widgets/thread: turn the body into a tree of _MIMEPartWidget subclasses

Rather than an ad-hoc collection of widgets. This will allow folding
body parts (such as quotes).

1 files changed, 108 insertions, 87 deletions

diff --git a/alot/widgets/thread.py b/alot/widgets/thread.py
index 09dd15fe..b410ff14 100644
--- a/alot/widgets/thread.py
+++ b/alot/widgets/thread.py
@@ -70,70 +70,19 @@ class MessageSummaryWidget(urwid.WidgetWrap):
     def keypress(self, size, key):
         return key
 
-class _MessageBodyWidget(urwid.WidgetWrap):
-    _QUOTE_CHARS = '>|:}#'
-    _QUOTE_REGEX = '(([ \t]*[{quote_chars}])+)'.format(quote_chars = _QUOTE_CHARS)
+class _MIMEPartWidget(urwid.WidgetWrap):
 
-    _prefer_plaintext = None
-
-    def __init__(self, mime_tree):
-        self._prefer_plaintext = settings.get('prefer_plaintext')
-        body_wgt = self._build_body(mime_tree);
-        if body_wgt is None:
-            body_wgt = urwid.Text('<<Message body is empty>>>', alignt = 'center')
+    # when not None, a list of child _MIMEPartWidget subclasses
+    _children = None
 
+    def __init__(self, body_wgt, children = None):
+        self._children   = children
         super().__init__(body_wgt)
 
-    def _build_body(self, mime_tree):
-        # handle encrypted/signed parts
-        if mime_tree.is_signed or mime_tree.is_encrypted:
-            return self._handle_crypt(mime_tree)
-
-        if mime_tree.children is not None:
-            # multipart MIME parts
-            if mime_tree.is_alternative:
-                return self._handle_alternative(mime_tree)
-
-            return self._handle_mixed(mime_tree)
-
-        # no children - this is a leaf node
-        # skip attachment parts
-        if mime_tree.attachment:
-            return None
-
-        # try rendering the message
-        text = mime_tree.render_str()
-        if text is not None:
-            return self._render_plain_text(text)
-
-        return urwid.Text('Undisplayable "%s" MIME part.' % mime_tree.content_type,
-                          align = 'center')
+class _CryptPartWidget(_MIMEPartWidget):
+    def __init__(self, mime_tree, alternative_pref):
+        children = None
 
-    def _handle_mixed(self, mime_tree):
-        children = []
-        for child in mime_tree.children:
-            ch = self._build_body(child)
-            if ch is not None:
-                children.append(ch)
-
-        if len(children) > 0:
-            return urwid.Pile(children)
-
-    def _handle_alternative(self, mime_tree):
-        # TODO: switching between alternatives
-        preferred = 'plain' if self._prefer_plaintext else 'html'
-
-        child = None
-        for ch in mime_tree.children:
-            if ch.content_subtype == preferred:
-                child = ch
-                break
-        if child is None:
-            child = mime_tree.children[0]
-
-        return self._build_body(child)
-
-    def _handle_crypt(self, mime_tree):
         # handle broken crypto parts where we could not get the payload
         if (mime_tree.children is None or
             len(mime_tree.children) != 1):
@@ -142,41 +91,52 @@ class _MessageBodyWidget(urwid.WidgetWrap):
             if mime_tree.crypt_error:
                 text += ': ' + mime_tree.crypt_error
 
-            return urwid.Text(text, align = 'center')
+            body_wgt = urwid.Text(text, align = 'center')
+        else:
+            text_parts = []
 
-        text_parts = []
+            if mime_tree.is_encrypted and mime_tree.is_signed:
+                desc = 'encrypted+signed'
+            if mime_tree.is_encrypted:
+                desc = 'encrypted'
+            elif mime_tree.is_signed:
+                desc = 'signed'
 
-        if mime_tree.is_encrypted and mime_tree.is_signed:
-            desc = 'encrypted+signed'
-        if mime_tree.is_encrypted:
-            desc = 'encrypted'
-        elif mime_tree.is_signed:
-            desc = 'signed'
+            text_parts.append(desc + ' MIME part')
 
-        text_parts.append(desc + ' MIME part')
+            if mime_tree.is_signed and mime_tree.sig_valid:
+                if mime_tree.sig_trusted:
+                    trust     = 'trusted'
+                    attr_name = 'crypt_trusted'
+                else:
+                    trust     = 'untrusted'
+                    attr_name = 'crypt_untrusted'
 
-        if mime_tree.is_signed and mime_tree.sig_valid:
-            if mime_tree.sig_trusted:
-                trust     = 'trusted'
-                attr_name = 'crypt_trusted'
+                t = 'valid %s signature from "%s"' % (trust, mime_tree.signer_id)
+                text_parts.append(t)
             else:
-                trust     = 'untrusted'
-                attr_name = 'crypt_untrusted'
+                attr_name = 'crypt_unsigned'
 
