @@
+#!/usr/bin/env ruby
+
+lib = File.expand_path("../../lib", __FILE__)
+$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
+
+require "govspeak/cli"
+
+Govspeak::CLI.new.run

govspeak.gemspec

@@ -15,13 +15,16 @@ Gem::Specification.new do |s|
 library for use in the UK Government Single Domain project}
 
   s.files         = Dir[
+    'bin/*',
     'lib/**/*',
     'README.md',
     'CHANGELOG.md',
     'Gemfile',
     'Rakefile'
   ]
   s.test_files    = Dir['test/**/*']
+  s.bindir        = "bin"
+  s.executables   = s.files.grep(%r{^bin/}) { |f| File.basename(f) }
   s.require_paths = ["lib"]
 
   s.add_dependency 'kramdown', '~> 1.10.0'
@@ -32,6 +35,7 @@ library for use in the UK Government Single Domain project}
   s.add_dependency 'actionview', '~> 4.1'
   s.add_dependency 'i18n', '~> 0.7'
   s.add_dependency 'money', '~> 6.7'
+  s.add_dependency 'commander', '~> 4.4'
 
   s.add_development_dependency 'rake', '~> 0.9.0'
   s.add_development_dependency 'gem_publisher', '~> 1.1.1'

lib/govspeak/cli.rb

@@ -0,0 +1,51 @@
+require 'govspeak/version'
+require 'govspeak'
+require 'commander'
+
+module Govspeak
+  class CLI
+    include Commander::Methods
+
+    def run
+      program(:name, 'Govspeak')
+      program(:version, Govspeak::VERSION)
+      program(:description, "A tool for rendering the GOV.UK dialect of markdown into HTML")
+      default_command(:render)
+      command(:render) do |command|
+        command.syntax = "govspeak render [options] <input>"
+        command.description = "Render Govspeak into HTML, can be sourced from stdin, as an argument or from a file"
+        command.option("--file FILENAME", String, "File to render")
+        command.option("--options JSON", String, "JSON to use as options")
+        command.option("--options-file FILENAME", String, "A file of JSON options")
+        command.action do |args, options|
+          input = get_input($stdin, args, options)
+          raise "Nothing to render. Use --help for assistance" unless input
+          puts Govspeak::Document.new(input, govspeak_options(options)).to_html
+        end
+      end
+      run!
+    end
+
+  private
+
+    def get_input(stdin, args, options)
+      return stdin.read unless stdin.tty?
+      return read_file(options.file) if options.file
+      args.empty? ? nil : args.join(" ")
+    end
+
+    def read_file(file_path)
+      path = Pathname.new(file_path).realpath
+      File.read(path)
+    end
+
+    def govspeak_options(command_options)
+      string = if command_options.options_file
+                read_file(command_options.options_file)
+               else
+                command_options.options
+               end
+      string ? JSON.load(string) : {}
+    end
+  end
+end