Cars: log what charging costs, and drag the provider readings

Three things, all on a car's page.

A Charging cost tab, which is the Fuel cost tab written for an electric
car: charges in kWh, consumption in kWh/100km beside km per kWh, cost per
km and price per kWh, and the same summary panel over the whole history.
It keeps the reference-point method too, and has to — a session records
the energy that went in, not what was left in the battery, so a given
number of kWh only maps to a distance between two charges that ended at
the same state. A charge to the car's usual full point plays the part of
the full tank; partial charges still count towards the cost and roll into
the next full one; and a charge taken without logging it leaves its
window uncomputed rather than reporting an implausibly good figure.
Sessions live in their own collection, the figures are derived on read
like the fuel ones, and logging a charge advances the odometer exactly as
a refill does. The tab switches off from the gear like every other, so a
petrol car need never see it.

The headline readings on the connected-service tab now drag into any
order, saved on drop. Stored on the car as metricOrder, like the
Information rows, rather than per device the way the collapsed cards are:
an arrangement is something everyone the car is shared with should see,
where a folded card is one browser's reading habit. Only what the
provider reported can be arranged, so a reading that turns up later joins
the end rather than displacing the arrangement.

Fuel is now Fuel cost, tab and heading, which is what the tab has always
been about and what pairs it with Charging cost.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

API Server/internal/api/cars.go

@@ -245,7 +245,7 @@ func (s *Server) updateCar(w http.ResponseWriter, r *http.Request) {
 // be a dead end.
 var hideableCarTabs = map[string]bool{
 	"provider": true, "services": true, "technical": true, "maintenance": true,
-	"fuel": true, "documents": true, "parts": true, "reminders": true,
+	"fuel": true, "charging": true, "documents": true, "parts": true, "reminders": true,
 }
 
 // hideableCarFields are the Information rows that can be switched off — every
@@ -258,6 +258,21 @@ var hideableCarFields = map[string]bool{
 	"vin": true, "fuelType": true, "buildDate": true, "firstRegistration": true,
 }
 
+// arrangeableCarMetrics are the headline readings on the connected-service tab,
+// and so the keys a car's arrangement of them may name. Derived from the reading
+// specs in vehicleproviders.go rather than written out again, so the set cannot
+// drift from what that panel actually shows.
+var arrangeableCarMetrics = func() map[string]bool {
+	out := make(map[string]bool, len(headlineMetricSpecs)+len(unmeasuredMetricKeys))
+	for _, spec := range headlineMetricSpecs {
+		out[spec.key] = true
+	}
+	for _, key := range unmeasuredMetricKeys {
+		out[key] = true
+	}
+	return out
+}()
+
 // normalizeKeys validates a list of tab or field keys against the keys that
 // exist, trimming blanks and duplicates. Unknown keys are rejected rather than
 // ignored: they can only come from a stale or wrong client, and dropping them
@@ -280,10 +295,11 @@ func normalizeKeys(in []string, allowed map[string]bool, what string) ([]string,
 }
 
 // PUT /api/cars/{id}/view — choose what this car's page shows: which tabs, which
-// rows of the Information tab, and the order those rows are laid out in. Body:
-// {hiddenTabs?: [...], hiddenFields?: [...], fieldOrder?: [...]}; only the lists
-// present are written, so a client can rearrange the rows without resending what
-// is hidden. Its own endpoint rather than fields on the car edit, so an ordinary
+// rows of the Information tab, and the order the Information rows and the
+// connected service's headline readings are laid out in. Body: {hiddenTabs?:
+// [...], hiddenFields?: [...], fieldOrder?: [...], metricOrder?: [...]}; only the
+// lists present are written, so a client can rearrange one group without
+// resending the others. Its own endpoint rather than fields on the car edit, so an ordinary
 // save of the car form — which sends every other field — can never reveal
 // something somebody deliberately switched off. Needs write access: the choice
 // belongs to the car, so it is the same permission as editing it.
@@ -292,6 +308,7 @@ func (s *Server) updateCarView(w http.ResponseWriter, r *http.Request) {
 		HiddenTabs   *[]string `json:"hiddenTabs"`
 		HiddenFields *[]string `json:"hiddenFields"`
 		FieldOrder   *[]string `json:"fieldOrder"`
+		MetricOrder  *[]string `json:"metricOrder"`
 	}
 	if err := decodeJSON(r, &in); err != nil {
 		writeError(w, http.StatusBadRequest, err.Error())
@@ -336,6 +353,18 @@ func (s *Server) updateCarView(w http.ResponseWriter, r *http.Request) {
 		}
 		payload["field_order"] = order
 	}
+	if in.MetricOrder != nil {
+		// A partial list again, and here it is the normal case: the client can
+		// only arrange the readings the provider actually reported, so one it
+		// reports later — an EV range on a car that was parked unplugged — joins
+		// at the end rather than displacing the arrangement.
+		order, err := normalizeKeys(*in.MetricOrder, arrangeableCarMetrics, "reading")
+		if err != nil {
+			writeError(w, http.StatusBadRequest, err.Error())
+			return
+		}
+		payload["metric_order"] = order
+	}
 	if len(payload) == 0 {
 		writeError(w, http.StatusBadRequest, "no changes provided")
 		return

