Make Stop stop: no replay, no restart, immediate feedback

Pressing Stop could look like the scan restarting, and for scheduled jobs
it really did restart the Google stage.

- Scheduler: check the abort flag between stages and never clear the
  Google abort after a Stop (that started a fresh all-users Google scan).
  A stopped job is recorded as "cancelled" and skips email/retention;
  scheduler_done carries cancelled=true.
- SSE: scan_cancelled and file_scan_done now end the current scan like
  scan_done, and sse.replay_messages() never replays a finished scan.
  Previously a stopped M365 scan (and every file scan) stayed "current",
  so each reconnect replayed it and re-showed Stop + progress.
- Frontend: scan_cancelled clears the M365 running flag and only tears
  down the UI when no Google/file scan is still running; scheduler_done /
  scheduler_error clear all running flags.
- run_scan: Stop during collection now ends the scan (checkpoint, finish,
  scan_cancelled) instead of announcing scan_start / "Scanning…".
- Stop button: switches to a disabled "Stopping…" state on click; all
  show/hide goes through _setStopBtnDisplay(), which resets it when hidden
  or when a new scan starts.

Adds tests/test_stop_scan.py (10 tests).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

static/js/CLAUDE.md

@@ -34,6 +34,11 @@ Never revert to `!!window._googleConnected` / `_fileSources.length > 0` — thos
 - **Do not close `S.es` in `scan_done` if other scans are still running** — M365 (`scan_done`), Google (`google_scan_done`), and File (`file_scan_done`) each emit their own done event. Close `S.es` only when all concurrent scans have finished: `scan_done` checks `!S._googleScanRunning && !S._fileScanRunning`; `google_scan_done` checks `!S._m365ScanRunning && !S._fileScanRunning`; `file_scan_done` checks `!S._m365ScanRunning && !S._googleScanRunning`.
 - **Scheduled scans** — `S._userStartedScan` is false for scheduler-triggered runs, so SSE is never closed and future scheduler events continue to arrive.
 - **Two separate abort events** — `state._scan_abort` (M365 + file) and `state._google_scan_abort` (Google). `POST /api/scan/stop` sets **both**. `_check_abort()` inside `_run_google_scan` must use the module-level `_scan_abort` alias (`= state._google_scan_abort`), not `gdpr_scanner._scan_abort`.
+- **Stop must never look like a restart** — four rules, each fixing a way Stop used to appear to restart the scan:
+  - `sse.replay_messages()` never replays a scan that has ended. `scan_done`, `scan_cancelled` and `file_scan_done` move `_current_scan_id` into `_finished_scan_ids`. Do not go back to clearing the id only on `scan_done`: stopped M365 scans and all file scans stayed "current", and every reconnect (page load, watchdog) replayed them, bringing back the Stop button and progress bar.
+  - The `scan_cancelled` handler clears `S._m365ScanRunning` and, like `scan_done`, keeps the Stop button and SSE only while a Google or file scan is still running. `scheduler_done` and `scheduler_error` clear all three running flags.
+  - The Stop button goes through `_setStopBtnDisplay(display, fresh)`; do not set `stopBtn.style.display` directly. `stopScan()` switches it to a disabled "Stopping…" state. Hiding it, or passing `fresh=true` (from `startScan()` and `scheduler_started`), resets it.
+  - Server side: `run_scan` checks for Stop straight after collection, before `scan_start`. The scheduler checks `_scan_abort` between stages and never clears the Google abort flag after a Stop. A stopped job is recorded as `cancelled`, with no email or retention.
 - **`_check_abort()` emits `google_scan_done`, not `scan_cancelled`** — `scan_cancelled` unconditionally closes the SSE; `google_scan_done` checks whether other scans are still running before closing.
 - **`scan_phase` replay sets running flags — handled by `sse_replay_done`** — the `scan_phase` handler sets running flags to `true` whenever all flags are `false` and a source keyword is found in the phase text. On page refresh this fires during SSE replay of a completed scan, temporarily making the scan appear running. The `sse_replay_done` handler retries `loadHistorySession(null)` if no scan is running and `S._historyRefScanId` is still `null` after replay. Do not remove either the flag-setting logic or the retry.
 - **Google Drive uses a lazy generator, not `list()`** — `iter_drive_files()` iterated directly so `_check_abort()` fires between items. Wrapping in `list()` blocks the thread for the entire enumeration.

