require 'rbconfig'
require 'bundler/vendored_thor'
require 'bundler'
require 'rubygems/command'
require 'fileutils'
require 'pathname'
require 'tmpdir'

# Options:
#
#   name        - the gem name
#   uri         - git repo uri
#   repo        - path to local checkout
#   ref         - the commit hash
#   version     - gem version
#   build-flags - build arguments

ruby = File.join(ENV["ruby"], "bin", RbConfig::CONFIG['ruby_install_name'])
out = ENV["out"]
bin_dir = File.join(ENV["out"], "bin")

name        = ARGV[0]
uri         = ARGV[1]
REPO        = ARGV[2]
ref         = ARGV[3]
version     = ARGV[4]
build_flags = ARGV[5]

# options to pass to bundler
options = {
  "name"    => name,
  "uri"     => uri,
  "ref"     => ref,
  "version" => version,
}

# Monkey-patch Bundler to use our local checkout.
# I wish we didn't have to do this, but bundler does not expose an API to do
# these kinds of things.
Bundler.module_eval do
  def self.requires_sudo?
    false
  end

  def self.root
    # we don't have a Gemfile, so it doesn't make sense to try to make paths
    # relative to the (non existent) parent directory thereof, so we give a
    # nonsense path here.
    Pathname.new("/no-root-path")
  end

  def self.bundle_path
    Pathname.new(ENV["GEM_HOME"])
  end

  def self.locked_gems
    nil
  end
end

Bundler::Source::Git.class_eval do
  def allow_git_ops?
    true
  end
end

Bundler::Source::Git::GitProxy.class_eval do
  def checkout
    unless path.exist?
      FileUtils.mkdir_p(path.dirname)
      FileUtils.cp_r(File.join(REPO, ".git"), path)
      system("chmod -R +w #{path}")
    end
  end

  def copy_to(destination, submodules=false)
    unless File.exist?(destination.join(".git"))
      FileUtils.mkdir_p(destination.dirname)
      FileUtils.cp_r(REPO, destination)
      system("chmod -R +w #{destination}")
    end
  end
end

# UI
verbose = false
no_color = false
Bundler.ui = Bundler::UI::Shell.new({"no-color" => no_color})
Bundler.ui.level = "debug" if verbose

# Install
source = Bundler::Source::Git.new(options)
spec = source.specs.search_all(name).first
Bundler.rubygems.with_build_args [build_flags] do
  source.install(spec)
end

msg = spec.post_install_message
if msg
  Bundler.ui.confirm "Post-install message from #{name}:"
  Bundler.ui.info msg
end

# Write out the binstubs
if spec.executables.any?
  FileUtils.mkdir_p(bin_dir)
  spec.executables.each do |exe|
    wrapper = File.join(bin_dir, exe)
    File.open(wrapper, "w") do |f|
      f.write(<<-EOF)
#!#{ruby}
#
# This file was generated by Nix.
#
# The application '#{exe}' is installed as part of a gem, and
# this file is here to facilitate running it.
#

require 'rubygems'
require 'bundler/setup'

load Gem.bin_path(#{spec.name.inspect}, #{exe.inspect})
EOF
    end

    FileUtils.chmod("+x", wrapper)
  end
end

# Write out metadata
meta = "#{out}/nix-support/gem-meta"
FileUtils.mkdir_p(meta)
FileUtils.ln_s(spec.loaded_from.to_s, "#{meta}/spec")
File.open("#{meta}/name", "w") do |f|
  f.write spec.name
end
File.open("#{meta}/install-path", "w") do |f|
  f.write source.install_path.to_s
end
File.open("#{meta}/require-paths", "w") do |f|
  f.write spec.require_paths.join(" ")
end
File.open("#{meta}/executables", "w") do |f|
  f.write spec.executables.join(" ")
end

# make the lib available during bundler/git installs
File.open("#{out}/nix-support/setup-hook", "a") do |f|
  spec.require_paths.each do |dir|
    f.puts("addToSearchPath RUBYLIB #{source.install_path}/#{dir}")
  end
end