#
# Author:: Adam Jacob (<adam@opscode.com>)
# Copyright:: Copyright (c) 2008 Opscode, Inc.
# License:: Apache License, Version 2.0
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
# 
#     http://www.apache.org/licenses/LICENSE-2.0
# 
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

require 'chef/log'
require 'chef/exceptions'
require 'tmpdir'
require 'fcntl'
require 'etc'
require 'io/wait'

class Chef
  module Mixin
    module Command
      
      # If command is a block, returns true if the block returns true, false if it returns false.
      # ("Only run this resource if the block is true")
      #
      # If the command is not a block, executes the command.  If it returns any status other than
      # 0, it returns false (clearly, a 0 status code is true)
      #
      # === Parameters
      # command<Block>, <String>:: A block to check, or a string to execute
      #
      # === Returns
      # true:: Returns true if the block is true, or if the command returns 0
      # false:: Returns false if the block is false, or if the command returns a non-zero exit code.
      def only_if(command, args = {})
        if command.kind_of?(Proc)
          chdir_or_tmpdir(args[:cwd]) do
            res = command.call
            unless res
              return false
            end
          end
        else  
          status = run_command({:command => command, :ignore_failure => true}.merge(args))
          if status.exitstatus != 0
            return false
          end
        end
        true
      end
      
      module_function :only_if
      
      # If command is a block, returns false if the block returns true, true if it returns false.
      # ("Do not run this resource if the block is true")
      #
      # If the command is not a block, executes the command.  If it returns a 0 exitstatus, returns false.
      # ("Do not run this resource if the command returns 0")
      #
      # === Parameters
      # command<Block>, <String>:: A block to check, or a string to execute
      #
      # === Returns
      # true:: Returns true if the block is false, or if the command returns a non-zero exit status.
      # false:: Returns false if the block is true, or if the command returns a 0 exit status.
      def not_if(command, args = {})
        if command.kind_of?(Proc)
          chdir_or_tmpdir(args[:cwd]) do
            res = command.call
            if res
              return false
            end
          end
        else  
          status = run_command({:command => command, :ignore_failure => true}.merge(args))
          if status.exitstatus == 0
            return false
          end
        end
        true
      end
      
      module_function :not_if
     
      # === Parameters
      # args<Hash>: A number of required and optional arguments
      #   command<String>, <Array>: A complete command with options to execute or a command and options as an Array 
      #   creates<String>: The absolute path to a file that prevents the command from running if it exists
      #   cwd<String>: Working directory to execute command in, defaults to Dir.tmpdir
      #   timeout<String>: How many seconds to wait for the command to execute before timing out
      #   returns<String>: The single exit value command is expected to return, otherwise causes an exception
      #   ignore_failure<Boolean>: Whether to raise an exception on failure, or just return the status
      #   output_on_failure<Boolean>: Return output in raised exception regardless of Log.level
      # 
      #   user<String>: The UID or user name of the user to execute the command as
      #   group<String>: The GID or group name of the group to execute the command as
      #   environment<Hash>: Pairs of environment variable names and their values to set before execution
      #
      # === Returns
      # Returns the exit status of args[:command]
      def run_command(args={})         
        command_output = ""
        
        args[:ignore_failure] ||= false
        args[:output_on_failure] ||= false

        if args.has_key?(:creates)
          if File.exists?(args[:creates])
            Chef::Log.debug("Skipping #{args[:command]} - creates #{args[:creates]} exists.")
            return false
          end
        end
        
        status, stdout, stderr = output_of_command(args[:command], args)
        command_output << "STDOUT: #{stdout}"
        command_output << "STDERR: #{stderr}"
        handle_command_failures(status, command_output, args)
        
        status
      end
      
      module_function :run_command
      
      def output_of_command(command, args)
        Chef::Log.debug("Executing #{command}")
        stderr_string, stdout_string, status = "", "", nil
        
        exec_processing_block = lambda do |pid, stdin, stdout, stderr|
          stdout_string, stderr_string = stdout.string.chomp, stderr.string.chomp
        end
        
        args[:cwd] ||= Dir.tmpdir
        unless File.directory?(args[:cwd])
          raise Chef::Exceptions::Exec, "#{args[:cwd]} does not exist or is not a directory"
        end
        
