#!/bin/csh -f
#+
# abba -- acquire spectra in an ABBA sequence
#
# Purpose:
#	Acquire one or more sequences of four spectra in which the
#	first and last images are offset to one side of the starting
#	point, and the second and third lie on the other side.
#
# Usage:
#	abba [size [repeats]]
# 
# Arguments:
#	size = dither size to each side of starting location 
#		[arcsec; default=1.0 arcsec]
#	repeats = number of times to repeat ABBA pattern [default=1]
# 
# Output:
#	To stdout
#
# Retrictions:
#	Slits must be untilted.
# 
# Side effects:
#	Marks base before starting exposure sequence
# 
# Exit values:
#	 0 = normal completion
#	 1 = wrong number of arguments
#
# Example:
#	1) Acquire a single ABBA sequence with 1.0-arcsec nods
#		abba
#
#	1) Acquire five single ABBA sequences with 1.5-arcsec nods
#		abba 1.5 5
#-
# Modification history:
#	2014-Jan-31	GDW	Original version
#-----------------------------------------------------------------------

set cmd = `basename $0`
set usage = "Usage: $cmd"
## set debug = 1

# defaults...
@ niter = 1
set nod = 1.0

# first arg is nod size...
if ( $#argv >= 1 ) then
    set nod = $1
    shift
endif

# second arg is repeats...
if ( $#argv >= 1 ) then
    @ niter = $1
    shift
endif

# no more args allowed...
if ( $#argv >= 1 ) then
  printf "$usage\n\a"
  exit 1
endif

# disable moves in debug mode...
if ( $?debug ) then
    alias markbase echo markbase
    alias gotobase echo gotobase
    alias mx echo mx
    alias goi echo goi
    alias is_float echo
endif

# confirm that the nod is a legal number...
is_float $nod > /dev/null
if ( $status != 0 ) then
    printf "[$cmd] ERROR: nodsize $nod is not a legal numerical value -- abort!\n\a"
    exit 1
endif

# verify that nod is positive...
set nod = `calc "abs($nod)"`

cat <<EOF
========================================================================
			Starting ABBA sequence
========================================================================

Nod size = +/-$nod arcsec
Repeats  = $niter

EOF

#  wait for FCS to track...
printf "Waiting for FCS to track..."
wffcs
if ( $status == 0 ) then
    printf "OK\n"
else 
    printf "\n\n[$cmd] ERROR: FCS is not tracking -- abort!\n"
    beep 3
    exit 1
endif

set offsets = ( 1 -2 0 2 )
set positions = ( A B B A )

# save starting location...
markbase

@ k = 0
while ( $k < $niter )
    @ k++
    @ sum = 0

    foreach i ( 1 2 3 4 )
	set j = $offsets[$i]
	set pos = $positions[$i]

	# keep track of location...
	@ sum += $j
	set dx = `calc "$sum*$nod"`

	# make telescope offset...
	set x = `calc "$j*$nod"`
	mx $x

	# build message...
	printf "\n-----------------------------------------------------------------\n"
	if ( $niter > 1 ) then
	    printf "Iteration: %d/%d " $k $niter
	endif
	printf "Nod position: %d/4 (%s) Offset: %+.1f arcsec from base)\n" $i $pos $dx
	printf "-----------------------------------------------------------------\n"

	goi
    end
    gotobase
end


# go home...
gotobase

cat <<EOF

========================================================================
		     Exposure sequence completed
========================================================================
EOF

beep 3
exit