require 'rbconfig'
require 'fileutils'

module Reap

  # = Installer
  #
  # The Installer class generates a specialized install.rb
  # script specifically for your project. It currently 
  # does not support c/c++ ext/ compilation.

  class Installer

    include TaskUtils

    def self.config(name)
      # XXX use pathname
      prefix = Regexp.quote(Config::CONFIG["prefix"])
      exec_prefix = Regexp.quote(Config::CONFIG["exec_prefix"])
      Config::CONFIG[name].gsub(/\A\/?(#{prefix}|#{exec_prefix})\/?/, '')
    end

    KINDS = [
      :bin, :lib, :ext, :data, :conf, :doc
    ]

    SITE_DIRS = {
      :bin  => config("bindir"),
      :lib  => config("sitelibdir"),
      :ext  => config("sitearchdir"),
      :data => config("datadir"),
      :conf => config("sysconfdir"),
      :doc  => File.join(config("datadir"), "doc"),
    }

    VEND_DIRS = {
      :bin  => config("bindir"),
      :lib  => config("rubylibdir"),
      :ext  => config("archdir"),
      :data => config("datadir"),
      :conf => config("sysconfdir"),
      :doc  => File.join(config("datadir"), "doc"),
    }

    MODES = {
      :bin  => 0755,
      :lib  => 0644,
      :ext  => 0755,  # was: 0555,
      :data => 0644,
      :conf => 0644,
      :doc  => 0644,
    }

    attr_accessor :trunk, :template, :options

    def initialize( ins )
      super
      @trunk = '.' unless @trunk
      @spec = parse( @template )
      @transfer = Hash.new { |h,k| h[k] = [] }
    end

    #--
    # TODO use shellwords
    #++
    def parse( spec )
      lines = spec.strip.split("\n")
      lines.each { |line|
        words = line.strip.split(/\s+/)
        send( *words )
      }
    end

    # substitute variables
    def vsub( str )
      return nil if str.nil?
      str = str.gsub( '$version', @options[:version].to_s )
      str = str.gsub( '$name', @options[:name].to_s )
      str
    end

    # Return the installation directory.
    def dir( kind, mode=:site )
      case mode
      when :site
        SITE_DIRS[ kind ]
      when :vendor
        VEND_DIRS[ kind ]
      else
        raise ArgumentError, "unknown mode -- #{mode}"
      end
    end

    # Return installation prefix.
    def prefix( kind )
      Config::CONFIG["prefix"]
    end

    #--
    # DSL methods for setting installation spec.
    #++

    # Setup a lib installation transfer.
    def lib( from, glob, to )
      to = '' if to == '.'
      @transfer[:lib] << { :from=>vsub(from), :glob=>vsub(glob), :to=>vsub(to) }
    end

    # Setup a bin installation transfer.
    def bin( from, glob, to )
      to = '' if to == '.'
      @transfer[:bin] << { :from=>vsub(from), :glob=>vsub(glob), :to=>vsub(to) }
    end

    # Compile script and write to install file (install.rb).

    def compile_and_write
      script = ""
      script << "# INSTALL SCRIPT\n"
      script << "# Generated by Reap\n"
      script << "# #{Time.now}\n"
      script << "\n"
      script << compile
      script << "\n"
      script << "# END"

      write( script )
    end

    alias_method :call, :compile_and_write

  private

    # Compile installation instructions.

    def compile
      mkdirp = []
      script = ''
      Dir.chdir( @trunk ) do
        KINDS.each { |kind|
          @transfer[kind].each { |trans|
            next unless File.directory?( trans[:from] )
            files = []
            Dir.chdir( trans[:from] ) {
              files = Dir.glob( trans[:glob] ).reject { |f| File.directory?( f ) }
            }
            files.each { |file|
              f = File.join( trans[:from], file )
              t = File.join( prefix(kind), dir(kind), trans[:to], file )
              m = MODES[kind]
              d = File.dirname(t)
              unless mkdirp.include?(d)
                script << "mkdir_p '%s'\n" % d
                mkdirp << d
              end
              script << "install '%s', '%s', :mode=>%o\n" % [ f, t, m ]
            }
          }
        }
      end
      script
    end

    def write( script )
      install_file = File.join( @trunk, 'install.rb' )
      if File.file?( install_file )
        script_template = File.read( install_file )
        script = script_template.gsub(/\# INSTALL SCRIPT.*\# END/, script)
        end
        File.open( install_file, 'w+' ) do |f|
          f << script
        end
      end
    end

  end

end #module Reap