---
phase: 06-config-package-and-sound-overrides
plan: 01
type: tdd
wave: 1
depends_on: []
files_modified:
  - config/config.go
  - config/config_test.go
  - go.mod
  - go.sum
autonomous: true
requirements:
  - CFG-01
  - CFG-02
  - CFG-04
  - CFG-05

must_haves:
  truths:
    - "Load with explicit path to valid TOML returns merged config map with overrides applied"
    - "Load with no config file found returns default ClassFreqConfigs unchanged"
    - "Load with unknown TOML key returns error naming the bad key"
    - "Load with partial override (only frequency set) leaves waveform unchanged"
    - "Load with partial override (only waveform set) leaves frequency unchanged"
    - "Load with unknown class name logs warning and does not error"
  artifacts:
    - path: "config/config.go"
      provides: "Load function, parse, validate, merge, discover"
      exports: ["Load"]
    - path: "config/config_test.go"
      provides: "Table-driven tests for CFG-01 through CFG-05"
      min_lines: 100
  key_links:
    - from: "config/config.go"
      to: "synth/config.go"
      via: "imports synth.FreqConfig, synth.WaveformType, synth.ClassFreqConfigs, synth.WaveformPresetHarmonics"
      pattern: "synth\\.FreqConfig|synth\\.ClassFreqConfigs|synth\\.WaveformPresetHarmonics"
    - from: "config/config.go"
      to: "classify/types.go"
      via: "imports classify.TrafficClass, classify.AllClasses"
      pattern: "classify\\.TrafficClass|classify\\.AllClasses"
    - from: "config/config.go"
      to: "github.com/BurntSushi/toml"
      via: "toml.DecodeFile, md.Undecoded()"
      pattern: "toml\\.DecodeFile|Undecoded"
---

<objective>
Create the `config` package with TOML loading, unknown-key validation, partial-merge semantics, and auto-discovery logic. This is the core of Phase 6 — all config behavior except CLI flag wiring.

Purpose: Implements CFG-01 (TOML override), CFG-02 (auto-discovery), CFG-04 (partial override), CFG-05 (unknown key error). The package exposes a single `Load(configPath string)` function that returns a ready-to-use `map[classify.TrafficClass]synth.FreqConfig`.

Output: `config/config.go`, `config/config_test.go`, updated `go.mod`/`go.sum`
</objective>

<execution_context>
@$HOME/.claude/get-shit-done/workflows/execute-plan.md
@$HOME/.claude/get-shit-done/templates/summary.md
</execution_context>

<context>
@.planning/PROJECT.md
@.planning/ROADMAP.md
@.planning/STATE.md
@.planning/phases/06-config-package-and-sound-overrides/06-CONTEXT.md
@.planning/phases/06-config-package-and-sound-overrides/06-RESEARCH.md

<interfaces>
<!-- Key types and contracts the executor needs. Extracted from codebase. -->

From synth/config.go:
```go
type WaveformType int
const (
    WaveformCustom   WaveformType = iota
    WaveformSine
    WaveformSquare
    WaveformSawtooth
    WaveformTriangle
)

type HarmonicDef struct {
    Ratio     int
    Amplitude float64
}

type FreqConfig struct {
    BaseHz       float64
    Harmonics    []HarmonicDef
    Pan          float64
    WaveformType WaveformType
}

var ClassFreqConfigs = map[classify.TrafficClass]FreqConfig{ /* 14 entries */ }
func WaveformPresetHarmonics(wt WaveformType, baseHz float64, sampleRate int) []HarmonicDef
const SampleRate = 44100
```

From classify/types.go:
```go
type TrafficClass string
const (
    ClassICMP     TrafficClass = "ICMP"
    ClassDNS      TrafficClass = "DNS"
    ClassHTTPS    TrafficClass = "HTTPS"
    ClassHTTP     TrafficClass = "HTTP"
    ClassSSH      TrafficClass = "SSH"
    ClassSMTP     TrafficClass = "SMTP"
    ClassNTP      TrafficClass = "NTP"
    ClassDHCP     TrafficClass = "DHCP"
    ClassOtherTCP TrafficClass = "other-TCP"
    ClassOtherUDP TrafficClass = "other-UDP"
    ClassUnknown1 TrafficClass = "unknown-1"
    ClassUnknown2 TrafficClass = "unknown-2"
    ClassUnknown3 TrafficClass = "unknown-3"
    ClassUnknown4 TrafficClass = "unknown-4"
)
func AllClasses() []TrafficClass
```

