require 'forwardable'
require 'shellwords'
require 'socket'

class Sh
	class ForkError < RuntimeError
	end
	class ForkFailed < ForkError
	end
	class ProcessError < ForkError
	end

	class Fork
		extend Forwardable
		def_delegators :@status, :exitstatus
		attr_reader :pid, :status

		def initialize &exe
			#@io, s = UNIXSocket.pair
			@pid =
				Process.fork do
					Thread.list.each do |th|
						th.kill  unless Thread.current == th
					end
					#STDOUT.reopen s.dup
					#STDIN.reopen s
					#STDOUT.close_read
					#STDIN.close_write
					yield
				end
			raise ForkFailed  unless @pid
			#s.close
		end

		def wait
			_, @status = Process.waitpid2 @pid
			@status
		end

		def kill signal = nil
			Process.kill signal||9, @pid
		end

		def ok?()      0 == @status.exitstatus  end
		def failed?()  0 != @status.exitstatus  end
	end

	class IOFork < Fork
		extend Forwardable
		def_delegators :@io, :close, :closed?, :close_read, :closed_read?, :close_write, :closed_write?
		def_delegators :@io, :getbyte, :getc, :getch, :getpass, :gets
		def_delegators :@io, :read, :read_nonblock, :readbyte, :readchar, :readline, :readlines, :readpartial, :sysread
		def_delegators :@io, :syswrite, :write, :write_nonblock
		def_delegators :@io, :putc, :puts, :print, :printf
		def_delegators :@io, :each_line
		attr_reader :io
		
		def initialize &exe
			@io, s = UNIXSocket.pair
			r = nil
			super do
				@io.close
				STDOUT.reopen s
				STDIN.reopen s
				#STDOUT.close_read
				#STDIN.close_write
				r = yield
			end
			s.close
			r
		end
	end

	class Command
		attr_reader :shell, :command, :args, :opts

		def initialize shell, command, *args, **opts
			@shell, @command, @args, @opts = shell, command, args, opts
		end

		def fork **opts
			opts = @opts.merge opts
			cl =
				case opts[:mode]
				when :io then IOFork
				when Class then opts[:mode]
				else Fork
				end
			cl.new do
				cmd = @command.to_s
				$0 = cmd
				#STDERR.printf "\n|\n| %p\n|\n", cmd: cmd, args: @args
				if opts.has_key? :stdio
					stdin, stdout, stderr = *opts[:stdio]
					stdin ? STDIN.reopen( stdin) : STDIN.close
					STDOUT.reopen stdout
					STDERR.reopen stderr  if stderr
				end
				if opts[:chroot]
					STDERR.printf "\e[1;34mchroot(%s)\e[0m ", opts[:chroot].to_s
					Dir.chroot opts[:chroot].to_s
				end
				if @shell.opts[:pwd]
					STDERR.printf "%s ", @shell.opts[:pwd]
					Dir.chdir @shell.opts[:pwd]
				end
				#STDERR.puts "\e[0m#{opts[:return] ? '<=' : '#'} \e[33m#{cmd.shellescape} \e[35m#{usable_args.shelljoin}\e[0m"
				STDERR.printf "\e[0m%s \e[33m%s \e[35m%s\e[0m\n",
					opts[:return] ? '<=' : '#',
					cmd.shellescape,
					usable_args.shelljoin
				exec cmd, *usable_args
				raise ForkFailed, "Cannot execute"
			end
		rescue ForkFailed => e
			raise ForkFailed, "<<#{self}>> cannot be forked"
		end

		def usable_args
			@uargs ||= @args.flatten.map &:to_s
		end

		def to_s
			"#{@command.to_s.shellescape}" + (usable_args.empty? ? '' : " #{usable_args.shelljoin}")
		end

		def run **opts, &exe
			opts = @opts.merge opts
			case opts[:return]
			when :lines
				opts[:mode], exe = :io, lambda( &:readlines)
			when :string
				opts[:mode], exe = :io, lambda( &:read)
			when :line
				opts[:mode], exe = :io, lambda{|f|f.read.chomp}
			end
			r = f = fork **opts
			begin
				r = exe.call f  if exe
			rescue Object
				f.kill
				raise $!
			ensure
				f.close  if f.respond_to? :close
				f.wait
			end
			unless opts[:expect_status].nil? or opts[:expect_status] == f.exitstatus
				raise ProcessError, "«#{self}» exited: #{f.status}"
			end
			r
		end

		def run! **opts, &exe
			run expect_status: 0, **opts, &exe
		end
		alias call run!
		alias !@ run!
	end

	attr_reader :opts

	def initialize dir = nil, **opts
		opts = opts.merge dir: dir  if dir
		@opts = opts.dup
		(@opts[:commands]||={}).each do |name, exe|
			define_singleton_method name, &exe
		end
		@opts.freeze
	end

	def chdir dir
		Sh.new dir, **opts
	end
	alias cd chdir
	def newopts **opts
		Sh.new **@opts.merge( opts)
	end

	def chroot dir
		newopts chroot: dir
	end

	def return_string
		newopts mode: nil, return: :string
	end

	alias _ return_string
	def return_lines
		newopts mode: nil, return: :lines
	end
	alias [] return_lines

	def with_io
		newopts mode: :io
	end
	alias io with_io

	def system command, *args, immediately: nil, **opts, &exe
		cmd = Command.new self, command, *args, **@opts.merge( opts)
		if immediately or @opts[:immediately] or block_given?
			cmd.run &exe
		else
			cmd
		end
	end

	def define_command name, &exe
		@opts[:commands][name] = exe
		define_singleton_method name, &exe
	end

	def def_system_command name, cmd = nil
		cmd ||= name
		define_command name do |*args, **opts, &exe|
			system cmd, *args, **opts, &exe
		end
		#e = <<-EOF
		#	def #{name}(*args, **opts, &exe)
		#		Command.new self, #{cmd.to_s.inspect}, *args, **opts
		#	end
		#EOF
		#eval e, nil, __FILE__, __LINE__ - 4
	end

	def def_system_commands *names
		names.each {|cmd| def_system_command cmd }
	end

	def alias_command name, cmd, *args, **opts, &exe
		opts = @opts.merge opts
		define_command name do |*as, **os, &e|
			*as = exe.call( *as)  if exe
			system cmd, *args, *as, **opts, **os
		end
	end
end

#f = Sh::IOFork.new do
#	STDERR.puts f.inspect
#	STDOUT.puts "hallo welt"
#	sleep 5
#end
#
#STDERR.puts "> #{f.inspect}"
#f.each_line do |l|
#	STDERR.puts "> #{l}"
#end
#f.wait
#exit 1