robust charset decoding + retry-failed endpoint

- fix: fetch_mail crashed on MIME pseudo-encodings like 'unknown-8bit',
  'x-unknown', '8bit'. New _safe_decode helper maps those (and any
  LookupError from unknown codecs) to latin-1, which never fails on
  8-bit input. Used in _extract_body and _decode_header_value.
- Consequence of the crash: scheduler marked the affected UIDs as
  processed to avoid retry loops, so those mails never got sorted
  even after the underlying issue was fixable.
- feat: POST /api/filters/retry-failed drops the ProcessedMail markers
  for UIDs that appear in "Fehler beim Abrufen" error logs, so the
  next poll re-evaluates them. Reachable via a button in the log UI
  ("Fehlgeschlagene neu einlesen"), optionally scoped per account.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/routers/filters.py

@@ -5,7 +5,15 @@ from sqlalchemy.orm import Session
 import logging
 
 from app.database import get_db
-from app.models.db_models import Account, FilterAction, FilterCondition, FilterRule, ProcessedMail
+from app.models.db_models import (
+    Account,
+    FilterAction,
+    FilterCondition,
+    FilterLog,
+    FilterRule,
+    LogLevel,
+    ProcessedMail,
+)
 from app.schemas.schemas import FilterRuleCreate, FilterRuleResponse, FilterRuleUpdate
 
 logger = logging.getLogger(__name__)
@@ -25,6 +33,36 @@ def _reset_processed_for_rule(db: Session, rule_id: int) -> int:
 router = APIRouter(prefix="/api/filters", tags=["filters"])
 
 
+@router.post("/retry-failed")
+def retry_failed_fetches(account_id: int | None = None, db: Session = Depends(get_db)):
+    """Löscht ProcessedMail-Einträge für UIDs, für die es einen ERROR-Log
+    mit 'Fehler beim Abrufen' gibt — damit der Scheduler sie beim nächsten
+    Poll neu versucht (z.B. nach einem Codec-Fix)."""
+    log_q = db.query(FilterLog.mail_uid, FilterLog.account_id).filter(
+        FilterLog.level == LogLevel.ERROR,
+        FilterLog.message.like("Fehler beim Abrufen%"),
+        FilterLog.mail_uid.isnot(None),
+    )
+    if account_id is not None:
+        log_q = log_q.filter(FilterLog.account_id == account_id)
+
+    pairs = {(row[0], row[1]) for row in log_q.all()}
+    if not pairs:
+        return {"reset": 0, "unique_uids": 0}
+
+    total = 0
+    for uid, acc_id in pairs:
+        q = db.query(ProcessedMail).filter(ProcessedMail.mail_uid == uid)
+        if acc_id is not None:
+            q = q.filter(ProcessedMail.account_id == acc_id)
+        total += q.delete(synchronize_session=False)
+    db.commit()
+    logger.info(
+        "Retry-Failed: %d ProcessedMail-Einträge für %d UIDs entfernt", total, len(pairs)
+    )
+    return {"reset": total, "unique_uids": len(pairs)}
+
+
 @router.get("/account/{account_id}", response_model=list[FilterRuleResponse])
 def list_filters(account_id: int, db: Session = Depends(get_db)):
     account = db.get(Account, account_id)

app/services/imap_client.py

@@ -33,6 +33,23 @@ def _quote_mailbox(name: str) -> str:
     return f'"{escaped}"'
 
 
+def _safe_decode(data: bytes, charset: str | None) -> str:
+    """Dekodiert Bytes robust: bekannten Codec normal, unbekannte oder MIME-Pseudo-
+    Encodings (unknown-8bit, x-unknown, 8bit, binary, ...) fallen auf latin-1 zurück —
+    latin-1 kann jedes Byte 1:1 abbilden und wirft nie einen Fehler."""
+    if not isinstance(data, (bytes, bytearray)):
+        return str(data)
+    charset = (charset or "").strip().lower() or "utf-8"
+    # Bekannte Pseudo-Encodings direkt auf latin-1 mappen
+    if charset in {"unknown-8bit", "x-unknown", "unknown", "8bit", "7bit", "binary", "us-ascii-8bit"}:
+        return data.decode("latin-1", errors="replace")
+    try:
+        return data.decode(charset, errors="replace")
+    except (LookupError, TypeError):
+        # Unbekannter Codec (z.B. proprietäre Schreibweisen) → latin-1 als sicherer Fallback
+        return data.decode("latin-1", errors="replace")
+
+
 def _decode_header_value(value: str | None) -> str:
     if not value:
         return ""
@@ -40,7 +57,7 @@ def _decode_header_value(value: str | None) -> str:
     decoded = []
     for part, charset in parts:
         if isinstance(part, bytes):
-            decoded.append(part.decode(charset or "utf-8", errors="replace"))
+            decoded.append(_safe_decode(part, charset))
         else:
             decoded.append(part)
     return " ".join(decoded)
@@ -78,13 +95,11 @@ def _extract_body(msg: Message) -> str:
             if content_type == "text/plain":
                 payload = part.get_payload(decode=True)
                 if payload:
-                    charset = part.get_content_charset() or "utf-8"
-                    return payload.decode(charset, errors="replace")
+                    return _safe_decode(payload, part.get_content_charset())
         return ""
     payload = msg.get_payload(decode=True)
     if payload:
-        charset = msg.get_content_charset() or "utf-8"
-        return payload.decode(charset, errors="replace")
+        return _safe_decode(payload, msg.get_content_charset())
     return ""
 
 

app/templates/logs.html

@@ -29,6 +29,7 @@
     </label>
     <div role="group" style="margin-bottom:0;">
         <button class="outline small" onclick="loadLogs()">Suchen</button>
+        <button class="outline small" onclick="retryFailed()" title="Löscht den 'verarbeitet'-Marker für Mails, die einen Fetch-Fehler hatten, damit sie beim nächsten Poll neu versucht werden">Fehlgeschlagene neu einlesen</button>
         <button class="outline small contrast" onclick="clearLogs()">Log leeren</button>
     </div>
     <label style="margin-bottom:0;">
@@ -236,6 +237,20 @@ async function clearLogs() {
     loadLogs();
 }
 
+async function retryFailed() {
+    if (!confirm('Alle Mails mit "Fehler beim Abrufen" für den nächsten Poll neu vormerken?')) return;
+    const accountId = document.getElementById('log-account').value;
+    let url = '/api/filters/retry-failed';
+    if (accountId) url += `?account_id=${accountId}`;
+    try {
+        const resp = await fetch(url, {method: 'POST'});
+        const data = await resp.json();
+        alert(`${data.unique_uids || 0} UID(s) neu vorgemerkt (${data.reset || 0} ProcessedMail-Einträge gelöscht). Werden beim nächsten Poll neu versucht.`);
+    } catch(e) {
+        alert('Fehler: ' + e.message);
+    }
+}
+
 function toggleAutoRefresh() {
     if (document.getElementById('auto-refresh').checked) {
         refreshTimer = setInterval(() => loadLogs(currentOffset), 5000);