Outputs cache, clear and interpolate data

Preparation to solve build new scheduling algorithm. See #78 (closed).

Use the ping mechanism to let outputs know their targets.

Outputs record pull time per target to determine data to store/clear. Store data, and clear after pull what can't be pulled anymore with strictly increasing pull time per target.

Outputs do nearest interpolation on pull and throw an arror when out of the data range.

Fixes #76 (closed)

docs/source/finam-book/development/adapters.rst

@@ -41,8 +41,8 @@ File ``src/scale.py``:
             super().__init__()
             self.scale = scale
 
-        def _get_data(self, time):
-            d = self.pull_data(time)
+        def _get_data(self, time, target):
+            d = self.pull_data(time, target)
             return d * self.scale
 
 .. testcode:: scale-adapter
@@ -141,7 +141,7 @@ This functionality is provided by :class:`.Adapter`'s methods :meth:`.Adapter._g
         def _source_updated(self, time):
             pass
 
-        def _get_data(self, time):
+        def _get_data(self, time, target):
             pass
 
 Note
@@ -165,10 +165,15 @@ In :meth:`.Adapter._source_updated`, we need to store incoming data:
             return True
 
         def _source_updated(self, time):
+            data = self.pull_data(time, self)
+
             self.old_data = self.new_data
-            self.new_data = (time, fm.data.strip_data(self.pull_data(time)))
+            self.new_data = (
+                time,
+                fm.data.strip_data(data)
+            )
 
-        def _get_data(self, time):
+        def _get_data(self, time, target):
             pass
 
 We "move" the previous ``new_data`` to ``old_data``, and replace ``new_data`` by the incoming data, as a ``(time, data)`` tuple.
@@ -192,10 +197,15 @@ In :meth:`.Adapter._get_data`, we can now do the interpolation whenever data is
             return True
 
         def _source_updated(self, time):
+            data = self.pull_data(time, self)
+
             self.old_data = self.new_data
-            self.new_data = (time, fm.data.strip_data(self.pull_data(time)))
+            self.new_data = (
+                time,
+                fm.data.strip_data(data)
+            )
 
-        def _get_data(self, time):
+        def _get_data(self, time, _target):
             if self.old_data is None:
                 if self.new_data is None:
                     return None