package speedport

import (
	"log/slog"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/prometheus/client_golang/prometheus"
)

const namespace = "speedport"

// Exporter collects Speedport metrics and exposes them as Prometheus metrics.
type Exporter struct {
	client *Client
	logger *slog.Logger

	mu            sync.Mutex
	scrapeErrors  prometheus.Counter
	scrapeDuration prometheus.Gauge
	up            prometheus.Gauge

	// DSL metrics
	dslUpRate      *prometheus.GaugeVec
	dslDownRate    *prometheus.GaugeVec
	dslSNR         *prometheus.GaugeVec
	dslAttenuation *prometheus.GaugeVec
	dslPower       *prometheus.GaugeVec
	dslErrors      *prometheus.GaugeVec
	dslUptime      prometheus.Gauge

	// Connection metrics
	onlineStatus prometheus.Gauge

	// Generic metric for all raw values
	rawValues *prometheus.GaugeVec
	rawInfo   *prometheus.GaugeVec
}

// NewExporter creates a new Speedport Prometheus exporter.
func NewExporter(client *Client, logger *slog.Logger) *Exporter {
	return &Exporter{
		client: client,
		logger: logger,

		scrapeErrors: prometheus.NewCounter(prometheus.CounterOpts{
			Namespace: namespace,
			Name:      "scrape_errors_total",
			Help:      "Total number of scrape errors.",
		}),
		scrapeDuration: prometheus.NewGauge(prometheus.GaugeOpts{
			Namespace: namespace,
			Name:      "scrape_duration_seconds",
			Help:      "Duration of the last scrape in seconds.",
		}),
		up: prometheus.NewGauge(prometheus.GaugeOpts{
			Namespace: namespace,
			Name:      "up",
			Help:      "Whether the Speedport is reachable (1=up, 0=down).",
		}),

		dslUpRate: prometheus.NewGaugeVec(prometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: "dsl",
			Name:      "rate_kbps",
			Help:      "DSL line rate in kbit/s.",
		}, []string{"direction", "type"}),

		dslSNR: prometheus.NewGaugeVec(prometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: "dsl",
			Name:      "snr_db",
			Help:      "DSL signal-to-noise ratio margin in dB.",
		}, []string{"direction"}),

		dslAttenuation: prometheus.NewGaugeVec(prometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: "dsl",
			Name:      "attenuation_db",
			Help:      "DSL line attenuation in dB.",
		}, []string{"direction"}),

		dslPower: prometheus.NewGaugeVec(prometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: "dsl",
			Name:      "power_dbm",
			Help:      "DSL signal power in dBm.",
		}, []string{"direction"}),

		dslErrors: prometheus.NewGaugeVec(prometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: "dsl",
			Name:      "errors_total",
			Help:      "DSL error counters (CRC, FEC, HEC).",
		}, []string{"direction", "type"}),

		dslUptime: prometheus.NewGauge(prometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: "dsl",
			Name:      "uptime_seconds",
			Help:      "Internet connection uptime in seconds.",
		}),

		onlineStatus: prometheus.NewGauge(prometheus.GaugeOpts{
			Namespace: namespace,
			Name:      "online_status",
			Help:      "Online status (1=online, 0=offline).",
		}),

		rawValues: prometheus.NewGaugeVec(prometheus.GaugeOpts{
			Namespace: namespace,
			Name:      "raw_value",
			Help:      "Raw numeric values from the router status page.",
		}, []string{"varid", "vartype"}),

		rawInfo: prometheus.NewGaugeVec(prometheus.GaugeOpts{
			Namespace: namespace,
			Name:      "info",
			Help:      "Router information as labels (value is always 1).",
		}, []string{"device_name", "firmware_version", "serial_number", "dsl_mode"}),
	}
}

// Describe implements prometheus.Collector.
func (e *Exporter) Describe(ch chan<- *prometheus.Desc) {
	e.scrapeErrors.Describe(ch)
	e.scrapeDuration.Describe(ch)
	e.up.Describe(ch)
	e.dslUpRate.Describe(ch)
	e.dslSNR.Describe(ch)
	e.dslAttenuation.Describe(ch)
	e.dslPower.Describe(ch)
	e.dslErrors.Describe(ch)
	e.dslUptime.Describe(ch)
	e.onlineStatus.Describe(ch)
	e.rawValues.Describe(ch)
	e.rawInfo.Describe(ch)
}

