From 0e25adaa1821a67c06c2a4e5a9ae0e6d593e8ab0 Mon Sep 17 00:00:00 2001
From: Sven Augustin <sven.augustin@psi.ch>
Date: Fri, 4 Jun 2021 16:00:13 +0200
Subject: [PATCH] added CacheView (single cache per source, one view on that
 cache per plot)

---
 kabuki/cacher.py | 49 ++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 41 insertions(+), 8 deletions(-)

diff --git a/kabuki/cacher.py b/kabuki/cacher.py
index 539b1eb..a9b6202 100644
--- a/kabuki/cacher.py
+++ b/kabuki/cacher.py
@@ -1,4 +1,5 @@
-from collections import deque
+import itertools
+from collections import deque, defaultdict
 from time import time
 
 
@@ -6,6 +7,7 @@ class Cacher:
 
     def __init__(self):
         self.caches = {}
+        self.views = defaultdict(list)
 
 
     def add_source(self, src, size=100):
@@ -15,15 +17,18 @@ class Cacher:
 
         caches = self.caches
         try:
-            return caches[name]
+            cache = caches[name]
         except KeyError:
             caches[name] = cache = Cache(size=size)
             src.add_callback(cache.callback_append)
-            return cache
+ 
+        view = CacheView(cache, size=size)
+        self.views[name].append(view)
+        return view
 
 
     def __repr__(self):
-        return repr(self.caches)
+        return repr(self.views)
 
 
 
@@ -66,12 +71,40 @@ class Cache:
 
 
 
+class CacheView:
+
+    def __init__(self, cache, size=100):
+        self.cache = cache
+        self.size = size
+
+    def __iter__(self):
+        return iter(self.data)
+
+    @property
+    def data(self):
+        return tuple(get_last(i, self.size) for i in self.cache.data)
+
+    def __repr__(self):
+        return f"CacheView ({self.size}) on {self.cache}"
+
+    def set_size(self, size):
+        self.size = size
+        if size > self.cache.size:
+            print("Adjust cache size to view size...")
+            self.cache.set_size(size)
+
+
+
+def get_last(d, n):
+    stop = len(d)
+    start = stop - n
+    start = max(start, 0)
+    return list(itertools.islice(d, start, stop))
+
+
+
 # need to create object here to share it between sessions
 cacher = Cacher()
 
 
 
-#TODO: copy data from existing cache for the same name but different size
-
-
-