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
	snapshots     map[string]*deviceSnapshot
	dirtyDevices  map[string]struct{}
	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"`
}

type deviceSnapshot struct {
	Device     string
	Alias      string
	LastSeen   time.Time
	StateSeen  time.Time
	SensorSeen time.Time
	Fields     map[string]any
}

func NewService(cfg config.Config, influxClient writer) *Service {
	normalizedAliases := normalizeDeviceAliases(cfg.DeviceAliases)
	return &Service{
		config:        cfg,
		deviceAliases: normalizedAliases,
		aliasRecords:  buildAliasRecords(normalizedAliases),
		snapshots:     make(map[string]*deviceSnapshot),
		dirtyDevices:  make(map[string]struct{}),
		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.flushPending(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.updateDeviceSnapshots(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.flushPending(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 && len(service.dirtyDevices) == 0 {
				continue
			}

			flushCtx, cancel := context.WithTimeout(ctx, service.config.App.FlushTimeout.Duration)
			err := service.flushPending(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) flushPending(ctx context.Context, batch []model.Record) error {
	flushBatch := append([]model.Record(nil), batch...)
	flushBatch = append(flushBatch, service.buildSnapshotRecords()...)

	if err := service.flush(ctx, flushBatch); err != nil {
		return err
	}

	service.clearDirtyDevices()
	return nil
}

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 (service *Service) updateDeviceSnapshots(records []model.Record) {
	for _, record := range records {
		device := normalizeDeviceKey(record.Tags["device"])
		if device == "" {
			continue
		}

		snapshot, ok := service.snapshots[device]
		if !ok {
			snapshot = &deviceSnapshot{
				Device: device,
				Fields: make(map[string]any),
			}
			service.snapshots[device] = snapshot
		}

		if record.Timestamp.After(snapshot.LastSeen) {
			snapshot.LastSeen = record.Timestamp
		}

		if alias, ok := record.Fields["device_alias"].(string); ok && strings.TrimSpace(alias) != "" {
			snapshot.Alias = alias
			snapshot.Fields["device_alias"] = alias
		}

		switch record.Tags["message_type"] {
		case "state":
			if record.Timestamp.After(snapshot.StateSeen) {
				snapshot.StateSeen = record.Timestamp
				copySnapshotFields(snapshot.Fields, record.Fields, "device_alias", "wifi_signal", "uptime_sec")
			}
		case "sensor":
			if record.Timestamp.After(snapshot.SensorSeen) {
				snapshot.SensorSeen = record.Timestamp
				copySnapshotFields(snapshot.Fields, record.Fields, "device_alias", "energy_power", "energy_today", "energy_total")
			}
		}

		service.dirtyDevices[device] = struct{}{}
	}
}

func copySnapshotFields(target map[string]any, source map[string]any, keys ...string) {
	for _, key := range keys {
		value, ok := source[key]
		if !ok {
			continue
		}
		target[key] = value
	}
}

func (service *Service) buildSnapshotRecords() []model.Record {
	if len(service.dirtyDevices) == 0 {
		return nil
	}

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

	records := make([]model.Record, 0, len(devices))
	for _, device := range devices {
		snapshot := service.snapshots[device]
		if snapshot == nil || snapshot.LastSeen.IsZero() {
			continue
		}

		fields := make(map[string]any, len(snapshot.Fields)+2)
		for key, value := range snapshot.Fields {
			fields[key] = value
		}
		if !snapshot.StateSeen.IsZero() {
			fields["state_last_seen_unix"] = snapshot.StateSeen.Unix()
		}
		if !snapshot.SensorSeen.IsZero() {
			fields["sensor_last_seen_unix"] = snapshot.SensorSeen.Unix()
		}

		records = append(records, model.Record{
			Measurement: "tasmota_device_snapshot",
			Tags: map[string]string{
				"device": device,
				"source": "derived",
			},
			Fields:    fields,
			Timestamp: snapshot.LastSeen,
		})
	}

	return records
}

func (service *Service) clearDirtyDevices() {
	for device := range service.dirtyDevices {
		delete(service.dirtyDevices, device)
	}
}

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
}