#!/usr/bin/env ruby

require "base64"
require "io/console"
require "optparse"
require "socket"

usage_output = "USAGE:\n    github-fast-env SCRIPT_PATH [options]"

$options = {:verbose => false, :interactive => false}
OptionParser.new do |options|
	options.banner = usage_output
	options.on("-v", "--verbose", "Show verbose output") do
		$options[:verbose] = true
	end
	options.on("-i", "--interactive", "Run an interactive session using a pseudoterminal") do
		$options[:interactive] = true
	end
end.parse!

if not ARGV or ARGV.empty?
	$stderr.puts "error: missing argument (script path)\n\n"
	$stderr.puts usage_output
	exit 1
end

if ARGV.length > 1
	$stderr.puts "error: only one script expected\n\n"
	$stderr.puts usage_output
	exit 1
end

# TODO: support arguments
# TODO: forward signals
script_path = File.realpath(ARGV[0])

control_socket_path = "/tmp/github-fast-envd.sock"

$control_socket = UNIXSocket.new(control_socket_path)

$original_stdin = $stdin.dup
$original_stdout = $stdout.dup
$original_stderr = $stderr.dup

def log(level, message)
	if level == "error" or $options[:verbose]
		$original_stderr.puts "[github-fast-env] #{level}: #{message}"
	end
end

def read_command
	ready_ios = IO.select([$control_socket], [], [], 10)

	if not ready_ios
		log "error", "timeout while communicating with github-fast-envd"
		exit 1
	end

	response = $control_socket.readline.strip.split(" ", 2)

	if response.empty?
		log "error", "malformed response from github-fast-envd"
		exit 1
	end

	command = response[0]

	if command == "error"
		if response.length < 2
			log "error", "malformed error response from github-fast-envd"
			exit 1
		end

		error_message = response[1]

		log "error", "#{error_message}"
		exit 1
	end

	if command == "script_error"
		if response.length < 2
			log "error", "malformed script error response from github-fast-envd"
			exit 1
		end

		error_message = Base64.decode64(response[1])

		$stderr.puts error_message
		exit 1
	end

	arguments = response[1].nil? ? [] : response[1].split(" ")

	return command, arguments
end

log "info", "connected to control socket"

encoded_script_path = Base64.encode64(script_path).delete("\n")

read_ios = [$control_socket]

if $options[:interactive]
	pseudoterminal_path = File.readlink("/proc/self/fd/0")
	encoded_pseudoterminal_path = Base64.encode64(pseudoterminal_path).delete("\n")

	$control_socket.puts "new v1 pseudoterminal #{encoded_pseudoterminal_path} #{encoded_script_path}"
else
	$control_socket.puts "new v1 named-pipes #{encoded_script_path}"
end

pipes = {"stdin" => nil, "stdout" => nil, "stderr" => nil}

while true
	command, arguments = read_command

	if command == "ready"
		break
	elsif command == "named-pipes"
		if arguments.empty?
			log "error", "malformed response"
			exit 1
		end

		pipe_base_path = Base64.decode64(arguments[0])

		log "info", "connecting to named pipes at #{pipe_base_path}"

		pipes["stdin"] = File::open("#{pipe_base_path}.stdin", "w")
		pipes["stdin"].sync = true
		pipes["stdout"] = File::open("#{pipe_base_path}.stdout", "r")
		pipes["stdout"].sync = true
		pipes["stderr"] = File::open("#{pipe_base_path}.stderr", "r")
		pipes["stderr"].sync = true

		read_ios += [$stdin, pipes["stdout"], pipes["stderr"]]

		log "info", "connected via named pipes"

		log "info", "ready"
		$control_socket.puts "ready"
	else
		log "error", "malformed response"
		exit 1
	end
end

exit_code = "unknown"

while read_ios.include?($control_socket) or read_ios.include?(pipes["stdout"]) or read_ios.include?(pipes["stderr"])
	log "trace", read_ios.inspect

	ready_read_ios, _, _ = IO.select(read_ios, [], [])

	log "trace", "ready read IOs: #{ready_read_ios.inspect}"

	ready_read_ios.each do |ready_read_io|
		begin
			if ready_read_io.equal? $stdin
				log "trace", "writing to stdin"
				pipes["stdin"].write ready_read_io.readpartial(4096)
			elsif ready_read_io.equal? pipes["stdout"]
				log "trace", "reading from stdout"
				$stdout.write ready_read_io.readpartial(4096)
			elsif ready_read_io.equal? pipes["stderr"]
				log "trace", "reading from stderr"
				$stderr.write ready_read_io.readpartial(4096)
			elsif ready_read_io.equal? $control_socket
				log "trace", "reading from control socket"
				command, arguments = read_command

				if command != "done"
					log "error", "malformed response from github-fast-envd"
				end

				if !arguments.empty?
					exit_code = arguments[0]
				end
			else
				log "warn", "received input from unknown stream"
			end
		rescue EOFError
			log "trace", "closing stream #{ready_read_io}"
			ready_read_io.close
		end
	end

	read_ios = read_ios.select {|x| not x.closed?}
end

exit_code_is_numeric = Integer(exit_code) != nil rescue false

if exit_code_is_numeric
	exit Integer(exit_code)
end