        Dir.chdir(args[:cwd]) do
          if args[:timeout]
            begin
              Timeout.timeout(args[:timeout]) do
                status = popen4(command, args, &exec_processing_block)
              end
            rescue Timeout::Error => e
              Chef::Log.error("#{command} exceeded timeout #{args[:timeout]}")
              raise(e)
            end
          else
            status = popen4(command, args, &exec_processing_block)
          end
          
          Chef::Log.debug("---- Begin output of #{command} ----")
          Chef::Log.debug("STDOUT: #{stdout_string}")
          Chef::Log.debug("STDERR: #{stderr_string}")
          Chef::Log.debug("---- End output of #{command} ----")
          Chef::Log.debug("Ran #{command} returned #{status.exitstatus}")
        end
        
        return status, stdout_string, stderr_string
      end
      
      module_function :output_of_command
      
      def handle_command_failures(status, command_output, opts={})
        unless opts[:ignore_failure]
          opts[:returns] ||= 0
          unless Array(opts[:returns]).include?(status.exitstatus)
            # if the log level is not debug, through output of command when we fail
            output = ""
            if Chef::Log.level == :debug || opts[:output_on_failure]
              output << "\n---- Begin output of #{opts[:command]} ----\n"
              output << command_output.to_s
              output << "\n---- End output of #{opts[:command]} ----\n"
            end
            raise Chef::Exceptions::Exec, "#{opts[:command]} returned #{status.exitstatus}, expected #{opts[:returns]}#{output}"
          end
        end
      end
      
      module_function :handle_command_failures
           
      # Call #run_command but set LC_ALL to the system's current environment so it doesn't get changed to C.
      #
      # === Parameters
      # args<Hash>: A number of required and optional arguments that will be handed out to #run_command
      #
      # === Returns
      # Returns the result of #run_command
      def run_command_with_systems_locale(args={})
        args[:environment] ||= {}
        args[:environment]["LC_ALL"] = ENV["LC_ALL"]
        run_command args
      end

      module_function :run_command_with_systems_locale

      # This is taken directly from Ara T Howard's Open4 library, and then 
      # modified to suit the needs of Chef.  Any bugs here are most likely
      # my own, and not Ara's.
      #
      # The original appears in external/open4.rb in its unmodified form. 
      #
      # Thanks Ara!
      def popen4(cmd, args={}, &b)
       
        # Waitlast - this is magic.  
        # 
        # Do we wait for the child process to die before we yield
        # to the block, or after?  That is the magic of waitlast.
        #
        # By default, we are waiting before we yield the block.
        args[:waitlast] ||= false
        
        args[:user] ||= nil
        unless args[:user].kind_of?(Integer)
          args[:user] = Etc.getpwnam(args[:user]).uid if args[:user]
        end
        args[:group] ||= nil
        unless args[:group].kind_of?(Integer)
          args[:group] = Etc.getgrnam(args[:group]).gid if args[:group]
        end
        args[:environment] ||= {}

        # Default on C locale so parsing commands output can be done
        # independently of the node's default locale.
        # "LC_ALL" could be set to nil, in which case we also must ignore it.
        unless args[:environment].has_key?("LC_ALL")
          args[:environment]["LC_ALL"] = "C"
        end
        
        pw, pr, pe, ps = IO.pipe, IO.pipe, IO.pipe, IO.pipe

        verbose = $VERBOSE
        begin
          $VERBOSE = nil
          ps.last.fcntl(Fcntl::F_SETFD, Fcntl::FD_CLOEXEC)

          cid = fork {
            pw.last.close
            STDIN.reopen pw.first
            pw.first.close

