crossmate

commit fcf2241bd54e354a9280aab0b766f5f4132df3af
parent 45d598f0b3409015d32510a2ac64ecf9ca631754
Author: Michael Camilleri <[email protected]>
Date:   Fri,  3 Jul 2026 14:21:18 +0900

Improve speed of diagnostics log sharing

Diffstat:
M
Crossmate/Views/Settings/DiagnosticsView.swift
 | 
38
++++++++++++++++++++++++++++++++------

1 file changed, 32 insertions(+), 6 deletions(-)
diff --git a/Crossmate/Views/Settings/DiagnosticsView.swift b/Crossmate/Views/Settings/DiagnosticsView.swift
@@ -125,7 +125,7 @@ struct DiagnosticsView: View {
         .toolbar {
             ToolbarItemGroup(placement: .topBarTrailing) {
                 ShareLink(
-                    item: DiagnosticsShareFile(render: { diagnosticDump }),
+                    item: DiagnosticsShareFile(snapshot: { diagnosticDump }),
                     preview: SharePreview(
                         "Crossmate Diagnostics",
                         image: Image(systemName: "doc.text")
@@ -224,7 +224,7 @@ struct DiagnosticsView: View {
         return "\(version) (\(build))"
     }
 
-    private var diagnosticDump: String {
+    private var diagnosticDump: DiagnosticsDump {
         var lines: [String] = []
         lines.append("Version: \(versionText)")
         lines.append("Account Status: \(accountStatusText)")
@@ -238,11 +238,33 @@ struct DiagnosticsView: View {
         lines.append("Last Error Code: \(syncMonitor.lastErrorCode.map(String.init) ?? "None")")
         lines.append("Last Error Description: \(syncMonitor.lastErrorDescription ?? "None")")
         lines.append("Recent Event Count: \(eventLog.entries.count)")
+        return DiagnosticsDump(headerLines: lines, entries: eventLog.entries)
+    }
+}
+
+/// The dump's inputs, captured on the main actor so the expensive per-entry
+/// formatting can run off it. `EventLogEntry` is a Sendable value type, so
+/// taking the buffer is a cheap copy-on-write retain, not a data copy.
+private struct DiagnosticsDump: Sendable {
+    let headerLines: [String]
+    let entries: [EventLogEntry]
+
+    /// Formats the full dump. Runs nonisolated on purpose: tens of thousands
+    /// of entries make this the slow part of a share, and it sits between the
+    /// share tap and the sheet appearing — on the main actor it both stalls
+    /// the UI and queues behind it. The formatter is created locally so the
+    /// loop shares nothing across the isolation boundary.
+    func rendered() -> String {
+        let formatter = DateFormatter()
+        formatter.dateFormat = "h:mm:ss a 'UTC'"
+        formatter.timeZone = TimeZone(secondsFromGMT: 0)
+
+        var lines = headerLines
         lines.append("")
         lines.append("Recent Events (UTC):")
-        for entry in eventLog.entries {
+        for entry in entries {
             lines.append(
-                "\(TimestampFormatter.string(from: entry.timestamp, in: .utc)) [\(entry.level.uppercased())] \(entry.message)"
+                "\(formatter.string(from: entry.timestamp)) [\(entry.level.uppercased())] \(entry.message)"
             )
         }
         return lines.joined(separator: "\n")
@@ -253,14 +275,18 @@ struct DiagnosticsView: View {
 /// buffer spans a full day (tens of thousands of entries during a co-solve),
 /// so building the joined text and writing it to disk eagerly — as the view
 /// once did on every log event — is multi-MB of wasted work per second.
+/// Only the cheap input snapshot runs on the main actor; the formatting and
+/// disk write happen in the export's own background context, since ShareLink
+/// won't present the sheet until this closure returns.
 private struct DiagnosticsShareFile: Transferable {
-    let render: @MainActor () -> String
+    let snapshot: @MainActor () -> DiagnosticsDump
 
     static var transferRepresentation: some TransferRepresentation {
         FileRepresentation(exportedContentType: .plainText) { file in
+            let dump = await file.snapshot()
             let url = FileManager.default.temporaryDirectory
                 .appendingPathComponent("crossmate-diagnostics.txt")
-            try await file.render().write(to: url, atomically: true, encoding: .utf8)
+            try dump.rendered().write(to: url, atomically: true, encoding: .utf8)
             return SentTransferredFile(url)
         }
     }