;+
;PURPOSE:	To return a data structure for a specific time from a FAST l1 common block.
;USEAGE:	dat=get_fa1_ses(t)
;			The routine assumes the l1 common block is already loaded into IDL.
;KEYWORDS:	/START to return data structure for the first time in l1 common block.
;			/EN to return data structure for the last time in l1 common block.
;			/ADVANCE to return the next data structure in the l1 common block.
;			/RETREAT to return the previous data structure in the l1 common block.
;			INDEX=INDEX to return the INDEXth data structure in the l1 common block.
;			/CALIB does nothing.
;			/TIMES returns array of starting times in l1 common block instead of data structure.
;			UNITS=UNITS allows you to choose the returned data's units.  Default is compressed.
;BUGS:		None that I know of.
;UPDATES:
;-

function get_fa1_ses,t, $
					start=start, $
					en=en, $
					advance=advance, $
					retreat=retreat, $
					index=index, $
					calib=calib, $
					times=times, $
					units=units

common fa_ses_l1,get_ind,all_dat

if keyword_set(times) then return,all_dat.time
ntimes=n_elements(all_dat.time)

time_threshold=.05
if n_elements(index) EQ 0 then begin
	if keyword_set(advance) then begin
		if get_ind EQ ntimes-1 then begin
			print,'Error: End of Data. Cannot Advance.'
			return,{data_name:'', valid:0}
		endif
		index=get_ind+1
	endif
	if keyword_set(retreat) then begin
		if get_ind EQ 0 then begin
			print,'Error: Beginning of Data. Cannot Retreat'
			return,{data_name:'', valid:0}
		endif
		index=get_ind-1
	endif
	if keyword_set(en) AND keyword_set(start) then begin
		print,'Error: Both /EN and /START Keywords Set'
		return,{data_name:'', valid:0}
	endif
	if keyword_set(start) then index=0
	if keyword_set(en) then index=ntimes-1
	if n_elements(index) EQ 0 then begin
		if keyword_set(t) then begin
			t=time_double(t)
			time_tmp=(all_dat.time+all_dat.end_time)/2
			min_tmp=min(time_tmp-t,index_tmp,/absolute)
			min_tmp=abs(min(all_dat.time-t,index_tmp2,/absolute))
			if min_tmp LT time_threshold then index_tmp=index_tmp2
			original_t=t
			index=index_tmp[0]
			if abs(min_tmp) GT 5 then begin
				print,'Warning: All Data Samples Further than 5 Seconds from t'
				original_flag=1
			endif
		endif else begin
			ctime,t,npoints=1
			if NOT keyword_set(t) then begin
				print,'Error @ fa_seb_struct_1l.pro: CTIME Failure!'
				return,{data_name:'', valid:0}
			endif
			time_tmp=(all_dat.time+all_dat.end_time)/2
			min_tmp=min(time_tmp-t,index_tmp,/absolute)
			min_tmp=abs(min(all_dat.time-t,index_tmp2,/absolute))
			if min_tmp LT time_threshold then index_tmp=index_tmp2
			original_t=t
			index=index_tmp[0]
			if abs(min_tmp) GT 5 then begin
				print,'Warning: All Data Samples Further than 5 Seconds from t'
				original_flag=1
			endif
		endelse
	endif
endif
if (index LT 0) OR (index GE ntimes) then begin
	print,'Error: Index Out of Bounds!'
	return,{data_name:'', valid:0}
endif
;t=all_dat.time[index]
get_ind=long(index)

nbins=all_dat.nbins[index]
nenergy=all_dat.nenergy[index]
mode_ind=all_dat.mode_ind[index]

if mode_ind EQ 0 then data=all_dat.data0[0:47,0:15,all_dat.data_ind[index]]
if mode_ind EQ 1 then data=all_dat.data1[0:23,0:15,all_dat.data_ind[index]]
if mode_ind EQ 2 then data=all_dat.data2[0:11,0:15,all_dat.data_ind[index]]
if mode_ind EQ 3 then data=all_dat.data3[0:5,0:15,all_dat.data_ind[index]]

end_time=all_dat.end_time[index]
units_procedure=all_dat.units_procedure
valid=all_dat.valid[index]

gf=shift(all_dat.gf[0:nenergy-1,0:nbins-1,all_dat.gf_ind[index]],0,-all_dat.gf_shift[index])
dtheta=replicate(22.5,nenergy,nbins)
theta=all_dat.theta[0:nenergy-1,0:nbins-1,all_dat.theta_ind[index]]+all_dat.theta_shift[index]
where_gt=where(theta GT all_dat.theta_max[index])
where_lt=where(theta LT all_dat.theta_min[index])
if where_gt[0] NE -1 then theta[where_gt]-=360.
if where_lt[0] Ne -1 then theta[where_lt]+=360.

if keyword_set(original_t) AND (NOT keyword_set(original_flag)) then begin
	if (original_t LT (all_dat.time[index]-time_threshold)) OR $
		(original_t GT (end_time+time_threshold)) then $
		print,'Warning: t Not Between TIME and END_TIME'
endif

datastr={data_name:all_dat.data_name, $
		valid:valid, $
		data_quality:all_dat.data_quality[index], $
		project_name:'FAST', $
		units_name:all_dat.units_name, $
		units_procedure:units_procedure, $
		time:all_dat.time[index], $
		end_time:end_time, $
		integ_t:all_dat.integ_t[index], $
		nbins:nbins, $
		nenergy:nenergy, $
		data:float(data), $
		energy:all_dat.energy[0:nenergy-1,0:nbins-1,all_dat.energy_ind[index]], $
		bins:all_dat.bins[0:nenergy-1,0:nbins-1,all_dat.bins_ind[index]], $
		theta:theta, $
		geom:gf, $
		gf:gf, $
		denergy:all_dat.denergy[0:nenergy-1,0:nbins-1,all_dat.energy_ind[index]], $
		dtheta:dtheta, $
		eff:all_dat.eff[0:nenergy-1,0:nbins-1,all_dat.energy_ind[index]], $
		dead:all_dat.dead, $
		mass:all_dat.mass, $
		geom_factor:all_dat.geom_factor[index], $
		geomfactor:all_dat.geom_factor[index], $
		sc_pot:all_dat.sc_pot[index], $
		charge:all_dat.charge, $
		header_bytes:all_dat.header_bytes[*,index], $
		index:index, $
		spin_phase:all_dat.spin_phase[index], $
		spin_num:all_dat.spin_num[index], $
		spin_ph_hdr:all_dat.spin_ph_hdr[index], $
		sweep_num:all_dat.sweep_num[index], $
		swps_per_set:all_dat.swps_per_set[index] }

if NOT keyword_set(units) then units='Counts'
if valid EQ 1 then call_procedure,units_procedure,datastr,units

return,datastr

end