ev-dev-labs
diff --git a/‎internal/api/journey/arrival.go‎
Lines changed: 263 additions & 0 deletions b/‎internal/api/journey/arrival.go‎
Lines changed: 263 additions & 0 deletions
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+package journey
+
+import (
+	"context"
+	"net/http"
+	"strconv"
+	"time"
+
+	"github.com/rs/zerolog/log"
+
+	"github.com/ev-dev-labs/teslasync/internal/api/httpx"
+)
+
+// Pace bounds in SI m/s. Below stopMS the car reads as parked (no
+// ETA — a stopped car has none); above implausibleMS the fix pair is
+// a GPS jump, not motion (~360 km/h).
+const (
+	stopMS        = 2.0
+	implausibleMS = 100.0
+)
+
+// Arrival is the GET response: ETA from recent pace plus the charge
+// advice for making the destination with buffer. LeftM stays the
+// straight-line remainder; ETA and advice apply the learned route
+// factor when history exists.
+type Arrival struct {
+	SessionID   int64      `json:"session_id"`
+	DestName    string     `json:"dest_name"`
+	LeftM       *float64   `json:"left_m"`
+	PaceMS      *float64   `json:"pace_ms"`
+	EtaAt       *time.Time `json:"eta_at"`
+	Moving      bool       `json:"moving"`
+	Verdict     string     `json:"verdict"` // ok, attention, action, unknown
+	ShortfallWh *float64   `json:"shortfall_wh"`
+	RouteFactor *float64   `json:"route_factor"`
+	RouteTrips  int        `json:"route_trips"`
+	Evidence    []string   `json:"evidence"`
+}
+
+// PaceMS derives speed from two fixes. Odometer delta wins when both
+// fixes carry one (road truth beats coordinates); otherwise the
+// haversine gap over elapsed time. Zero/negative time, odometer
+// rollback, and implausible speeds all read as no pace. Pure.
+func PaceMS(older, newer *Checkpoint) (float64, bool) {
+	if older == nil || newer == nil {
+		return 0, false
+	}
+	dt := newer.RecordedAt.Sub(older.RecordedAt).Seconds()
+	if dt <= 0 {
+		return 0, false
+	}
+	dist := haversineM(older.Lat, older.Lng, newer.Lat, newer.Lng)
+	if older.OdometerM != nil && newer.OdometerM != nil {
+		if *newer.OdometerM < *older.OdometerM {
+			return 0, false
+		}
+		dist = *newer.OdometerM - *older.OdometerM
+	}
+	pace := dist / dt
+	if pace < 0 || pace > implausibleMS {
+		return 0, false
+	}
+	return pace, true
+}
+
+// ArrivalETA projects arrival from distance left and pace. A stopped
+// car (below stopMS) has no ETA — moving=false, eta nil. Pure.
+func ArrivalETA(leftM, paceMS float64, now time.Time) (eta *time.Time, moving bool) {
+	if paceMS < stopMS || leftM <= 0 {
+		return nil, paceMS >= stopMS
+	}
+	t := now.Add(time.Duration(leftM / paceMS * float64(time.Second)))
+	return &t, true
+}
+
+// ChargeAdvice grades destination energy (via ComputeRange, the single
+// verdict source) and sizes the top-up that restores the buffer when
+// short. Shortfall is nil when energy already covers need×buffer or
+// when inputs are missing. Pure.
+func ChargeAdvice(haveWh *float64, leftM float64, effWhKm *float64) (verdict string, shortfallWh *float64) {
+	r := ComputeRange(haveWh, leftM, effWhKm)
+	if r.Verdict == ItemOK || r.NeedWh == nil || haveWh == nil {
+		return r.Verdict, nil
+	}
+	short := *r.NeedWh*rangeBuffer - *haveWh
+	if short <= 0 {
+		return r.Verdict, nil
+	}
+	return r.Verdict, &short
+}
+
+// ArrivalHandler serves arrival prep. Stateless beyond constructor
+// inputs; safe for concurrent use.
+type ArrivalHandler struct {
+	store SessionStore
+	trail TrailStore
+	live  LiveSignals
+	now   func() time.Time
+}
+
+// NewArrivalHandler wires the handler. Panics on nil inputs (fail-fast
+// wiring contract, matching sibling handlers).
+func NewArrivalHandler(store SessionStore, trail TrailStore, live LiveSignals) *ArrivalHandler {
+	if store == nil || trail == nil || live == nil {
+		panic("journey: nil dependency")
+	}
+	return &ArrivalHandler{store: store, trail: trail, live: live, now: time.Now}
+}
+
+// Prep serves GET /journey/sessions/{id}/arrival: ETA from recent pace
+// plus the charge advice for the destination. Degrades honestly — no
+// fixes, no pace, or no energy each narrow the answer instead of
+// failing it.
