/* 
 *  call-seq:
 *     MappingFilter.new(token_stream, mapping) -> token_stream
 *
 *  Create an MappingFilter which maps strings in tokens. This is usually used
 *  to map UTF-8 characters to ASCII characters for easier searching and
 *  better search recall. The mapping is compiled into a Deterministic Finite
 *  Automata so it is super fast. This Filter can therefor be used for
 *  indexing very large datasets. Currently regular expressions are not
 *  supported. If you are really interested in the feature, please contact me
 *  at dbalmain@gmail.com.
 *
 *  token_stream:: TokenStream to be filtered
 *  mapping::      Hash of mappings to apply to tokens. The key can be a
 *                 String or an Array of Strings. The value must be a String
 *
 *  == Example
 *
 *     filt = MappingFilter.new(token_stream,
 *                              {
 *                                ['à','á','â','ã','ä','å'] => 'a',
 *                                ['è','é','ê','ë','ē','ę'] => 'e'
 *                              })
 */
static VALUE
frt_mapping_filter_init(VALUE self, VALUE rsub_ts, VALUE mapping) 
{
    TokenStream *ts;
    ts = frt_get_cwrapped_rts(rsub_ts);
    ts = mapping_filter_new(ts);
    rb_hash_foreach(mapping, frt_add_mappings_i, (VALUE)ts);
    mulmap_compile(((MappingFilter *)ts)->mapper);
    object_add(&(TkFilt(ts)->sub_ts), rsub_ts);

    Frt_Wrap_Struct(self, &frt_tf_mark, &frt_tf_free, ts);
    object_add(ts, self);
    return self;
}