Environment with defaults, system overrides, and user overrides

environment.rb

require 'yaml'
require 'active_support'

WINDOWS_PLATFORM = /mswin|win32|mingw/ unless defined?(WINDOWS_PLATFORM)

$env = YAML.load_file("#{File.dirname(__FILE__)}/environment.yml")
  DEFAULT_ENVIRONMENT = "#{RUBY_PLATFORM =~ WINDOWS_PLATFORM ? 'windows_' : ''}default"

$default_env = $env[DEFAULT_ENVIRONMENT]

#
# Allow user to specify an environment with env=?
# Otherwise use the HOSTNAME (Linux) or COMPUTERNAME (Windows)
#
SPECIFIC_ENVIRONMENT = (ENV['env'] || ENV['HOSTNAME'] || ENV['COMPUTERNAME'] || "").downcase

  if SPECIFIC_ENVIRONMENT and $env.include?(SPECIFIC_ENVIRONMENT)
    $log.info "Loading Environment: #{(SPECIFIC_ENVIRONMENT).downcase.strip} #{RUBY_PLATFORM =~ WINDOWS_PLATFORM ? '(WINDOWS)' : ''}"

    $specific_env = $env[(SPECIFIC_ENVIRONMENT).downcase.strip]
    $env = $default_env.deep_merge($specific_env)
end

environment.yml

#
# When the environment is loaded at run-time, the system will use the default
# values and then merge the specific values of the environment.  As most of
# our properties remain the same, this allows for easy configuration.
#
# Windows Environments have some different requirements for some of the paths,
# scripts and tools.
#
---
default: &DEFAULT
  host:
    name: testsystem
    http_port: '8080'
    username: defaultuser
  database:
    host: db01/db01
    username:
    password:
  test:
    browser: FIREFOX
#
# Windows Overrides
#
windows_default: &WIN_DEFAULT
  <<: *DEFAULT
  test:
    browser: IE
#
# Custom User/System Environments
#
profile1:
  host:
    name: usersystem1
    username: user
  database:
    username: user_db
    password: foobar