1 files changed, 54 insertions, 0 deletions
diff --git a/gitlint-core/gitlint/cache.py b/gitlint-core/gitlint/cache.py
new file mode 100644
index 0000000..a3dd0c8
--- /dev/null
+++ b/gitlint-core/gitlint/cache.py
@@ -0,0 +1,54 @@
+class PropertyCache:
+    """Mixin class providing a simple cache."""
+
+    def __init__(self):
+        self._cache = {}
+
+    def _try_cache(self, cache_key, cache_populate_func):
+        """Tries to get a value from the cache identified by `cache_key`.
+        If no value is found in the cache, do a function call to `cache_populate_func` to populate the cache
+        and then return the value from the cache."""
+        if cache_key not in self._cache:
+            cache_populate_func()
+        return self._cache[cache_key]
+
+
+def cache(original_func=None, cachekey=None):
+    """Cache decorator. Caches function return values.
+    Requires the parent class to extend and initialize PropertyCache.
+    Usage:
+        # Use function name as cache key
+        @cache
+        def myfunc(args):
+            ...
+
+        # Specify cache key
+        @cache(cachekey="foobar")
+        def myfunc(args):
+            ...
+    """
+
+    # Decorators with optional arguments are a bit convoluted in python, see some of the links below for details.
+
+    def cache_decorator(func):
+        # Use 'nonlocal' keyword to access parent function variable:
+        # https://stackoverflow.com/a/14678445/381010
+        nonlocal cachekey
+        if not cachekey:
+            cachekey = func.__name__
+
+        def wrapped(*args):
+            def cache_func_result():
+                # Call decorated function and store its result in the cache
+                args[0]._cache[cachekey] = func(*args)
+
+            return args[0]._try_cache(cachekey, cache_func_result)
+
+        return wrapped
+
+    # To support optional kwargs for decorators, we need to check if a function is passed as first argument or not.
+    # https://stackoverflow.com/a/24617244/381010
+    if original_func:
+        return cache_decorator(original_func)
+
+    return cache_decorator