Implementing playback auto-advance and user-advance

[watersofshiloah] / src / stream_index.py

diff --git a/src/stream_index.py b/src/stream_index.py
index 8d5aae3..492de77 100644 (file)
--- a/src/stream_index.py
+++ b/src/stream_index.py
@@ -408,3 +408,102 @@ def common_paths(targetNode, currentNode):
        )
 
        return ancestors, currentNode, descendants
+
+
+class AsyncWalker(object):
+
+       def __init__(self, func):
+               self._func = func
+               self._run = None
+
+       def start(self, *args, **kwds):
+               assert self._run is None
+               self._run = self._func(*args, **kwds)
+               node = self._run.send(None) # priming the function
+               node.get_children(self.on_success, self.on_error)
+
+       @misc_utils.log_exception(_moduleLogger)
+       def on_success(self, children):
+               _moduleLogger.debug("Processing success for: %r", self._func)
+               try:
+                       node = self._run.send(children)
+               except StopIteration, e:
+                       pass
+               else:
+                       node.get_children(self.on_success, self.on_error)
+
+       @misc_utils.log_exception(_moduleLogger)
+       def on_error(self, error):
+               _moduleLogger.debug("Processing error for: %r", self._func)
+               try:
+                       node = self._run.throw(error)
+               except StopIteration, e:
+                       pass
+               else:
+                       node.get_children(self.on_success, self.on_error)
+
+
+def get_next(node, on_success, on_error):
+       try:
+               assert node.is_leaf(), node
+
+               # Find next branch
+               childNode = node
+               while True:
+                       parent = childNode.get_parent()
+                       siblings = yield parent
+                       for i, sibling in enumerate(siblings):
+                               if sibling is childNode:
+                                       break
+                       i += 1
+                       if i < len(siblings):
+                               sibling = siblings[i]
+                               break
+                       else:
+                               childNode = parent
+
+               # dig into that branch to find the first leaf
+               nodes = [sibling]
+               while nodes:
+                       child = nodes.pop(0)
+                       if child.is_leaf():
+                               on_success(child)
+                               return
+                       children = yield child
+                       nodes[0:0] = children
+               raise RuntimeError("Ran out of nodes when hunting for first leaf of %s" % node)
+       except Exception, e:
+               on_error(e)
+
+
+def get_previous(node, on_success, on_error):
+       try:
+               assert node.is_leaf(), node
+
+               # Find next branch
+               childNode = node
+               while True:
+                       parent = childNode.get_parent()
+                       siblings = yield parent
+                       for i, sibling in enumerate(siblings):
+                               if sibling is childNode:
+                                       break
+                       i -= 1
+                       if 0 <= i:
+                               sibling = siblings[i]
+                               break
+                       else:
+                               childNode = parent
+
+               # dig into that branch to find the first leaf
+               nodes = [sibling]
+               while nodes:
+                       child = nodes.pop(-1)
+                       if child.is_leaf():
+                               on_success(child)
+                               return
+                       children = yield child
+                       nodes[0:0] = children
+               raise RuntimeError("Ran out of nodes when hunting for first leaf of %s" % node)
+       except Exception, e:
+               on_error(e)