package realtime

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

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

type RealtimeKVField struct {
	Protocol     envelope.Protocol
	VIN          string
	Domain       string
	Field        string
	Value        string
	ValueType    string
	EventTimeMS  int64
	ReceivedAtMS int64
	EventID      string
}

type protocolFieldMapping struct {
	Prefix       string
	GBDataUnits  bool
	TopLevelName map[string]string
	ArrayName    map[string]string
}

var realtimeFieldMappings = map[envelope.Protocol]protocolFieldMapping{
	envelope.ProtocolGB32960: {
		Prefix:      "gb32960",
		GBDataUnits: true,
		TopLevelName: map[string]string{
			"header":         "header",
			"platform_name":  "platform",
			"platform_login": "platform_login",
		},
		ArrayName: map[string]string{
			"motors":     "motor",
			"probes":     "probe",
			"subsystems": "subsystem",
			"summaries":  "",
		},
	},
	envelope.ProtocolJT808: {
		Prefix: "jt808",
		TopLevelName: map[string]string{
			"header":         "header",
			"location":       "location",
			"registration":   "registration",
			"authentication": "authentication",
		},
		ArrayName: map[string]string{
			"additional": "additional",
		},
	},
	envelope.ProtocolYutongMQTT: {
		Prefix: "yutong_mqtt",
		TopLevelName: map[string]string{
			"data":     "data",
			"root":     "root",
			"endpoint": "metadata",
			"topic":    "metadata",
		},
	},
}

const realtimeFieldMappingVersion = "2026-07-03.v1"

func realtimeKVFields(env envelope.FrameEnvelope, parsed map[string]any) []RealtimeKVField {
	vin := strings.TrimSpace(env.VIN)
	if vin == "" {
		return nil
	}
	eventID := env.StableEventID()
	mapping := realtimeMapping(env.Protocol)
	add := func(rows []RealtimeKVField, domain string, fields any) []RealtimeKVField {
		flat := map[string]any{}
		flattenKV("", fields, flat, mapping)
		names := make([]string, 0, len(flat))
		for name := range flat {
			names = append(names, name)
		}
		sort.Strings(names)
		for _, name := range names {
			value, valueType, ok := stringifyKVValue(flat[name])
			if !ok {
				continue
			}
			rows = append(rows, RealtimeKVField{
				Protocol:     env.Protocol,
				VIN:          vin,
				Domain:       domain,
				Field:        name,
				Value:        value,
				ValueType:    valueType,
				EventTimeMS:  env.EventTimeMS,
				ReceivedAtMS: env.ReceivedAtMS,
				EventID:      eventID,
			})
		}
		return rows
	}

	var rows []RealtimeKVField
	if mapping.GBDataUnits {
		rows = append(rows, gb32960KVFields(env, parsed, mapping, eventID)...)
		return rows
	}

	keys := make([]string, 0, len(parsed))
	for key := range parsed {
		keys = append(keys, key)
	}
	sort.Strings(keys)
	for _, key := range keys {
		domain := mappedTopLevelDomain(mapping, key)
		if domain == "" {
			continue
		}
		rows = addMappedValue(rows, add, domain, key, parsed[key])
	}
	return rows
}

func gb32960KVFields(env envelope.FrameEnvelope, parsed map[string]any, mapping protocolFieldMapping, eventID string) []RealtimeKVField {
	addRows := func(rows []RealtimeKVField, domain string, fields any) []RealtimeKVField {
		flat := map[string]any{}
		flattenKV("", fields, flat, mapping)
		names := make([]string, 0, len(flat))
		for name := range flat {
			names = append(names, name)
		}
		sort.Strings(names)
		for _, name := range names {
			value, valueType, ok := stringifyKVValue(flat[name])
			if !ok {
				continue
			}
			rows = append(rows, RealtimeKVField{
				Protocol:     env.Protocol,
				VIN:          strings.TrimSpace(env.VIN),
				Domain:       domain,
				Field:        name,
				Value:        value,
				ValueType:    valueType,
				EventTimeMS:  env.EventTimeMS,
				ReceivedAtMS: env.ReceivedAtMS,
				EventID:      eventID,
			})
		}
		return rows
	}

	var rows []RealtimeKVField
	for key, value := range parsed {
		if key == "data_units" {
			continue
		}
		if domain := mappedTopLevelDomain(mapping, key); domain != "" {
			rows = addMappedValue(rows, addRows, domain, key, value)
		}
	}
	units, ok := asAnySlice(parsed["data_units"])
	if !ok {
		return rows
	}
	for _, unit := range units {
		unitMap, ok := unit.(map[string]any)
		if !ok {
			continue
		}
		name := sanitizeFieldPart(strconvAny(unitMap["name"]))
		if name == "" || name == "<nil>" {
			name = strings.ToLower(strings.TrimPrefix(strings.TrimSpace(strconvAny(unitMap["type"])), "0x"))
		}
		if name == "" {
			continue
		}
		domain := mapping.Prefix + "." + name
		if value, ok := unitMap["value"]; ok {
			rows = addRows(rows, domain, value)
		}
		if unitType := strings.TrimSpace(strconvAny(unitMap["type"])); unitType != "" && unitType != "<nil>" {
			rows = addRows(rows, domain, map[string]any{"type": unitType})
		}
	}
	return rows
}

