package envelope

import (
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"strings"
)

type Protocol string

const (
	ProtocolGB32960    Protocol = "GB32960"
	ProtocolJT808      Protocol = "JT808"
	ProtocolYutongMQTT Protocol = "YUTONG_MQTT"
)

type ParseStatus string

const (
	ParseOK       ParseStatus = "OK"
	ParsePartial  ParseStatus = "PARTIAL"
	ParseBadFrame ParseStatus = "BAD_FRAME"
)

const (
	FieldSpeedKMH       = "speed_kmh"
	FieldTotalMileageKM = "total_mileage_km"
	FieldLongitude      = "longitude"
	FieldLatitude       = "latitude"
	FieldSOCPercent     = "soc_percent"
)

type FrameEnvelope struct {
	EventID        string         `json:"event_id"`
	TraceID        string         `json:"trace_id"`
	Protocol       Protocol       `json:"protocol"`
	MessageID      string         `json:"message_id"`
	Sequence       uint16         `json:"sequence"`
	VIN            string         `json:"vin,omitempty"`
	VehicleKeyHint string         `json:"vehicle_key,omitempty"`
	Phone          string         `json:"phone,omitempty"`
	DeviceID       string         `json:"device_id,omitempty"`
	Plate          string         `json:"plate,omitempty"`
	SourceEndpoint string         `json:"source_endpoint,omitempty"`
	EventTimeMS    int64          `json:"event_time_ms"`
	ReceivedAtMS   int64          `json:"received_at_ms"`
	RawHex         string         `json:"raw_hex,omitempty"`
	RawText        string         `json:"raw_text,omitempty"`
	Parsed         map[string]any `json:"parsed,omitempty"`
	Fields         map[string]any `json:"fields,omitempty"`
	ParseStatus    ParseStatus    `json:"parse_status"`
	ParseError     string         `json:"parse_error,omitempty"`
}

func (e FrameEnvelope) VehicleKey() string {
	if key := strings.TrimSpace(e.VIN); key != "" {
		return key
	}
	if key := strings.TrimSpace(e.VehicleKeyHint); key != "" {
		return key
	}
	if key := strings.TrimSpace(e.Phone); key != "" {
		return string(e.Protocol) + ":" + key
	}
	if key := strings.TrimSpace(e.DeviceID); key != "" {
		return string(e.Protocol) + ":" + key
	}
	return string(e.Protocol) + ":unknown"
}

func (e FrameEnvelope) StableEventID() string {
	if strings.TrimSpace(e.EventID) != "" {
		return e.EventID
	}
	input := fmt.Sprintf("%s|%s|%s|%d|%d|%s",
		e.Protocol, e.MessageID, e.VehicleKey(), e.Sequence, e.EventTimeMS, e.RawHex)
	sum := sha256.Sum256([]byte(input))
	return hex.EncodeToString(sum[:16])
}

func (e FrameEnvelope) KafkaKey() []byte {
	return []byte(e.VehicleKey())
}

func (e FrameEnvelope) MarshalJSONBytes() ([]byte, error) {
	if e.EventID == "" {
		e.EventID = e.StableEventID()
	}
	if e.ParseStatus == "" {
		e.ParseStatus = ParseOK
	}
	return json.Marshal(e)
}