feat(discovery): schedule saved-search alerts

JobTrackerApi/Services/SavedJobSearchRunner.cs

@@ -0,0 +1,44 @@
+using JobTrackerApi.Data;
+using JobTrackerApi.Models;
+
+namespace JobTrackerApi.Services;
+
+public sealed record SavedJobSearchRunResult(
+    IReadOnlyList<SavedJobSearchJobResult> Jobs,
+    int NewCount,
+    bool WasInitialRun);
+
+public sealed record SavedJobSearchJobResult(DiscoveredJob Job, bool IsNew, bool IsDismissed);
+
+public sealed class SavedJobSearchRunner(
+    JobTrackerContext db,
+    IJobDiscoverySearchService discovery,
+    TimeProvider timeProvider)
+{
+    public async Task<SavedJobSearchRunResult> RunAsync(SavedJobSearch search, CancellationToken cancellationToken)
+    {
+        var jobs = await discovery.SearchAsync(search.Query, search.Location, cancellationToken);
+        var now = timeProvider.GetUtcNow();
+        var wasInitialRun = search.LastRunAtUtc is null;
+        var existing = search.Results.ToDictionary(item => item.ExternalJobId, StringComparer.OrdinalIgnoreCase);
+        var results = new List<SavedJobSearchJobResult>(jobs.Count);
+        var newCount = 0;
+        foreach (var job in jobs)
+        {
+            var isNew = !existing.TryGetValue(job.Id, out var state);
+            if (state is null)
+            {
+                state = new SavedJobSearchResult { ExternalJobId = job.Id, FirstSeenAtUtc = now, LastSeenAtUtc = now };
+                search.Results.Add(state);
+                db.SavedJobSearchResults.Add(state);
+                newCount++;
+            }
+            else state.LastSeenAtUtc = now;
+            results.Add(new SavedJobSearchJobResult(job, isNew, state.IsDismissed));
+        }
+
+        search.LastRunAtUtc = now;
+        search.UpdatedAtUtc = now;
+        return new SavedJobSearchRunResult(results, newCount, wasInitialRun);
+    }
+}