package main

import (
	"context"
	"encoding/json"
	"flag"
	"fmt"
	"log"
	"os"
	"os/signal"
	"strings"
	"syscall"

	"github.com/coder/websocket"
	"github.com/coder/websocket/wsjson"

	"realtime-gateway/internal/model"
)

type consumerConfig struct {
	URL           string               `json:"url"`
	Token         string               `json:"token"`
	ChannelID     string               `json:"channelId"`
	DeviceID      string               `json:"deviceId"`
	GroupID       string               `json:"groupId"`
	Topic         string               `json:"topic"`
	Topics        []string             `json:"topics"`
	Subscriptions []model.Subscription `json:"subscriptions"`
	Snapshot      *bool                `json:"snapshot"`
}

func main() {
	configPath := findConfigPath(os.Args[1:])
	fileConfig, err := loadConsumerConfig(configPath)
	if err != nil {
		log.Fatalf("load config: %v", err)
	}

	flag.StringVar(&configPath, "config", configPath, "path to consumer config file")
	url := flag.String("url", valueOr(fileConfig.URL, "ws://127.0.0.1:8080/ws"), "gateway websocket url")
	token := flag.String("token", fileConfig.Token, "consumer token, leave empty if anonymous consumers are allowed")
	channelID := flag.String("channel-id", fileConfig.ChannelID, "channel id to join before subscribe")
	deviceID := flag.String("device-id", valueOr(fileConfig.DeviceID, "child-001"), "device id to subscribe")
	groupID := flag.String("group-id", fileConfig.GroupID, "group id to subscribe")
	topic := flag.String("topic", valueOr(fileConfig.Topic, "telemetry.location"), "single topic to subscribe")
	topics := flag.String("topics", strings.Join(fileConfig.Topics, ","), "comma-separated topics to subscribe, overrides -topic when set")
	snapshot := flag.Bool("snapshot", boolValue(fileConfig.Snapshot, true), "request latest snapshot after subscribe")
	flag.Parse()

	subscriptions := resolveSubscriptions(fileConfig, *deviceID, *groupID, *topic, *topics)
	if len(subscriptions) == 0 {
		log.Fatalf("no subscriptions configured")
	}

	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
	defer stop()

	conn, _, err := websocket.Dial(ctx, *url, nil)
	if err != nil {
		log.Fatalf("dial gateway: %v", err)
	}
	defer conn.Close(websocket.StatusNormalClosure, "consumer closed")

	var welcome model.ServerMessage
	if err := wsjson.Read(ctx, conn, &welcome); err != nil {
		log.Fatalf("read welcome: %v", err)
	}
	log.Printf("connected: session=%s", welcome.SessionID)

	if *token != "" || *channelID != "" {
		authReq := model.ClientMessage{
			Type:  "authenticate",
			Role:  model.RoleConsumer,
			Token: *token,
		}
		if *channelID != "" {
			authReq.Type = "join_channel"
			authReq.ChannelID = *channelID
		}
		if err := wsjson.Write(ctx, conn, authReq); err != nil {
			log.Fatalf("send authenticate: %v", err)
		}
		var authResp model.ServerMessage
		if err := wsjson.Read(ctx, conn, &authResp); err != nil {
			log.Fatalf("read authenticate response: %v", err)
		}
		if authResp.Type == "error" {
			log.Fatalf("authenticate failed: %s", authResp.Error)
		}
		log.Printf("authenticated: session=%s", authResp.SessionID)
	}

	subReq := model.ClientMessage{
		Type:          "subscribe",
		Subscriptions: subscriptions,
	}
	if err := wsjson.Write(ctx, conn, subReq); err != nil {
		log.Fatalf("send subscribe: %v", err)
	}

	var subResp model.ServerMessage
	if err := wsjson.Read(ctx, conn, &subResp); err != nil {
		log.Fatalf("read subscribe response: %v", err)
	}
	if subResp.Type == "error" {
		log.Fatalf("subscribe failed: %s", subResp.Error)
	}
	log.Printf("subscribed: %s", describeSubscriptions(subscriptions))