Go module path: `github.com/netsynth/netsynth`
</interfaces>
</context>

<feature>
  <name>Config package: TOML load, validate, merge</name>
  <files>config/config.go, config/config_test.go</files>
  <behavior>
    - Test: Load(explicitPath) with valid TOML `[sounds.ICMP]\nfrequency = 100.0` returns map where ICMP.BaseHz == 100.0 and all other classes unchanged (CFG-01, CFG-04)
    - Test: Load(explicitPath) with `[sounds.ICMP]\nwaveform = "square"` returns map where ICMP.WaveformType == WaveformSquare and ICMP.BaseHz unchanged (CFG-04)
    - Test: Load(explicitPath) with `[sounds.ICMP]\nfrequncy = 440` returns error containing "frequncy" (CFG-05)
    - Test: Load("") in a directory with no netsynth.toml returns default ClassFreqConfigs map with no error (CFG-02)
    - Test: Load(explicitPath) where file does not exist returns error containing "not found" (CFG-03 prep)
    - Test: Load(explicitPath) with `[sounds.BOGUS]\nfrequency = 100.0` returns no error but stderr contains "unknown class" (D-09)
    - Test: Load(explicitPath) with `[sounds.ICMP]\nfrequency = 100.0\nwaveform = "square"` returns ICMP with both overrides applied and harmonics regenerated
    - Test: Load(explicitPath) with `[sounds.ICMP]\nwaveform = "invalid"` returns error containing "invalid waveform"
    - Test: All 14 default classes present in result map regardless of override count
  </behavior>
  <implementation>
    Create `config/config.go` with:
    1. `SoundOverride` struct with pointer fields `Frequency *float64` and `Waveform *string` (toml tags)
    2. `rawConfig` struct with `Sounds map[string]SoundOverride` (toml tag "sounds")
    3. `Load(configPath string) (map[classify.TrafficClass]synth.FreqConfig, error)` — public entry point
    4. `resolvePath(configPath string) (path string, explicit bool, err error)` — handles D-05 discovery order
    5. `discoverPath() string` — probes ./netsynth.toml then ~/.config/netsynth/config.toml
    6. `parseFile(path string) (rawConfig, error)` — uses toml.DecodeFile + md.Undecoded() for CFG-05
    7. `validate(raw rawConfig) error` — validates waveform strings
    8. `merge(defaults map[classify.TrafficClass]synth.FreqConfig, overrides map[string]SoundOverride) map[classify.TrafficClass]synth.FreqConfig` — per-field overlay
    9. `copyDefaults() map[classify.TrafficClass]synth.FreqConfig` — shallow copy of ClassFreqConfigs
    10. `parseWaveform(s string) (synth.WaveformType, error)` — string-to-enum map
    11. `validWaveforms` map: "sine"->WaveformSine, "square"->WaveformSquare, "sawtooth"->WaveformSawtooth, "triangle"->WaveformTriangle

    Add `github.com/BurntSushi/toml@v1.6.0` to go.mod via `go get`.

    Per D-03: Per-field overlay merge — only non-nil pointer fields override defaults.
    Per D-07: Unknown keys detected via md.Undecoded(), error names the key.
    Per D-09: Unknown class names in [sounds.<name>] produce warning to stderr, not error.
    Per D-05: Discovery order: --config > ./netsynth.toml > ~/.config/netsynth/config.toml.
    Per D-06: Only one config file loaded, first found wins.
    Per D-08: Type mismatches produce clear error with field name.
    Per D-11: All validation happens before returning — fail fast.

    When frequency is overridden and WaveformType != WaveformCustom, regenerate Harmonics via WaveformPresetHarmonics(cfg.WaveformType, newBaseHz, synth.SampleRate).
    When waveform is overridden, regenerate Harmonics via WaveformPresetHarmonics(newWt, cfg.BaseHz, synth.SampleRate).
  </implementation>
</feature>

