starting to implement a pad filler + tests

onetimepad.py

@@ -12,7 +12,7 @@ def decode(msg, pad):
 def create_pad(length, width=72):
     chars = _create_chars_for_pad(length)
     lines = _chunk_chars_into_lines(chars, width=width)
-    return lines
+    return '\n\n\n'.join(lines)
 
 
 def _create_chars_for_pad(length):
@@ -26,7 +26,7 @@ def _chunk_chars_into_lines(chars, width=72):
     lines = []
     for chunk in _as_line_chunks(chars, width=width):
         lines.append(chunk)
-    return '\n\n\n'.join(lines)
+    return lines
 
 
 def _as_line_chunks(chars, width=72):
@@ -41,6 +41,33 @@ def _as_line_chunks(chars, width=72):
     yield ''.join(chunk)
 
 
+def _padfill(text, pad):
+    padlines = pad.splitlines()
+    textlines = _chunk_chars_into_lines(text, _get_textwidth(pad))
+    for lineno, padline in enumerate(padlines[:]):
+        if _is_padline(lineno) or _is_cypherline(lineno):
+            continue
+        else:
+            padlines[lineno] = textlines.pop(0) if textlines[1:] else ''
+    return '\n'.join(padlines)
+
+
+def _get_textwidth(text):
+    return max([len(line) for line in text.splitlines()])
+
+
+def _is_padline(lineno):
+    return not lineno % 3
+
+
+def _is_txtline(lineno):
+    return (lineno % 2 and not lineno % 3)
+
+
+def _is_cypherline(lineno):
+    return lineno % 3
+
+
 def _mk_as_alpha():
     as_alpha = dict()
     a_chr = ord('A')

test_onetimepad.py

@@ -1,10 +1,10 @@
-import random
-
 import unittest
 import onetimepad as OT
 
 
 class TestOneTimePad(unittest.TestCase):
+    msg = ('HOWMUCHCHUCKCOULDAWOODCHUCKCHUCKIFA'
+           'WOODCHUCKCOULDCHUCKWOOD' * 50)
 
     def test_mk_as_alpha_excludes_j(self):
         self.assertTrue('J' not in OT._AS_ALPHA.values())
@@ -20,14 +20,40 @@ class TestOneTimePad(unittest.TestCase):
 
     def test_two_out_of_every_three_lines_are_empty_on_new_pad(self):
         pad = OT.create_pad(2000)
-        for i, line in enumerate(pad.splitlines()):
-            lineno = i + 3
-            if not lineno % 3:
+        for lineno, line in enumerate(pad.splitlines()):
+            line = line.strip()
+            if OT._is_padline(lineno):
                 self.assertTrue(bool(len(line)),
-                                'line {0} is non-empty'.format(lineno))
+                                'pad line {0} is non-empty'.format(lineno))
+            elif OT._is_txtline(lineno):
+                self.assertFalse(bool(len(line)),
+                                 'text line {0} is empty'.format(lineno))
+            elif OT._is_cypherline(lineno):
+                self.assertFalse(bool(len(line)),
+                                 'cypher line {0} is empty'.format(lineno))
             else:
+                raise NotImplementedError(lineno)
+
+    def test_padfill_leaves_every_third_line_empty(self):
+        msg = self.msg[:]
+        pad = OT.create_pad(len(msg))
+        filled = OT._padfill(msg, pad)
+        # print filled
+        # raise Exception
+        self.assertTrue(bool(filled))
+        for lineno, line in enumerate(filled.splitlines()):
+            line = line.strip()
+            if OT._is_cypherline(lineno):
                 self.assertFalse(bool(len(line)),
                                  'line {0} is empty'.format(lineno))
+            elif OT._is_txtline(lineno):
+                self.assertTrue(bool(len(line)),
+                                'text line {0} is non-empty'.format(lineno))
+            elif OT._is_padline(lineno):
+                self.assertTrue(bool(len(line)),
+                                'pad line {0} is non-empty'.format(lineno))
+            else:
+                raise NotImplementedError(lineno)
 
 
 if __name__ == '__main__':