implement format_fingerprint method

Signed-off-by: Maxime “pep” Buquet <pep@bouah.net>

poezio_omemo/__init__.py

@@ -18,8 +18,10 @@ import logging
 from pathlib import Path
 from typing import Dict, List, Optional
 
+from poezio import colors
 from poezio.plugin_e2ee import E2EEPlugin
 from poezio.xdg import DATA_HOME
+from poezio.theming import Theme
 from poezio.tabs import ChatTab, DynamicConversationTab, StaticConversationTab, MucTab
 
 from omemo.exceptions import MissingBundleException
@@ -123,6 +125,31 @@ class Plugin(E2EEPlugin):
             if trust is not None
         ]
 
+    @staticmethod
+    def format_fingerprint(fingerprint: str, theme: Theme) -> str:
+        """
+            Color fingerprint as specified in in XEP-0384 0.8.3 Ҥ8 Security
+            Considerations”.
+
+            “When displaying the fingerprint as a hex-string, the RECOMMENDED
+            way to make it easier to compare the fingerprint is to split the
+            lowercase hex-string into 8 substrings of 8 chars each, then
+            coloring each group of 8 lowercase hex chars using Consistent
+            Color Generation (XEP-0392)”
+        """
+        size = len(fingerprint) // 8
+        parts = map(''.join, zip(*[iter(fingerprint)]*8))
+        colored_fp = ''
+        for i, part in enumerate(parts):
+            fg_color = colors.ccg_text_to_color(theme.ccg_palette, part)
+            separator = ' '
+            if i == (size // 2 - 1):
+                separator = '\n'
+            elif i == size - 1:
+                separator = ''
+            colored_fp += f'\x19{fg_color}}}{part}{separator}'
+        return colored_fp
+
     async def decrypt(self, message: Message, jid: Optional[JID], tab: ChatTab) -> None:
         if jid is None:
             self.display_error('Unable to decrypt the message.')