<tasks>

<task type="auto" tdd="true">
  <name>Task 1: Config package — TDD red-green-refactor</name>
  <files>config/config.go, config/config_test.go, go.mod, go.sum</files>
  <read_first>
    synth/config.go (FreqConfig, WaveformType, ClassFreqConfigs, WaveformPresetHarmonics, SampleRate)
    classify/types.go (TrafficClass, AllClasses, class constants)
    go.mod (current dependencies)
    .planning/phases/06-config-package-and-sound-overrides/06-RESEARCH.md (patterns 1-5, pitfalls 1-4)
  </read_first>
  <behavior>
    - TestLoadPartialOverrideFrequency: Load TOML `[sounds.ICMP]\nfrequency = 100.0` -> ICMP.BaseHz == 100.0, ICMP.WaveformType == synth.WaveformCustom (unchanged), DNS.BaseHz == 110.0 (unchanged)
    - TestLoadPartialOverrideWaveform: Load TOML `[sounds.ICMP]\nwaveform = "square"` -> ICMP.WaveformType == synth.WaveformSquare, ICMP.BaseHz == 65.0 (unchanged), len(ICMP.Harmonics) > 0
    - TestLoadBothOverrides: Load TOML `[sounds.ICMP]\nfrequency = 100.0\nwaveform = "square"` -> ICMP.BaseHz == 100.0, ICMP.WaveformType == synth.WaveformSquare
    - TestLoadUnknownKey: Load TOML `[sounds.ICMP]\nfrequncy = 440` -> error != nil, error contains "frequncy"
    - TestLoadNoConfig: Load("") in temp dir with no netsynth.toml -> err == nil, result has 14 entries, ICMP.BaseHz == 65.0
    - TestLoadExplicitMissing: Load("/nonexistent/file.toml") -> error != nil, error contains "not found"
    - TestLoadUnknownClass: Load TOML `[sounds.BOGUS]\nfrequency = 100.0` -> err == nil, result has 14 entries (BOGUS not present)
    - TestLoadInvalidWaveform: Load TOML `[sounds.ICMP]\nwaveform = "invalid"` -> error != nil, error contains "invalid waveform"
    - TestLoadAllDefaultsPresent: Load with any valid override -> len(result) == 14
  </behavior>
  <action>
    **RED phase:** Create `config/config_test.go` with all 9 test functions listed in behavior above. Each test:
    - Creates a temp TOML file with `os.CreateTemp(t.TempDir(), "*.toml")`
    - Calls `config.Load(tmpFile.Name())` (or `config.Load("")` for no-config test)
    - Asserts expected outcomes

    For TestLoadNoConfig: use `t.Chdir(t.TempDir())` (Go 1.24 testing.T.Chdir) to ensure no netsynth.toml exists in working directory.

    Create a minimal `config/config.go` with just `package config` and a stub `Load` function returning nil, nil so the test file compiles. Run `go test ./config/... -count=1` — all tests must FAIL (red).

    **GREEN phase:** Implement `config/config.go` fully:

    1. Run `go get github.com/BurntSushi/toml@v1.6.0` to add the dependency.

    2. Package declaration and imports:
       ```
       package config
       imports: errors, fmt, io/fs, os, path/filepath, strings
       github.com/BurntSushi/toml
       github.com/netsynth/netsynth/classify
       github.com/netsynth/netsynth/synth
       ```

    3. Types:
       - `SoundOverride` struct: `Frequency *float64 \`toml:"frequency"\``, `Waveform *string \`toml:"waveform"\``
       - `rawConfig` struct: `Sounds map[string]SoundOverride \`toml:"sounds"\``

    4. `validWaveforms` var: map[string]synth.WaveformType with entries "sine"->WaveformSine, "square"->WaveformSquare, "sawtooth"->WaveformSawtooth, "triangle"->WaveformTriangle

    5. `Load(configPath string) (map[classify.TrafficClass]synth.FreqConfig, error)`:
       - Call resolvePath(configPath) -> path, explicit, err
       - If err != nil, return nil, err
       - If path == "", return copyDefaults(), nil (CFG-02: silent default)
       - Call parseFile(path) -> raw, err
       - If err != nil AND explicit AND errors.Is(err, fs.ErrNotExist): return nil, fmt.Errorf("config file not found: %s", configPath)
       - If err != nil (other): return nil, err
       - Call validate(raw) -> err; if err, return nil, err
       - Return merge(copyDefaults(), raw.Sounds), nil

    6. `resolvePath(configPath string) (string, bool, error)`:
       - If configPath != "": return configPath, true, nil
       - path := discoverPath()
       - return path, false, nil

    7. `discoverPath() string`:
       - Check `os.Stat("netsynth.toml")` — if err == nil, return "netsynth.toml"
       - dir, err := os.UserConfigDir(); if err != nil, return ""
       - p := filepath.Join(dir, "netsynth", "config.toml")
       - Check os.Stat(p) — if err == nil, return p
       - return ""