static/js/results.js

@@ -779,7 +779,7 @@ function _sseWatchdog() {
       _ensureSSE();
       if (status.running && !S._m365ScanRunning && !S._googleScanRunning && !S._fileScanRunning) {
         document.getElementById('scanBtn').disabled = true;
-        document.getElementById('stopBtn').style.display = 'inline-block';
+        _setStopBtnDisplay('inline-block');
         // status.running reflects the M365 + file lock; treat as an M365 reconnect
         S._m365ScanRunning = true; _renderProgressSegments();
         document.getElementById('progressFile').textContent = t('m365_sse_reconnecting', 'Reconnecting to running scan…');

static/js/scan.js

@@ -317,7 +317,7 @@ function _attachScanListeners(source) {
       else if (phaseSrc === 'file') { S._fileScanRunning   = true; }
       else                          { S._m365ScanRunning   = true; }
       document.getElementById('scanBtn').disabled = true;
-      document.getElementById('stopBtn').style.display = 'inline-block';
+      _setStopBtnDisplay('inline-block');
       _renderProgressSegments();
     }
     _setProgressPhase(d.phase);
@@ -330,9 +330,9 @@ function _attachScanListeners(source) {
             : (d.total > 0 ? Math.round((d.index || d.completed || 0) / d.total * 100) : 0);
     S._srcPct[src] = pct;
     // If reconnecting mid-scan the running flag may not be set yet — ensure segment exists
-    if (src === 'm365'    && !S._m365ScanRunning)   { S._m365ScanRunning   = true; document.getElementById('scanBtn').disabled = true; document.getElementById('stopBtn').style.display = 'inline-block'; _renderProgressSegments(); }
-    if (src === 'google'  && !S._googleScanRunning) { S._googleScanRunning = true; document.getElementById('scanBtn').disabled = true; document.getElementById('stopBtn').style.display = 'inline-block'; _renderProgressSegments(); }
-    if (src === 'file'    && !S._fileScanRunning)   { S._fileScanRunning   = true; document.getElementById('scanBtn').disabled = true; document.getElementById('stopBtn').style.display = 'inline-block'; _renderProgressSegments(); }
+    if (src === 'm365'    && !S._m365ScanRunning)   { S._m365ScanRunning   = true; document.getElementById('scanBtn').disabled = true; _setStopBtnDisplay('inline-block'); _renderProgressSegments(); }
+    if (src === 'google'  && !S._googleScanRunning) { S._googleScanRunning = true; document.getElementById('scanBtn').disabled = true; _setStopBtnDisplay('inline-block'); _renderProgressSegments(); }
+    if (src === 'file'    && !S._fileScanRunning)   { S._fileScanRunning   = true; document.getElementById('scanBtn').disabled = true; _setStopBtnDisplay('inline-block'); _renderProgressSegments(); }
     var fill = document.getElementById('progressFill_' + src);
     if (fill) fill.style.width = pct + '%';
     document.getElementById('progressFile').textContent = d.file || '';
@@ -368,15 +368,20 @@ function _attachScanListeners(source) {
     log((d.file ? d.file + ': ' : '') + d.error, 'err');
   });
   source.addEventListener('scan_cancelled', function() {
-    if (S._userStartedScan) {
+    // scan_cancelled is the M365 engine's "stopped" event. Clear its running
+    // flag (leaving it set made later replays/status polls treat the stopped
+    // scan as live) and, like scan_done, only tear down the UI once no Google
+    // or file scan is still running.
+    S._m365ScanRunning = false;
+    var _anyRunning = S._googleScanRunning || S._fileScanRunning;
+    if (S._userStartedScan && !_anyRunning) {
       S._userStartedScan = false;
       if (S.es) { S.es.close(); S.es = null; }
     }
-    document.getElementById('scanBtn').disabled = false;
-    document.getElementById('stopBtn').style.display = 'none';
-    _clearProgressBar();
-    setLogLive('');
-    log('Scan stopped.', 'warn');
+    document.getElementById('scanBtn').disabled = _anyRunning;
+    _setStopBtnDisplay(_anyRunning ? 'inline-block' : 'none');
+    if (_anyRunning) { _renderProgressSegments(); } else { _clearProgressBar(); setLogLive(''); }
+    log(t('m365_scan_stopped', 'Scan stopped.'), 'warn');
   });
   source.addEventListener('scan_done', function(e) {
     var d = JSON.parse(e.data);
@@ -401,7 +406,7 @@ function _attachScanListeners(source) {
     }
     if (!_anyRunning) setLogLive('');
     document.getElementById('scanBtn').disabled = _anyRunning;
-    document.getElementById('stopBtn').style.display = _anyRunning ? 'inline-block' : 'none';
+    _setStopBtnDisplay(_anyRunning ? 'inline-block' : 'none');
     if (!_anyRunning) _clearProgressBar();
     document.getElementById('statsSection').style.display = 'block';
