#!/usr/bin/env ruby
#
# Create a chunk morphology to integrate a RubyGem in Baserock
#
# Copyright (C) 2014  Codethink Limited
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; version 2 of the License.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

require 'bundler'
require 'logger'
require 'optparse'
require 'yaml'

BASEROCK_RUBY_VERSION = '2.0.0'

# I'm no longer convinced about 'ignoring' Gems. My thinking is that it is
# much easier to add a missing dependency than it is to detect and remove
# unneeded dependencies. Therefore, a whilelist is perhaps the way forwards
# instead.

BUILD_DEPENDENCY_WHITELIST = [
  'hoe',
  # rake is bundled with Ruby, so it is not included in the whitelist.
]

#IGNORED_GROUPS = [:compat_testing, :test]
#
# Users of traditional distros seem to find it useful to override the versions
# of these Gems that come bundled with the MRI Ruby intepreter with newer
# versions from rubygems.org. In Baserock it should be just as easy to update
# MRI. We should avoid building components from two places.
#BUNDLED_GEMS = [
#  'rake',
#]

# Ignoring the :test group isn't enough for these Gems, they are often in the
# :development group too and thus we need to explicitly ignore them.
#TEST_GEMS = [
#  'rspec',
#  'rspec_junit_formatter',
#  'rspec-core',
#  'rspec-expectations',
#  'rspec-mocks',
#  'simplecov',
#]
#
#IGNORED_GEMS = BUNDLED_GEMS + TEST_GEMS

# Log information was passed in from the main import process, probably.
# This global constant approach seems a little ugly, but it seems to be
# recommended here:
# <https://stackoverflow.com/questions/1681745/share-global-logger-among-module-classes>
#
log_file = ENV['BASEROCK_IMPORT_LOG'] || '/dev/null'

if log_file.length == 0 then log_file = '/dev/null' end

Log = Logger.new(log_file)

Log.level = case ENV['BASEROCK_IMPORT_LOG_LEVEL']
                when 'debug' then Logger::DEBUG
                when 'warning' then Logger::WARN
                when 'error' then Logger::ERROR
                when 'critical', 'fatal' then Logger::FATAL
                else Logger::INFO
                end

Log.formatter = proc do |severity, datetime, progname, msg|
    "rubygem.to_chunk: #{severity}: #{msg}\n"
end

class << Bundler
  def default_gemfile
    # This is a hack to make things not crash when there's no Gemfile
    Pathname.new('.')
  end
end

def spec_is_from_current_source_tree(spec)
  spec.source.instance_of? Bundler::Source::Path and
    spec.source.path.fnmatch?('.')
end

class Dsl < Bundler::Dsl
  # The Bundler::Dsl class parses the Gemfile. We override it so that we can
  # extend the class of the Bundler::Definition instance that is created, and
  # so we can filter the results down to a specific Gem from the repo rather
  # than the top-level one.

  def self.evaluate(gemfile, lockfile, unlock, target_gem_name)
    builder = new
    builder.eval_gemfile(gemfile)
    builder.to_definition(lockfile, unlock, target_gem_name)
  end

  def to_definition(lockfile, unlock, target_gem_name)
    @sources << rubygems_source unless @sources.include?(rubygems_source)

    #@dependencies = filter_dependencies_for_target_gem(@dependencies,
    #                                                   target_gem_name)
    #Log.debug "The modified list of dependencies is: #{@dependencies}"

    Definition.new(lockfile, @dependencies, @sources, unlock, @ruby_version)
  end

  def filter_dependencies_for_target_gem(dependencies, target_gem_name)
    # Find the local Bundler::Source object, remove everything from that
    # source except the Gem we actually care about. This is necessary
    # because Bundler is designed for people who want to develop or deploy
    # all Gems from a given repo, but in this case we only care about *one*
    # Gem from the repo, which may not be the top level one.

    # Note that this doesn't solve all our problems!!!! For Rails, for
    # example, the top-level Gemfile lists a bunch of stuff that isn't
    # needed for all the Gems. For example some databases, which are not at
    # all necessary for activesupport! And jquery-rails, which brings in
    # railties, which brings in actionpack, which is just not needed!
    #
    # To be honest, I have no idea what to do about this right now. Maybe
    # a blacklist for certain nested Gems?
    #
    # One possible solution is to ignore everything the Gemfile says except
    # for the target gemspec. So ditch @dependencies altogether except for
    # the one Gem we want. Will need to test this with the whole dependency
    # graph of Chef and see if it works ....
    local_source = nil
    new_deps = []
    have_target = false
    dependencies.each do |dep|
      Log.debug "  - #{dep} #{dep.source} #{dep.groups}"
      if spec_is_from_current_source_tree(dep)
        local_source = local_source || dep.source
        if dep.name == target_gem_name
          new_deps << dep
          have_target = true
        end
      else
        new_deps << dep
      end
    end

