Ruby helloweb

Let's show how to do simple helloweb in Ruby. The program generates the
same output as Python version, only the comment about language is
different.

Comes with minimal gem specification, so it could be worked with /
installed via Bundler, together with dependency gems, if needed.

So far we use only stdlib without external gems.

/cc @kazuhiko

README.rst

@@ -10,5 +10,6 @@ The programs are used in SlapOS helloworld_ software release.
 The following languages are demonstrated:
 
 - Python
+- Ruby
 
 .. _helloworld: https://lab.nexedi.com/nexedi/slapos/tree/master/software/helloworld

ruby/Gemfile

+source 'https://rubygems.org'
+
+# gem's dependencies are in .gemspec
+gemspec

ruby/helloweb.gemspec

+# minimal gem specification for helloweb.rb
+Gem::Specification.new do |gem|
+    gem.name            = "helloweb"
+    gem.version         = "0.1"
+    gem.summary         = "Hello Web in Ruby"
+
+    gem.bindir          = ''
+    gem.executables     = 'helloweb.rb'
+
+    # NOTE we can require other gems via
+    # gem.add_runtime_dependency ...
+end

ruby/helloweb.rb

+#!/usr/bin/env ruby
+# Simple web-server that says "Hello World" for every path
+#
+# helloweb.rb [--logfile <logfile>] <bind-ip> <bind-port> ...
+require 'webrick'
+require 'time'
+require 'optparse'
+require 'ostruct'
+
+def main
+    args = OpenStruct.new
+    args.logfile = nil
+    opt = OptionParser.new
+    opt.banner = "Usage: helloweb.rb [options] bind_ip bind_port ..."
+    opt.on('--logfile LOGFILE')       { |o| args.logfile = o }
+    opt.parse!
+
+    args.bind_ip = ARGV.delete_at(0)
+    args.bind_port = ARGV.delete_at(0)
+    args.argv_extra = ARGV
+    if args.bind_ip.nil? or args.bind_port.nil?
+        puts opt
+        exit 1
+    end
+
+    args.bind_port = Integer(args.bind_port)
+
+    log = nil
+    access_log = nil
+    if args.logfile
+        log_file = File.open args.logfile, 'a+'
+        log_file.sync = true
+        log = WEBrick::Log.new log_file
+        access_log = [[log_file, WEBrick::AccessLog::COMBINED_LOG_FORMAT]]
+    end
+
+    httpd = WEBrick::HTTPServer.new :BindAddress => args.bind_ip,
+                :Port => args.bind_port,
+                :Logger => log,
+                :AccessLog => access_log
+    httpd.mount_proc '/' do |req, resp|
+        name = args.argv_extra.join(' ')
+        name = 'world' if name.empty?
+        resp.body = "Hello #{name} at `#{req.path}`  ; #{Time.now.asctime}  (ruby)"
+    end
+
+    httpd.start
+end
+
+main