require 'open3'
require 'fileutils'

module Canals

  class Exception < ::RuntimeError; end

  class << self

    def create_tunnel(tunnel_opts)
      Canals.repository.add tunnel_opts
    end

    def start(tunnel_opts)
      if tunnel_opts.instance_of? String
        tunnel_opts = Canals.repository.get(tunnel_opts)
      end
      exit_code = tunnel_start(tunnel_opts)
      raise Canals::Exception, "could not start tunnel" unless exit_code.success?
      pid = tunnel_pid(tunnel_opts)
      session_data = {name: tunnel_opts.name, pid: pid, socket: socket_file(tunnel_opts)}
      session_data = tunnel_opts.to_hash(:full).merge(session_data) if tunnel_opts.adhoc
      Canals.session.add(session_data)
      pid.to_i
    end

    def stop(tunnel_opts, remove_from_session: true)
      if tunnel_opts.instance_of? String
        if (Canals.repository.has?(tunnel_opts))
          tunnel_opts = Canals.repository.get(tunnel_opts)
        else
          tunnel_opts = Canals.session.get_obj(tunnel_opts)
        end
      end
      tunnel_close(tunnel_opts)
      Canals.session.del(tunnel_opts.name) if remove_from_session
    end

    def restart(tunnel_opts)
      stop(tunnel_opts)
      start(tunnel_opts)
    end

    def isalive?(tunnel_opts)
      if tunnel_opts.instance_of? String
        if (Canals.repository.has?(tunnel_opts))
          tunnel_opts = Canals.repository.get(tunnel_opts)
        else
          tunnel_opts = Canals.session.get_obj(tunnel_opts)
        end
      end
      !!tunnel_pid(tunnel_opts)
    end

    private

    def socket_file(tunnel_opts)
      "/tmp/canals/canal.#{tunnel_opts.name}.sock"
    end

    def tunnel_start(tunnel_opts)
      FileUtils.mkdir_p("/tmp/canals")
      if (tunnel_opts.socks)
        cmd = "ssh -M -S #{socket_file(tunnel_opts)} -o 'ExitOnForwardFailure=yes' -fnNT -D \"#{tunnel_opts.bind_address}:#{tunnel_opts.local_port}\" #{tunnel_opts.proxy}"
      else
        cmd = "ssh -M -S #{socket_file(tunnel_opts)} -o 'ExitOnForwardFailure=yes' -fnNT -L #{tunnel_opts.bind_address}:#{tunnel_opts.local_port}:#{tunnel_opts.remote_host}:#{tunnel_opts.remote_port} #{tunnel_opts.proxy}"
      end
      system(cmd)
      $?
    end

    def tunnel_check(tunnel_opts)
      cmd = "ssh -S #{socket_file(tunnel_opts)} -O check #{tunnel_opts.proxy}"
      Open3.capture2e(cmd)
    end

    def tunnel_close(tunnel_opts)
      cmd = "ssh -S #{socket_file(tunnel_opts)} -O exit #{tunnel_opts.proxy}"
      Open3.capture2e(cmd)
    end

    def tunnel_pid(tunnel_opts)
      stdout, _ = tunnel_check(tunnel_opts)
      m = /\(pid=(.*)\)/.match(stdout)
      m[1].to_i if m
    end

  end
end