FUNCTION dustem_plugin_freefree,key=key $
                                ,val=val $
                                ,scope=scope $
                                ,paramtag=paramtag $
                                ,paramdefault=paramdefault $
                                ,help=help

;+
; NAME:
;    dustem_plugin_freefree
;
; PURPOSE:
;    DustEMWrap plugin to compute free-free emission
;
; CATEGORY:
;    DustEM, Distributed, Mid-Level, Plugin
;
; CALLING SEQUENCE:
;    freefree=dustem_plugin_freefree([,key=][,val=])
;
; INPUTS:
;    None
;
; OPTIONAL INPUT PARAMETERS:
;    key  = input parameter number
;         1 : Tgas [K]
;         2 : free-free Amplitude []
;         3 : polarization fraction [%] (default=0)
;         4 : polarization angle [deg]
;    val  = input parameter value
;
; OUTPUTS:
;    freefree = free-free spectrum (on dustem wavelengths)
;
; OPTIONAL OUTPUT PARAMETERS:
;    scope = scope of the plugin
;    paramdefault = default values of parameters
;    paramtag = plugin parameter names as strings
;
; ACCEPTED KEY-WORDS:
;    help                  = if set, print this help
;
; COMMON BLOCKS:
;    None
;
; SIDE EFFECTS:
;    None
;
; RESTRICTIONS:
;    The DustEMWrap IDL code must be installed
;
; PROCEDURE:
;    This is a DustEMWrap plugin
;
; EXAMPLES
;    dustem_init
;    vec=dustem_plugin_freefree(scope=scope)
;
; MODIFICATION HISTORY:
;    Written by JPB 2022 
;    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_plugin_freefree'
     output=0.
     goto,the_end
  ENDIF
  
;default values of input parameters
  Tgas=10000.                   ;default gas temperature
  Amplitude=1.                  ;Amplitude
  smallp=0.0                    ;default polarization fraction
  psi=0.                        ;default polarization angle
  scope='ADD_SED'
  paramtag=[textoidl('T_{gas}')+' [K]','Amp','p','Psi [deg]']
  paramdefault=[Tgas,Amplitude,smallp,psi]
  IF keyword_set(key) THEN BEGIN 
     a=where(key EQ 1,count1)
     b=where(key EQ 2,count2)
     c=where(key EQ 3,count3)   ;default polarization fraction -newly added
     d=where(key EQ 4,count4)   ;default polarization angle -newly added
     IF count1 NE 0 then Tgas=val[a[0]]
     IF count2 NE 0 then Amplitude=val[b[0]]
     IF count3 NE 0 then smallp=val[c[0]]
     IF count4 NE 0 then psi=val[d[0]]
  ENDIF
  
  lambir=dustem_get_wavelengths()
  Nwavs=n_elements(lambir)
  cmic=3.e14
  nu=cmic/lambir                ;Hz
  mjy=1                         ;output is in MJy/sr
  lambir_ref=10000.             ;in mic (this is 1cm)
  
  output=fltarr(Nwavs,3)
  
;use_method='Deschenes2008'
;use_method='WallsGabaud1998'
  use_method='Dickinson2003_norm'
  
  CASE use_method OF
     'WallsGabaud1998':BEGIN
        em=1.                   ;This is a stupid value for the Emission measure. Result will be rescaled based on I_halpha_R anyway
        output[*,0]=intensity_free_free(nu,Tgas,em,I_halpha_R=I_halpha_R,nHe=nHe,ergs=ergs,mjy=mjy)
        fact=Amplitude/I_halpha_R
                                ;=== normalize to the requested Halpha value.
        output[*,0]=output[*,0]*fact
     END
     'WallsGabaud1998_scaled':BEGIN
        em=1.                   ;This is a stupid value for the Emission measure. Result will be rescaled based on I_halpha_R anyway
        output[*,0]=intensity_free_free(nu,Tgas,em,I_halpha_R=I_halpha_R,nHe=nHe,ergs=ergs,mjy=mjy)
        norm=interpol(output[*,0],lambir,lambir_ref)
        output[*,0]=output[*,0]/norm*Amplitude
     END
     'Deschenes2008':BEGIN
        beta_freefree=2.+1./(10.48+1.5*alog(Tgas/8.e3)-alog(nu/1.e9))
        output[*,0]=nu^(-1.*beta_freefree)
        norm=interpol(output[*,0],lambir,lambir_ref)
        output[*,0]=output[*,0]/norm*Amplitude
     END
     'Dickinson2003_norm':BEGIN
                                ;stop
        em=1.
        T4=Tgas/1.e4
        nu_ghz=nu/1.e9
        a=0.366*(nu_ghz/1.e9)^(-0.15)*(alog(4.995*1e-2*(nu_ghz)^(-1.))+1.5*alog(Tgas))
        Tb=8.369e3*a*(nu_ghz)^(-2.)*T4^0.667*10^(0.029*T4)*(1.+0.08) ;in mK for 1 Rayleigh
        psm_convert_mk2mjy, lambir, Tb, I_Mjy, /RJ
        norm=interpol(I_Mjy,lambir,lambir_ref)
        output[*,0]=I_Mjy/norm*Amplitude
     END
  ENDCASE
  
  polar_ippsi2iqu,output[*,0],Q,U,replicate(smallp,Nwavs),replicate(psi,Nwavs)
  
  output[*,1]=Q
  output[*,2]=U 
  
the_end:
  RETURN,output
  
END