Reload --vosk-grammar-file JSON on SIGHUP

This commit adds support for reloading the grammar configuration on SIGHUP.
This is accomplished by moving the recognizer initialization into its own
function so that the signal handler can call it on reload.

A reload of the recognizer is fast because it does not reload the model and
only applies the grammar.

Signed-off-by: Eric Wheeler <vosk-git@z.ewheeler.org>

Author: Eric Wheeler

nerd-dictation

@@ -939,21 +939,29 @@ def text_from_vosk_pipe(
 
     vosk.SetLogLevel(-1)
 
-    if not vosk_grammar_file:
-        grammar_json = ""
-    else:
-        with open(vosk_grammar_file, encoding="utf-8") as fh:
-            grammar_json = fh.read()
-
     # Allow for loading the model to take some time:
     if verbose >= 1:
         sys.stderr.write("Loading model...\n")
     model = vosk.Model(vosk_model_dir)
 
-    if grammar_json == "":
-        rec = vosk.KaldiRecognizer(model, sample_rate)
-    else:
-        rec = vosk.KaldiRecognizer(model, sample_rate, grammar_json)
+    rec = None
+
+    def vosk_load_recognizer():
+        nonlocal vosk_grammar_file
+        nonlocal rec
+
+        if not vosk_grammar_file:
+            grammar_json = ""
+        else:
+            with open(vosk_grammar_file, encoding="utf-8") as fh:
+                grammar_json = fh.read()
+
+        if grammar_json == "":
+            rec = vosk.KaldiRecognizer(model, sample_rate)
+        else:
+            rec = vosk.KaldiRecognizer(model, sample_rate, grammar_json)
+
+    vosk_load_recognizer()
 
     if verbose >= 1:
         sys.stderr.write("Model loaded.\n")
@@ -1119,6 +1127,7 @@ def text_from_vosk_pipe(
         if verbose >= 1:
             sys.stderr.write("Reload.\n")
         process_fn("")
+        vosk_load_recognizer()
         return
 
     import signal