    if not local_source
      # While Bundler recommends using 'gemspec' in the Gemfile[1] it's not
      # required, and some Gems are old enough to not have a .gemspec anyway.
      # In this case the code will fail later on at get_spec_for_gem(), right
      # now :) We need to manually search for Gemspecs.
      Log.info "No gemspecs were included in the Gemfile, so the full " +
               "list of specified dependencies will be used."
      return dependencies
    end

    if not have_target
      target_dep = Bundler::Dependency.new(
        target_gem_name, '>= 0',
        {"type" => :runtime, "source" => local_source}
      )
      new_deps << target_dep
      Log.debug "The target gem #{target_dep} was not found in the " +
                    "dependencies list, so I have added it."
      Log.debug "Its source is: #{target_dep.source.inspect}"
    end
    new_deps
  end
end

class Definition < Bundler::Definition
  # The Bundler::Definition class holds the dependency info we need.

  def self.build(gemfile, lockfile, unlock, target_gem_name)
    # Overridden so that our subclassed Dsl is used.
    unlock ||= {}
    gemfile = Pathname.new(gemfile).expand_path

    unless gemfile.file?
      raise Bundler::GemfileNotFound, "#{gemfile} not found"
    end

    Dsl.evaluate(gemfile, lockfile, unlock, target_gem_name)
  end

  def requested_dependencies
    # Overridden to remove more stuff from the list: excluding certain
    # groups using Bundler.settings.without is a good first step, but some
    # test tools seem to be in the generic :development group and thus
    # need to be explicitly removed from the list.
    #result = super.reject { |d| IGNORED_GEMS.member? d.name }
    #removed = dependencies - result
    #Log.info "Removed dependencies: #{removed.collect {|d| d.name}}"

    #result
    super
  end

  def resolve_dependencies
    # The term "build dependencies" is my own. RubyGems seem to mostly care
    # about "needed at runtime" (:runtime) vs. "useful during development"
    # (:development). We actually want "needed at runtime or during `rake
    # install`" but we have to work this out for ourselves.

    # Note you can set ENV['DEBUG_RESOLVER'] for more debug info.

    # Here we do the equivalent of resolve_remotely! and resolve_cached!
    # combined. In the hope that they work OK together. Ideally we'd
    # cache the specs after fetching them the first time so that on the
    # next run we only needed to fetch the ones we didn't already have. Not
    # sure the Bundler code makes this at all easy though. Probably
    # extending Source::Rubygems would be the way forwards.
    @remote = true
    @sources.each { |s| s.remote! }
    @sources.each { |s| s.cached! }

    build_deps = specs_for([:development])
    # FIXME: this list seems to always just contain 'bundler'.
    # not what I want, I think. Any value achieves the same thing so
    # I guess ':runtime' is not right. Maybe Bundler doesn't track
    # runtime deps at all?
    runtime_deps = specs_for([:runtime])
    STDERR.puts "Build deps: "
    build_deps.each { |s| STDERR.puts "  - #{s.name}" }
    STDERR.puts "Runtime deps:"
    runtime_deps.each { |s| STDERR.puts "  - #{s.name}" }
    return [build_deps, runtime_deps]
  end
end

class RubyGemChunkMorphologyGenerator
  def parse_options(arguments)
    # No options so far ..
    opts = OptionParser.new

    opts.banner = "Usage: rubygem.import SOURCE_DIR GEM_NAME"
    opts.separator ""
    opts.separator "This tool reads the Gemfile and optionally the " +
             "Gemfile.lock from a Ruby project "
    opts.separator "source tree in SOURCE_DIR. It outputs a chunk " +
             "morphology for GEM_NAME on stdout."
    opts.separator ""
    opts.separator "It is intended for use with the `baserock-import` tool."

    parsed_arguments = opts.parse!(arguments)

    if parsed_arguments.length != 2
      STDERR.puts opts.help
      exit 1
    end

    parsed_arguments
  end

  def error(message)
    Log.error(message)
    STDERR.puts(message)
  end

  def load_local_gemspecs()
    # Look for .gemspec files in the source repo.
    #
    # If there is no .gemspec, but you set 'name' and 'version' then
    # inside Bundler::Source::Path.load_spec_files this call will create a
    # fake gemspec matching that name and version. That's probably not useful.

    dir = '.'

    source = Bundler::Source::Path.new({
      'path' => dir,
    })