API Server/internal/api/cartabs_test.go

@@ -33,13 +33,16 @@ func TestNormalizeHiddenTabs(t *testing.T) {
 
 	// The hideable set is the contract the web app's HIDEABLE_TABS mirrors:
 	// every tab the car page renders beside Information.
-	for _, key := range []string{"provider", "services", "technical", "maintenance", "fuel", "documents", "parts", "reminders"} {
+	for _, key := range []string{
+		"provider", "services", "technical", "maintenance", "fuel", "charging",
+		"documents", "parts", "reminders",
+	} {
 		if !hideableCarTabs[key] {
 			t.Errorf("tab %q should be hideable", key)
 		}
 	}
-	if len(hideableCarTabs) != 8 {
-		t.Errorf("hideableCarTabs has %d entries, want the 8 tabs beside Information", len(hideableCarTabs))
+	if len(hideableCarTabs) != 9 {
+		t.Errorf("hideableCarTabs has %d entries, want the 9 tabs beside Information", len(hideableCarTabs))
 	}
 }
 
@@ -99,6 +102,32 @@ func TestNormalizeFieldOrder(t *testing.T) {
 	}
 }
 
+// The connected service's headline readings arrange the same way, against the
+// key set derived from what that panel renders.
+func TestNormalizeMetricOrder(t *testing.T) {
+	got, err := normalizeKeys([]string{"evRangeWithAc", "odometer"}, arrangeableCarMetrics, "reading")
+	if err != nil {
+		t.Fatalf("normalizeKeys: %v", err)
+	}
+	assertKeys(t, got, []string{"evRangeWithAc", "odometer"})
+
+	// Every reading the panel can show has to be arrangeable, the two that are
+	// not measures included.
+	for _, key := range []string{
+		"odometer", "fuelLevel", "fuelRange", "batteryLevel", "evRange",
+		"evRangeWithAc", "chargingStatus", "location",
+	} {
+		if !arrangeableCarMetrics[key] {
+			t.Errorf("reading %q should be arrangeable", key)
+		}
+	}
+
+	// A field key is not a reading key — a car's two arrangements are separate.
+	if _, err := normalizeKeys([]string{"vin"}, arrangeableCarMetrics, "reading"); err == nil {
+		t.Error("normalizeKeys accepted a field key as a reading, want an error")
+	}
+}
+
 func assertKeys(t *testing.T, got, want []string) {
 	t.Helper()
 	if len(got) != len(want) {

