python: Implement phogen encode

Implement phogen.encode() to encode Bhashes to phogen strings. This
commit also adds unit tests for the above function.

python/passgeny/phogen.py

@@ -0,0 +1,19 @@
+from passgeny import bhash, phogen_map
+
+def encode(bh: bhash.Bhash, ph_len: int):
+    """
+    Consume the Bhash and return a string of length ph_len
+
+    This function generates a phonetic representation of the binary data in
+    Bhash.
+    """
+    phogen = ''
+    ngram = '  '
+    for x in range(ph_len):
+        ngram_space = phogen_map.g_phonetic_map[ngram]
+        n = bh.modulo(len(ngram_space))
+        letter = ngram_space[n]
+        ngram = ngram[1:] + letter
+        phogen += letter
+
+    return phogen

tests/meson.build

@@ -9,8 +9,11 @@ test('test_phogen_map',
            'PHOGEN_MAP_PY=@0@'.format(_phogen_map_py),
            'PHOGEN_WORD_LIST=@0@'.format(_word_list)])
 
-test('test_bhash',
+test('test_bhash_py',
     find_program('test_bhash.py'),
-    env: ['SOURCE_ROOT=' + meson.project_source_root(),
+    env: ['PYTHONPATH=' + PYTHONPATH])
-          'PYTHONPATH=' + PYTHONPATH])
+
+test('test_phogen_py',
+    find_program('test_phogen.py'),
+    env: ['PYTHONPATH=' + PYTHONPATH])
 

tests/test_phogen.py

@@ -0,0 +1,27 @@
+#!/usr/bin/env python3
+import hashlib
+
+from passgeny import phogen
+from passgeny import bhash
+
+PHO_GEN_TEST = [
+        [ b"passgeny",  "herang xiasem zitend qibele" ],
+        [ b"phonetic",  "lineum foneum zybale mangur" ],
+        [ b"generator", "latole elitab ackina exprou" ],
+        [ b"password",  "nulize nomere fonici crednt" ],
+        [ b"duck",      "catabb rompor cricin prunsi" ] ]
+
+for pt in PHO_GEN_TEST:
+    bh = bhash.Bhash()
+    bh.from_bytes(hashlib.sha256(pt[0]).digest())
+    wa = []
+
+    for x in range(4):
+        wa.append(phogen.encode(bh, 6))
+
+    word = " ".join(wa)
+
+    if word != pt[1]:
+        raise Exception("Test failed: {} != {}".format(word, pt1))
+
+    print(word)