thread: implement tree decorations

They were temporarily removed in the previous commit.
Still not working:
- theming for the decorations
- drawing the connector line properly for expanded messages
- configurable indentation

4 files changed, 94 insertions, 20 deletions

diff --git a/alot/buffers/thread.py b/alot/buffers/thread.py
index bc467ded..6c92fe64 100644
--- a/alot/buffers/thread.py
+++ b/alot/buffers/thread.py
@@ -8,7 +8,7 @@ import logging
 
 from .buffer import Buffer
 from ..settings.const import settings
-from ..widgets.thread import MessageWidget
+from ..widgets.thread import MessageWidget, ThreadNode
 from .. import commands
 from ..db.errors import NonexistantObjectError
 
@@ -18,6 +18,8 @@ class ThreadBuffer(Buffer):
 
     modename = 'thread'
 
+    _msg_widgets = None
+
     def __init__(self, ui, thread):
         """
         :param ui: main UI
@@ -59,11 +61,17 @@ class ThreadBuffer(Buffer):
             self.body = urwid.SolidFill()
             return
 
-        self._msg_walker = urwid.SimpleFocusListWalker(
-            [MessageWidget(msg, idx & 1) for (idx, msg) in
-                enumerate(self.thread.message_list)])
+        self._msg_widgets = []
+
+        body_walker = urwid.SimpleFocusListWalker([])
+        for pos, msg in enumerate(self.thread.message_list):
+            msg_wgt = MessageWidget(msg, pos & 1)
+            wgt     = ThreadNode(msg_wgt, self.thread, pos, self._indent_width)
+
+            self._msg_widgets.append(msg_wgt)
+            body_walker.append(wgt)
 
-        self.body = urwid.ListBox(self._msg_walker)
+        self.body = urwid.ListBox(body_walker)
 
     def get_selected_message_position(self):
         """Return position of focussed message in the thread tree."""
@@ -71,7 +79,8 @@ class ThreadBuffer(Buffer):
 
     def get_selected_message_widget(self):
         """Return currently focused :class:`MessageWidget`."""
-        return self.body.focus
+        pos = self.get_selected_message_position()
+        return self._msg_widgets[pos]
 
     def get_selected_message(self):
         """Return focussed :class:`~alot.db.message.Message`."""
@@ -81,7 +90,7 @@ class ThreadBuffer(Buffer):
         """
         Iterate over all the message widgets in this buffer
         """
-        for w in self._msg_walker:
+        for w in self._msg_widgets:
             yield w
 
     # needed for ui.get_deep_focus..
@@ -99,7 +108,7 @@ class ThreadBuffer(Buffer):
         self.set_focus(0)
 
     def focus_last(self):
-        self.set_focus(max(self.thread.total_messages - 1), 0)
+        self.set_focus(max(self.thread.total_messages - 1, 0))
 
     def focus_selected_message(self):
         """focus the summary line of currently focused message"""
@@ -107,14 +116,9 @@ class ThreadBuffer(Buffer):
 
     def focus_parent(self):
         """move focus to parent of currently focused message"""
-        pos = self.get_selected_message_position()
-        cur_depth = self.get_selected_message().depth
-
-        for idx in reversed(range(0, pos)):
-            msg = self.thread.message_list[idx]
-            if msg.depth < cur_depth:
-                self.set_focus(idx)
-                break
+        msg = self.get_selected_message()
+        if msg.parent:
+            self.set_focus(self.thread.message_list.index(msg.parent))
 
     def focus_first_reply(self):
         """move focus to first reply to currently focused message"""
@@ -171,7 +175,7 @@ class ThreadBuffer(Buffer):
             walk = reversed(range(0, cur_pos))
 
         for pos in walk:
-            if prop(self._msg_walker[pos]):
+            if prop(self._msg_widgets[pos]):
                 self.set_focus(pos)
                 break
 
diff --git a/alot/db/message.py b/alot/db/message.py
index 62b85788..4adb0816 100644
--- a/alot/db/message.py
+++ b/alot/db/message.py
@@ -41,6 +41,12 @@ class Message:
     """A list of replies to this message"""
     replies = None
 
