package main

import (
	"context"
	"database/sql"
	"encoding/json"
	"os"
	"os/signal"
	"strings"
	"syscall"
	"time"

	"github.com/segmentio/kafka-go"
	_ "github.com/taosdata/driver-go/v3/taosWS"

	"lingniu-vehicle-ingest/go/vehicle-gateway/internal/envelope"
	"lingniu-vehicle-ingest/go/vehicle-gateway/internal/health"
	"lingniu-vehicle-ingest/go/vehicle-gateway/internal/history"
	"lingniu-vehicle-ingest/go/vehicle-gateway/internal/observability"
)

func main() {
	logger := observability.NewLogger("vehicle-history-writer")
	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
	defer stop()

	cfg := loadConfig()
	db, err := sql.Open(cfg.TDengineDriver, cfg.TDengineDSN)
	if err != nil {
		logger.Error("tdengine open failed", "error", err)
		os.Exit(1)
	}
	defer db.Close()
	if err := db.PingContext(ctx); err != nil {
		logger.Error("tdengine ping failed", "error", err)
		os.Exit(1)
	}
	health.Start(ctx, logger, health.NewServer(env("HEALTH_ADDR", ""), "vehicle-history-writer", []health.Check{
		{Name: "tdengine", Check: db.PingContext},
	}))

	writer := history.NewWriter(db)
	if cfg.EnsureSchema {
		if err := writer.EnsureSchema(ctx, cfg.TDengineDatabase); err != nil {
			logger.Error("tdengine schema bootstrap failed", "error", err)
			os.Exit(1)
		}
	}

	reader := kafka.NewReader(kafka.ReaderConfig{
		Brokers:     cfg.KafkaBrokers,
		GroupID:     cfg.KafkaGroup,
		GroupTopics: cfg.KafkaTopics,
		MinBytes:    1,
		MaxBytes:    10e6,
	})
	defer reader.Close()

	logger.Info("history writer started",
		"driver", cfg.TDengineDriver,
		"group", cfg.KafkaGroup,
		"topics", strings.Join(cfg.KafkaTopics, ","))

	for {
		message, err := reader.FetchMessage(ctx)
		if err != nil {
			if ctx.Err() != nil {
				return
			}
			logger.Error("kafka fetch failed", "error", err)
			continue
		}
		processHistoryMessage(ctx, logger, writer, reader, message)
	}
}

const kafkaMessageOperationTimeout = 30 * time.Second

type historyAppender interface {
	AppendAll(context.Context, envelope.FrameEnvelope) error
}

type kafkaMessageCommitter interface {
	CommitMessages(context.Context, ...kafka.Message) error
}

func processHistoryMessage(ctx context.Context, logger interface {
	Error(string, ...any)
	Warn(string, ...any)
}, appender historyAppender, committer kafkaMessageCommitter, message kafka.Message) {
	messageCtx, cancel := context.WithTimeout(context.WithoutCancel(ctx), kafkaMessageOperationTimeout)
	defer cancel()

	var env envelope.FrameEnvelope
	if err := json.Unmarshal(message.Value, &env); err != nil {
		logger.Warn("skip invalid envelope json", "topic", message.Topic, "partition", message.Partition, "offset", message.Offset, "error", err)
		_ = committer.CommitMessages(messageCtx, message)
		return
	}
	if err := appender.AppendAll(messageCtx, env); err != nil {
		logger.Error("tdengine append failed", "topic", message.Topic, "partition", message.Partition, "offset", message.Offset, "event_id", env.StableEventID(), "error", err)
		return
	}
	if err := committer.CommitMessages(messageCtx, message); err != nil {
		logger.Error("kafka commit failed", "topic", message.Topic, "partition", message.Partition, "offset", message.Offset, "error", err)
	}
}

type config struct {
	KafkaBrokers     []string
	KafkaTopics      []string
	KafkaGroup       string
	TDengineDriver   string
	TDengineDSN      string
	TDengineDatabase string
	EnsureSchema     bool
}

func loadConfig() config {
	return config{
		KafkaBrokers:     splitCSV(env("KAFKA_BROKERS", "127.0.0.1:9092")),
		KafkaTopics:      splitCSV(env("KAFKA_TOPICS", "vehicle.raw.gb32960.v1,vehicle.raw.jt808.v1,vehicle.raw.yutong-mqtt.v1")),
		KafkaGroup:       env("KAFKA_GROUP", "go-history-writer"),
		TDengineDriver:   env("TDENGINE_DRIVER", "taosWS"),
		TDengineDSN:      env("TDENGINE_DSN", ""),
		TDengineDatabase: env("TDENGINE_DATABASE", history.DefaultDatabase),
		EnsureSchema:     env("TDENGINE_ENSURE_SCHEMA", "true") != "false",
	}
}

func env(key string, fallback string) string {
	value := strings.TrimSpace(os.Getenv(key))
	if value == "" {
		return fallback
	}
	return value
}

func splitCSV(value string) []string {
	var out []string
	for _, item := range strings.Split(value, ",") {
		item = strings.TrimSpace(item)
		if item != "" {
			out = append(out, item)
		}
	}
	return out
}