package pipeline

import (
	"context"
	"log/slog"
	"regexp"
	"sort"
	"strings"
	"sync/atomic"
	"time"

	"mqqt-scrubber/internal/config"
	"mqqt-scrubber/internal/model"
	"mqqt-scrubber/internal/parser"
)

var invalidDeviceAliasCharacters = regexp.MustCompile(`[^a-z0-9_]+`)

type writer interface {
	Write(ctx context.Context, records []model.Record) error
}

type Service struct {
	config        config.Config
	deviceAliases map[string]string
	aliasRecords  []model.Record
	influxClient  writer
	input         chan model.RawMessage
	received      atomic.Uint64
	parsed        atomic.Uint64
	written       atomic.Uint64
	dropped       atomic.Uint64
	failed        atomic.Uint64
}

type Snapshot struct {
	Received uint64 `json:"received"`
	Parsed   uint64 `json:"parsed"`
	Written  uint64 `json:"written"`
	Dropped  uint64 `json:"dropped"`
	Failed   uint64 `json:"failed"`
}

func NewService(cfg config.Config, influxClient writer) *Service {
	normalizedAliases := normalizeDeviceAliases(cfg.DeviceAliases)
	return &Service{
		config:        cfg,
		deviceAliases: normalizedAliases,
		aliasRecords:  buildAliasRecords(normalizedAliases),
		influxClient:  influxClient,
		input:         make(chan model.RawMessage, cfg.App.BufferSize),
	}
}

func (service *Service) Enqueue(message model.RawMessage) {
	service.received.Add(1)

	select {
	case service.input <- message:
	default:
		service.dropped.Add(1)
		slog.Warn("dropping message because buffer is full", "topic", message.Topic)
	}
}

func (service *Service) Run(ctx context.Context) error {
	ticker := time.NewTicker(service.config.App.FlushInterval.Duration)
	defer ticker.Stop()

	batch := append(make([]model.Record, 0, service.config.App.BatchSize+len(service.aliasRecords)), service.aliasRecords...)
	if len(batch) > 0 {
		flushCtx, cancel := context.WithTimeout(ctx, service.config.App.FlushTimeout.Duration)
		err := service.flush(flushCtx, batch)
		cancel()
		if err != nil {
			slog.Error("failed to flush alias metadata to influx; will retry on next interval", "count", len(batch), "error", err)
		} else {
			batch = batch[:0]
		}
	}

	var input <-chan model.RawMessage = service.input

	for {
		if len(batch) >= service.config.App.BatchSize {
			input = nil
		} else {
			input = service.input
		}

		select {
		case <-ctx.Done():
			flushCtx, cancel := context.WithTimeout(context.Background(), service.config.App.FlushTimeout.Duration)
			err := service.flush(flushCtx, batch)
			cancel()
			if err != nil {
				return err
			}

			service.logCounters()
			return nil
		case message := <-input:
			records, err := parser.ParseTasmota(message)
			if err != nil {
				service.failed.Add(1)
				slog.Warn("failed to parse message", "topic", message.Topic, "error", err)
				continue
			}

			service.applyDeviceAliases(records)

			service.parsed.Add(uint64(len(records)))
			batch = append(batch, records...)

			if len(batch) >= service.config.App.BatchSize {
				flushCtx, cancel := context.WithTimeout(ctx, service.config.App.FlushTimeout.Duration)
				err := service.flush(flushCtx, batch)
				cancel()
				if err != nil {
					slog.Error("failed to flush full batch to influx; keeping batch in memory", "count", len(batch), "error", err)
					continue
				}
				batch = batch[:0]
			}
		case <-ticker.C:
			if len(batch) == 0 {
				continue
			}

			flushCtx, cancel := context.WithTimeout(ctx, service.config.App.FlushTimeout.Duration)
			err := service.flush(flushCtx, batch)
			cancel()
			if err != nil {
				slog.Error("failed to flush batch to influx; will retry on next interval", "count", len(batch), "error", err)
				continue
			}
			batch = batch[:0]
		}
	}
}

func (service *Service) flush(ctx context.Context, batch []model.Record) error {
	if len(batch) == 0 {
		return nil
	}

	if err := service.influxClient.Write(ctx, batch); err != nil {
		service.failed.Add(uint64(len(batch)))
		return err
	}

	service.written.Add(uint64(len(batch)))
	slog.Info("flushed records to influx", "count", len(batch))
	return nil
}

func (service *Service) logCounters() {
	slog.Info("service counters",
		"received", service.received.Load(),
		"parsed", service.parsed.Load(),
		"written", service.written.Load(),
		"dropped", service.dropped.Load(),
		"failed", service.failed.Load(),
	)
}

func (service *Service) Snapshot() Snapshot {
	return Snapshot{
		Received: service.received.Load(),
		Parsed:   service.parsed.Load(),
		Written:  service.written.Load(),
		Dropped:  service.dropped.Load(),
		Failed:   service.failed.Load(),
	}
}

func (service *Service) applyDeviceAliases(records []model.Record) {
	if len(service.deviceAliases) == 0 {
		return
	}

	for index := range records {
		device := normalizeDeviceKey(records[index].Tags["device"])
		alias, ok := service.deviceAliases[device]
		if !ok || alias == "" {
			continue
		}
		records[index].Fields["device_alias"] = alias
	}
}

func normalizeDeviceAliases(aliases map[string]string) map[string]string {
	if len(aliases) == 0 {
		return nil
	}

	normalized := make(map[string]string, len(aliases))
	for device, alias := range aliases {
		cleanDevice := normalizeDeviceKey(device)
		cleanAlias := strings.TrimSpace(alias)
		if cleanDevice == "" || cleanAlias == "" {
			continue
		}
		normalized[cleanDevice] = cleanAlias
	}

	if len(normalized) == 0 {
		return nil
	}

	return normalized
}

func normalizeDeviceKey(value string) string {
	normalized := strings.ToLower(strings.TrimSpace(value))
	normalized = strings.ReplaceAll(normalized, "-", "_")
	normalized = strings.ReplaceAll(normalized, " ", "_")
	normalized = invalidDeviceAliasCharacters.ReplaceAllString(normalized, "_")
	normalized = strings.Trim(normalized, "_")
	return normalized
}

func buildAliasRecords(aliases map[string]string) []model.Record {
	if len(aliases) == 0 {
		return nil
	}

	devices := make([]string, 0, len(aliases))
	for device := range aliases {
		devices = append(devices, device)
	}
	sort.Strings(devices)

	timestamp := time.Now().UTC()
	records := make([]model.Record, 0, len(devices))
	for _, device := range devices {
		records = append(records, model.Record{
			Measurement: "tasmota_device_meta",
			Tags: map[string]string{
				"device": device,
				"source": "config",
			},
			Fields: map[string]any{
				"device_alias": aliases[device],
			},
			Timestamp: timestamp,
		})
	}

	return records
}