// Package router is maven's reactive path — the cascade that turns a free-form
// utterance into a deterministic Decision.
//
// Spec contract (from maven.md § reactive path — router):
//
//   - routing is a DECISION, and every decision in maven stays deterministic.
//     a classifier owns the route; the SLM stays in its phrasing lane. same
//     boundary as "rules decide, llm phrases," extended to the reactive path.
//   - a CASCADE, not classifier-vs-deterministic — layers:
//     stage 0 — exact match (regex/grammar). wake-word + known command
//     grammar. "maven, restart nginx" hits the allowlist directly,
//     skips the classifier. lowest latency — the vosk command path.
//     stage 1 — intent classifier. embed utterance, nearest-centroid over
//     labeled intents. one forward pass, ~30ms cpu, similarity score.
//     stage 2 — slot extraction, per intent. classification gives *what kind*,
//     not *the args*. reminders need a datetime, acts need fn+params.
//     stage 3 — confidence gate. below threshold → clarify, don't guess.
//     same pattern as since(key)==null → don't fire: a misrouted
//     fact is a confident wrong write — worse than a gap.
//   - save-where is the routing axis: act | reminder | fact | note | query.
//   - misroute correction = new centroid example — append-only, grows the
//     classifier as used. same shape as nudges.outcome tuning cooldowns.
//
// The Embedder is the one impure seam (the ONNX int8 model is a later module).
// Given a deterministic embedder, the classifier + cascade are pure and unit-
// testable with zero infra — same instinct as the loop's gather/pure split.
package router

import "time"

// Intent — the six save-where labels from the spec's routing table. The
// discriminator is "does the loop evaluate a predicate against it?":
//
//   - act:      command now, not stored (function call into the allowlist)
//   - reminder: has a fire-time → reminders table (sqlite). bypasses the gate
//   - fact:     structured state the loop reasons over → facts (sqlite)
//   - note:     recall/preference, no predicate touches it → chroma
//   - query:    answer, don't store → slm reads sqlite or chroma (RAG)
//   - chat:     conversational, no store side-effect — LLM replies from
//     dialogue history + general knowledge
//
// fact-vs-note is the whole line: predicate will read it → structured facts
// row; just "recall when relevant" → semantic store. reminder splits off by
// future timestamp; act splits off by being imperative-now.
type Intent string

const (
	IntentAct      Intent = "act"
	IntentReminder Intent = "reminder"
	IntentFact     Intent = "fact"
	IntentNote     Intent = "note"
	IntentQuery    Intent = "query"
	IntentChat     Intent = "chat"
	IntentSystem   Intent = "system"
)

// Slots — per-intent extracted arguments (stage 2). Not every field is set for
// every intent; the Intent decides which matter. A slot that doesn't parse
// leaves its Has* flag false — the daemon's SLM last-resort lane picks it up
// for free-form notes the parsers choke on. Never an error to be missing.
type Slots struct {
	// Reminder: absolute fire time. The router resolves relative→absolute AT
	// CAPTURE ("in 4h" → now+4h, never the string) per spec — the reminders
	// table stores only absolute fire_ts. HasTime=false ⇒ no datetime parsed.
	Time    time.Time
	HasTime bool

	// Act: the function name from the allowlist + positional args. The router
	// fuzzy-matches the verb against the allowlist; not on the list → refuse,
	// don't improvise. Fn empty ⇒ no allowlist match. Destructive acts still
	// gate behind confirm at the daemon layer, not here.
	Fn    string
	Args  []string
	HasFn bool

	// Fact: structured (key,value) the loop will evaluate predicates against.
	// "drank water" → key=water; "slept 6h" → key=sleep, value=6h. The value
	// is the raw string the daemon json-encodes before WriteFact.
	Key    string
	Value  string
	HasKey bool

	// Note/Query: free-form payload (chroma-bound for note, RAG input for query).
	// Always set to the utterance for those intents.
	Text string
}

// Decision — the router's output. The cascade is deterministic: stage 0 wins
// outright; otherwise classify (1) → extract (2) → gate (3). Clarify=true ⇒
// the daemon asks instead of guessing — "shuts up when uncertain" for routing,
// same shape as since(key)==null → don't fire for the loop.
type Decision struct {
	Utterance  string
	Stage      int // 0 exact-match, 1 classified, 2 slots-extracted, 3 clarify-gated
	Intent     Intent
	Confidence float64 // 1.0 for stage-0; classifier cosine similarity for 1+
	Slots      Slots
	Clarify    bool // stage 3: below threshold — ask, don't guess
}