From 70c770635199cfa473608162ec7d31e030a11c5f Mon Sep 17 00:00:00 2001
From: Folker Bernitt <fbernitt@thoughtworks.com>
Date: Wed, 28 Oct 2015 12:05:59 +0100
Subject: Add markov-generate to load-mails

- Allows to generat mails based
  on a sample mails

- use it with:
   pixelated-maintenance markov-generate --seed 21 --limit 10
---
 service/pixelated/support/markov.py | 94 +++++++++++++++++++++++++++++++++++++
 1 file changed, 94 insertions(+)
 create mode 100644 service/pixelated/support/markov.py

(limited to 'service/pixelated/support/markov.py')

diff --git a/service/pixelated/support/markov.py b/service/pixelated/support/markov.py
new file mode 100644
index 00000000..8f7c0ef3
--- /dev/null
+++ b/service/pixelated/support/markov.py
@@ -0,0 +1,94 @@
+#
+# Copyright (c) 2015 ThoughtWorks, Inc.
+#
+# Pixelated is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Pixelated is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with Pixelated. If not, see <http://www.gnu.org/licenses/>.
+
+from random import Random
+
+NEW_PARAGRAPH = '\n\n'
+
+
+class MarkovGenerator(object):
+
+    def __init__(self, texts, random=None, add_paragraph_on_empty_chain=False):
+        self._markov_chain = {}
+        self._random = random if random else Random()
+        self._add_paragraph_on_empty_chain = add_paragraph_on_empty_chain
+
+        for text in filter(lambda _: _ is not None, texts):
+            self._extend_chain_with(text)
+
+    def add(self, text):
+        self._extend_chain_with(text)
+
+    @staticmethod
+    def _triplet_generator(words):
+        if len(words) < 3:
+            raise ValueError('Expected input with at least three words')
+
+        for i in xrange(len(words) - 2):
+            yield ((words[i], words[i + 1]), words[i + 2])
+
+    def _extend_chain_with(self, input_text):
+        words = input_text.split()
+        gen = self._triplet_generator(words)
+
+        for key, value in gen:
+            if key in self._markov_chain:
+                self._markov_chain[key].add(value)
+            else:
+                self._markov_chain[key] = {value}
+
+    def _generate_chain(self, length):
+        seed_pair = self._find_good_seed()
+        word, next_word = seed_pair
+        new_seed = False
+
+        for i in xrange(length):
+            yield word
+
+            if new_seed:
+                word, next_word = self._find_good_seed()
+                if self._add_paragraph_on_empty_chain:
+                    yield NEW_PARAGRAPH
+                new_seed = False
+            else:
+                prev_word, word = word, next_word
+
+                try:
+                    next_word = self._random_next_word(prev_word, word)
+                except KeyError:
+                    new_seed = True
+
+    def _random_next_word(self, prev_word, word):
+        return self._random.choice(list(self._markov_chain[(prev_word, word)]))
+
+    def _find_good_seed(self):
+        max_tries = len(self._markov_chain.keys())
+        try_count = 0
+
+        seed_pair = self._random.choice(self._markov_chain.keys())
+        while not seed_pair[0][0].isupper() and try_count <= max_tries:
+            seed_pair = self._random.choice(self._markov_chain.keys())
+            try_count += 1
+
+        if try_count > max_tries:
+            raise ValueError('Not able find start word with captial letter')
+
+        return seed_pair
+
+    def generate(self, length):
+        if len(self._markov_chain.keys()) == 0:
+            raise ValueError('Expected at least three words input')
+        return ' '.join(self._generate_chain(length))
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