API Server/internal/api/charging.go

@@ -0,0 +1,233 @@
+package api
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/url"
+	"sort"
+
+	"drivervault/apiserver/internal/models"
+)
+
+// Charging tracking: a log of charges per car, plus the efficiency derived from
+// it. The EV counterpart of fuel.go, and deliberately the same shape — a car
+// that runs on electrons still has a cost per km, and the two tabs read alike.
+//
+// Nothing about consumption is stored — it is recomputed from the whole history
+// on every read (models.ComputeChargingDerived), so correcting a session three
+// months back fixes every window it touches with no rows to migrate.
+
+// fetchChargingSessions loads a car's charges oldest-first and fills in the
+// derived efficiency fields. Ordering is by odometer rather than date because
+// the windows are spans of distance, and a session logged with the wrong date
+// would otherwise scramble the chain.
+func (s *Server) fetchChargingSessions(r *http.Request, carID string) ([]models.ChargingSession, error) {
+	res, err := s.pb.List(r.Context(), colCharging, url.Values{
+		"filter":  {fmt.Sprintf("car='%s'", carID)},
+		"sort":    {"km"},
+		"perPage": {"1000"},
+	})
+	if err != nil {
+		return nil, err
+	}
+	var recs []chargingRecord
+	if err := json.Unmarshal(res.Items, &recs); err != nil {
+		return nil, err
+	}
+	out := make([]models.ChargingSession, 0, len(recs))
+	for _, rec := range recs {
+		out = append(out, rec.toModel())
+	}
+	// PocketBase sorts numerically here, but re-sorting locally keeps the
+	// invariant ComputeChargingDerived depends on explicit and cheap.
+	sort.SliceStable(out, func(i, j int) bool { return out[i].Km < out[j].Km })
+	models.ComputeChargingDerived(out)
+	return out, nil
+}
+
+// listCarChargingSessions serves GET /api/cars/{id}/charging-sessions, newest first.
+func (s *Server) listCarChargingSessions(w http.ResponseWriter, r *http.Request) {
+	carID := r.PathValue("id")
+	if !s.requireCarAccess(w, r, carID, accessRead) {
+		return
+	}
+	entries, err := s.fetchChargingSessions(r, carID)
+	if err != nil {
+		writePBError(w, err)
+		return
+	}
+	writeJSON(w, http.StatusOK, reverseCharging(entries))
+}
+
+// listChargingSessions serves GET /api/charging-sessions?car={id}.
+func (s *Server) listChargingSessions(w http.ResponseWriter, r *http.Request) {
+	carID := r.URL.Query().Get("car")
+	if !s.requireCarAccess(w, r, carID, accessRead) {
+		return
+	}
+	entries, err := s.fetchChargingSessions(r, carID)
+	if err != nil {
+		writePBError(w, err)
+		return
+	}
+	writeJSON(w, http.StatusOK, reverseCharging(entries))
+}
+
+// listCarChargingStats serves GET /api/cars/{id}/charging-stats.
+func (s *Server) listCarChargingStats(w http.ResponseWriter, r *http.Request) {
+	carID := r.PathValue("id")
+	if !s.requireCarAccess(w, r, carID, accessRead) {
+		return
+	}
+	entries, err := s.fetchChargingSessions(r, carID)
+	if err != nil {
+		writePBError(w, err)
+		return
+	}
+	writeJSON(w, http.StatusOK, models.ComputeChargingStats(entries))
+}
+
+// reverseCharging flips the oldest-first working order into the newest-first
+// order clients display.
+func reverseCharging(in []models.ChargingSession) []models.ChargingSession {
+	out := make([]models.ChargingSession, len(in))
+	for i, e := range in {
+		out[len(in)-1-i] = e
+	}
+	return out
+}
+
+// withChargingDerived recomputes the whole history and returns the one session
+// the caller just wrote, so a create/update response carries the same derived
+// figures the list would show.
+func (s *Server) withChargingDerived(r *http.Request, carID, id string) (models.ChargingSession, error) {
+	entries, err := s.fetchChargingSessions(r, carID)
+	if err != nil {
+		return models.ChargingSession{}, err
+	}
+	for _, e := range entries {
+		if e.ID == id {
+			return e, nil
+		}
+	}
+	return models.ChargingSession{}, fmt.Errorf("charging session %s not found after write", id)
+}
+
+func (s *Server) getChargingSession(w http.ResponseWriter, r *http.Request) {
+	var rec chargingRecord
+	if err := s.pb.GetOne(r.Context(), colCharging, r.PathValue("id"), &rec); err != nil {
+		writePBError(w, err)
+		return
+	}
+	if !s.requireCarAccess(w, r, rec.Car, accessRead) {
+		return
+	}
+	entry, err := s.withChargingDerived(r, rec.Car, rec.ID)
+	if err != nil {
+		writePBError(w, err)
+		return
+	}
+	writeJSON(w, http.StatusOK, entry)
+}
+
+func (s *Server) createChargingSession(w http.ResponseWriter, r *http.Request) {
+	var in models.ChargingSession
+	if err := decodeJSON(r, &in); err != nil {
+		writeError(w, http.StatusBadRequest, err.Error())
+		return
+	}
+	if err := validateChargingSession(in); err != "" {
+		writeError(w, http.StatusBadRequest, err)
+		return
+	}
+	if !s.requireCarAccess(w, r, in.Car, accessWrite) {
+		return
+	}
+	var rec chargingRecord
+	if err := s.pb.Create(r.Context(), colCharging, chargingPayload(in), &rec); err != nil {
+		writePBError(w, err)
+		return
+	}
+	// A charge is also the freshest odometer reading there is, exactly as a
+	// refill is; keeping the car in step means the km-based service and reminder
+	// status stay honest without the user retyping the number on the car itself.
+	s.advanceOdometer(r, in.Car, in.Km)
+
+	entry, err := s.withChargingDerived(r, rec.Car, rec.ID)
+	if err != nil {
+		writePBError(w, err)
+		return
+	}
+	writeJSON(w, http.StatusCreated, entry)
+}
+
+func (s *Server) updateChargingSession(w http.ResponseWriter, r *http.Request) {
+	var in models.ChargingSession
+	if err := decodeJSON(r, &in); err != nil {
+		writeError(w, http.StatusBadRequest, err.Error())
+		return
+	}
+	var existing chargingRecord
+	if err := s.pb.GetOne(r.Context(), colCharging, r.PathValue("id"), &existing); err != nil {
+		writePBError(w, err)
+		return
+	}
+	if !s.requireCarAccess(w, r, existing.Car, accessWrite) {
+		return
+	}
+	// The car is fixed by the record being edited; a body claiming another car
+	// must not move the session across the access boundary just checked.
+	in.Car = existing.Car
+	if err := validateChargingSession(in); err != "" {
+		writeError(w, http.StatusBadRequest, err)
+		return
+	}
+	var rec chargingRecord
+	if err := s.pb.Update(r.Context(), colCharging, r.PathValue("id"), chargingPayload(in), &rec); err != nil {
+		writePBError(w, err)
+		return
+	}
+	s.advanceOdometer(r, rec.Car, in.Km)
+
+	entry, err := s.withChargingDerived(r, rec.Car, rec.ID)
+	if err != nil {
+		writePBError(w, err)
+		return
+	}
+	writeJSON(w, http.StatusOK, entry)
+}
+
+func (s *Server) deleteChargingSession(w http.ResponseWriter, r *http.Request) {
+	var existing chargingRecord
+	if err := s.pb.GetOne(r.Context(), colCharging, r.PathValue("id"), &existing); err != nil {
+		writePBError(w, err)
+		return
+	}
+	if !s.requireCarAccess(w, r, existing.Car, accessWrite) {
+		return
+	}
+	if err := s.pb.Delete(r.Context(), colCharging, r.PathValue("id")); err != nil {
+		writePBError(w, err)
+		return
+	}
+	w.WriteHeader(http.StatusNoContent)
+}
+
+// validateChargingSession returns a human-readable reason the session is
+// unusable, or "" when it is fine.
+func validateChargingSession(c models.ChargingSession) string {
+	switch {
+	case c.Car == "":
+		return "car is required"
+	case c.Date.IsZero():
+		return "date is required"
+	case c.Km <= 0:
+		return "odometer (km) is required"
+	case c.Kwh <= 0:
+		return "kwh must be greater than zero"
+	case c.Cost < 0:
+		return "cost cannot be negative"
+	}
+	return ""
+}

API Server/internal/api/records.go

@@ -68,12 +68,14 @@ type carRecord struct {
 	Created                    string `json:"created"`
 	Updated                    string `json:"updated"`
 
