feat: align Alertmanager notifications with the CrowdSec feed format

Alertmanager notifications were hard to read: the alert name appeared
twice, the instance was repeated between the header and the summary, the
count was restated in the body, and details ran flat with no visual
structure.

They now follow the same grammar as the CrowdSec feed: a title carrying
the counts, then one block per alert made of an identity line
("<icon> <name> (<context>)") and details indented under a tree marker.
Severity moves into the icon (red/orange/blue, green once resolved)
instead of a "[critical]" suffix, which keeps the identity line short
enough to read at a glance on a phone.

app.py

@@ -61,6 +61,43 @@ def format_scenario(scenario):
         return "unknown"
     return scenario.replace("crowdsecurity/", "").replace("_", " ")
 
+# One icon per alert, mirroring the per-IP icon used by the CrowdSec feed.
+# Severity is carried by the icon instead of a "[critical]" suffix, which
+# keeps the identity line short enough to read at a glance on a phone.
+SEVERITY_ICONS = {
+    "critical": "🔴",
+    "warning": "🟠",
+    "info": "🔵",
+}
+
+def format_alert_block(alert, resolved=False):
+    """Render one alert the way the CrowdSec feed renders one IP: an identity
+    line (icon, name, context in parentheses), then the details indented under
+    a tree marker. Returns the block as a single string."""
+    labels = alert.get("labels", {})
+    annotations = alert.get("annotations", {})
+
+    name = labels.get("alertname", "alerte")
+    severity = labels.get("severity", "")
+    # "name" is what cAdvisor-based rules use to carry the container name
+    context = (labels.get("instance") or labels.get("container")
+               or labels.get("name") or labels.get("job") or "")
+
+    icon = "✅" if resolved else SEVERITY_ICONS.get(severity, "🔥")
+    head = f"{icon} {name}"
+    if context:
+        head += f" ({context})"
+
+    summary = annotations.get("summary")
+    description = annotations.get("description")
+    details = [summary] if summary else []
+    # description often just restates summary; only keep it when it adds something
+    if description and description != summary:
+        details.append(description)
+
+    lines = [head] + [f"   └ {d}" for d in details]
+    return "\n".join(lines)
+
 @app.route('/crowdsec', methods=['POST'])
 def handle_crowdsec():
     try:
@@ -120,48 +157,23 @@ def handle_alertmanager():
             logger.debug("Received empty Alertmanager payload")
             return jsonify({"status": "no data"}), 200
 
-        def format_alert(alert):
-            labels = alert.get("labels", {})
-            annotations = alert.get("annotations", {})
-            name = labels.get("alertname", "alerte")
-            severity = labels.get("severity", "")
-            instance = labels.get("instance") or labels.get("container") or labels.get("job") or ""
-
-            head = name
-            if severity:
-                head += f" [{severity}]"
-            if instance:
-                head += f" — {instance}"
-
-            out = [head]
-            summary = annotations.get("summary")
-            description = annotations.get("description")
-            if summary:
-                out.append(f"   {summary}")
-            if description and description != summary:
-                out.append(f"   {description}")
-            return "\n".join(out)
-
         firing = [a for a in alerts if a.get("status") == "firing"]
         resolved = [a for a in alerts if a.get("status") == "resolved"]
 
-        lines = []
+        # One block per alert, blank-line separated, like the CrowdSec feed
+        blocks = [format_alert_block(a) for a in firing]
+        blocks += [format_alert_block(a, resolved=True) for a in resolved]
+
+        # Title carries the counts, so the body never has to repeat them
+        counts = []
         if firing:
-            lines.append(f"🔥 {len(firing)} alerte(s) active(s)")
+            plural = "s" if len(firing) > 1 else ""
-            lines.extend(format_alert(a) for a in firing)
+            counts.append(f"{len(firing)} alerte{plural} active{plural}")
         if resolved:
-            if lines:
+            counts.append(f"{len(resolved)} résolue{'s' if len(resolved) > 1 else ''}")
-                lines.append("")
-            lines.append(f"✅ {len(resolved)} résolue(s)")
-            lines.extend(format_alert(a) for a in resolved)
 
-        status = data.get("status", "firing")
+        title = ("🔥" if firing else "✅") + f" Alertmanager - {', '.join(counts)}"
-        group_name = data.get("groupLabels", {}).get("alertname", "")
+        body = "\n\n".join(blocks)
-        title = ("🔥" if status == "firing" else "✅") + " Alertmanager"
-        if group_name:
-            title += f" — {group_name}"
-
-        body = "\n".join(lines).strip()
 
         # Send to Apprise
         response = requests.post(APPRISE_URL, json={"title": title, "body": body}, timeout=10)