     document.getElementById('statScanned').textContent = d.total_scanned;
@@ -437,7 +442,7 @@ function _attachScanListeners(source) {
       }
       setLogLive('');
       document.getElementById('scanBtn').disabled = false;
-      document.getElementById('stopBtn').style.display = 'none';
+      _setStopBtnDisplay('none');
       _clearProgressBar();
       document.getElementById('statsSection').style.display = 'block';
       document.getElementById('statsPill').style.display = 'block';
@@ -466,7 +471,7 @@ function _attachScanListeners(source) {
       }
       setLogLive('');
       document.getElementById('scanBtn').disabled = false;
-      document.getElementById('stopBtn').style.display = 'none';
+      _setStopBtnDisplay('none');
       _clearProgressBar();
       document.getElementById('statsSection').style.display = 'block';
       document.getElementById('statsPill').style.display = 'block';
@@ -502,7 +507,7 @@ function _attachSchedulerListeners(source) {
     log('\uD83D\uDD50 ' + t('m365_sched_title','Scheduled scan') + ': ' + (d.job_name||'') + '\u2026');
     // Show progress UI so scan_phase / scan_progress events are visible
     document.getElementById('scanBtn').disabled = true;
-    document.getElementById('stopBtn').style.display = 'inline-block';
+    _setStopBtnDisplay('inline-block', true);
     S._srcPct = { m365: 0, google: 0, file: 0 }; S._m365ScanRunning = true; _renderProgressSegments();
     _setProgressPhase((d.job_name||'') + '\u2026');
     document.getElementById('progressFile').textContent = '';
@@ -512,25 +517,32 @@ function _attachSchedulerListeners(source) {
     // scheduler_started was missed (e.g. browser reconnected mid-scan)
     console.log('[SSE] scan_start received');
     document.getElementById('scanBtn').disabled = true;
-    document.getElementById('stopBtn').style.display = 'inline-block';
+    _setStopBtnDisplay('inline-block');
     // Ensure at least the M365 segment is rendered (scan_start is M365-only)
     if (!S._m365ScanRunning) { S._m365ScanRunning = true; _renderProgressSegments(); }
   });
   source.addEventListener('scheduler_done', function(e) {
     var d = JSON.parse(e.data);
     console.log('[SSE] scheduler_done received:', d);
+    // The job's stages are all over — scheduler_started set the M365 flag
+    S._m365ScanRunning = S._googleScanRunning = S._fileScanRunning = false;
     document.getElementById('scanBtn').disabled = false;
-    document.getElementById('stopBtn').style.display = 'none';
+    _setStopBtnDisplay('none');
     _clearProgressBar();
-    log('\u2713 ' + t('m365_sched_title','Scheduled scan') + ' ' + (d.job_name||'') + ' \u2014 ' + (d.flagged||0) + ' flagged', 'ok');
+    if (d.cancelled) {
+      log('\u23f9 ' + t('m365_sched_title','Scheduled scan') + ' ' + (d.job_name||'') + ' \u2014 ' + t('m365_sched_stopped','stopped') + ' (' + (d.flagged||0) + ' flagged)', 'warn');
+    } else {
+      log('\u2713 ' + t('m365_sched_title','Scheduled scan') + ' ' + (d.job_name||'') + ' \u2014 ' + (d.flagged||0) + ' flagged', 'ok');
+    }
     markOverdueCards();
     loadTrend();
   });
   source.addEventListener('scheduler_error', function(e) {
     var d = JSON.parse(e.data);
     console.log('[SSE] scheduler_error received:', d);
+    S._m365ScanRunning = S._googleScanRunning = S._fileScanRunning = false;
     document.getElementById('scanBtn').disabled = false;
-    document.getElementById('stopBtn').style.display = 'none';
+    _setStopBtnDisplay('none');
     _clearProgressBar();
     log('\u26A0 ' + t('m365_sched_title','Scheduled scan') + ' failed: ' + (d.error||''), 'err');
   });
@@ -564,7 +576,7 @@ function startScan(resume) {
   S._progressCurrentUser = '';
   _renderProgressSegments();
   document.getElementById('scanBtn').disabled = true;
-  document.getElementById('stopBtn').style.display = 'inline-block';
+  _setStopBtnDisplay('inline-block', true);
   // progress segments rendered by _renderProgressSegments() called above
   document.getElementById('progressFile').textContent = '';
   _setProgressPhase(t('scan_preparing', 'Preparing…'));
@@ -594,7 +606,7 @@ function startScan(resume) {
     if (label === 'google')  S._googleScanRunning  = false;
     if (!S._m365ScanRunning && !S._googleScanRunning && !S._fileScanRunning) {
       document.getElementById('scanBtn').disabled = false;
-      document.getElementById('stopBtn').style.display = 'none';
+      _setStopBtnDisplay('none');
       if (S.es) { S.es.close(); S.es = null; }
       S._userStartedScan = false;
     }
@@ -664,8 +676,30 @@ function startScan(resume) {
 