func flattenKV(prefix string, value any, out map[string]any, mapping protocolFieldMapping) {
	switch typed := value.(type) {
	case map[string]any:
		keys := make([]string, 0, len(typed))
		for key := range typed {
			keys = append(keys, key)
		}
		sort.Strings(keys)
		for _, key := range keys {
			part := sanitizeFieldPart(key)
			if part == "" {
				continue
			}
			if arrayName, ok := mapping.ArrayName[part]; ok && arrayName == "" {
				if items, ok := asAnySlice(typed[key]); ok && len(items) == 1 {
					flattenKV(prefix, items[0], out, mapping)
					continue
				}
			}
			next := part
			if prefix != "" {
				next = prefix + "." + part
			}
			flattenKV(next, typed[key], out, mapping)
		}
	case []any:
		for index, item := range typed {
			itemMap, ok := item.(map[string]any)
			if !ok {
				out[prefix] = typed
				return
			}
			arrayName, hasArrayName := mapping.ArrayName[lastPathPart(prefix)]
			itemKey := strconv.Itoa(index)
			if hasArrayName {
				if arrayName == "" && len(typed) == 1 {
					flattenKV(prefix, itemMap, out, mapping)
					continue
				}
				if arrayName != "" {
					itemKey = arrayName + "_" + strconv.Itoa(index+1)
				}
			}
			next := itemKey
			if prefix != "" {
				next = prefix + "." + itemKey
			}
			flattenKV(next, itemMap, out, mapping)
		}
	case []map[string]any:
		items := make([]any, len(typed))
		for index, item := range typed {
			items[index] = item
		}
		flattenKV(prefix, items, out, mapping)
	default:
		if prefix != "" && value != nil {
			out[prefix] = value
		}
	}
}

func addMappedValue(rows []RealtimeKVField, add func([]RealtimeKVField, string, any) []RealtimeKVField, domain string, key string, value any) []RealtimeKVField {
	switch typed := value.(type) {
	case map[string]any:
		return add(rows, domain, typed)
	case []any:
		return add(rows, domain, typed)
	case []map[string]any:
		return add(rows, domain, typed)
	default:
		return add(rows, domain, map[string]any{key: value})
	}
}

func realtimeMapping(protocol envelope.Protocol) protocolFieldMapping {
	if mapping, ok := realtimeFieldMappings[protocol]; ok {
		return mapping
	}
	return protocolFieldMapping{Prefix: strings.ToLower(string(protocol))}
}

func mappedTopLevelDomain(mapping protocolFieldMapping, key string) string {
	key = strings.TrimSpace(key)
	if key == "" {
		return ""
	}
	name := mapping.TopLevelName[key]
	if name == "" {
		name = sanitizeFieldPart(key)
	}
	if name == "" {
		return ""
	}
	return mapping.Prefix + "." + name
}

func sanitizeFieldPart(value string) string {
	value = strings.TrimSpace(value)
	if value == "" {
		return ""
	}
	var b strings.Builder
	for _, r := range value {
		switch {
		case r >= 'a' && r <= 'z':
			b.WriteRune(r)
		case r >= 'A' && r <= 'Z':
			b.WriteRune(r + ('a' - 'A'))
		case r >= '0' && r <= '9':
			b.WriteRune(r)
		case r == '_':
			b.WriteRune(r)
		default:
			b.WriteByte('_')
		}
	}
	return strings.Trim(b.String(), "_")
}

func lastPathPart(path string) string {
	if index := strings.LastIndex(path, "."); index >= 0 {
		return path[index+1:]
	}
	return path
}

func stringifyKVValue(value any) (string, string, bool) {
	switch typed := value.(type) {
	case string:
		text := strings.TrimSpace(typed)
		return text, "string", text != ""
	case bool:
		return strconv.FormatBool(typed), "bool", true
	case float64:
		return strconv.FormatFloat(typed, 'f', -1, 64), "number", true
	case float32:
		return strconv.FormatFloat(float64(typed), 'f', -1, 64), "number", true
	case json.Number:
		return typed.String(), "number", strings.TrimSpace(typed.String()) != ""
	case int:
		return strconv.Itoa(typed), "number", true
	case int8, int16, int32, int64:
		return fmt.Sprintf("%d", typed), "number", true
	case uint, uint8, uint16, uint32, uint64:
		return fmt.Sprintf("%d", typed), "number", true
	default:
		data, err := json.Marshal(typed)
		if err != nil || string(data) == "null" {
			return "", "", false
		}
		return string(data), "json", true
	}
}