-	// Switched-off tabs and Information fields, plus the arrangement of the
-	// Information rows. Raw because PocketBase hands back whatever a json field
-	// holds — null on a car nobody has configured — which is not a []string.
+	// Switched-off tabs and Information fields, plus the arrangements of the
+	// Information rows and the connected service's readings. Raw because
+	// PocketBase hands back whatever a json field holds — null on a car nobody
+	// has configured — which is not a []string.
 	HiddenTabs   json.RawMessage `json:"hidden_tabs"`
 	HiddenFields json.RawMessage `json:"hidden_fields"`
 	FieldOrder   json.RawMessage `json:"field_order"`
+	MetricOrder  json.RawMessage `json:"metric_order"`
 }
 
 func (rec carRecord) toModel() models.Car {
@@ -103,6 +105,7 @@ func (rec carRecord) toModel() models.Car {
 		HiddenTabs:                 decodeStringList(rec.HiddenTabs),
 		HiddenFields:               decodeStringList(rec.HiddenFields),
 		FieldOrder:                 decodeStringList(rec.FieldOrder),
+		MetricOrder:                decodeStringList(rec.MetricOrder),
 		Owner:                      rec.Owner,
 		Created:                    rec.Created,
 		Updated:                    rec.Updated,
@@ -359,6 +362,57 @@ func fuelPayload(f models.FuelEntry) map[string]any {
 	}
 }
 
+// --- charging sessions ---
+
+type chargingRecord struct {
+	ID            string  `json:"id"`
+	Car           string  `json:"car"`
+	Date          string  `json:"date"`
+	Km            int     `json:"km"`
+	Kwh           float64 `json:"kwh"`
+	Cost          float64 `json:"cost"`
+	FullCharge    bool    `json:"full_charge"`
+	MissedSession bool    `json:"missed_session"`
+	Location      string  `json:"location"`
+	Notes         string  `json:"notes"`
+	File          string  `json:"file"`
+	Created       string  `json:"created"`
+	Updated       string  `json:"updated"`
+}
+
+func (rec chargingRecord) toModel() models.ChargingSession {
+	return models.ChargingSession{
+		ID:            rec.ID,
+		Car:           rec.Car,
+		Date:          parsePBDate(rec.Date),
+		Km:            rec.Km,
+		Kwh:           rec.Kwh,
+		Cost:          rec.Cost,
+		FullCharge:    rec.FullCharge,
+		MissedSession: rec.MissedSession,
+		Location:      rec.Location,
+		Notes:         rec.Notes,
+		Attachment:    attachmentOf(rec.File),
+		Created:       rec.Created,
+		Updated:       rec.Updated,
+	}
+}
+
+// chargingPayload omits the file field — see attachmentOf.
+func chargingPayload(c models.ChargingSession) map[string]any {
+	return map[string]any{
+		"car":            c.Car,
+		"date":           formatPBDate(c.Date),
+		"km":             c.Km,
+		"kwh":            c.Kwh,
+		"cost":           c.Cost,
+		"full_charge":    c.FullCharge,
+		"missed_session": c.MissedSession,
+		"location":       c.Location,
+		"notes":          c.Notes,
+	}
+}
+
 // --- maintenance entries ---
 
 type maintenanceRecord struct {

API Server/internal/api/server.go

@@ -85,6 +85,13 @@
 //	GET    /api/fuel-entries/{id}      PATCH  /api/fuel-entries/{id}
 //	DELETE /api/fuel-entries/{id}
 //
+//	# charging tracking (EV counterpart of fuel; efficiency derived on read)
+//	GET    /api/cars/{id}/charging-sessions
+//	GET    /api/cars/{id}/charging-stats
+//	GET    /api/charging-sessions      POST   /api/charging-sessions
+//	GET    /api/charging-sessions/{id} PATCH  /api/charging-sessions/{id}
+//	DELETE /api/charging-sessions/{id}
+//
 //	# maintenance log (workshop visits + repairs; distinct from service records)
 //	GET    /api/cars/{id}/maintenance
 //	GET    /api/maintenance            POST   /api/maintenance
@@ -99,7 +106,7 @@
 //
 //	# attachments — one optional file per record, same three verbs everywhere.
 //	# {records} is car-documents | service-records | technical-checks | maintenance
-//	#            | fuel-entries | parts
+//	#            | fuel-entries | charging-sessions | parts
 //	POST   /api/{records}/{id}/file
 //	GET    /api/{records}/{id}/file
 //	DELETE /api/{records}/{id}/file
@@ -136,6 +143,7 @@ const (
 	colShares          = "car_shares"
 	colOrgs            = "organizations"
 	colFuel            = "fuel_entries"
+	colCharging        = "charging_sessions"
 	colMaintenance     = "maintenance_entries"
 	colDocuments       = "car_documents"
 	colReminders       = "reminders"
@@ -360,6 +368,8 @@ func (s *Server) Handler() http.Handler {
 	mux.HandleFunc("GET /api/cars/{id}/parts", s.listCarParts)
 	mux.HandleFunc("GET /api/cars/{id}/fuel-entries", s.listCarFuelEntries)
 	mux.HandleFunc("GET /api/cars/{id}/fuel-stats", s.listCarFuelStats)
+	mux.HandleFunc("GET /api/cars/{id}/charging-sessions", s.listCarChargingSessions)
+	mux.HandleFunc("GET /api/cars/{id}/charging-stats", s.listCarChargingStats)
 	mux.HandleFunc("GET /api/cars/{id}/maintenance", s.listCarMaintenance)
 	mux.HandleFunc("GET /api/cars/{id}/documents", s.listCarDocuments)
 	mux.HandleFunc("GET /api/cars/{id}/reminders", s.listCarReminders)
@@ -398,6 +408,13 @@ func (s *Server) Handler() http.Handler {
 	mux.HandleFunc("PATCH /api/fuel-entries/{id}", s.updateFuelEntry)
 	mux.HandleFunc("DELETE /api/fuel-entries/{id}", s.deleteFuelEntry)
 
