;+
;Procedure: tt89
;
;Purpose:  tplot wrapper for the functional interface to the idl
;geopack implementation of the Tsyganenko 1989 and IGRF fields model.
;
;Keywords: 
;          pos_gsm_tvar: the tplot variable storing the position in
;          gsm coordinates(can use standard globbing)
;          kp(optional): the requested value of the kp
;          parameter(default: 2) can also be a tplot variable name
;          if it is a tplot variable name the kp values stored in the
;          variable will be interpolated to match the time grid of the 
;          position input values
;
;          period(optional): the amount of time between recalculations of
;             geodipole tilt in seconds(default: 600)  increase this
;             value to decrease run time
;
;          newname(optional):the name of the output variable. 
;          (default: pos_gsm_tvar+'_bt89') This option is ignored if
;          globbing is used.
;
;          error(optional): named variable in which to return the
;          error state of this procedure call. 1 = success, 0 = failure
;        
;          igrf_only(optional): Set this keyword to turn off the t89 component of
;            the model and return only the igrf component
;
;
; Output: Stores the result of the field model calculations in tplot variables
;          
; Notes: 1, converts from normal gsm to rgsm by dividing vectors by earth's
; radius(6374 km) ie inputs should be in km
;        2. Input must be in GSM coordinates
;        3. Haje Korth's IDL/Geopack DLM must be installed for this
;        procedure to work
;
; $LastChangedBy: pcruce $
; $LastChangedDate: 2009-04-22 18:05:37 -0700 (Wed, 22 Apr 2009) $
; $LastChangedRevision: 5721 $
; $URL: svn+ssh://thmsvn@ambrosia.ssl.berkeley.edu/repos/idl_socware/tags/tdas_5_11/external/IDL_GEOPACK/t89/tt89.pro $
;-

pro tt89, pos_gsm_tvar, kp = kp, period = period, newname = newname, error = error,igrf_only=igrf_only

  error = 0

  if not keyword_set(pos_gsm_tvar) then begin
    message, /continue, 'pos_gsm_tvar must be set'
    return
  endif

  var_names = tnames(pos_gsm_tvar)

  if(var_names[0] eq '') then begin
    message, /continue, 'No valid tplot_variables match pos_gsm_tvar'
    return
  endif


  if keyword_set(kp) then begin

    ;if kp is a string, assume kp is stored in a tplot variable
      if size(kp,/type) eq 7 then begin
          if tnames(kp) eq '' then begin
              message,/continue,'kp is of type string but no tplot variable of that name exists'
              return
          endif
          
          ;for the sake of simplicity
          if n_elements(var_names) gt 1 then begin
              message,/continue,'cannot use globbing AND arrayed kp values'
              return
          endif
          
          ;make sure there are an appropriate number of kp values in the array
          tinterpol_mxn,kp,var_names[0],newname='kp_int_temp',error=e

          if e ne 0 then begin
              get_data,'kp_int_temp',data=d_kp
              kp_dat = d_kp.y
          endif else begin
              message,/continue,'error interpolating kp onto position data'
              return
          endelse
     
      endif else kp_dat = kp

  endif

  for i = 0, n_elements(var_names)-1L do begin

      get_data, var_names[i], data = d, dlimits = dl, limits = l

    ;several nested ifs to check this
    ;variable's coordinate system in a
    ;safe way(ie won't reference any struct elements that don't exist)
    if not keyword_set(dl) then begin
      message, /continue, 'dlimits structure not set, make sure input variables are in gsm coordinates or results will be invalid'
    endif else begin
      str_element, dl, 'data_att', success = s
      if s eq 0 then begin
        message, /continue, 'dlimits.data_att structure not set, make sure input variables are in gsm coordinates or results will be invalid'
      endif else begin
        str_element, dl.data_att, 'coord_sys', success = s
        if s eq 0 then begin
          message, /continue, 'dlimits.data_att.coord_sys value not set, make sure input variables are in gsm coordinates or results will be invalid'
        endif else if dl.data_att.coord_sys ne 'gsm' then begin
          message, /continue, 'input variable is in the wrong coordinate system, returning'
          return ;definitely wrong coordinate system=error
        endif
      endelse
    endelse

    ;do the calculation, division converts position into earth radii units
    mag_array = t89(d.x, d.y/6374, kp = kp_dat, period = period,igrf_only=keyword_set(igrf_only))

    if size(mag_array, /n_dim) eq 0 && mag_array[0] eq -1L then begin
      message, /continue, 'Tysganenko model query failed, returning'
      return
    endif

    ;sometimes v element is present, sometimes not 
    ;if it is around it is stored in output so information is not lost 
    str_element, d, 'v', success = s

    if s eq 1 then $
      d_out = {x:d.x, y:mag_array, v:d.v} $
    else $
      d_out = {x:d.x, y:mag_array}

    if keyword_set(newname) && n_elements(var_names) eq 1 then $
      store_data, newname, data = d_out, dlimits = dl, limits = l $
    else $
      store_data, var_names[i]+'_bt89', data = d_out, dlimits = dl, limits = l

  endfor

  ;signal success
  error = 1 

  return

end