    Log.info "Loaded #{source.specs.count} specs from source dir."
    source.specs.each do |spec|
      Log.debug "  * #{spec.inspect} #{spec.dependencies.inspect}"
    end

    source
  end

  def load_definition(target_gem_name)
    # Load and parse the Gemfile and, if found, the Gemfile.lock file.
    Log.info("Loading Gemfile and Gemfile.lock for gem #{target_gem_name}")
    definition = Definition.build(
      'Gemfile', 'Gemfile.lock', update=false, target_gem_name)
  end

  def get_spec_for_gem(specs, gem_name)
    found = specs[gem_name].select {|s| Gem::Platform.match(s.platform)}
    if found.empty?
      raise Exception,
        "No Gemspecs found matching '#{gem_name}'"
    elsif found.length != 1
      raise Exception,
        "Unsure which Gem to use for #{gem_name}, got #{found}"
    end
    found[0]
  end

  def chunk_name_for_gemspec(spec)
    # Chunk names are the Gem's "full name" (name + version number), so
    # that we don't break in the rare but possible case that two different
    # versions of the same Gem are required for something to work. It'd be
    # nicer to only use the full_name if we detect such a conflict.
    spec.full_name
  end

  def generate_chunk_morph_for_gem(spec)
    description = 'Automatically generated by rubygem.import'

    bin_dir = "\"$DESTDIR/$PREFIX/bin\""
    gem_dir = "\"$DESTDIR/$PREFIX/lib/ruby/gems/#{BASEROCK_RUBY_VERSION}\""

    # There's more splitting to be done, but putting the docs in the
    # correct artifact is the single biggest win for enabling smaller
    # system images.
    split_rules = [
      {
        'artifact' => "#{spec.full_name}-doc",
        'include' => [
          "usr/lib/ruby/gems/#{BASEROCK_RUBY_VERSION}/doc/.*"
        ]
      }
    ]

    build_commands = [
      "gem build #{spec.name}.gemspec",
    ]

    install_commands = [
      "mkdir -p #{gem_dir}",
      "gem install --install-dir #{gem_dir} --bindir #{bin_dir} " +
        "--ignore-dependencies --local ./#{spec.full_name}.gem"
    ]

    {
      'name' => chunk_name_for_gemspec(spec),
      'kind' => 'chunk',
      'description' => description,
      'build-system' => 'manual',
      ##'gem-url' => "http://rubygems.org/downloads/#{spec.full_name}.gem",
      'products' => split_rules,
      'build-commands' => build_commands,
      'install-commands' => install_commands,
    }
  end

  def build_deps_for_gem(spec)
    deps = spec.dependencies.select do |d|
      d.type == :development && BUILD_DEPENDENCY_WHITELIST.member?(d.name)
    end
  end

  def runtime_deps_for_gem(spec)
    spec.dependencies.select {|d| d.type == :runtime}
  end

  def write_morph(file, morph)
    file.write(YAML.dump(morph))
  end

  def run
    source_dir_name, gem_name = parse_options(ARGV)

    Log.info("Creating chunk morph for #{gem_name} based on " +
             "source code in #{source_dir_name}")

    Dir.chdir(source_dir_name)

    ## Find the .gemspec file in the project repo corresponding to the Gem
    ## requested on the commandline.
    #local_source = load_local_gemspecs
    #local_specset = Bundler::SpecSet.new(local_source.local_specs)
    #spec = get_spec_for_gem(local_specset, gem_name)

    # Instead of reading the real Gemfile, invent one that simply includes the
    # chosen .gemspec. If present, the Gemfile.lock will be honoured.
    fake_gemfile = Bundler::Dsl.new
    fake_gemfile.source('https://rubygems.org')
    fake_gemfile.gemspec({:name => gem_name})

    definition = fake_gemfile.to_definition('Gemfile.lock', true)
    resolved_specs = definition.resolve_remotely!

    #build_specs, runtime_specs = definition.resolve_dependencies

    spec = get_spec_for_gem(resolved_specs, gem_name)

    if not spec_is_from_current_source_tree(spec)
      error "Specified gem '#{spec.name}' doesn't live in the source in " +
            "'#{source_dir_name}'"
      Log.debug "SPEC: #{spec.inspect} #{spec.source}"
      exit 1
    end

    morph = generate_chunk_morph_for_gem(spec)

    # One might think that you could use the Bundler::Dependency.groups
    # field to filter but it doesn't seem to be useful. Instead we go back to
    # the Gem::Specification of the target Gem and use the dependencies fild
    # there. We look up each dependency in the resolved_specset to find out
    # what version Bundler has chosen of it.

    def format_deps_for_morphology(specset, dep_list)
      info = dep_list.collect do |dep|
        spec = specset[dep][0]
        [spec.name, spec.version.to_s]
      end
      Hash[info]
    end

    build_deps = format_deps_for_morphology(
      resolved_specs, build_deps_for_gem(spec))
    runtime_deps = format_deps_for_morphology(
      resolved_specs, runtime_deps_for_gem(spec))

    morph['x-build-dependencies-rubygem'] = build_deps
    morph['x-runtime-dependencies-rubygem'] = runtime_deps

    write_morph(STDOUT, morph)
  end
end

RubyGemChunkMorphologyGenerator.new.run