# AGENTS.md

This file provides guidance to AI coding assistants working with the I/O Riot NG (ior) codebase.

## Build/Test Commands

**Prerequisites**: Ensure `libbpfgo` is cloned at `../libbpfgo` relative to this repository (or set `LIBBPFGO`), pinned to `v0.9.2-libbpf-1.5.1`, and rebuilt with:

```bash
git -C ../libbpfgo checkout v0.9.2-libbpf-1.5.1
git -C ../libbpfgo submodule update --init --recursive
make -C ../libbpfgo libbpfgo-static
```

If builds/tests fail with missing libbpf headers (for example `bpf/bpf.h` not found), rerun the commands above and then run `mage world`. Prefer Mage targets over raw `go test` for packages that import `libbpfgo`; Mage wires the required `CGO_CFLAGS`, `CGO_LDFLAGS`, and `LIBBPFGO` values.

```bash
mage build                             # Build BPF object + Go binary (all is an alias)
mage buildDocker                       # Build ior inside a Rocky Linux 9 container (writes binary to repo root)
mage buildDockerEl8                    # Build ior inside a Rocky Linux 8 container (writes ior.el8 to repo root)
mage test                              # Run all tests
mage testRace                          # Run all tests with the race detector enabled (-race)
TEST_NAME=TestEventloop mage testWithName  # Run specific test
mage integrationTest                   # Build + run integration tests in parallel (parallelism capped to NumCPU)
mage integrationTestSerial             # Build + run integration tests one at a time
mage generate     # Generate code (required after modifying tracepoint definitions)
mage bench        # Run benchmarks
mage prReview     # Run PR review baseline: world + benchProf
mage clean        # Clean build artifacts
mage mrproper     # Clean + remove generated outputs (*.zst, *.svg, *.prof, *.pdf, *.tmp…)
mage world        # Clean + generate + test + build (recommended reset path)
mage demo         # Regen docs/tutorial/ GIFs + screenshots (needs vhs+ttyd, sudo -v warmed)
TAPE=07-stream-live mage demoOne       # Regen one demo tape only
mage installDemoTools  # One-time: install vhs (go install) + ttyd (dnf) — Fedora/RHEL/Rocky only
```

## Demo Pipeline

`docs/tutorial/` holds the reproducible TUI demo: 14 [VHS](https://github.com/charmbracelet/vhs) `.tape` files under `docs/tutorial/tapes/` drive every dashboard tab and headless mode, write GIFs and PNGs into `docs/tutorial/assets/`, and the resulting tutorial is `docs/tutorial/tutorial.md`. Background workload is generated by `docs/tutorial/scripts/workload.sh`. `mage demo` is fully headless (no real terminal window) — safe to run in the background while editing code; the only foreground requirement is one `sudo -v` to pre-warm the sudo timestamp.

## Code Generation

**Run `mage generate` before building when tracepoint definitions change!**

A Mage target generates code from Linux kernel tracepoint data:

```bash
mage generate              # Generate all code (C and Go)
mage generateTracepointsC  # Generate C tracepoint handlers from /sys/kernel/tracing
mage generateTypesGo       # Generate Go types from C structs
mage generateTracepointsGo # Generate Go tracepoint list
```

Generated files (do not edit manually):
- `internal/c/generated_tracepoints.c` - BPF C handlers for syscall tracepoints
- `internal/types/generated_types.go` - Go structs matching C structs + type mappings
- `internal/tracepoints/generated_tracepoints.go` - List of available syscall tracepoints

Generator source code:
- `internal/generate/` - Parser, classifier, and code generation logic

## Architecture

- **Entry point**: `cmd/ior/main.go` - Linux-only BPF-based I/O syscall tracer
- **Core packages**: `/internal/event/` (BPF event handling), `/internal/flamegraph/` (FlameGraph generation), `/internal/c/` (BPF programs)  
- **Output**: TUI dashboard and TUI flamegraphs (no embedded web flamegraph server mode)
- **TUI package**: `/internal/tui/` contains top-level Bubble Tea orchestration (`tui.go`), shared key map (`keys.go`), and styles (`styles.go`).
- **Dashboard tabs**: `/internal/tui/dashboard/` contains tab renderers (overview/syscalls/files/processes/latency/gaps) and tab framework model.
- **Export modal**: `/internal/tui/export/model.go` implements the centered modal used for CSV export flow in TUI mode.

## TUI Behavior

- **Default mode** is TUI (`-plain` disables TUI and prints CSV rows to stdout).
- **TUI trace flow** ingests events into the in-memory stats engine; it does **not** continuously write trace rows to disk.
- **File output in TUI** is explicit export only (`e`), writing `ior-stream-<timestamp>.csv` in the current directory from the current filtered stream snapshot.
- **Export toggle flag**: `-tuiExport=true|false` (default `true`) enables or disables TUI stream CSV export at runtime.
- **Tab navigation** supports `tab/shift+tab`, numeric keys `1..7`, and directional keys `left/right` and `h/l`.
- **When export is disabled**, export key hints are hidden from dashboard help and `e` does not open export modal.

## Code Style

- Standard Go conventions with static linking (`-ldflags '-w -extldflags "-static"'`)
- Keep functions under 50 lines, refactor larger code to `/internal/` packages  
- Use generated types from `/internal/types/generated_types.go` for kernel-userspace communication
- BPF C code in `/internal/c/ior.bpf.c` should be minimal for verification
- Import style: `"ior/internal/packagename"` for internal packages
- Error handling: Return errors, don't panic except for setup validation

## Rollback

If `v0.9.2-libbpf-1.5.1` stops working, roll the local checkout back to commit
`90dbffffbdab` (module version
`v0.6.0-libbpf-1.3.0.20240111220235-90dbffffbdab`), update `go.mod`/`go.sum`
accordingly, and rebuild:

```bash
git -C ../libbpfgo checkout 90dbffffbdab
git -C ../libbpfgo submodule update --init --recursive
make -C ../libbpfgo libbpfgo-static
```