Start work on the diff kitten

kittens/diff/collect.py

@@ -0,0 +1,101 @@
+#!/usr/bin/env python
+# vim:fileencoding=utf-8
+# License: GPL v3 Copyright: 2018, Kovid Goyal <kovid at kovidgoyal.net>
+
+import os
+from functools import lru_cache
+from hashlib import md5
+from mimetypes import guess_type
+
+
+class Collection:
+
+    def __init__(self):
+        self.changes = []
+        self.renames = {}
+        self.adds = []
+        self.removes = []
+
+    def add_change(self, left_path, right_path):
+        self.changes.append((left_path, right_path))
+
+    def add_rename(self, left_path, right_path):
+        self.renames[left_path] = right_path
+
+    def add_add(self, right_path):
+        self.adds.append(right_path)
+
+    def add_removal(self, left_path):
+        self.removes.append(left_path)
+
+
+def collect_files(collection, left, right):
+    left_names, right_names = set(), set()
+    left_path_map, right_path_map = {}, {}
+
+    def walk(base, names, pmap):
+        for dirpath, dirnames, filenames in os.walk(base):
+            for filename in filenames:
+                path = os.path.abspath(os.path.join(dirpath, filename))
+                path_name_map[path] = name = os.path.relpath(path, base)
+                names.add(name)
+                pmap[name] = path
+
+    walk(left, left_names, left_path_map), walk(right, right_names, right_path_map)
+    common_names = left_names & right_names
+    changed_names = {n for n in common_names if data_for_path(left_path_map[n]) != data_for_path(right_path_map[n])}
+    for n in changed_names:
+        collection.add_change(left_path_map[n], right_path_map[n])
+
+    removed = left_names - common_names
+    added = right_names - common_names
+    ahash = {a: hash_for_path(right_path_map[a]) for a in added}
+    rhash = {r: hash_for_path(left_path_map[r]) for r in removed}
+    for name, rh in rhash.items():
+        for n, ah in ahash.items():
+            if ah == rh and data_for_path(left_path_map[name]) == data_for_path(right_path_map[n]):
+                collection.add_rename(left_path_map[name], right_path_map[name])
+                added.discard(n)
+                break
+        else:
+            collection.add_removal(left_path_map[name])
+
+    for name in added:
+        collection.add_add(right_path_map[name])
+
+
+@lru_cache(maxsize=1024)
+def mime_type_for_path(path):
+    return guess_type(path)[0] or 'application/octet-stream'
+
+
+@lru_cache(maxsize=1024)
+def data_for_path(path):
+    with open(path, 'rb') as f:
+        ans = f.read()
+    if not mime_type_for_path(path).startswith('image/'):
+        try:
+            ans = ans.decode('utf-8')
+        except UnicodeDecodeError:
+            pass
+    return ans
+
+
+@lru_cache(maxsize=1024)
+def hash_for_path(path):
+    md5(data_for_path(path)).digest()
+
+
+path_name_map = {}
+
+
+def create_collection(left, right):
+    collection = Collection()
+    if os.path.isdir(left):
+        collect_files(collection, left, right)
+    else:
+        pl, pr = os.path.abspath(left), os.path.abspath(right)
+        path_name_map[left] = pl
+        path_name_map[right] = pr
+        collection.add_change(pl, pr)
+    return collection