perf(parser): cut redundant NNTP reads and cap PAR2 scan

go.mod

@@ -22,7 +22,7 @@ require (
 	github.com/javi11/nntppool/v4 v4.10.0
 	github.com/javi11/nxg v0.1.0
 	github.com/javi11/nzbparser v0.5.4
-	github.com/javi11/rardecode/v2 v2.1.2-0.20260402111111-85298dd02bf6
+	github.com/javi11/rardecode/v2 v2.1.2-0.20260424080037-11b2fa852f05
 	github.com/javi11/sevenzip v1.6.2-0.20251026160715-ca961b7f1239
 	github.com/jinzhu/copier v0.4.0
 	github.com/klauspost/compress v1.18.0

go.sum

@@ -382,6 +382,8 @@ github.com/javi11/nzbparser v0.5.4 h1:0aYyORZipp7iX8eNpT/efnzCeVO+9C0sE2HWCGc/Ja
 github.com/javi11/nzbparser v0.5.4/go.mod h1:ikF7WI3BUGs5IHQJmKzmtTkX29NZW5nvUdo6ZWFZgL4=
 github.com/javi11/rardecode/v2 v2.1.2-0.20260402111111-85298dd02bf6 h1:V/OLStIqC6nAlfL+iD5VvcrjTFkkhyfDAbWxp5zpMys=
 github.com/javi11/rardecode/v2 v2.1.2-0.20260402111111-85298dd02bf6/go.mod h1:Bv+b+FzxIO1GhbQB6Rl+um+6nGsfcB+1eug62+8P9OM=
+github.com/javi11/rardecode/v2 v2.1.2-0.20260424080037-11b2fa852f05 h1:zTxsTHCgYTqG7AQzE0ngczTeWSneDOLyEWDrPVMzcnU=
+github.com/javi11/rardecode/v2 v2.1.2-0.20260424080037-11b2fa852f05/go.mod h1:Bv+b+FzxIO1GhbQB6Rl+um+6nGsfcB+1eug62+8P9OM=
 github.com/javi11/sevenzip v1.6.2-0.20251026160715-ca961b7f1239 h1:XbptA/1kHKOeDZChh599BXNGQ9jfuW1RG8y/e5Oclkc=
 github.com/javi11/sevenzip v1.6.2-0.20251026160715-ca961b7f1239/go.mod h1:+nqMTvWJKqRUQRE0uWjip5scep1PoEk+ZPDX2YwWSSo=
 github.com/jgautheron/goconst v1.8.2 h1:y0XF7X8CikZ93fSNT6WBTb/NElBu9IjaY7CCYQrCMX4=

internal/importer/parser/par2/descriptor.go

@@ -104,9 +104,11 @@ func readFileDescriptors(
 		return descriptors, fmt.Errorf("PAR2 file has no segments")
 	}
 
-	// Create context with timeout (30 seconds per segment should be enough)
-	// For multi-segment files, this gives adequate time
-	ctx, cancel := context.WithTimeout(ctx, time.Second*30*time.Duration(len(par2File.Segments)))
+	// Create context with timeout (30s per segment, capped at 90s ceiling).
+	// Capping prevents runaway waits on large index files where the real cost
+	// is dominated by latency, not sequential segment fetches.
+	timeout := min(time.Second*30*time.Duration(len(par2File.Segments)), 90*time.Second)
+	ctx, cancel := context.WithTimeout(ctx, timeout)
 	defer cancel()
 
 	// Build segment loader and compute total size
@@ -132,6 +134,11 @@ func readFileDescriptors(
 	// Increase limit to accommodate larger PAR2 files with many FileDesc packets
 	maxPackets := 1000 // Limit the number of packets to process
 	packetCount := 0
+	// Once FileDesc packets stop appearing, PAR2 index files typically have no
+	// more ahead. Break after a window of non-FileDesc packets past the last
+	// descriptor to avoid draining the entire index unnecessarily.
+	const noNewDescWindow = 50
+	packetsSinceLastDesc := 0
 	var lastError error
 
 	for packetCount < maxPackets {
@@ -168,6 +175,7 @@ func readFileDescriptors(
 			}
 
 			descriptors = append(descriptors, *desc)
+			packetsSinceLastDesc = 0
 		} else {
 			// Skip non-FileDesc packets
 			if err := packetReader.SkipPacketBody(header); err != nil {
@@ -177,6 +185,15 @@ func readFileDescriptors(
 				slog.DebugContext(ctx, "Corrupted packet body encountered, returning partial PAR2 descriptors", "error", err, "descriptors_found", len(descriptors))
 				break
 			}
+			if len(descriptors) > 0 {
+				packetsSinceLastDesc++
+				if packetsSinceLastDesc >= noNewDescWindow {
+					slog.DebugContext(ctx, "No new FileDesc packets in window, ending PAR2 scan early",
+						"descriptors_found", len(descriptors),
+						"window", noNewDescWindow)
+					break
+				}
+			}
 		}
 	}