1 files changed, 108 insertions, 0 deletions
diff --git a/src/knowledge/knowledge_get_random_target.c b/src/knowledge/knowledge_get_random_target.c
new file mode 100644
index 0000000..d9bf8a9
--- /dev/null
+++ b/src/knowledge/knowledge_get_random_target.c
@@ -0,0 +1,108 @@
+#include <stdlib.h>
+
+#include "../core/char.h"
+#include "../core/index.h"
+#include "../sequence/sequence.h"
+
+#include "../pipe/pipe.h"
+
+#include "knowledge.h"
+
+static int weighted_random_pick
+(
+   const struct ZoO_knowledge_sequence_data sd [const restrict static 1],
+   ZoO_index result [const restrict static 1]
+)
+{
+   ZoO_index accumulator, random_number;
+
+   accumulator = 0;
+
+   if (sd->occurrences == 0)
+   {
+      return -1;
+   }
+
+   random_number = ZoO_index_random_up_to(sd->occurrences);
+   /*@ ensures (0 <= random_number <= weights_sum); @*/
+
+   *result = 0;
+
+   for (;;)
+   {
+      accumulator += sd->targets[*result].occurrences;
+
+      if (accumulator < random_number)
+      {
+         *result += 1;
+      }
+      else
+      {
+         *result = sd->targets[*result].id;
+
+         return 0;
+      }
+   }
+}
+
+int ZoO_knowledge_random_tws_target
+(
+   const struct ZoO_knowledge k [const static 1],
+   ZoO_index target [const restrict static 1],
+   const ZoO_index word_id,
+   const ZoO_index sequence_id
+)
+{
+   ZoO_index s_index;
+
+   if
+   (
+      ZoO_knowledge_find_markov_sequence
+      (
+         sequence_id,
+         &(k->words[word_id].tws),
+         &s_index
+      ) < 0
+   )
+   {
+      return -1;
+   }
+
+   return
+      weighted_random_pick
+      (
+         &(k->words[word_id].tws.sequences_ref[s_index]),
+         target
+      );
+}
+
+int ZoO_knowledge_random_swt_target
+(
+   const struct ZoO_knowledge k [const static 1],
+   const ZoO_index sequence_id,
+   const ZoO_index word_id,
+   ZoO_index target [const restrict static 1]
+)
+{
+   ZoO_index s_index;
+
+   if
+   (
+      ZoO_knowledge_find_markov_sequence
+      (
+         sequence_id,
+         &(k->words[word_id].swt),
+         &s_index
+      ) < 0
+   )
+   {
+      return -1;
+   }
+
+   return
+      weighted_random_pick
+      (
+         &(k->words[word_id].swt.sequences_ref[s_index]),
+         target
+      );
+}