feat(sitecallaudit): query, KPI and detail backend for the Site Calls page

src/ScadaLink.ConfigurationDatabase/Repositories/SiteCallAuditRepository.cs

@@ -201,6 +201,141 @@ ORDER BY CreatedAtUtc DESC, TrackedOperationId DESC;";
             ct);
     }
 
+    // Terminal status string literals for the interval-throughput KPIs. The
+    // Status column is a plain varchar (no value converter), so these compare
+    // directly in translated SQL.
+    //
+    // NOTE on the "buffered/non-terminal" definition: the SiteCalls operational
+    // mirror stores AuditStatus-derived strings (Attempted/Delivered/Parked/
+    // Failed/...), NOT the tracking-lifecycle Pending/Retrying names the spec's
+    // KPI section uses. There is therefore no Status string that means
+    // "buffered". The schema-honest predicate for "non-terminal / buffered" is
+    // TerminalAtUtc IS NULL — consistent with PurgeTerminalAsync's terminal
+    // predicate and with the SiteCall entity's own contract ("TerminalAtUtc ...
+    // null while still active"). All buffered / stuck / oldest-pending counts
+    // below key off TerminalAtUtc, not Status.
+    private const string StatusParked = "Parked";
+    private const string StatusDelivered = "Delivered";
+    private const string StatusFailed = "Failed";
+
+    /// <summary>
+    /// Computes the global KPI snapshot with five server-side aggregate queries
+    /// against <c>dbo.SiteCalls</c>. No rows are materialised — every count is a
+    /// translated <c>COUNT</c> and the oldest-pending age is a translated
+    /// <c>MIN(CreatedAtUtc)</c>. The <c>Status</c> and <c>CreatedAtUtc</c>/<c>TerminalAtUtc</c>
+    /// columns have no value converter, so the aggregates translate cleanly to
+    /// SQL Server (unlike the NotificationOutbox's <c>DateTimeOffset</c>-converted
+    /// column, which forces an order-and-take). "Buffered" / "stuck" key off
+    /// <c>TerminalAtUtc IS NULL</c> — see the field comments above.
+    /// </summary>
+    public async Task<SiteCallKpiSnapshot> ComputeKpisAsync(
+        DateTime stuckCutoff, DateTime intervalSince, CancellationToken ct = default)
+    {
+        var now = DateTime.UtcNow;
+
+        var bufferedCount = await _context.SiteCalls
+            .CountAsync(s => s.TerminalAtUtc == null, ct);
+
+        var parkedCount = await _context.SiteCalls
+            .CountAsync(s => s.Status == StatusParked, ct);
+
+        var failedLastInterval = await _context.SiteCalls
+            .CountAsync(s => s.Status == StatusFailed
+                && s.TerminalAtUtc != null
+                && s.TerminalAtUtc >= intervalSince, ct);
+
+        var deliveredLastInterval = await _context.SiteCalls
+            .CountAsync(s => s.Status == StatusDelivered
+                && s.TerminalAtUtc != null
+                && s.TerminalAtUtc >= intervalSince, ct);
+
+        var stuckCount = await _context.SiteCalls
+            .CountAsync(s => s.TerminalAtUtc == null && s.CreatedAtUtc < stuckCutoff, ct);
+
+        var nonTerminal = _context.SiteCalls.Where(s => s.TerminalAtUtc == null);
+
+        TimeSpan? oldestPendingAge = null;
+        if (await nonTerminal.AnyAsync(ct))
+        {
+            var oldestCreatedAt = await nonTerminal.MinAsync(s => s.CreatedAtUtc, ct);
+            oldestPendingAge = now - oldestCreatedAt;
+        }
+
+        return new SiteCallKpiSnapshot(
+            BufferedCount: bufferedCount,
+            ParkedCount: parkedCount,
+            FailedLastInterval: failedLastInterval,
+            DeliveredLastInterval: deliveredLastInterval,
+            OldestPendingAge: oldestPendingAge,
+            StuckCount: stuckCount);
+    }
+
+    /// <summary>
+    /// Computes the per-source-site KPI breakdown. The five counts are
+    /// <c>GROUP BY SourceSite</c> aggregates; the oldest-pending age is a
+    /// per-site <c>MIN(CreatedAtUtc)</c> over the (bounded) non-terminal set —
+    /// all run server-side. A site appears in the result only if it has at
+    /// least one row matched by one of the count queries. "Buffered" / "stuck"
+    /// key off <c>TerminalAtUtc IS NULL</c> — see <see cref="ComputeKpisAsync"/>.
+    /// </summary>
+    public async Task<IReadOnlyList<SiteCallSiteKpiSnapshot>> ComputePerSiteKpisAsync(
+        DateTime stuckCutoff, DateTime intervalSince, CancellationToken ct = default)
+    {
+        var now = DateTime.UtcNow;
+
+        var buffered = await CountBySiteAsync(s => s.TerminalAtUtc == null, ct);
+
+        var parked = await CountBySiteAsync(s => s.Status == StatusParked, ct);
+
+        var failed = await CountBySiteAsync(
+            s => s.Status == StatusFailed
+                && s.TerminalAtUtc != null && s.TerminalAtUtc >= intervalSince, ct);
+
+        var delivered = await CountBySiteAsync(
+            s => s.Status == StatusDelivered
+                && s.TerminalAtUtc != null && s.TerminalAtUtc >= intervalSince, ct);
+
+        var stuck = await CountBySiteAsync(
+            s => s.TerminalAtUtc == null && s.CreatedAtUtc < stuckCutoff, ct);
+
+        // Oldest non-terminal CreatedAtUtc per site — a server-side GROUP BY MIN.
+        var oldest = (await _context.SiteCalls
+                .Where(s => s.TerminalAtUtc == null)
+                .GroupBy(s => s.SourceSite)
+                .Select(g => new { Site = g.Key, Oldest = g.Min(s => s.CreatedAtUtc) })
+                .ToListAsync(ct))
+            .ToDictionary(x => x.Site, x => x.Oldest);
+
+        var siteIds = buffered.Keys
+            .Concat(parked.Keys).Concat(failed.Keys)
+            .Concat(delivered.Keys).Concat(stuck.Keys)
+            .Distinct()
+            .OrderBy(s => s, StringComparer.Ordinal);
+
+        return siteIds.Select(site => new SiteCallSiteKpiSnapshot(
+            SourceSite: site,
+            BufferedCount: buffered.GetValueOrDefault(site),
+            ParkedCount: parked.GetValueOrDefault(site),
+            FailedLastInterval: failed.GetValueOrDefault(site),
+            DeliveredLastInterval: delivered.GetValueOrDefault(site),
+            OldestPendingAge: oldest.TryGetValue(site, out var createdAt)
+                ? now - createdAt
+                : null,
+            StuckCount: stuck.GetValueOrDefault(site))).ToList();
+    }
+
+    /// <summary>Counts <c>SiteCalls</c> rows matching <paramref name="predicate"/>, grouped by source site.</summary>
+    private async Task<Dictionary<string, int>> CountBySiteAsync(
+        System.Linq.Expressions.Expression<Func<SiteCall, bool>> predicate,
+        CancellationToken ct)
+    {
+        return await _context.SiteCalls
+            .Where(predicate)
+            .GroupBy(s => s.SourceSite)
+            .Select(g => new { Site = g.Key, Count = g.Count() })
+            .ToDictionaryAsync(x => x.Site, x => x.Count, ct);
+    }
+
     private static int GetRankOrThrow(string status)
     {
         if (!StatusRank.TryGetValue(status, out var rank))