	if *snapshot {
		req := model.ClientMessage{
			Type: "snapshot",
			Subscriptions: []model.Subscription{
				{DeviceID: firstSnapshotDeviceID(subscriptions, *deviceID)},
			},
		}
		if err := wsjson.Write(ctx, conn, req); err != nil {
			log.Fatalf("send snapshot: %v", err)
		}
		var resp model.ServerMessage
		if err := wsjson.Read(ctx, conn, &resp); err != nil {
			log.Fatalf("read snapshot response: %v", err)
		}
		if resp.Type == "snapshot" {
			log.Printf("snapshot: %s", compactJSON(resp.State))
		} else if resp.Type == "error" {
			log.Printf("snapshot unavailable: %s", resp.Error)
		}
	}

	for {
		var message model.ServerMessage
		if err := wsjson.Read(ctx, conn, &message); err != nil {
			log.Fatalf("read event: %v", err)
		}
		switch message.Type {
		case "event":
			log.Printf("event: %s", describeEnvelope(message.Envelope))
		case "error":
			log.Printf("server error: %s", message.Error)
		default:
			log.Printf("message: type=%s", message.Type)
		}
	}
}

func loadConsumerConfig(path string) (consumerConfig, error) {
	if strings.TrimSpace(path) == "" {
		return consumerConfig{}, nil
	}

	data, err := os.ReadFile(path)
	if err != nil {
		return consumerConfig{}, fmt.Errorf("read %s: %w", path, err)
	}

	var cfg consumerConfig
	if err := json.Unmarshal(data, &cfg); err != nil {
		return consumerConfig{}, fmt.Errorf("parse %s: %w", path, err)
	}
	return cfg, nil
}

func findConfigPath(args []string) string {
	for index := 0; index < len(args); index++ {
		arg := args[index]
		if strings.HasPrefix(arg, "-config=") {
			return strings.TrimSpace(strings.TrimPrefix(arg, "-config="))
		}
		if arg == "-config" && index+1 < len(args) {
			return strings.TrimSpace(args[index+1])
		}
		if strings.HasPrefix(arg, "--config=") {
			return strings.TrimSpace(strings.TrimPrefix(arg, "--config="))
		}
		if arg == "--config" && index+1 < len(args) {
			return strings.TrimSpace(args[index+1])
		}
	}
	return ""
}

func valueOr(value string, fallback string) string {
	if strings.TrimSpace(value) == "" {
		return fallback
	}
	return value
}

func boolValue(value *bool, fallback bool) bool {
	if value == nil {
		return fallback
	}
	return *value
}

func resolveSubscriptions(fileConfig consumerConfig, deviceID string, groupID string, topic string, topicsCSV string) []model.Subscription {
	if len(fileConfig.Subscriptions) > 0 && strings.TrimSpace(topicsCSV) == "" && strings.TrimSpace(topic) == valueOr(fileConfig.Topic, "telemetry.location") {
		return filterValidSubscriptions(fileConfig.Subscriptions)
	}

	topics := parseTopics(topicsCSV)
	if len(topics) == 0 {
		topics = []string{topic}
	}

	subscriptions := make([]model.Subscription, 0, len(topics))
	for _, entry := range topics {
		subscriptions = append(subscriptions, model.Subscription{
			DeviceID: deviceID,
			GroupID:  groupID,
			Topic:    entry,
		})
	}
	return filterValidSubscriptions(subscriptions)
}

func parseTopics(value string) []string {
	if strings.TrimSpace(value) == "" {
		return nil
	}
	parts := strings.Split(value, ",")
	topics := make([]string, 0, len(parts))
	for _, part := range parts {
		topic := strings.TrimSpace(part)
		if topic == "" {
			continue
		}
		topics = append(topics, topic)
	}
	return topics
}

