module Simp
  # Various utilities for dealing with YUM repos
  class Simp::YUM

    class Error < StandardError
    end

    require 'tmpdir'
    require 'facter'
    require 'simp/rpm'

    attr_reader :yum_conf

    def initialize(yum_conf, initialize_cache = false)
      if File.exist?(yum_conf)
        @yum_conf = File.absolute_path(yum_conf)
      else
        raise(Error, "Could not find yum configuration at '#{yum_conf}'")
      end

      # Only need to look these up once!
      @@yum_cmd ||= %x(which yum).strip
      raise(Error, "Error: Could not find 'yum'. Please install and try again.") if @@yum_cmd.empty?

      tmp_dir = ENV['TMPDIR'] || '/tmp'

      # Ensure that yumdownloader uses a fresh cache directory for each run of a given platform
      @@yum_cache ||= File.join(tmp_dir, 'yum_cache-' +
        Facter.fact('operatingsystem').value + '-' +
        Facter.fact('operatingsystemmajrelease').value + '-' +
        Facter.fact('architecture').value)

      FileUtils.mkdir_p(@@yum_cache)

      @@yum ||= "TMPDIR=#{@@yum_cache} #{@@yum_cmd} -c #{@yum_conf}"

      @@yumdownloader_cmd ||= %x(which yumdownloader).strip
      raise(Error, "Error: Could not find 'yumdownloader'. Please install and try again.") if @@yumdownloader_cmd.empty?

      @@yumdownloader ||= "TMPDIR=#{@@yum_cache} #{@@yumdownloader_cmd} -c #{@yum_conf}"

      @@curl ||= %x(which curl).strip
      raise(Error, "Error: Could not find 'curl'. Please install and try again.") if @@curl.empty?

      @@file ||= %x(which file).strip
      raise(Error, "Error: Could not find 'file'. Please install and try again.") if @@file.empty?

      generate_cache if initialize_cache
    end

    def clean_yum_cache_dir
      # Make this as safe as we can
      if @@yum_cache =~ /yum_cache/
        FileUtils.remove_entry(@@yum_cache)
      end
    end

    def generate_cache
      puts "Attempting to generate build-specific YUM cache from\n  #{@yum_conf}"

      %x(#{@@yum} clean all 2>/dev/null)
      %x(#{@@yum} makecache 2>/dev/null)

      unless $?.success?
        puts "WARNING: Unable to generate build-specific YUM cache from #{@yum_conf}"
      end
    end

    # Create a reasonable YUM config file
    # * yum_tmp => The directory in which to store the YUM DB and any other temporary files
    #
    # Returns the location of the YUM configuration
    def self.generate_yum_conf(yum_dir=nil)
      yum_dir ||= Dir.pwd

      raise(Error, "Could not find YUM data dir at '#{yum_dir}'") unless File.directory?(yum_dir)

      yum_conf = nil
      Dir.chdir(yum_dir) do
        # Create the target directory
        yum_tmp = File.join('packages','yum_tmp')

        FileUtils.mkdir_p(yum_tmp) unless File.directory?(yum_tmp)

        yum_cache = File.expand_path('yum_cache', yum_tmp)
        FileUtils.mkdir_p(yum_cache) unless File.directory?(yum_cache)

        yum_logfile = File.expand_path('yum.log', yum_tmp)

        repo_dirs = []

        # Add the global directory
        repo_dirs << File.expand_path('../my_repos')

        if File.directory?('my_repos')
          # Add the local user repos if they exist
          repo_dirs << File.expand_path('my_repos')
        else
          # Add the default Internet repos otherwise
          repo_dirs << File.expand_path('repos')
        end

        # Create our YUM config file
        yum_conf = File.expand_path('yum.conf', yum_tmp)

        File.open(yum_conf, 'w') do |fh|
          fh.puts <<-EOM.gsub(/^\s+/,'')
          [main]
          keepcache = 0
          persistdir = #{yum_cache}
          logfile = #{yum_logfile}
          exactarch = 1
          obsoletes = 0
          gpgcheck = 0
          plugins = 1
          reposdir = #{repo_dirs.join(' ')}
          assumeyes = 1
          EOM
        end
      end

      return yum_conf
    end

    # Returns the full name of the latest package of the given name
    #
    # Returns nil if nothing found
    def available_package(rpm)
      yum_output = %x(#{@@yum} list #{rpm} 2>/dev/null)

      found_rpm = nil
      if $?.success?
        pkg_name, pkg_version = yum_output.lines.last.strip.split(/\s+/)
        pkg_name, pkg_arch = pkg_name.split('.')

        found_rpm = %(#{pkg_name}-#{pkg_version}.#{pkg_arch}.rpm)
      end

      return found_rpm
    end

    def get_sources(rpm)
      sources = %x(#{@@yumdownloader} --urls #{File.basename(rpm,'.rpm')} 2>/dev/null).split("\n").grep(%r(\.rpm$))

      raise(Error, "No sources found for '#{rpm}'") if sources.empty?

      return sources
    end

    def get_source(rpm, arch=nil)
      sources = get_sources(rpm)

      if arch
        native_sources = sources.grep(%r((#{arch}|noarch)\.rpm$))

        if native_sources.size > 1
          # We can't have more than one native source
          raise(Error, "More than one native source found for #{rpm}:\n  * #{native_sources.join("\n  *")}")
        end
      end

      return sources.first
    end

    def download(rpm, opts={:target_dir => nil})
      target_dir = Dir.pwd

      if opts[:target_dir]
        target_dir = File.absolute_path(opts[:target_dir])
      end

      Dir.mktmpdir do |dir|
        Dir.chdir(dir) do
          # If just passed an RPM name, use yumdownloader
          if rpm !~ %r(://)
            # In case someone passed a path
            rpm_name = rpm.split(File::SEPARATOR).last

            #FIXME Should really report stderr output so user can
            # diagnose the problem
            %x(#{@@yumdownloader} #{File.basename(rpm_name, '.rpm')} 2>/dev/null)
          else
            # If passed a URL, curl it and fall back to yumdownloader
            rpm_name = rpm.split('/').last

            %x(#{@@curl} -L --max-redirs 10 -s -o #{rpm_name} -k #{rpm})

            # Check what we've just downloaded
            if !(File.exist?(rpm_name) || %x(#{@@file} #{rpm_name}).include('RPM'))
              # Fall back on yumdownloader
              FileUtils.rm_f(rpm_name)

              %x(#{@@yumdownloader} #{File.basename(rpm_name, '.rpm')} 2> /dev/null)
            end
          end

          rpms = Dir.glob('*.rpm')
          raise(Error, "Could not find any remote RPMs for #{rpm}") if rpms.empty?

          # Copy over all of the RPMs
          rpms.each do |new_rpm|
            FileUtils.mkdir_p(target_dir)
            FileUtils.mv(new_rpm, target_dir)
          end
        end
      end
    end
  end
end