PRO dustem_write_mix,dir,st,help=help

;+
; NAME:
;   dustem_write_mix
;
; PURPOSE:
;   writes information relating to grain mixture parameters in the .DAT files 
;
; CATEGORY:
;    DustEMWrap, Distributed, LowLevel, Initialization
;
; CALLING SEQUENCE:
;   dustem_write_mix,dir,st
;
; INPUTS:
;    st   : dustem data structure
;    dir  : output directory where file will be written
;
; OPTIONAL INPUT PARAMETERS:
;    None
;
; OUTPUTS:
;    None
;
; OPTIONAL OUTPUT PARAMETERS:
;    None
;
; ACCEPTED KEY-WORDS:
;    help     : writes this help
;
; COMMON BLOCKS:
;    None
;
; SIDE EFFECTS:
;    Files are written
;
; 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_write_mix'
     goto,the_end
  ENDIF
 
IF ptr_valid(st[0]) THEN BEGIN
  comments=(*st[0]).comments
  Ncomments=n_elements(comments)
ENDIF ELSE BEGIN
  Ncomments=0L
ENDELSE
  
Nst=n_elements(st)
  
frmts=[ $
         '(A)', $
         '(A)', $
         '(A)', $
         '(A)', $
         '(A)']

;Start loop over type of grain
FOR i=0L,Nst-1 DO BEGIN
  ;Test if the pointer is pointing to something
  IF ptr_valid(st(i)) THEN BEGIN
    frmts=replicate('(A)',n_elements((*st(i)).fmix))
    ;Get filename
    ffile=(*st(i)).file
    fv=str_sep(ffile,'/')
    file=dir+fv(n_elements(fv)-1)
    ;Open file
    message,'Will write MIX file '+file,/info
    openw,unit,file,/get_lun
    ;Print comments
    IF Ncomments NE 0 THEN BEGIN
      FOR ii=0,Ncomments-1 DO BEGIN
        printf,unit,comments[ii]
      ENDFOR
    ENDIF
    ;Print FMIX to file
    FOR k=0L,n_elements((*st(i)).fmix)-1 DO BEGIN
      printf,unit,((*st(i)).fmix)(k),format=frmts[k]
    ENDFOR
    close,unit
    free_lun,unit
  ENDIF ELSE BEGIN
    ;left blank intentionally
  ENDELSE
ENDFOR

the_end:
END