Merge pull request #1732 from inkstitch/lexelby/cache-stitch-plan

stitch plan caching

3 files changed, 130 insertions, 2 deletions

diff --git a/lib/utils/cache.py b/lib/utils/cache.py
index c0313ebe..1ede8ce1 100644
--- a/lib/utils/cache.py
+++ b/lib/utils/cache.py
@@ -2,14 +2,73 @@
 #
 # Copyright (c) 2010 Authors
 # Licensed under the GNU GPL version 3.0 or later.  See the file LICENSE for details.
+import os
+import atexit
+import hashlib
+import pickle
+
+import appdirs
+import diskcache
+
+from lib.utils.settings import global_settings
 
 try:
     from functools import lru_cache
 except ImportError:
     from backports.functools_lru_cache import lru_cache
 
-# simplify use of lru_cache decorator
-
 
+# simplify use of lru_cache decorator
 def cache(*args, **kwargs):
     return lru_cache(maxsize=None)(*args, **kwargs)
+
+
+__stitch_plan_cache = None
+
+
+def get_stitch_plan_cache():
+    global __stitch_plan_cache
+
+    if __stitch_plan_cache is None:
+        cache_dir = os.path.join(appdirs.user_config_dir('inkstitch'), 'cache', 'stitch_plan')
+        size_limit = global_settings['cache_size'] * 1024 * 1024
+        __stitch_plan_cache = diskcache.Cache(cache_dir, size=size_limit)
+        __stitch_plan_cache.size_limit = size_limit
+        atexit.register(__stitch_plan_cache.close)
+
+    return __stitch_plan_cache
+
+
+class CacheKeyGenerator(object):
+    """Generate cache keys given arbitrary data.
+
+    Given arbitrary data, generate short cache key that is extremely likely
+    to be unique.
+
+    Use example:
+
+        >>> generator = CacheKeyGenerator()
+        >>> generator.update(b'12345')
+        >>> generator.update([1, 2, 3, {4, 5, 6}])
+        >>> generator.get_cache_key()
+    """
+
+    def __init__(self):
+        # SHA1 is chosen for speed.  We don't need cryptography-grade hashing
+        # for this use case.
+        self._hasher = hashlib.sha1()
+
+    def update(self, data):
+        """Provide data to be hashed into a cache key.
+
+        Arguments:
+            data -- a bytes object or any object that can be pickled
+        """
+
+        if not isinstance(data, bytes):
+            data = pickle.dumps(data)
+
+        self._hasher.update(data)
+
+    def get_cache_key(self):
+        return self._hasher.hexdigest()
diff --git a/lib/utils/paths.py b/lib/utils/paths.py
index 2a95f6e7..10d72de9 100755
--- a/lib/utils/paths.py
+++ b/lib/utils/paths.py
@@ -7,6 +7,8 @@ import sys
 import os
 from os.path import dirname, realpath
 
+import appdirs
+
 
 def get_bundled_dir(name):
     if getattr(sys, 'frozen', None) is not None:
@@ -26,3 +28,12 @@ def get_resource_dir(name):
             return realpath(os.path.join(sys._MEIPASS, name))
     else:
         return realpath(os.path.join(dirname(realpath(__file__)), '..', '..', name))
+
+
+def get_user_dir(name=None):
+    path = appdirs.user_config_dir("inkstitch")
+
+    if name is not None:
+        path = os.path.join(path, name)
+
+    return path
diff --git a/lib/utils/settings.py b/lib/utils/settings.py
new file mode 100644
index 00000000..f2ce276d
--- /dev/null
+++ b/lib/utils/settings.py
@@ -0,0 +1,58 @@
+from collections.abc import MutableMapping
+import json
+import os
+
+from .paths import get_user_dir
+
+# These settings are the defaults for SVG metadata settings of the same name in
+# lib.extensions.base.InkstitchMetadata
+DEFAULT_METADATA = {
+    "min_stitch_len_mm": 0,
+    "collapse_len_mm": 3,
+}
+
+DEFAULT_SETTINGS = {
+    "cache_size": 100
+}
+
+
+class GlobalSettings(MutableMapping):
+    def __init__(self):
+        super().__init__()
+        self.__settings_file = os.path.join(get_user_dir(), "settings.json")
+        self.__settings = {}
+
+        for name, value in DEFAULT_METADATA.items():
+            self.__settings[f"default_{name}"] = value
+
+        self.__settings.update(DEFAULT_SETTINGS)
+
+        try:
+            with open(self.__settings_file, 'r') as settings_file:
+                self.__settings.update(json.load(settings_file))
+        except (OSError, json.JSONDecodeError, ValueError):
+            pass
+
+    def __setitem__(self, item, value):
+        self.__settings[item] = value
+
+        with open(self.__settings_file, 'w') as settings_file:
+            json.dump(self.__settings, settings_file)
+
+    def __getitem__(self, item):
+        return self.__settings[item]
+
+    def __delitem__(self, item):
+        del self.__settings[item]
+
+    def __iter__(self):
+        return iter(self.__settings)
+
+    def __len__(self):
+        return len(self.__settings)
+
+    def __json__(self):
+        return self.__settings
+
+
+global_settings = GlobalSettings()