 }
 
+// Show/hide the Stop button. Hiding — or passing fresh=true when a new scan
+// starts — resets it from its "Stopping…" state, so a new scan always gets a
+// normal, clickable Stop button even if a previous scan never reported its end.
+function _setStopBtnDisplay(display, fresh) {
+  const btn = document.getElementById('stopBtn');
+  if (!btn) return;
+  btn.style.display = display;
+  if (display === 'none' || fresh) {
+    btn.disabled = false;
+    btn.textContent = t('m365_btn_stop', 'Stop');
+  }
+}
+
 function stopScan() {
-  fetch('/api/scan/stop', {method:'POST'});
+  // Immediate feedback: the scan only notices the stop between items, which
+  // can take a while (e.g. OCR on a large PDF). Stays "Stopping…" until the
+  // scan's done/stopped event hides the button.
+  const btn = document.getElementById('stopBtn');
+  if (btn) { btn.disabled = true; btn.textContent = t('m365_btn_stopping', 'Stopping…'); }
+  log(t('m365_scan_stopping', 'Stopping scan — finishing the current item…'), 'warn');
+  fetch('/api/scan/stop', {method:'POST'}).catch(function(e) {
+    if (btn) { btn.disabled = false; btn.textContent = t('m365_btn_stop', 'Stop'); }
+    log('Stop failed: ' + e, 'err');
+  });
 }
 
 // ── Trend sparkline (#7) ──────────────────────────────────────────────────────
@@ -795,6 +829,7 @@ window._attachScanListeners = _attachScanListeners;
 window._attachSchedulerListeners = _attachSchedulerListeners;
 window.startScan = startScan;
 window.stopScan = stopScan;
+window._setStopBtnDisplay = _setStopBtnDisplay;
 window.drawSparkline = drawSparkline;
 window.loadTrend = loadTrend;
 window.updateStats = updateStats;

static/js/scheduler.js

@@ -242,7 +242,8 @@ function schedLoadHistory() {
     var html = '';
     runs.forEach(function(r) {
       var ts = r.started_at ? new Date(r.started_at * 1000).toLocaleString() : '-';
-      var icon = r.status === 'completed' ? '\u2713' : r.status === 'failed' ? '\u2716' : '\u23f3';
+      var icon = r.status === 'completed' ? '\u2713' : r.status === 'failed' ? '\u2716'
+               : r.status === 'cancelled' ? '\u23f9' : '\u23f3';
       var jname = r.job_name ? '<strong>' + _esc(r.job_name) + '</strong> - ' : '';
       html += icon + ' ' + jname + ts + ' - ' + (r.flagged||0) + ' flagged';
       if (r.emailed) html += ' \u2709';