gem_visit command line utility

gem_visit.rb

#!/usr/bin/env ruby

# Call the file just `gem-visit`, not `gem-visit.rb`, and put it in your path
# (maybe you want ~/bin in your $PATH), to be able to do:
#
# .   gem-visit name_of_gem
#
# And have a browser window opened pointing to the (preferable, if it can) github
# homepage of the gem, or other gem project page (last resort). 

require 'net/http'
require 'json'

API_HOST = "rubygems.org"
PREFERRED_URI_RE = %r{\Ahttps?\://github.com}
OPEN_CMD = 'open %s'

def usage(err_msg = nil)
  usage = "USAGE: gem_visit gem_name"
  if err_msg
    usage = "Error: #{err_msg}\n#{usage}"
  end
  usage
end

def present?(str)
  str && ! str.empty?
end

gem_name = ARGV[0]

unless gem_name
  $stderr.puts usage("Need a gem name")
  exit 1
end

http = Net::HTTP.new(API_HOST, 443).tap { |h| h.use_ssl = true }
response = http.get("/api/v1/gems/#{gem_name}.json")

if response.code == "404"
  $stderr.puts "rubygems can't find gem named `#{gem_name}`"
  exit 1
end

unless response.code == "200"
  $stderr.puts "Error from rubygems: #{response}"
  exit 1
end

data = JSON.parse(response.body)
go_to_url = if present?(data["homepage_uri"]) && data["homepage_uri"] =~ PREFERRED_URI_RE
  data["homepage_uri"]
elsif present?(data["source_code_uri"]) && data["source_code_uri"] =~ PREFERRED_URI_RE
  data["source_code_uri"]
elsif present?(data["homepage_uri"])
  data["homepage_uri"]
elsif present?(data["source_code_uri"])
  data["source_code_uri"]
else
  data["project_uri"]
end

`#{OPEN_CMD % go_to_url}`