func filterValidSubscriptions(items []model.Subscription) []model.Subscription {
	subscriptions := make([]model.Subscription, 0, len(items))
	for _, item := range items {
		if strings.TrimSpace(item.ChannelID) == "" && strings.TrimSpace(item.DeviceID) == "" && strings.TrimSpace(item.GroupID) == "" {
			continue
		}
		subscriptions = append(subscriptions, model.Subscription{
			ChannelID: strings.TrimSpace(item.ChannelID),
			DeviceID:  strings.TrimSpace(item.DeviceID),
			GroupID:   strings.TrimSpace(item.GroupID),
			Topic:     strings.TrimSpace(item.Topic),
		})
	}
	return subscriptions
}

func describeSubscriptions(items []model.Subscription) string {
	parts := make([]string, 0, len(items))
	for _, item := range items {
		scope := item.DeviceID
		if scope == "" {
			if item.GroupID != "" {
				scope = "group:" + item.GroupID
			} else {
				scope = "all"
			}
		}
		if item.ChannelID != "" {
			scope = "channel:" + item.ChannelID + " / " + scope
		}
		if item.Topic != "" {
			scope += "/" + item.Topic
		}
		parts = append(parts, scope)
	}
	return strings.Join(parts, ", ")
}

func firstSnapshotDeviceID(items []model.Subscription, fallback string) string {
	for _, item := range items {
		if strings.TrimSpace(item.DeviceID) != "" {
			return item.DeviceID
		}
	}
	return fallback
}

func describeEnvelope(envelope *model.Envelope) string {
	if envelope == nil {
		return "{}"
	}
	switch envelope.Topic {
	case "telemetry.location":
		return describeLocationEnvelope(envelope)
	case "telemetry.heart_rate":
		return describeHeartRateEnvelope(envelope)
	default:
		return compactEnvelope(envelope)
	}
}

func describeLocationEnvelope(envelope *model.Envelope) string {
	var payload struct {
		Lat         float64 `json:"lat"`
		Lng         float64 `json:"lng"`
		Speed       float64 `json:"speed"`
		Bearing     float64 `json:"bearing"`
		Accuracy    float64 `json:"accuracy"`
		CoordSystem string  `json:"coordSystem"`
	}
	if err := json.Unmarshal(envelope.Payload, &payload); err != nil {
		return compactEnvelope(envelope)
	}
	return fmt.Sprintf(
		"gps device=%s lat=%.6f lng=%.6f speed=%.2f bearing=%.1f accuracy=%.1f coord=%s",
		envelope.Target.DeviceID,
		payload.Lat,
		payload.Lng,
		payload.Speed,
		payload.Bearing,
		payload.Accuracy,
		payload.CoordSystem,
	)
}

func describeHeartRateEnvelope(envelope *model.Envelope) string {
	var payload struct {
		BPM        int     `json:"bpm"`
		Confidence float64 `json:"confidence"`
	}
	if err := json.Unmarshal(envelope.Payload, &payload); err != nil {
		return compactEnvelope(envelope)
	}
	if payload.Confidence > 0 {
		return fmt.Sprintf("heart_rate device=%s bpm=%d confidence=%.2f", envelope.Target.DeviceID, payload.BPM, payload.Confidence)
	}
	return fmt.Sprintf("heart_rate device=%s bpm=%d", envelope.Target.DeviceID, payload.BPM)
}

func compactEnvelope(envelope *model.Envelope) string {
	if envelope == nil {
		return "{}"
	}
	data, err := json.Marshal(envelope)
	if err != nil {
		return "{}"
	}
	return compactJSON(data)
}

func compactJSON(data []byte) string {
	var value any
	if err := json.Unmarshal(data, &value); err != nil {
		return string(data)
	}
	compact, err := json.Marshal(value)
	if err != nil {
		return string(data)
	}
	return string(compact)
}