FUNCTION dustem_read_gcosth,file,silent=silent $
                             ,gcosth_values=gcosth_values 

;+
; NAME:
;   dustem_read_gcosth
;
; PURPOSE:
;   reads information relating to the grain G=cos(theta) scattering factors
;   from the corresponding .DAT file 
;
; CATEGORY:
;    DustEMWrap, Distributed, LowLevel, Initialization
;
; CALLING SEQUENCE:
;   st=dustem_read_gcosth(file)
;
; INPUTS:
;   file  : input file to be read
;
; OPTIONAL INPUT PARAMETERS:
;
; OUTPUTS:
;    st   : dustem data structure
;
; OPTIONAL OUTPUT PARAMETERS:
;    gcosth_values : values of gcosth read from file [Nsize x Nwav]
;  
; ACCEPTED KEY-WORDS:
;    help     : writes this help
;
; COMMON BLOCKS:
;    None
;
; SIDE EFFECTS:
;
; RESTRICTIONS:
;    The DustEM fortran code must be installed
;    The DustEMWrap IDL code must be installed
;
; PROCEDURES AND SUBROUTINES USED:  
;
; EXAMPLES:
;
; MODIFICATION HISTORY:
;    Evolution details on the DustEMWrap gitlab.
;    See http://dustemwrap.irap.omp.eu/ for FAQ and help.  
;-
  
IF keyword_set(help) THEN BEGIN
   doc_library,'dustem_read_gcosth'
   full_st=0.
   goto,the_end
ENDIF
  

st=''
Nmax=10000L ; we assume that there are less than this many lines in the file
sts=strarr(Nmax)
openr,unit,file,/get_lun

;==read comments
str='' & first_char='#'
WHILE first_char EQ '#' DO BEGIN
  readf,unit,str
  first_char=strmid(str,0,1)
ENDWHILE

;read number of sizes
Nsizes=fix(str)

;Get sizes
readf,unit,str
sizes=float(str_sep(strcompress(strtrim(str,2)),' '))
Ncol=Nsizes

; test read the next line to see if it contains densities 
;readf,unit,str
;first_char=strmid(str,0,1)
;IF first_char ne '#' THEN BEGIN
;  sizes=float(str_sep(strcompress(strtrim(str,2)),' '))
;ENDIF ELSE BEGIN
;  sizes=fltarr(Nsizes)+la_undef()
;ENDELSE

;==read comments
str='' & first_char='#'
WHILE first_char EQ '#' DO BEGIN
  readf,unit,str
  first_char=strmid(str,0,1)
ENDWHILE

;== read Gcosth
sts[0]=str
nlines=1L
first_char=' '
WHILE  not eof(unit) and first_char NE '#' DO BEGIN
    readf,unit,st
    sts[nlines]=st
    nlines=nlines+1
    first_char=strmid(st,0,1)
ENDWHILE
gcosth_str=sts[0:nlines-1]
close,unit
free_lun,unit

Nlines=n_elements(gcosth_str)
gcosth_values=fltarr(Nlines,Ncol)

FOR i=0L,Nlines-1 DO gcosth_values[i,*]=str_sep(strcompress(strtrim(gcosth_str[i],2)),' ')

;== Make output structure
cmd='one_st={'
FOR i=0L,Ncol-1 DO BEGIN
  cmd=cmd+'v'+strtrim(i+1,2)+':'+'0.'
  IF i NE Ncol-1 THEN BEGIN
    cmd=cmd+','
  ENDIF ELSE BEGIN
    cmd=cmd+'}'
  ENDELSE
ENDFOR
toto=execute(cmd)
gcosth_st=replicate(one_st,Nlines)

;=== fill in the gcosth structure
FOR j=0L,Ncol-1 DO BEGIN
  gcosth_st.(j)=reform(gcosth_values(*,j))
ENDFOR

full_st={file:file,Nsizes:Nsizes,sizes:sizes,Gcosth:gcosth_st}

the_end:
return,full_st

END