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