pro polar_read_ebv, time, id=datatype, $
    print_datatype=print_datatype, errmsg=errmsg, $
    local_files=files, file_times=file_times, version=version, $
    local_root=local_root, remote_root=remote_root

    compile_opt idl2
    on_error, 0
    errmsg = ''


;---Check inputs.
    sync_threshold = 0
    if n_elements(probe) eq 0 then probe = 'x'
    if n_elements(local_root) eq 0 then local_root = join_path([default_local_root(),'sdata'])
    if n_elements(version) eq 0 then version = 'v01'

;---Init settings.
    type_dispatch = hash()
    valid_range = ['1996-02-28','2008-04-28']
    base_name = 'po_ebv_%Y_%m%d_'+version+'.cdf'
    local_path = [local_root,'polar_ebv','%Y']
    ; Survey E field.
    type_dispatch['e_spc'] = dictionary($
        'pattern', dictionary($
            'local_file', join_path([local_path,base_name]), $
            'local_index_file', join_path([local_path,default_index_file()])), $
        'valid_range', time_double(valid_range), $
        'cadence', 'day', $
        'extension', fgetext(base_name), $
        'var_list', list($
            dictionary($
                'in_vars', ['e_spc'], $
                'out_vars', ['po_e_spc'], $
                'time_var_name', 'ut_e', $
                'time_var_type', 'unix')))
    type_dispatch['quaternion'] = dictionary($
        'pattern', dictionary($
            'local_file', join_path([local_path,base_name]), $
            'local_index_file', join_path([local_path,default_index_file()])), $
        'valid_range', time_double(valid_range), $
        'cadence', 'day', $
        'extension', fgetext(base_name), $
        'var_list', list($
            dictionary($
                'in_vars', 'q_spc2gsm', $
                'out_vars', 'po_q_spc2gsm', $
                'time_var_name', 'ut_cotran', $
                'time_var_type', 'unix')))
    ; Survey B field.
    type_dispatch['b_spc'] = dictionary($
        'pattern', dictionary($
            'local_file', join_path([local_path,base_name]), $
            'local_index_file', join_path([local_path,default_index_file()])), $
        'valid_range', time_double(valid_range), $
        'cadence', 'day', $
        'extension', fgetext(base_name), $
        'var_list', list($
            dictionary($
                'in_vars', ['b_spc'], $
                'out_vars', ['po_b_spc'], $
                'time_var_name', 'ut_b', $
                'time_var_type', 'unix')))
    ; Survey V field.
    type_dispatch['v_uvw'] = dictionary($
        'pattern', dictionary($
            'local_file', join_path([local_path,base_name]), $
            'local_index_file', join_path([local_path,default_index_file()])), $
        'valid_range', time_double(valid_range), $
        'cadence', 'day', $
        'extension', fgetext(base_name), $
        'var_list', list($
            dictionary($
                'in_vars', ['v_uvw'], $
                'out_vars', ['po_v_uvw'], $
                'time_var_name', 'ut_v', $
                'time_var_type', 'unix')))

    if keyword_set(print_datatype) then begin
        print, 'Suported data type: '
        ids = type_dispatch.keys()
        foreach id, ids do print, '  * '+id
        return
    endif

;---Dispatch patterns.
    if n_elements(datatype) eq 0 then begin
        errmsg = handle_error('No input datatype ...')
        return
    endif
    if not type_dispatch.haskey(datatype) then begin
        errmsg = handle_error('Do not support type '+datatype+' yet ...')
        return
    endif
    request = type_dispatch[datatype]

;---Find files, read variables, and store them in memory.
    files = prepare_files(request=request, errmsg=errmsg, local_files=files, $
        file_times=file_times, time=time, nonexist_files=nonexist_files)

;---Read data from files and save to memory.
    read_files, time, files=files, request=request

end