+	// Charging sessions.
+	mux.HandleFunc("GET /api/charging-sessions", s.listChargingSessions)
+	mux.HandleFunc("POST /api/charging-sessions", s.createChargingSession)
+	mux.HandleFunc("GET /api/charging-sessions/{id}", s.getChargingSession)
+	mux.HandleFunc("PATCH /api/charging-sessions/{id}", s.updateChargingSession)
+	mux.HandleFunc("DELETE /api/charging-sessions/{id}", s.deleteChargingSession)
+
 	// Maintenance log.
 	mux.HandleFunc("GET /api/maintenance", s.listMaintenance)
 	mux.HandleFunc("POST /api/maintenance", s.createMaintenance)
@@ -429,6 +446,7 @@ func (s *Server) Handler() http.Handler {
 	s.attachmentRoutes(mux, "/api/technical-checks", colTechnicalChecks, s.getTechnicalCheck)
 	s.attachmentRoutes(mux, "/api/maintenance", colMaintenance, s.getMaintenance)
 	s.attachmentRoutes(mux, "/api/fuel-entries", colFuel, s.getFuelEntry)
+	s.attachmentRoutes(mux, "/api/charging-sessions", colCharging, s.getChargingSession)
 	s.attachmentRoutes(mux, "/api/parts", colParts, s.getPart)
 
 	return s.withMiddleware(mux)

API Server/internal/api/vehicleproviders.go

@@ -633,25 +633,33 @@ type metricSpec struct {
 	distance bool   // convert an imperial reading to kilometres
 }
 
+// headlineMetricSpecs are the measured readings, in the order they are reported
+// when a car has no arrangement of its own. Package-level so the set of keys a
+// car's arrangement may name (arrangeableCarMetrics, in cars.go) is derived from
+// it and the two cannot drift apart.
+var headlineMetricSpecs = []metricSpec{
+	{key: "odometer", keys: []string{"odometer", "mileage", "totalMileage", "odometerReading", "distanceTotal"}, unit: "km", distance: true},
+	{key: "fuelLevel", keys: []string{"fuelLevel", "fuelPercentage", "fuelRemainingPercent"}, unit: "%"},
+	{key: "fuelRange", keys: []string{"fuelRange", "rangeRemaining", "drivingRange", "fuelRangeTotal"}, unit: "km", distance: true},
+	{key: "batteryLevel", keys: []string{"batteryLevel", "chargeRemainingAmount", "stateOfCharge", "socLevel"}, unit: "%"},
+	{key: "evRange", keys: []string{"evRange", "electricRange", "batteryRange"}, unit: "km", distance: true},
+	// Range with the climate control running, which Toyota reports beside the
+	// plain one. Its own reading rather than a fallback for evRange: the two
+	// are different numbers and the gap between them is the point — a driver
+	// deciding whether to run the A/C wants to see both.
+	{key: "evRangeWithAc", keys: []string{"evRangeWithAc"}, unit: "km", distance: true},
+}
+
+// unmeasuredMetricKeys are the headline readings that are not measures — a state
+// and a pair of coordinates — picked out separately below.
+var unmeasuredMetricKeys = []string{"chargingStatus", "location"}
+
 // headlineMetrics lifts the readings worth showing large out of the section
 // payloads. Everything not listed here still reaches the UI as a flattened
 // field — this is about prominence, not about filtering.
 func headlineMetrics(trees []any) []providerMetric {
-	specs := []metricSpec{
-		{key: "odometer", keys: []string{"odometer", "mileage", "totalMileage", "odometerReading", "distanceTotal"}, unit: "km", distance: true},
-		{key: "fuelLevel", keys: []string{"fuelLevel", "fuelPercentage", "fuelRemainingPercent"}, unit: "%"},
-		{key: "fuelRange", keys: []string{"fuelRange", "rangeRemaining", "drivingRange", "fuelRangeTotal"}, unit: "km", distance: true},
-		{key: "batteryLevel", keys: []string{"batteryLevel", "chargeRemainingAmount", "stateOfCharge", "socLevel"}, unit: "%"},
-		{key: "evRange", keys: []string{"evRange", "electricRange", "batteryRange"}, unit: "km", distance: true},
-		// Range with the climate control running, which Toyota reports beside the
-		// plain one. Its own reading rather than a fallback for evRange: the two
-		// are different numbers and the gap between them is the point — a driver
-		// deciding whether to run the A/C wants to see both.
-		{key: "evRangeWithAc", keys: []string{"evRangeWithAc"}, unit: "km", distance: true},
-	}
-
 	out := []providerMetric{}
-	for _, spec := range specs {
+	for _, spec := range headlineMetricSpecs {
 		for _, tree := range trees {
 			n, unit, ok := findMeasure(tree, spec.keys...)
 			if !ok {

