buffers/search: rewrite PipeWalker

Convert it to the v2 API and avoid constructing widgets until they are
needed.

1 files changed, 56 insertions, 45 deletions

diff --git a/alot/buffers/search.py b/alot/buffers/search.py
index ef05c667..15e9f41f 100644
--- a/alot/buffers/search.py
+++ b/alot/buffers/search.py
@@ -14,62 +14,74 @@ class PipeWalker(urwid.ListWalker):
     urwid.ListWalker that reads next items from a pipe and wraps them in
     ThreadlineWidget widgets for displaying
     """
+
+    _pipe  = None
+    _dbman = None
+
+    _pipe_eof = False
+
+    # list of the thread IDs
+    _tids  = None
+    # a dictionary of threadline widgets, indexed by position
+    _wgts  = None
+
+    _focus = None
+
     def __init__(self, pipe, dbman):
-        self.pipe = pipe
+        self._pipe  = pipe
         self._dbman = dbman
-        self.lines = []
-        self.focus = 0
-        self.empty = False
+
+        self._tids = []
+        self._wgts = {}
+
+        self._focus = 0
+
+        super().__init__()
 
     def __len__(self):
-        while not self.empty:
+        while not self._pipe_eof:
             self._get_next_item()
-        return len(self.lines)
+        return len(self._tids)
 
-    def get_focus(self):
-        return self._get_at_pos(self.focus)
+    def __getitem__(self, pos):
+        self._check_pos(pos)
+        if not pos in self._wgts:
+            self._wgts[pos] = ThreadlineWidget(self._tids[pos], self._dbman)
+        return self._wgts[pos]
 
-    def set_focus(self, focus):
-        self.focus = focus
-        self._modified()
+    def _check_pos(self, pos):
+        if pos < 0:
+            raise IndexError
+
+        while not self._pipe_eof and pos >= len(self._tids):
+            self._get_next_item()
+
+        if pos >= len(self._tids):
+            raise IndexError
 
-    def get_next(self, start_from):
-        return self._get_at_pos(start_from + 1)
-
-    def get_prev(self, start_from):
-        return self._get_at_pos(start_from - 1)
-
-    def _get_at_pos(self, pos):
-        if pos < 0:  # pos too low
-            return (None, None)
-        elif pos > len(self.lines):  # pos too high
-            return (None, None)
-        elif len(self.lines) > pos:  # pos already cached
-            return (self.lines[pos], pos)
-        else:  # pos not cached yet, look at next item from iterator
-            if self.empty:  # iterator is empty
-                return (None, None)
-            else:
-                widget = self._get_next_item()
-                if widget:
-                    return (widget, pos)
-                else:
-                    return (None, None)
+        return pos
+    def next_position(self, pos):
+        return self._check_pos(pos + 1)
+    def prev_position(self, pos):
+        return self._check_pos(pos - 1)
+
+    @property
+    def focus(self):
+        return self._focus
+
+    def set_focus(self, pos):
+        self._check_pos(pos)
+        self._focus = pos
+        self._modified()
 
     def _get_next_item(self):
-        if self.empty:
+        if self._pipe_eof:
             return None
+
         try:
-            # the next line blocks until it can read from the pipe or
-            # EOFError is raised. No races here.
-            next_obj = self.pipe.recv()
-            next_widget = ThreadlineWidget(next_obj, self._dbman)
-            self.lines.append(next_widget)
+            self._tids.append(self._pipe.recv())
         except EOFError:
-            logging.debug('EMPTY PIPE')
-            next_widget = None
-            self.empty = True
-        return next_widget
+            self._pipe_eof = True
 
 class SearchBuffer(Buffer):
     """shows a result list of threads for a query"""
@@ -145,8 +157,7 @@ class SearchBuffer(Buffer):
         returns curently focussed :class:`alot.widgets.ThreadlineWidget`
         from the result list.
         """
-        threadlinewidget, _ = self.threadlist.get_focus()
-        return threadlinewidget
+        return self.threadlist[self.threadlist.focus]
 
     def get_selected_thread(self):
         """returns currently selected :class:`~alot.db.Thread`"""