// Collect implements prometheus.Collector.
func (e *Exporter) Collect(ch chan<- prometheus.Metric) {
	e.mu.Lock()
	defer e.mu.Unlock()

	start := time.Now()

	// Reset vector metrics to avoid stale entries
	e.dslUpRate.Reset()
	e.dslSNR.Reset()
	e.dslAttenuation.Reset()
	e.dslPower.Reset()
	e.dslErrors.Reset()
	e.rawValues.Reset()
	e.rawInfo.Reset()

	status, err := e.client.GetStatus()
	if err != nil {
		e.logger.Error("failed to fetch status", "error", err)
		e.scrapeErrors.Inc()
		e.up.Set(0)
	} else {
		e.up.Set(1)
		e.processStatus(status)
	}

	e.scrapeDuration.Set(time.Since(start).Seconds())

	// Collect all metrics
	e.scrapeErrors.Collect(ch)
	e.scrapeDuration.Collect(ch)
	e.up.Collect(ch)
	e.dslUpRate.Collect(ch)
	e.dslSNR.Collect(ch)
	e.dslAttenuation.Collect(ch)
	e.dslPower.Collect(ch)
	e.dslErrors.Collect(ch)
	e.dslUptime.Collect(ch)
	e.onlineStatus.Collect(ch)
	e.rawValues.Collect(ch)
	e.rawInfo.Collect(ch)
}

// processStatus extracts metrics from status data.
func (e *Exporter) processStatus(sd *StatusData) {
	dsl := ExtractDSLInfo(sd)

	// Online status
	if strings.EqualFold(dsl.OnlineStatus, "online") {
		e.onlineStatus.Set(1)
	} else {
		e.onlineStatus.Set(0)
	}

	// DSL rates
	if dsl.UpstreamRate > 0 {
		e.dslUpRate.WithLabelValues("upstream", "current").Set(dsl.UpstreamRate)
	}
	if dsl.DownstreamRate > 0 {
		e.dslUpRate.WithLabelValues("downstream", "current").Set(dsl.DownstreamRate)
	}
	if dsl.UpstreamMaxRate > 0 {
		e.dslUpRate.WithLabelValues("upstream", "max").Set(dsl.UpstreamMaxRate)
	}
	if dsl.DownstreamMaxRate > 0 {
		e.dslUpRate.WithLabelValues("downstream", "max").Set(dsl.DownstreamMaxRate)
	}

	// SNR
	if dsl.UpstreamNoise > 0 {
		e.dslSNR.WithLabelValues("upstream").Set(dsl.UpstreamNoise)
	}
	if dsl.DownstreamNoise > 0 {
		e.dslSNR.WithLabelValues("downstream").Set(dsl.DownstreamNoise)
	}

	// Attenuation
	if dsl.UpstreamAttn > 0 {
		e.dslAttenuation.WithLabelValues("upstream").Set(dsl.UpstreamAttn)
	}
	if dsl.DownstreamAttn > 0 {
		e.dslAttenuation.WithLabelValues("downstream").Set(dsl.DownstreamAttn)
	}

	// Power
	e.dslPower.WithLabelValues("upstream").Set(dsl.UpstreamPower)
	e.dslPower.WithLabelValues("downstream").Set(dsl.DownstreamPower)

	// Error counters
	e.dslErrors.WithLabelValues("upstream", "crc").Set(dsl.UpstreamCRC)
	e.dslErrors.WithLabelValues("downstream", "crc").Set(dsl.DownstreamCRC)
	e.dslErrors.WithLabelValues("upstream", "fec").Set(dsl.UpstreamFEC)
	e.dslErrors.WithLabelValues("downstream", "fec").Set(dsl.DownstreamFEC)
	e.dslErrors.WithLabelValues("upstream", "hec").Set(dsl.UpstreamHEC)
	e.dslErrors.WithLabelValues("downstream", "hec").Set(dsl.DownstreamHEC)

	// Uptime
	if dsl.Uptime > 0 {
		e.dslUptime.Set(dsl.Uptime)
	}

	// Info metric
	e.rawInfo.WithLabelValues(
		sd.Get("device_name"),
		sd.Get("firmware_version"),
		sd.Get("serial_number"),
		dsl.DSLOperatingMode,
	).Set(1)

	// Export all numeric raw values
	for _, entry := range sd.Raw {
		if v, err := strconv.ParseFloat(strings.TrimSpace(entry.VarValue), 64); err == nil {
			e.rawValues.WithLabelValues(entry.VarID, entry.VarType).Set(v)
		}
	}
}