API Server/internal/bootstrap/schema.go

@@ -46,9 +46,11 @@ var collectionsSchema = map[string][]fieldDef{
 		// release is on by default. Keys are validated in internal/api/cars.go.
 		fJSON("hidden_tabs", 2000),
 		fJSON("hidden_fields", 2000),
-		// The order the Information rows are laid out in, as field keys. Empty
-		// means the page's own default order.
+		// The order the Information rows are laid out in, as field keys, and the
+		// same for the connected service's headline readings. Empty means the
+		// page's own default order.
 		fJSON("field_order", 2000),
+		fJSON("metric_order", 2000),
 		// Owner of this car. Non-cascading: deleting a user must not wipe their cars.
 		fRelation("owner", "users", false, false),
 	},
@@ -94,6 +96,20 @@ var collectionsSchema = map[string][]fieldDef{
 		fText("notes", false),
 		attachment(), // the pump receipt
 	},
+	// Charging sessions for an electric car — the EV counterpart of fuel_entries,
+	// same shape so the two logs behave alike. Consumption is derived on read.
+	"charging_sessions": {
+		fRelation("car", "cars", true, true),
+		fDate("date", true),
+		fNumber("km"), // odometer when plugging in
+		fNumber("kwh"),
+		fNumber("cost"),
+		fBool("full_charge"),
+		fBool("missed_session"),
+		fText("location", false), // "Home", "Ionity Køge"
+		fText("notes", false),
+		attachment(), // the charge point's receipt
+	},
 	// Workshop visits and repairs (unplanned/one-off garage work with a labour bill).
 	"maintenance_entries": {
 		fRelation("car", "cars", true, true),
@@ -199,6 +215,7 @@ var createOrder = []string{
 	"parts",
 	"car_shares",
 	"fuel_entries",
+	"charging_sessions",
 	"maintenance_entries",
 	"car_documents",
 	"reminders",
@@ -216,6 +233,7 @@ var reconcileOrder = []string{
 	"parts",
 	"car_shares",
 	"fuel_entries",
+	"charging_sessions",
 	"maintenance_entries",
 	"car_documents",
 	"reminders",
@@ -226,6 +244,7 @@ var reconcileOrder = []string{
 var indexes = map[string][]string{
 	"organizations":       {"CREATE UNIQUE INDEX `idx_organizations_name` ON `organizations` (`name`)"},
 	"fuel_entries":        {"CREATE INDEX `idx_fuel_entries_car_km` ON `fuel_entries` (`car`, `km`)"},
+	"charging_sessions":   {"CREATE INDEX `idx_charging_sessions_car_km` ON `charging_sessions` (`car`, `km`)"},
 	"maintenance_entries": {"CREATE INDEX `idx_maintenance_entries_car_date` ON `maintenance_entries` (`car`, `date`)"},
 	"car_documents":       {"CREATE INDEX `idx_car_documents_car_expiry` ON `car_documents` (`car`, `expiry_date`)"},
 	"reminders":           {"CREATE INDEX `idx_reminders_car_due` ON `reminders` (`car`, `due_date`)"},

API Server/internal/models/charging_test.go

@@ -0,0 +1,103 @@
+package models
+
+import (
+	"math"
+	"testing"
+	"time"
+)
+
+// The charging figures are derived from the whole history on every read, so the
+// window rules are the thing worth pinning down: what closes a window, what
+// folds into it, and what makes one uncomputable.
+
+func day(n int) time.Time { return time.Date(2026, 3, n, 8, 0, 0, 0, time.UTC) }
+
+func TestComputeChargingDerivedWindows(t *testing.T) {
+	// A first full charge (no window before it), then 300 km on 45 kWh split
+	// across a partial top-up and the full charge that closes the window.
+	entries := []ChargingSession{
+		{Date: day(1), Km: 10000, Kwh: 50, Cost: 100, FullCharge: true},
+		{Date: day(3), Km: 10120, Kwh: 15, Cost: 45},
+		{Date: day(6), Km: 10300, Kwh: 30, Cost: 75, FullCharge: true},
+	}
+	ComputeChargingDerived(entries)
+
+	// The first full charge has nothing before it to measure against.
+	if entries[0].ConsumptionKwh100 != nil {
+		t.Errorf("first full charge got a consumption figure: %v", *entries[0].ConsumptionKwh100)
+	}
+	// A partial charge never closes a window — it folds into the next full one.
+	if entries[1].ConsumptionKwh100 != nil {
+		t.Errorf("partial charge got a consumption figure: %v", *entries[1].ConsumptionKwh100)
+	}
+
+	closing := entries[2]
+	if closing.DistanceKm == nil || *closing.DistanceKm != 300 {
+		t.Fatalf("distance = %v, want 300", closing.DistanceKm)
+	}
+	// 15 + 30 kWh over 300 km: the partial counts, the opening charge does not.
+	if closing.KwhUsed == nil || *closing.KwhUsed != 45 {
+		t.Fatalf("kwhUsed = %v, want 45", closing.KwhUsed)
+	}
+	assertFloat(t, "consumption", closing.ConsumptionKwh100, 15)  // 45/300*100
+	assertFloat(t, "kmPerKwh", closing.KmPerKwh, 300.0/45.0)      //  6.67
+	assertFloat(t, "costPerKm", closing.CostPerKm, (45+75)/300.0) //  0.40
+	assertFloat(t, "pricePerKwh", closing.PricePerKwh, 75.0/30.0) //  2.50
+}
+
+func TestComputeChargingDerivedMissedSession(t *testing.T) {
+	// The car was charged somewhere without being logged, so the kWh on record
+	// do not account for the distance: reporting a figure would be fiction.
+	entries := []ChargingSession{
+		{Date: day(1), Km: 10000, Kwh: 50, Cost: 100, FullCharge: true},
+		{Date: day(5), Km: 10400, Kwh: 40, Cost: 80, FullCharge: true, MissedSession: true},
+	}
+	ComputeChargingDerived(entries)
+	if entries[1].ConsumptionKwh100 != nil {
+		t.Errorf("window with a missed session got a figure: %v", *entries[1].ConsumptionKwh100)
+	}
+	// The price of that charge is still known — it is on the receipt.
+	assertFloat(t, "pricePerKwh", entries[1].PricePerKwh, 2)
+}
+
+func TestComputeChargingStats(t *testing.T) {
+	// Two computable windows of different lengths: 100 km at 20 kWh/100km and
+	// 300 km at 10 kWh/100km. The average has to be distance-weighted (40 kWh
+	// over 400 km = 10 kWh/100km), not the mean of the two figures (15).
+	entries := []ChargingSession{
+		{Date: day(1), Km: 10000, Kwh: 10, Cost: 20, FullCharge: true},
+		{Date: day(2), Km: 10100, Kwh: 20, Cost: 40, FullCharge: true},
+		{Date: day(4), Km: 10400, Kwh: 30, Cost: 60, FullCharge: true},
+	}
+	ComputeChargingDerived(entries)
+	st := ComputeChargingStats(entries)
+
+	if st.Entries != 3 || st.TotalKwh != 60 || st.TotalCost != 120 {
+		t.Fatalf("totals = %d entries, %v kWh, %v cost", st.Entries, st.TotalKwh, st.TotalCost)
+	}
+	if st.TrackedDistanceKm != 400 {
+		t.Fatalf("trackedDistance = %d, want 400", st.TrackedDistanceKm)
+	}
+	assertFloat(t, "avg", st.AvgConsumptionKwh100, 12.5) // 50 kWh over 400 km
+	assertFloat(t, "best", st.BestConsumptionKwh100, 10) // the 300 km window
+	assertFloat(t, "worst", st.WorstConsumptionKwh100, 20)
+	assertFloat(t, "avgPricePerKwh", st.AvgPricePerKwh, 2)
+	assertFloat(t, "costPerKm", st.CostPerKm, 0.25) // 100 spent over 400 km
+}
+
+func TestComputeChargingStatsEmpty(t *testing.T) {
+	st := ComputeChargingStats(nil)
+	if st.Entries != 0 || st.AvgConsumptionKwh100 != nil || st.FirstDate != nil {
+		t.Errorf("empty history summarised as %+v", st)
+	}
+}
+
+func assertFloat(t *testing.T, name string, got *float64, want float64) {
+	t.Helper()
+	if got == nil {
+		t.Fatalf("%s = nil, want %v", name, want)
+	}
+	if math.Abs(*got-want) > 1e-9 {
+		t.Fatalf("%s = %v, want %v", name, *got, want)
+	}
+}

