#!/usr/bin/env ruby

# This script can be used to engage a particular Gemfile for the purposes of
# continuous integration testing.
#
# Usage: script/with <variant> <env|bootstrap|bundle|rake>
#
# Here <variant> refers to a pre-defined Gemfile located in test/gemfiles
# and the commands include:
#
#  * env - Display the current BUNDLE_GEMFILE environment
#  * bootstrap - Install the necessary hard dependencies (rubygems, bundler)
#  * bundle - Execute arbitrary Bundler command
#  * rake - Execute arbitrary rake command via `bundle exec`
#
# Examples:
#  * script/with rails-3.0.x bootstrap
#  * script/with rails-3.0.x bundle install
#  * script/with rails-3.0.x rake test

# == Constants ==============================================================

GEMFILE_DIR = File.expand_path('../test/gemfiles', File.dirname(__FILE__))
GEMFILE_ROOT = File.expand_path('../Gemfile', File.dirname(__FILE__))

# == Support Methods ========================================================

def dependencies(gemfile)
  dependencies = { }

  File.open(gemfile) do |f|
    f.each do |line|
      if (line.match(/\Agem\s+['"]bundler['"]\s*,\s*['"]([^'"]+)['"]/))
        dependencies[:bundler] = $1
      elsif (line.match(/\A\#\s*rubygems\s+(\S+)/))
        dependencies[:rubygems] = $1
      end
    end
  end

  dependencies
end

def gemfile_list
  Dir.entries(GEMFILE_DIR).reject do |name|
    name[/\A\./] or name[/\.lock\z/]
  end.collect do |name|
    name.sub(/\AGemfile\./, '')
  end
end

def with_variant(variant, &block)
  case (variant)
  when 'current'
    if (ENV['BUNDLE_GEMFILE'])
      yield(dependencies(ENV['BUNDLE_GEMFILE']))
    else
      yield(dependencies(GEMFILE_ROOT))
    end
  when 'each', 'all'
    gemfile_list.each do |_variant|
      with_variant(_variant, &block)
    end
  else
    ENV['BUNDLE_GEMFILE'] = File.expand_path('Gemfile.%s' % variant, GEMFILE_DIR)

    yield(dependencies(ENV['BUNDLE_GEMFILE']))
  end
end

def shell(*args)
  if (ENV['WITH_VERBOSE'])
    puts args.join(' ')
  end

  unless (system(*args))
    exit($?.to_i)
  end
end

# == Main ===================================================================

variant = ARGV[0]

unless (variant)
  puts "Usage: with <gemspec variant> <env|bootstrap|bundle|rake> ..."


  puts
  puts "Available variants:"
  gemfile_list.each do |name|
    puts name
  end

  exit(-1)
end

with_variant(variant) do |dependencies|
  bundle_version_args = dependencies[:bundler] ? [ '_%s_' % dependencies[:bundler] ] : [ ]

  case (ARGV[1])
  when 'env'
    puts 'BUNDLE_GEMFILE=%s' % ENV['BUNDLE_GEMFILE']
  when 'bootstrap'
    if (dependencies[:rubygems])
      shell('gem', 'update', '--system', dependencies[:rubygems])
    end
    if (dependencies[:bundler])
      shell('gem', 'install', 'bundler', '-v', dependencies[:bundler])
    end
  when 'bundle'
    shell("bundle", *bundle_version_args, *ARGV.to_a[2, ARGV.length])
  when 'rake'
    shell("bundle", *bundle_version_args, "exec", "rake", *ARGV.to_a[2, ARGV.length])
  end
end