#!/usr/bin/env ruby

# Copyright (c) 2010 Samuel Williams. Released under the GNU GPLv3.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
# 
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
# 
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

require 'rubygems'

require 'rexec'
require 'optparse'

OPTIONS = {
	:out => "/tmp/daemon-exec.log",
	:err => "/tmp/daemon-exec-error.log",
	:in => "/dev/null",
	:print_pid => false,
	:root => "/",
	:verbose => false,
	:relocate => true,
	:read_stdin => false,
}

ARGV.options do |o|
	script_name = File.basename($0)

	o.set_summary_indent("\t")
	o.banner = "Usage: #{script_name} [-I stdin] [-O stdout] [-E stderr] [script/stdin]"
	o.define_head "Copyright (c) 2010 Samuel Williams <http://www.oriontransfer.co.nz/>."

	o.on("-d [dir]", String, "Daemons working path, default /") do |dir|
		OPTIONS[:root] = dir
	end
	
	o.on("-s", "Don't attempt to relocate arguments to absolute paths") do
		OPTIONS[:relocate] = false
	end

	o.define "File / Pipe Options:"

	o.on("-I [path]", String, "File for STDIN, defaults to #{OPTIONS[:in]}") do |path|
		OPTIONS[:in] = path
	end
	
	o.on("--stdin", "Read from current STDIN to daemon process.") do
		OPTIONS[:in] = "-"
	end
	
	o.on("-O [path]", String, "File for STDOUT, defaults to #{OPTIONS[:out]}") do |path|
		OPTIONS[:out] = path
	end
	
	o.on("-E [path]", String, "File for STDERR, defaults to #{OPTIONS[:err]}") do |path|
		OPTIONS[:err] = path
	end
	
	o.define "Misc Options:"
	
	o.on("-p", "Print out the PID of the forked process") do
		OPTIONS[:print_pid] = true
	end
	
	o.on("-V", "Print verbose information about what is going on") do
		OPTIONS[:verbose] = true
	end
	
	o.on("-h", "Show this help/version information and exit") do
		puts o
		exit 0
	end
end.parse!

if OPTIONS[:relocate]
	ARGV.collect! do |value|
		if File.exist?(value)
			File.expand_path(value)
		else
			value
		end
	end

	[:in, :out, :err].each do |path|
		OPTIONS[path] = File.expand_path(OPTIONS[path]) if File.exist?(OPTIONS[path])
	end
end

if OPTIONS[:verbose]
	puts "Running #{ARGV.inspect}"
end

task_options = {
	:daemonize => true,
	:out => File.open(OPTIONS[:out], "a"),
	:err => File.open(OPTIONS[:err], "a")
}

if OPTIONS[:in] == '-'
	task_options[:passthrough] = [:in]
end

daemon = lambda do
	Dir.chdir(OPTIONS[:root])
	system("env", *ARGV)
end

task = RExec::Task.open(daemon, task_options)

if OPTIONS[:print_pid]
	puts task.pid
end