API Server/internal/models/models.go

@@ -83,6 +83,12 @@ type Car struct {
 	// arranged ones rather than appearing in the middle.
 	FieldOrder []string `json:"fieldOrder"`
 
+	// MetricOrder is the same thing for the headline readings on the connected
+	// service's tab, as the reading keys ("odometer", "evRange", …). A reading
+	// the provider didn't report at the time it was arranged simply isn't in the
+	// list, and joins the end when it does turn up.
+	MetricOrder []string `json:"metricOrder"`
+
 	// Owner is the user id that owns this car. Access is the requesting user's
 	// permission on it — "owner", "write", or "read" — computed by the API at
 	// read time and never persisted (omitempty; not part of the write payload).
@@ -233,6 +239,75 @@ type FuelStats struct {
 	LastDate  *time.Time `json:"lastDate,omitempty"`
 }
 
+// ChargingSession is one charge of an electric car — the EV counterpart of
+// FuelEntry, and it works the same way: energy and money are recorded, and the
+// efficiency is derived by the same reference-point method (see
+// ComputeChargingDerived).
+//
+// A charge to the car's usual full point plays the role of the full tank. It has
+// to, for the same reason: a session only says how much energy went in, not how
+// much was left in the battery, so the distance a given number of kWh covered is
+// only knowable between two charges that ended at the same state.
+type ChargingSession struct {
+	ID   string    `json:"id"`
+	Car  string    `json:"car"`  // relation -> Car.ID
+	Date time.Time `json:"date"` // date of the charge
+	Km   int       `json:"km"`   // odometer when plugging in
+	Kwh  float64   `json:"kwh"`  // energy delivered
+	Cost float64   `json:"cost"` // total paid for this charge
+
+	// FullCharge marks a charge taken to the car's usual full point — the
+	// reference the efficiency windows are measured between.
+	FullCharge bool `json:"fullCharge"`
+
+	// MissedSession records that the car was charged before this without being
+	// logged — a top-up at a friend's socket, say. The odometer span is then not
+	// accounted for by the kWh on record, so any window containing it is left
+	// uncomputed rather than reported as implausibly efficient.
+	MissedSession bool `json:"missedSession"`
+
+	// Location is where it was charged ("Home", "Ionity Køge"). Free text: an
+	// operator list would go stale and this is only ever read by a person.
+	Location string `json:"location,omitempty"`
+	Notes    string `json:"notes,omitempty"`
+
+	// The charge point's receipt.
+	Attachment
+
+	// Derived (not stored): filled in by the API on read.
+	PricePerKwh       *float64 `json:"pricePerKwh,omitempty"`
+	DistanceKm        *int     `json:"distanceKm,omitempty"`        // since the previous full charge
+	KwhUsed           *float64 `json:"kwhUsed,omitempty"`           // energy used over that distance
+	ConsumptionKwh100 *float64 `json:"consumptionKwh100,omitempty"` // kWh per 100 km
+	KmPerKwh          *float64 `json:"kmPerKwh,omitempty"`
+	CostPerKm         *float64 `json:"costPerKm,omitempty"`
+
+	Created string `json:"created,omitempty"`
+	Updated string `json:"updated,omitempty"`
+}
+
+// ChargingStats summarises a car's whole charging history.
+type ChargingStats struct {
+	Entries   int     `json:"entries"`
+	TotalKwh  float64 `json:"totalKwh"`
+	TotalCost float64 `json:"totalCost"`
+
+	// TrackedDistanceKm is the distance covered by computable windows, which is
+	// less than the odometer span whenever the history starts or ends on a
+	// partial charge. The averages below describe exactly this distance.
+	TrackedDistanceKm int `json:"trackedDistanceKm"`
+
+	AvgConsumptionKwh100   *float64 `json:"avgConsumptionKwh100,omitempty"`
+	BestConsumptionKwh100  *float64 `json:"bestConsumptionKwh100,omitempty"`
+	WorstConsumptionKwh100 *float64 `json:"worstConsumptionKwh100,omitempty"`
+	AvgKmPerKwh            *float64 `json:"avgKmPerKwh,omitempty"`
+	AvgPricePerKwh         *float64 `json:"avgPricePerKwh,omitempty"`
+	CostPerKm              *float64 `json:"costPerKm,omitempty"`
+
+	FirstDate *time.Time `json:"firstDate,omitempty"`
+	LastDate  *time.Time `json:"lastDate,omitempty"`
+}
+
 // MaintenanceEntry is one workshop visit or repair — work done on the car
 // outside the routine service schedule (which lives in ServiceRecord). A broken
 // alternator replaced at a garage belongs here; the annual oil change does not.
@@ -573,6 +648,127 @@ func ComputeFuelStats(entries []FuelEntry) FuelStats {
 	return st
 }
 