+func (h *ArrivalHandler) Prep(w http.ResponseWriter, r *http.Request) {
+	id, err := sessionIDParam(r)
+	if err != nil {
+		httpx.WriteError(w, http.StatusBadRequest, err.Error())
+		return
+	}
+	ctx := r.Context()
+	session, err := h.store.Get(ctx, id)
+	if err != nil {
+		log.Error().Err(err).Int64("id", id).Msg("journey: get failed")
+		httpx.WriteError(w, http.StatusInternalServerError, "failed to read journey")
+		return
+	}
+	if session == nil {
+		httpx.WriteError(w, http.StatusNotFound, "journey not found")
+		return
+	}
+	now := h.now().UTC()
+	latest, err := h.trail.LatestCheckpoint(ctx, id)
+	if err != nil {
+		log.Error().Err(err).Int64("id", id).Msg("journey: latest checkpoint failed")
+		httpx.WriteError(w, http.StatusInternalServerError, "failed to read trail")
+		return
+	}
+	progress := ComputeProgress(session.OriginLat, session.OriginLng, session.DestLat, session.DestLng, latest)
+	pace, paceOK, err := h.pace(ctx, id)
+	if err != nil {
+		log.Error().Err(err).Int64("id", id).Msg("journey: trail failed")
+		httpx.WriteError(w, http.StatusInternalServerError, "failed to read trail")
+		return
+	}
+	var left *float64
+	if progress != nil {
+		left = &progress.LeftM
+	}
+	factor, trips, err := routeFactorFor(ctx, h.trail, session)
+	if err != nil {
+		log.Error().Err(err).Int64("id", id).Msg("journey: route history failed")
+		httpx.WriteError(w, http.StatusInternalServerError, "failed to read route history")
+		return
+	}
+	effLeft := left
+	if left != nil && factor != nil {
+		adjusted := *left * *factor
+		effLeft = &adjusted
+	}
+	var eta *time.Time
+	moving := false
+	if effLeft != nil && paceOK {
+		eta, moving = ArrivalETA(*effLeft, pace, now)
+	} else if paceOK {
+		_, moving = ArrivalETA(1, pace, now)
+	}
+	verdict, shortfall, err := h.advice(ctx, session, effLeft)
+	if err != nil {
+		log.Error().Err(err).Int64("id", id).Msg("journey: arrival advice failed")
+		httpx.WriteError(w, http.StatusInternalServerError, "failed to read vehicle state")
+		return
+	}
+	out := Arrival{
+		SessionID: id, DestName: session.DestName, LeftM: left,
+		EtaAt: eta, Moving: moving, Verdict: verdict, ShortfallWh: shortfall,
+		RouteFactor: factor, RouteTrips: trips,
+	}
+	if paceOK {
+		out.PaceMS = &pace
+	}
+	out.Evidence = arrivalEvidence(session, left, out.PaceMS, eta, moving, verdict, shortfall, factor, trips)
+	httpx.WriteJSON(w, http.StatusOK, out)
+}
+
+// pace orders the two newest fixes by time (stores order either way)
+// and derives speed. False when fewer than two fixes exist.
+func (h *ArrivalHandler) pace(ctx context.Context, sessionID int64) (float64, bool, error) {
+	pair, err := h.trail.Trail(ctx, sessionID, 2)
+	if err != nil {
+		return 0, false, err
+	}
+	if len(pair) < 2 {
+		return 0, false, nil
+	}
+	older, newer := pair[0], pair[1]
+	if newer.RecordedAt.Before(older.RecordedAt) {
+		older, newer = newer, older
+	}
+	pace, ok := PaceMS(older, newer)
+	return pace, ok, nil
+}
+
+func (h *ArrivalHandler) advice(ctx context.Context, session *Session, left *float64) (string, *float64, error) {
+	if left == nil {
+		return ItemUnknown, nil, nil
+	}
+	energyKWh, err := signalFloat(h.live, ctx, session.VehicleID, "EnergyRemaining")
+	if err != nil {
+		return "", nil, err
+	}
+	var haveWh *float64
+	if energyKWh != nil {
+		have := *energyKWh * 1000
+		haveWh = &have
+	}
+	eff, ok, err := h.trail.VehicleEfficiency(ctx, session.VehicleID)
+	if err != nil {
+		return "", nil, err
+	}
+	var effPtr *float64
+	if ok {
+		effPtr = &eff
+	}
+	verdict, shortfall := ChargeAdvice(haveWh, *left, effPtr)
+	return verdict, shortfall, nil
+}
+
+func arrivalEvidence(session *Session, left, pace *float64, eta *time.Time, moving bool, verdict string, shortfall *float64, factor *float64, trips int) []string {
+	out := []string{}
+	dest := session.DestName
+	if dest == "" {
+		dest = "the destination"
+	}
+	if left == nil {
+		out = append(out, "route coordinates missing — distance to "+dest+" unavailable")
+	} else {
+		out = append(out, formatKm("", *left/1000)+" to "+dest)
+	}
+	if factor != nil {
+		out = append(out, "adjusted by your "+strconv.FormatFloat(*factor, 'f', 2, 64)+"× history on this route ("+strconv.Itoa(trips)+" trips)")
+	}
+	switch {
+	case pace == nil:
+		out = append(out, "need two fixes to read pace")
+	case !moving:
+		out = append(out, "parked — ETA once moving")
+	case eta != nil:
+		out = append(out, "ETA "+eta.Format("15:04"))
+	}
+	switch verdict {
+	case ItemOK:
+		out = append(out, "arrive with buffer")
+	case ItemAttention, ItemAction:
+		if shortfall != nil {
+			out = append(out, "top up ≈ "+strconv.FormatFloat(*shortfall/1000, 'f', 1, 64)+" kWh en route to hold the buffer")
+		} else {
+			out = append(out, "arrival energy tight — charge soon")
+		}
+	default:
+		out = append(out, "arrival energy unknown: needs live energy + drive history")
+	}
+	return out
+}