#! /bin/sh
# The next line is executed by /bin/sh, but not Tcl \
exec $TCLADAM_DIR/atclsh $0 ${1+"$@"}
#
# This script acts as a "go-between" between a tk application and adam 
# tasks. The tk application cannot communicate directly with an adam
# task because adam_receive blocks waiting for messages and so if it 
# was called within the tk application, the user interface would "hang".
#
# The go-between waits for adam messages; if a message is received from 
# the tk application, the message value is executed as a tcl command and
# the result sent to the tk application in an Adam inform message. If a 
# message is received from an adam task its contents are written to 
# standard output (for the tk application to read).

# Initialise the adam message system using comand line argument as our
# task name.
    set name [lindex $argv 0]
    set myname "${name}_relay"
    adam_start $myname

# Send an initial OBEY to the tk application.
    set transaction [adam_send ${name} action OBEY ""]

# Extract the path and messys id.
    set path [lindex $transaction 0]
    set messid [lindex $transaction 1]

# Fetch the reply to the obey.
    adam_receive

# Loop for ever collecting adam messages.
    for {} {1} {} {

	set message [adam_receive]

#     Extract the task name
	set task [lindex $message 1]

#     Compare the task name with the name of the tk application.
	if [string compare $task $name] {

#         Task did not match the name of the tk application so this must be
#         a message from and adam application. Send the message to the
#         tk application.
	    puts stdout $message
	    flush stdout
	} {

#   Message came from the tk application. Execute the message value as a
#   tcl command and send the result back to the tk application in a message
#   system message.
	    set value [lindex $message 6]
	    set status [catch {eval $value} result]
            if $status {
		adam_reply $path $messid SYNCREP TCL_ERROR $result
            } {
		adam_reply $path $messid SYNCREP TCL_OK $result
            }
	}
    }