package stats

import (
	"encoding/json"
	"fmt"
	"strconv"
	"strings"

	"lingniu-vehicle-ingest/go/vehicle-gateway/internal/envelope"
)

const (
	gb32960FuelCellEngineWorkMode = 2
	yutongFuelCellRunningMode     = 4
	yutongFuelCellDrivingMode     = 11
)

// PureHydrogenModeFromEnvelope returns whether the reported vehicle is in a
// fuel-cell-only work mode and whether the source value is understood.
//
// The 32960 fuel-cell extension reports engine_work_state; production frames
// use mode 2 for normal fuel-cell operation. Yutong reports the equivalent
// state through TRIANGLE_STATE; production frames use 1 for inactive and 4/11
// for active fuel-cell operating modes.
func PureHydrogenModeFromEnvelope(env envelope.FrameEnvelope) (active bool, known bool) {
	value, exists := env.Fields[envelope.FieldFuelCellWorkMode]
	if !exists {
		return false, false
	}
	mode, ok := integerMode(value)
	if !ok {
		return false, false
	}
	switch env.Protocol {
	case envelope.ProtocolGB32960:
		switch mode {
		case gb32960FuelCellEngineWorkMode:
			return true, true
		case 0, 1:
			return false, true
		default:
			return false, false
		}
	case envelope.ProtocolYutongMQTT:
		switch mode {
		case yutongFuelCellRunningMode, yutongFuelCellDrivingMode:
			return true, true
		case 1:
			return false, true
		default:
			return false, false
		}
	default:
		return false, false
	}
}

// PureHydrogenMileageDelta returns the odometer delta that can be attributed
// to pure-hydrogen operation. Both endpoints must report a known active mode;
// this deliberately leaves transitions and missing mode data unclassified.
func PureHydrogenMileageDelta(
	previousKM float64,
	currentKM float64,
	previousActive bool,
	previousKnown bool,
	currentActive bool,
	currentKnown bool,
) float64 {
	delta := currentKM - previousKM
	if !previousKnown || !previousActive || !currentKnown || !currentActive {
		return 0
	}
	if delta < 0 || delta > maxSelectedDailyMileageKM {
		return 0
	}
	return delta
}

func integerMode(value any) (int, bool) {
	switch typed := value.(type) {
	case json.Number:
		parsed, err := strconv.Atoi(typed.String())
		return parsed, err == nil
	case string:
		parsed, err := strconv.Atoi(strings.TrimSpace(typed))
		return parsed, err == nil
	case int:
		return typed, true
	case int8:
		return int(typed), true
	case int16:
		return int(typed), true
	case int32:
		return int(typed), true
	case int64:
		return int(typed), true
	case uint:
		return int(typed), true
	case uint8:
		return int(typed), true
	case uint16:
		return int(typed), true
	case uint32:
		return int(typed), true
	case uint64:
		if typed > uint64(^uint(0)>>1) {
			return 0, false
		}
		return int(typed), true
	case float32:
		parsed := int(typed)
		return parsed, float32(parsed) == typed
	case float64:
		parsed := int(typed)
		return parsed, float64(parsed) == typed
	default:
		parsed, err := strconv.Atoi(strings.TrimSpace(fmt.Sprint(value)))
		return parsed, err == nil
	}
}