module Bundler::Patch
  class Gemfile < UpdateSpec
    attr_reader :gem_name

    def initialize(target_dir: Dir.pwd,
                   gem_name:,
                   patched_versions: [])
      super(target_file: 'Gemfile',
            target_dir: target_dir,
            patched_versions: patched_versions)
      @gem_name = gem_name
    end

    def to_s
      "#{@gem_name} #{patched_versions}"
    end

    def update
      # Bundler evals the whole Gemfile in Bundler::Dsl.evaluate
      # It has a few magics to parse all possible calls to `gem`
      # command. It doesn't have anything to output the entire
      # Gemfile, I don't think it ever does that. (There is code
      # to init a Gemfile from a gemspec, but it doesn't look
      # like it's intended to recreate one just evaled - I don't
      # see any code that would handle additional sources or
      # groups - see lib/bundler/rubygems_ext.rb #to_gemfile).
      #
      # So without something in Bundler that round-trips from
      # Gemfile back to disk and maintains integrity, then we
      # couldn't re-use it to make modifications to the Gemfile
      # like we'd want to, so we'll do this ourselves.
      #
      # We'll still instance_eval the gem line though, to properly
      # handle the various options and possible multiple reqs.
      @target_file = 'Gemfile'
      @regexes = /^\s*gem.*['"]\s*#{@gem_name}\s*['"].*$/
      file_replace do |match, re|
        update_to_new_gem_version(match)
      end
    end

    def update_to_new_gem_version(match)
      dep = instance_eval(match)
      req = dep.requirement

      prefix = req.exact? ? '' : req.specific? ? '~> ' : '>= '

      current_version = req.requirements.first.last.to_s
      new_version = calc_new_version(current_version)

      # return match if req.satisfied_by?(Gem::Version.new(new_version))
      #
      # TODO: This ^^ could be acceptable, slightly less complex, to not ever
      # touch the requirement if it already covers the patched version.
      # But I can't recall Bundler behavior in all these cases, to ensure
      # at least the patch version is updated and/or we would like to be as
      # conservative as possible in updating - can't recall how much influence
      # we have over `bundle update` (not much)

      return match if req.compound? && req.satisfied_by?(Gem::Version.new(new_version))

      if new_version && prefix =~ /~/
        # could Gem::Version#approximate_recommendation work here?

        # match segments. if started with ~> 1.2 and new_version is 3 segments, replace with 2 segments.
        count = current_version.split(/\./).length
        new_version = new_version.split(/\./)[0..(count-1)].join('.')
      end

      if new_version
        match.sub(requirements_args_regexp, " '#{prefix}#{new_version}'").tap { |s| "Updating to #{s}" }
      else
        match
      end
    end

    private

    def requirements_args_regexp
      ops = Gem::Requirement::OPS.keys.join "|"
      /(\s*['\"]\s*(#{ops})?\s*#{Gem::Version::VERSION_PATTERN}\s*['"],*)+/
    end

    # See Bundler::Dsl for reference
    def gem(name, *args)
      # we're not concerned with options here.
      _options = args.last.is_a?(Hash) ? args.pop.dup : {}
      version = args || ['>= 0']

      # there is a normalize_options step that DOES involve
      # the args captured in version for `git` and `path`
      # sources that's skipped here ... need to dig into that
      # at some point.

      Gem::Dependency.new(name, version)
    end
  end
end

class Gem::Requirement
  def compound?
    @requirements.length > 1
  end
end