            pr.first.close
            STDOUT.reopen pr.last
            pr.last.close

            pe.first.close
            STDERR.reopen pe.last
            pe.last.close

            STDOUT.sync = STDERR.sync = true

            if args[:group]
              Process.egid = args[:group]
              Process.gid = args[:group]
            end

            if args[:user]
              Process.euid = args[:user]
              Process.uid = args[:user]
            end
            
            args[:environment].each do |key,value|
              ENV[key] = value
            end

            if args[:umask]
              umask = ((args[:umask].respond_to?(:oct) ? args[:umask].oct : args[:umask].to_i) & 007777)
              File.umask(umask)
            end
            
            begin
              if cmd.kind_of?(Array)
                exec(*cmd)
              else
                exec(cmd)
              end
              raise 'forty-two' 
            rescue Exception => e
              Marshal.dump(e, ps.last)
              ps.last.flush
            end
            ps.last.close unless (ps.last.closed?)
            exit!
          }
        ensure
          $VERBOSE = verbose
        end

        [pw.first, pr.last, pe.last, ps.last].each{|fd| fd.close}

        begin
          e = Marshal.load ps.first
          raise(Exception === e ? e : "unknown failure!")
        rescue EOFError # If we get an EOF error, then the exec was successful
          42
        ensure
          ps.first.close
        end

        pw.last.sync = true

        pi = [pw.last, pr.first, pe.first]

        if b 
          begin
            if args[:waitlast]
              b[cid, *pi]
              # send EOF so that if the child process is reading from STDIN
              # it will actually finish up and exit
              pi[0].close_write
              Process.waitpid2(cid).last
            else
              # This took some doing.
              # The trick here is to close STDIN
              # Then set our end of the childs pipes to be O_NONBLOCK
              # Then wait for the child to die, which means any IO it
              # wants to do must be done - it's dead.  If it isn't,
              # it's because something totally skanky is happening,
              # and we don't care.
              o = StringIO.new
              e = StringIO.new

              pi[0].close
              
              stdout = pi[1]
              stderr = pi[2]

              stdout.sync = true
              stderr.sync = true

              stdout.fcntl(Fcntl::F_SETFL, pi[1].fcntl(Fcntl::F_GETFL) | Fcntl::O_NONBLOCK)
              stderr.fcntl(Fcntl::F_SETFL, pi[2].fcntl(Fcntl::F_GETFL) | Fcntl::O_NONBLOCK)
              
              stdout_finished = false
              stderr_finished = false
             
              results = nil

              while !stdout_finished || !stderr_finished
                begin
                  channels_to_watch = []
                  channels_to_watch << stdout if !stdout_finished
                  channels_to_watch << stderr if !stderr_finished
                  ready = IO.select(channels_to_watch, nil, nil, 1.0)
                rescue Errno::EAGAIN
                ensure
                  results = Process.waitpid2(cid, Process::WNOHANG)
                  if results
                    stdout_finished = true
                    stderr_finished = true 
                  end
                end

                if ready && ready.first.include?(stdout)
                  line = results ? stdout.gets(nil) : stdout.gets
                  if line
                    o.write(line)
                  else
                    stdout_finished = true
                  end
                end
                if ready && ready.first.include?(stderr)
                  line = results ? stderr.gets(nil) : stderr.gets
                  if line
                    e.write(line)
                  else
                    stderr_finished = true
                  end
                end
              end
              results = Process.waitpid2(cid) unless results
              o.rewind
              e.rewind
              b[cid, pi[0], o, e]
              results.last
            end
          ensure
            pi.each{|fd| fd.close unless fd.closed?}
          end
        else
          [cid, pw.last, pr.first, pe.first]
        end
      end      
      
      module_function :popen4

      def chdir_or_tmpdir(dir, &block)
        dir ||= Dir.tmpdir
        unless File.directory?(dir)
          raise Chef::Exceptions::Exec, "#{dir} does not exist or is not a directory"
        end
        Dir.chdir(dir) do
          block.call
        end
      end

      module_function :chdir_or_tmpdir
    end
  end
end