implementing a bare bones fuel calculator

telemetry/fuel_calculator.go

@@ -0,0 +1,101 @@
+package telemetry
+
+import (
+	"fmt"
+	"log/slog"
+	"strconv"
+)
+
+type fuelCalcState int
+
+const (
+	outlap fuelCalcState = iota
+	firstLap
+	normal
+)
+
+// FuelCalculator acts as a Virtual Field middleware
+type FuelCalculator struct {
+	Logger *slog.Logger
+
+	// --- Internal State (The Memory) ---
+	lastLapNumber  int     // Tracks when we cross the start/finish line
+	fuelAtLapStart float64 // Snapshot of fuel when the lap began
+
+	lapHistory     []float64 // Buffer holding the last N valid laps
+	maxHistoryLaps int       // How many laps to keep in the buffer (e.g., 3)
+
+	// --- Validation Flags ---
+
+	isOutLap       bool // True if we just left the pits
+	isUnderCaution bool // True if safety car is out (optional, based on flags)
+
+	// --- The Outputs (What gets pushed back to the TUI) ---
+
+	lastLapUsage float64
+	avgUsage     float64
+	maxUsage     float64
+
+	state fuelCalcState
+}
+
+func NewFuelCalculator(logger *slog.Logger) *FuelCalculator {
+	return &FuelCalculator{
+		Logger:         logger,
+		lapHistory:     make([]float64, 0, 5), // Pre-allocate space for 5 laps
+		maxHistoryLaps: 3,                     // We want a 3-lap rolling average
+		lastLapNumber:  0,
+		state:          outlap,
+	}
+}
+
+// func (fc *FuelCalculator) isOutlap(lap int) {
+// 	if fc.isOutLap
+// }
+
+func (fc *FuelCalculator) Process(td *TelemetryData) {
+	currentLap := int(td.Values[LapNumber].Raw)
+	// NOTE: this is stupid as, fix it
+	currentFuelLevel, err := strconv.ParseFloat(td.Values[FuelLevel].Str, 64)
+	if err != nil {
+		fc.Logger.Debug(fmt.Sprintf("error parsing fuel level: %+v", err))
+		return
+	}
+
+	if currentLap == 0 {
+		td.Values[FuelLastLap].Type = DataTypeSTRING
+		td.Values[FuelLastLap].Str = "No Data"
+
+		td.Values[FuelCurrentLap].Type = DataTypeSTRING
+		td.Values[FuelCurrentLap].Str = "No Data"
+
+		return
+	}
+
+	if currentLap > fc.lastLapNumber {
+		fc.Logger.Debug(fmt.Sprintf("crossed the line: %+v -> %+v", currentLap, fc.lastLapNumber))
+		fc.state = firstLap
+		fc.lastLapNumber = currentLap
+		fc.fuelAtLapStart = currentFuelLevel
+	}
+
+	td.Values[FuelLastLap].Type = DataTypeSTRING
+	td.Values[FuelLastLap].Str = "No Data"
+
+	td.Values[FuelCurrentLap].Type = DataTypeSTRING
+	fc.Logger.Debug(fmt.Sprintf("calculate: %+v - %+v = %+v", fc.fuelAtLapStart,
+		currentFuelLevel, fc.fuelAtLapStart-currentFuelLevel))
+	td.Values[FuelCurrentLap].Str = fmt.Sprintf("%.2f", fc.fuelAtLapStart-currentFuelLevel)
+}
+
+// Simple helper to wipe state on session changes
+func (fc *FuelCalculator) resetHistory() {
+	fc.lapHistory = make([]float64, 0, fc.maxHistoryLaps)
+	fc.lastLapNumber = 0
+	fc.avgUsage = 0
+	fc.maxUsage = 0
+}
+
+func (fc *FuelCalculator) EnsureSubscribed() []FieldID {
+	return []FieldID{FuelLevel, LapNumber}
+}