FUNCTION dustem_plugin_dl07_isrf_model, key=key, val=val, scope=scope, paramtag=paramtag, help=help, Umean=Umean,st=st

;+
; NAME:
;    dustem_plugin_dl07_isrf_model
;
; PURPOSE:
;    Returns the dust spectrum after heating by a Draine-like ISRF
;            with Umin, Umax, gamma, alpha parameters described by the val keyword
;  
; CATEGORY:
;    DUSTEM Wrapper, Plugin
;
; CALLING SEQUENCE:
;    sed=dustem_plugin_dl07_isrf_model(key=,val=,Umean=,/paramtag][,/scope][,/help])
;
; INPUTS:
;    None
;
; OPTIONAL INPUT PARAMETERS:
;    key = input parameter number.
;           1: gamma
;           2: alpha
;           3: Umin
;           4: Umax
;    val = input parameter values for the above.
;
; OUTPUTS:
;    None
;
; OPTIONAL OUTPUT PARAMETERS:
;    Umean = the average radiation field
;  
; ACCEPTED KEY-WORDS:
;    help                  = if set, print this help
;
; COMMON BLOCKS:
;    None
;
; SIDE EFFECTS:
;    None
;
; RESTRICTIONS:
;    The DustEM fortran code must be installed
;    The DustEMWrap IDL code must be installed
;    The path of the ISRF must be assigned to one of the DustEMWrap free pointers.
;    The user-defined ISRF needs to be on the same dustem ISRF grid.
;
; PROCEDURE:
;    
; EXAMPLES
;    res=dustem_dl07_isrf_model()
;
; 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_dl07_isrf_model'
  goto,the_end
ENDIF

spec=0.

IF keyword_set(scope) THEN BEGIN 
    out=0 & st=0
    goto, the_end
ENDIF 

IF keyword_set(paramtag) THEN BEGIN
    out=0 & st=0
    goto, the_end 
ENDIF

;dustem_print_params
;stop

;==== default parameter values
Umin=1.
Umax=1.e6
alpha=2.
gamma=0.     ;default is no contribution from U<>1.
IF keyword_set(key) THEN BEGIN
    ind=where(key EQ 1,count) ;gamma parameter as in DL07
    IF count NE 0 then begin
       gamma=val[ind[0]]
    ENDIF
    ind=where(key EQ 2,count) ;gamma parameter as in DL07
    IF count NE 0 then begin
       alpha=val[ind[0]]
    ENDIF
    ind=where(key EQ 3,count) ;gamma parameter as in DL07
    IF count NE 0 then begin
       Umin=val[ind[0]]
    ENDIF
    ind=where(key EQ 4,count) ;gamma parameter as in DL07
    IF count NE 0 then begin
       Umax=val[ind[0]]
    ENDIF
ENDIF

;This is the average radiation field in DL07
Umean=(1.-gamma)*Umin+gamma*Umin*alog(Umax/Umin)/(1.-Umin/Umax)

lambir=dustem_get_wavelengths()

Nwavs=n_elements(lambir)
;spec=fltarr(Nwavs,3) ; if ever one day we enforce IQU outputs
;spec2=fltarr(Nwavs,3)
spec=fltarr(Nwavs) 
spec2=fltarr(Nwavs)

Ngrains=(*!dustem_params).ngrains
spec_grains=fltarr(Nwavs,ngrains) 
spec2_grains=fltarr(Nwavs,ngrains)

;==== save everything to put back later
saved_params=0 & saved_pd=0 & saved_pinfo=0 & saved_fpd=0
IF ptr_valid(!dustem_params) THEN BEGIN
   dparams=*!dustem_params
   saved_params=1
END
IF ptr_valid((*!dustem_fit).param_descs) THEN BEGIN
  pd=*(*!dustem_fit).param_descs
  iv=*(*!dustem_fit).param_init_values
  cv=*(*!dustem_fit).current_param_values
  saved_pd=1
ENDIF
IF ptr_valid(!dustem_parinfo) THEN BEGIN
   parinfo=*(!dustem_parinfo)
  saved_pinfo=1
ENDIF
IF ptr_valid((*!dustem_fit).fixed_param_descs) THEN BEGIN
  fpd=*(*!dustem_fit).fixed_param_descs
  fiv=*(*!dustem_fit).fixed_param_init_values
  saved_fpd=1
ENDIF

;==== Run dustem with G0(a.k.a. U)=1.
param_desc=['(*!dustem_params).G0']
param_values=[Umin]
dustem_init_params,!dustem_model,param_desc,param_values

;stop
st=dustem_run(param_values)
spec1=st.sed.em_tot
spec=(1.-gamma)*spec1
for k=0,ngrains-1 do begin
   this_spec=st.sed.(k+1)    ; position 0 is the wavelengths
   spec_grains[*,k]=(1.-gamma)*this_spec
endfor

;==== add contribution of dust seeing a power law of U
spec2[*]=0.
;NUs=3L
NUs=10L   ;This seems sufficient
;NUs=50L
;U values over which integration will be performed
Us=range_gen(NUs,[Umin,Umax],/log)
specs=fltarr(NUs,Nwavs)
specs_grains=fltarr(NUs,Nwavs,Ngrains)
;stop

ffacts=fltarr(NUs)
IF gamma NE 0. THEN BEGIN
    fact=gamma*(alpha-1.)/(Umin^(1.-alpha)-Umax^(1.-alpha))
    FOR i=0L,NUs-1 DO BEGIN
        param_values[0]=Us[i];^(-1.*alpha)
        ;stop
        st=dustem_run(param_values)
        ffacts[i]=Us[i]^(-1.*alpha)*fact
        specs[i,*]=ffacts[i]*st.sed.em_tot
        for k=0,ngrains-1 do specs_grains[i,*,k]=ffacts[i]*st.sed.(k+1)
    ENDFOR
    ;integrate over U
    ;stop
    FOR j=0L,Nwavs-1 DO BEGIN
        integ=integral(Us,reform(specs[*,j]),Umin,Umax,/no_check)
        spec[j]=spec[j]+integ[0]
        for k=0,ngrains-1 do begin
           integ_grains=integral(Us,reform(specs_grains[*,j,k]),Umin,Umax,/no_check)
           spec_grains[j,k]=spec_grains[j,k]+integ_grains[0]
        endfor
    ENDFOR
ENDIF

;This is to update keyword st with the final spectra. 
;Not necessary here, but to be used in plugins with scope 'REPLACE_FORTRAN' which actually do not call the Fortran at all.
;Ngrains=3
;st=dustem_make_empty_fortran_st(Ngrains)
st.sed.em_tot=spec
for k=0,ngrains-1 do st.sed.(k+1)=spec_grains[*,k]

;restore params to their original values
if saved_pd eq 1 then begin
  (*!dustem_fit).param_descs=ptr_new(pd)
  (*!dustem_fit).param_init_values=ptr_new(iv)
  (*!dustem_fit).current_param_values=ptr_new(cv)
end
if saved_fpd eq 1 then begin
  (*!dustem_fit).fixed_param_descs=ptr_new(fpd)
  (*!dustem_fit).fixed_param_init_values=ptr_new(fiv)
end
if saved_pinfo eq 1 then begin
   !dustem_parinfo=ptr_new(parinfo)
end
if saved_params eq 1 then begin
   !dustem_params=ptr_new(dparams)
end


the_end:
scope='REPLACE_FORTRAN'
;parameter tags. 
paramtag=['gamma','alpha','Umin','Umax']

RETURN,spec
END