-            t = 'valid %s signature from "%s"' % (trust, mime_tree.signer_id)
-            text_parts.append(t)
-        else:
-            attr_name = 'crypt_unsigned'
+            if mime_tree.crypt_error:
+                text_parts.append('crypto processing error: ' + mime_tree.crypt_error)
+                attr_name = 'crypt_invalid'
+
+            child    = _render_mime_tree(mime_tree.children[0], alternative_pref)
+            attr     = settings.get_theming_attribute('thread', attr_name)
+            body_wgt = urwid.AttrMap(urwid.LineBox(child, title = ':'.join(text_parts)), attr)
+            children = [child]
+
+        super().__init__(body_wgt, children)
 
-        if mime_tree.crypt_error:
-            text_parts.append('crypto processing error: ' + mime_tree.crypt_error)
-            attr_name = 'crypt_invalid'
+class _AltMixedPart(_MIMEPartWidget):
+    def __init__(self, children):
+        super().__init__(urwid.Pile(children), children)
 
-        body = self._build_body(mime_tree.children[0])
-        attr = settings.get_theming_attribute('thread', attr_name)
-        return urwid.AttrMap(urwid.LineBox(body, title = ':'.join(text_parts)), attr)
+class _TextPart(_MIMEPartWidget):
+    _QUOTE_CHARS = '>|:}#'
+    _QUOTE_REGEX = '(([ \t]*[{quote_chars}])+)'.format(quote_chars = _QUOTE_CHARS)
 
-    def _render_plain_text(self, text):
+    def __init__(self, text):
         attr_text   = settings.get_theming_attribute('thread', 'body')
         attrs_quote = settings.get_quote_theming()
 
@@ -202,7 +162,60 @@ class _MessageBodyWidget(urwid.WidgetWrap):
                 attr = attrs_quote[(level - 1) % len(attrs_quote)]
             line_widgets.append(urwid.Text((attr, line)))
 
-        return urwid.Pile(line_widgets)
+        super().__init__(urwid.Pile(line_widgets))
+
+class _EmptyMessageWidget(_MIMEPartWidget):
+    def __init__(self):
+        body_wgt = urwid.Text('<<Message body is empty>>>', align = 'center')
+        super().__init__(body_wgt)
+
+def _handle_mixed(mime_tree, alternative_pref):
+    children = []
+    for child in mime_tree.children:
+        ch = _render_mime_tree(child, alternative_pref)
+        if ch is not None:
+            children.append(ch)
+
+    if len(children) > 0:
+        return _AltMixedPart(children)
+
+def _handle_alternative(mime_tree, alternative_pref):
+    # TODO: switching between alternatives
+    child = None
+    for ch in mime_tree.children:
+        if ch.content_type == alternative_pref:
+            child = ch
+            break
+    if child is None:
+        child = mime_tree.children[0]
+
+    return _render_mime_tree(child, alternative_pref)
+
+def _render_mime_tree(mime_tree, alternative_pref):
+    # handle encrypted/signed parts
+    if mime_tree.is_signed or mime_tree.is_encrypted:
+        return _CryptPartWidget(mime_tree, alternative_pref)
+
+    if mime_tree.children is not None:
+        # multipart MIME parts
+        if mime_tree.is_alternative:
+            return _handle_alternative(mime_tree, alternative_pref)
+
+        return _AltMixedPart(mime_tree, alternative_pref)
+
+    # no children - this is a leaf node
+    # skip attachment parts
+    if mime_tree.attachment:
+        return None
+
+    # try rendering the message
+    text = mime_tree.render_str()
+    if text is not None:
+        return _TextPart(text)
+
+    body_wgt =  urwid.Text('Undisplayable "%s" MIME part.' % mime_tree.content_type,
+                           align = 'center')
+    return _MIMEPartWidget(body_wgt)
 
 class HeadersWidget(urwid.WidgetWrap):
     """
@@ -308,11 +321,19 @@ class MessageWidget(urwid.WidgetWrap):
         """
         self._message       = message
 
+        if settings.get('prefer_plaintext'):
+            alternative_pref = 'text/plain'
+        else:
+            alternative_pref = 'text/html'
+
         self._headers_wgt = self._get_headers()
         self._source_wgt  = _RawMessageWidget(message.as_bytes())
-        self._body_wgt    = _MessageBodyWidget(message.body)
         self._attach_wgt  = self._get_attachments()
 
+        self._body_wgt = _render_mime_tree(message.body, alternative_pref)
+        if self._body_wgt is None:
+            self._body_wgt = _EmptyMessageWidget()
+
         super().__init__(urwid.ListBox(urwid.SimpleListWalker([])))
 
         self.display_all_headers = False