+    """
+    This message parent in the list (i.e. the message this message is a reply
+    to). None when this message is top-level.
+    """
+    parent = None
+
     def __init__(self, dbman, thread, msg, depth):
         """
         :param dbman: db manager that is used for further lookups
@@ -248,3 +254,13 @@ class Message:
         """tests if this messages is in the resultset for `querystring`"""
         searchfor = '( {} ) AND id:{}'.format(querystring, self.id)
         return self._dbman.count_messages(searchfor) > 0
+
+    def parents(self):
+        """
+        A generator iterating over this message's parents up to the topmost
+        level.
+        """
+        m = self.parent
+        while m:
+            yield m
+            m = m.parent
diff --git a/alot/db/thread.py b/alot/db/thread.py
index a76997f8..3dc90325 100644
--- a/alot/db/thread.py
+++ b/alot/db/thread.py
@@ -107,22 +107,23 @@ class Thread:
         msg_tree = []
         msg_list = []
 
-        def thread_tree_walk(nm_msg, depth):
+        def thread_tree_walk(nm_msg, depth, parent):
             msg = Message(self._dbman, self, nm_msg, depth)
 
             msg_list.append(msg)
 
             replies = []
             for m in nm_msg.get_replies():
-                replies.append(thread_tree_walk(m, depth + 1))
+                replies.append(thread_tree_walk(m, depth + 1, msg))
 
             msg.replies  = replies
+            msg.parent   = parent
             msgs[msg.id] = msg
 
             return msg
 
         for m in nm_thread.get_toplevel_messages():
-            msg_tree.append(thread_tree_walk(m, 0))
+            msg_tree.append(thread_tree_walk(m, 0, None))
 
         return msgs, msg_tree, msg_list
 
diff --git a/alot/widgets/thread.py b/alot/widgets/thread.py
index 0b4e2404..ebbc4704 100644
--- a/alot/widgets/thread.py
+++ b/alot/widgets/thread.py
@@ -290,3 +290,56 @@ class MessageWidget(urwid.WidgetWrap):
         matches given `querystring`
         """
         self.display_content = not self._message.matches(querystring)
+
+class ThreadNode(urwid.WidgetWrap):
+    _ARROW  = '➤'
+    _HBAR   = '─'
+    _VBAR   = '│'
+    _TNODE  = '├'
+    _CORNER = '└'
+
+    _decor_text        = None
+    _have_next_sibling = None
+
+    def __init__(self, msg_wgt, thread, pos, indent):
+        msg = msg_wgt.get_message()
+
+        if msg.depth == 0:
+            wgt = msg_wgt
+        else:
+            self._decor_text = urwid.Text('')
+            wgt = urwid.Columns([('pack', self._decor_text), msg_wgt])
+
+            ancestor_chain = [msg]
+            for p in msg.parents():
+                ancestor_chain.insert(0, p)
+
+            have_sibling = []
+            for d, m in enumerate(ancestor_chain):
+                if d == 0:
+                    have_sibling.append(m != thread.toplevel_messages[-1])
+                else:
+                    have_sibling.append(m != ancestor_chain[d - 1].replies[-1])
+
+            self._have_next_sibling = have_sibling
+
+        super().__init__(wgt)
+
+        self.set_indent(indent)
+
+    def set_indent(self, indent):
+        if self._decor_text is None:
+            return
+
+        seg_text = []
+        if indent > 0:
+            depth = len(self._have_next_sibling) - 1
+            for d in range(depth):
+                if d == depth - 1:
+                    corner = self._TNODE if self._have_next_sibling[d + 1] else self._CORNER
+                    seg_text.append(corner + self._ARROW)
+                else:
+                    bar = self._VBAR if self._have_next_sibling[d + 1] else ' '
+                    seg_text.append(bar + ' ')
+
+        self._decor_text.set_text(''.join(seg_text))