yoloyolo/.planning/phases/04-power-user-features/04-02-SUMMARY.md

phase, plan, subsystem, tags, dependency_graph, tech_stack, key_files, decisions, metrics

phase	plan	subsystem	tags	dependency_graph	tech_stack	key_files	decisions	metrics
04-power-user-features	02	cmd/netsynth	cli bpf pcap-reader mutual-exclusion output-derivation	requires provides affects 04-01 --filter flag --read flag runPcapMode deriveOutputPath cmd/netsynth	added patterns path/filepath run() branches into runLiveMode/runPcapMode based on readPath flag BPF filter pre-validated before any capture begins Output filename derived from input pcap by replacing extension	created modified cmd/netsynth/main.go cmd/netsynth/main_test.go	bpfFilter and readPath are package-level globals (same pattern as other flags) for Cobra flag binding run() validates mutual exclusion before any I/O to give early clear errors runPcapMode checks for empty snapshots after PrintSummary so user sees zero-count table before error deriveOutputPath uses filepath.Ext (last extension only) matching tcpdump convention	duration completed_date tasks_completed files_changed 4 minutes 2026-03-26 1 2

Phase 04 Plan 02: CLI wiring for --filter and --read flags

One-liner: --filter and --read flags wired into Cobra CLI with mutual exclusion, BPF pre-validation, pcap file processing path, output filename derivation, and bookend messages.

What Was Built

cmd/netsynth/main.go

New global variables:

• bpfFilter string — bound to --filter flag (BPF expression in tcpdump syntax)
• readPath string — bound to --read flag (pcap file path)

New deriveOutputPath function: Replaces file extension with .mp3. capture.pcap → capture.mp3, noext → noext.mp3. Uses filepath.Ext so only the last extension is replaced (e.g., traffic.pcap.gz → traffic.pcap.mp3).

Updated run() function:

1. Validates --read and -i mutual exclusion with clear error (D-03)
2. Returns error mentioning --read when neither source is provided
3. Pre-validates BPF filter via capture.ValidateBPFFilter before any capture starts (CAPT-05)
4. Derives output path from input pcap if --output not given (D-05)
5. Branches to runLiveMode or runPcapMode

New runLiveMode function: Extracted from the original run(). Now passes bpfFilter to capture.StartCapture(ctx, ifaceName, bpfFilter).

New runPcapMode function:

• Prints "Reading <file>..." bookend start message (D-06)
• Opens pcap via capture.ReadPcapFile(readPath, bpfFilter) with optional software BPF
• Classifies packets, sets cp.Timestamp = pkt.Metadata().CaptureInfo.Timestamp for timestamp-based windowing (D-01)
• Aggregates via aggregate.AggregatePcap (offline, timestamp-based)
• --verbose supported via onSnapshot callback (D-07)
• Prints protocol summary before encoding (D-08 pattern preserved)
• Returns clear error if zero snapshots: "pcap file %q contains no packets (after filtering)" (Pitfall 4)
• Encodes and prints "Saved..." bookend end message (D-06)

cmd/netsynth/main_test.go

New test functions:

Test	What it checks
TestFlagMutualExclusion	--read + -i together returns "mutually exclusive" error
TestMissingSource	No source returns "interface required" error mentioning --read
TestDeriveOutputPath	Path derivation: .pcap→.mp3, no ext→.mp3, /tmp/net.pcap→/tmp/net.mp3
TestFilterFlagRegistered	--filter flag is registered on rootCmd
TestReadFlagRegistered	--read flag is registered on rootCmd
TestInvalidBPFFilter	Invalid BPF expression returns error containing "invalid"
TestHelpOutputNewFlags	Usage string contains --filter and --read

Updated newTestCmd() helper to wire bpfFilter, readPath, outputPath globals. Updated TestMissingInterfaceFlag to verify error also mentions --read.

Commits

Task	Commit	Description
Task 1 (RED)	09e78bf	test(04-02): add failing tests for --filter, --read flags
Task 1 (GREEN)	4adb3c4	feat(04-02): wire --filter and --read flags into CLI

Deviations from Plan

None — plan executed exactly as written.

Known Stubs

None. All flags are fully wired and functional. The pcap mode end-to-end path is complete.

Self-Check: PASSED

Files verified:

• /home/dev/workspace/yoloyolo/.claude/worktrees/agent-a90dedf3/cmd/netsynth/main.go: FOUND
• /home/dev/workspace/yoloyolo/.claude/worktrees/agent-a90dedf3/cmd/netsynth/main_test.go: FOUND

Commits verified: 09e78bf, 4adb3c4 in git log.

All tests green: go test ./... -count=1 passed 6 packages. Build succeeded: go build ./... clean.