    8. `parseFile(path string) (rawConfig, error)`:
       - var raw rawConfig
       - md, err := toml.DecodeFile(path, &raw)
       - If err != nil, return raw, err (this handles file-not-found and parse errors including D-08 type mismatches)
       - undecoded := md.Undecoded()
       - If len(undecoded) > 0: keyPath := strings.Join(undecoded[0].String() ... ) — actually undecoded is []toml.Key where Key is []string. Use `undecoded[0].String()` which returns dot-joined path. Return raw, fmt.Errorf("config: unknown key %q — check spelling", undecoded[0].String())
       - Return raw, nil

    9. `validate(raw rawConfig) error`:
       - For each className, override in raw.Sounds:
         - If override.Waveform != nil: call parseWaveform(*override.Waveform); if err, return err

    10. `parseWaveform(s string) (synth.WaveformType, error)`:
        - If wt, ok := validWaveforms[s]; ok: return wt, nil
        - valid := []string{"sine", "square", "sawtooth", "triangle"}
        - Return 0, fmt.Errorf("config: invalid waveform %q — valid values: %s", s, strings.Join(valid, ", "))

    11. `copyDefaults() map[classify.TrafficClass]synth.FreqConfig`:
        - result := make(map[...], len(synth.ClassFreqConfigs))
        - For k, v := range synth.ClassFreqConfigs: result[k] = v
        - Return result
        - Comment: "Shallow copy is safe because merge assigns fresh Harmonics slices from WaveformPresetHarmonics, never mutates the original."

    12. `merge(defaults map[classify.TrafficClass]synth.FreqConfig, overrides map[string]SoundOverride) map[classify.TrafficClass]synth.FreqConfig`:
        - For className, override := range overrides:
          - class := classify.TrafficClass(className)
          - cfg, known := defaults[class]
          - If !known: fmt.Fprintf(os.Stderr, "Warning: config: unknown class %q (ignored)\n", className); continue (D-09)
          - If override.Frequency != nil:
            - cfg.BaseHz = *override.Frequency
            - If cfg.WaveformType != synth.WaveformCustom: cfg.Harmonics = synth.WaveformPresetHarmonics(cfg.WaveformType, cfg.BaseHz, synth.SampleRate)
          - If override.Waveform != nil:
            - wt, _ := parseWaveform(*override.Waveform) (already validated)
            - cfg.WaveformType = wt
            - cfg.Harmonics = synth.WaveformPresetHarmonics(wt, cfg.BaseHz, synth.SampleRate)
          - defaults[class] = cfg
        - Return defaults

    Run `go test ./config/... -count=1` — all tests must PASS (green).

    **REFACTOR:** Review for clarity. Run `go vet ./config/...` clean.
  </action>
  <verify>
    <automated>cd /home/dev/workspace/yoloyolo && go test ./config/... -count=1 -v</automated>
  </verify>
  <acceptance_criteria>
    - config/config.go contains `func Load(configPath string) (map[classify.TrafficClass]synth.FreqConfig, error)`
    - config/config.go contains `type SoundOverride struct` with `Frequency *float64` and `Waveform *string`
    - config/config.go contains `type rawConfig struct` with `Sounds map[string]SoundOverride`
    - config/config.go contains `toml.DecodeFile` call
    - config/config.go contains `md.Undecoded()` call
    - config/config.go contains `validWaveforms` map with 4 entries
    - config/config.go contains `os.UserConfigDir()` call in discoverPath
    - config/config_test.go contains at least 9 test functions (TestLoad*)
    - go.mod contains `github.com/BurntSushi/toml`
    - `go test ./config/... -count=1` exits 0
    - `go vet ./config/...` exits 0
  </acceptance_criteria>
  <done>
    config package exists with Load function that handles TOML parsing, unknown-key detection, partial-merge, auto-discovery, and waveform validation. All 9+ tests pass. BurntSushi/toml dependency in go.mod.
  </done>
</task>

</tasks>

<verification>
- `go test ./config/... -count=1 -v` — all tests pass
- `go vet ./config/...` — no issues
- `go build ./config/...` — compiles cleanly
</verification>

<success_criteria>
- config.Load("path/to/valid.toml") returns merged map with overrides applied (CFG-01)
- config.Load("") with no config file returns defaults silently (CFG-02)
- config.Load("") with partial TOML returns map where unset fields retain defaults (CFG-04)
- config.Load("path/to/typo.toml") with unknown key returns error naming the key (CFG-05)
- All 14 default classes always present in result map
</success_criteria>

<output>
After completion, create `.planning/phases/06-config-package-and-sound-overrides/06-01-SUMMARY.md`
</output>