+// ComputeChargingDerived fills the derived efficiency fields on a car's charging
+// history. `entries` must be ordered oldest-first by odometer.
+//
+// The same window method as ComputeFuelDerived, with charges to the usual full
+// point as the endpoints: between two of them the car used exactly the energy
+// put in over that span, since both ends are the same battery state. Partial
+// charges in between fold into the window that closes them. A window is left
+// uncomputed when a session inside it is flagged MissedSession, when the
+// odometer did not advance, or when no energy was recorded.
+func ComputeChargingDerived(entries []ChargingSession) {
+	for i := range entries {
+		if entries[i].Kwh > 0 && entries[i].Cost > 0 {
+			p := entries[i].Cost / entries[i].Kwh
+			entries[i].PricePerKwh = &p
+		}
+	}
+
+	lastFull := -1
+	for i := range entries {
+		if !entries[i].FullCharge {
+			continue
+		}
+		if lastFull < 0 {
+			// First full charge: nothing before it to measure against.
+			lastFull = i
+			continue
+		}
+
+		dist := entries[i].Km - entries[lastFull].Km
+		kwh, cost := 0.0, 0.0
+		usable := true
+		for j := lastFull + 1; j <= i; j++ {
+			if entries[j].MissedSession {
+				usable = false
+			}
+			kwh += entries[j].Kwh
+			cost += entries[j].Cost
+		}
+
+		if usable && dist > 0 && kwh > 0 {
+			d, k := dist, kwh
+			entries[i].DistanceKm = &d
+			entries[i].KwhUsed = &k
+
+			kwh100 := kwh / float64(dist) * 100
+			entries[i].ConsumptionKwh100 = &kwh100
+
+			kmpkwh := float64(dist) / kwh
+			entries[i].KmPerKwh = &kmpkwh
+
+			if cost > 0 {
+				cpk := cost / float64(dist)
+				entries[i].CostPerKm = &cpk
+			}
+		}
+		lastFull = i
+	}
+}
+
+// ComputeChargingStats summarises a charging history whose derived fields have
+// already been filled in by ComputeChargingDerived. `entries` must be ordered
+// oldest-first.
+//
+// Averages are distance-weighted, as with fuel: total energy over total distance
+// across every computable window, so a long motorway run counts for more than a
+// short trip across town — which is what actually happened to the battery.
+func ComputeChargingStats(entries []ChargingSession) ChargingStats {
+	st := ChargingStats{Entries: len(entries)}
+	if len(entries) == 0 {
+		return st
+	}
+
+	var windowKwh, windowCost float64
+	for i := range entries {
+		e := &entries[i]
+		st.TotalKwh += e.Kwh
+		st.TotalCost += e.Cost
+
+		if e.ConsumptionKwh100 == nil {
+			continue
+		}
+		st.TrackedDistanceKm += *e.DistanceKm
+		windowKwh += *e.KwhUsed
+		if e.CostPerKm != nil {
+			windowCost += *e.CostPerKm * float64(*e.DistanceKm)
+		}
+		if st.BestConsumptionKwh100 == nil || *e.ConsumptionKwh100 < *st.BestConsumptionKwh100 {
+			v := *e.ConsumptionKwh100
+			st.BestConsumptionKwh100 = &v
+		}
+		if st.WorstConsumptionKwh100 == nil || *e.ConsumptionKwh100 > *st.WorstConsumptionKwh100 {
+			v := *e.ConsumptionKwh100
+			st.WorstConsumptionKwh100 = &v
+		}
+	}
+
+	if st.TrackedDistanceKm > 0 && windowKwh > 0 {
+		avg := windowKwh / float64(st.TrackedDistanceKm) * 100
+		st.AvgConsumptionKwh100 = &avg
+		kmpkwh := float64(st.TrackedDistanceKm) / windowKwh
+		st.AvgKmPerKwh = &kmpkwh
+		if windowCost > 0 {
+			cpk := windowCost / float64(st.TrackedDistanceKm)
+			st.CostPerKm = &cpk
+		}
+	}
+	if st.TotalKwh > 0 && st.TotalCost > 0 {
+		ppk := st.TotalCost / st.TotalKwh
+		st.AvgPricePerKwh = &ppk
+	}
+
+	first, last := entries[0].Date, entries[len(entries)-1].Date
+	if !first.IsZero() {
+		st.FirstDate = &first
+	}
+	if !last.IsZero() {
+		st.LastDate = &last
+	}
+	return st
+}
+
 // ComputeMaintenanceDerived fills the derived cost and warranty fields.
 func (m *MaintenanceEntry) ComputeMaintenanceDerived(now time.Time) {
 	m.TotalCost = m.LaborCost + m.PartsCost