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

;+
; NAME:
;    dustem_plugin_dl07_isrf_model
;
; PURPOSE:
;    
;
; CATEGORY:
;    DUSTEM Wrapper
;
; CALLING SEQUENCE:
;    sed=dustem_plugin_dl07_isrf_model(key=,val=,/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:
;    None
;
; 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

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

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

spec=0.

;==== 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)
spec2=fltarr(Nwavs,3)

;==== 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
st=dustem_run(param_values)
spec1=st.sed.em_tot
spec=(1.-gamma)*spec1

;==== 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)
;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)
        st=dustem_run(param_values)
        ffacts[i]=Us[i]^(-1.*alpha)*fact
        specs[i,*]=ffacts[i]*st.sed.em_tot
    ENDFOR
    ;integrate over U
    FOR j=0L,Nwavs-1 DO BEGIN
        integ=integral(Us,reform(specs[*,j]),Umin,Umax)
        spec[j]=spec[j]+integ[0]
    ENDFOR
    ;FOR i=0L,Nus-1 DO BEGIN
    ;    print,Us[i],ffacts[i]
    ;ENDFOR
ENDIF

;This is to update keyword st with final spectrum
st.sed.em_tot=spec

the_end:
scope='REPLACE_FORTRAN'

;parameter tags. 
paramtag=['gamma','alpha','Umin','Umax']

RETURN,spec
END