package metrics

import (
	"github.com/prometheus/client_golang/prometheus"

	controllerExtraction "proxy-pool/internal/controller/extraction"
)

// ExtractionCollector exposes bounded Distribution business metrics. Client,
// proxy, upstream, filter, request, and error values are never labels.
type ExtractionCollector struct {
	requests  *prometheus.CounterVec
	requested prometheus.Counter
	returned  prometheus.Counter
}

var _ controllerExtraction.MetricsObserver = (*ExtractionCollector)(nil)

func NewExtractionCollector(registerer prometheus.Registerer) (*ExtractionCollector, error) {
	if registerer == nil {
		return nil, ErrInvalidDependencies
	}
	requests, err := registerCounterVec(registerer, prometheus.NewCounterVec(prometheus.CounterOpts{
		Namespace: "proxy_pool", Subsystem: "controller", Name: "extraction_requests_total",
		Help: "Number of completed Distribution extraction requests by fixed result.",
	}, []string{"result"}))
	if err != nil {
		return nil, err
	}
	requested, err := registerCounter(registerer, prometheus.NewCounter(prometheus.CounterOpts{
		Namespace: "proxy_pool", Subsystem: "controller", Name: "extraction_requested_proxies_total",
		Help: "Number of proxies requested from completed Distribution extraction requests.",
	}))
	if err != nil {
		return nil, err
	}
	returned, err := registerCounter(registerer, prometheus.NewCounter(prometheus.CounterOpts{
		Namespace: "proxy_pool", Subsystem: "controller", Name: "extraction_returned_proxies_total",
		Help: "Number of proxies returned in Distribution extraction responses, including idempotent replays.",
	}))
	if err != nil {
		return nil, err
	}
	return &ExtractionCollector{requests: requests, requested: requested, returned: returned}, nil
}

func (collector *ExtractionCollector) ObserveExtraction(event controllerExtraction.MetricsEvent) {
	if collector == nil || collector.requests == nil || !validExtractionMetricResult(event.Result) {
		return
	}
	collector.requests.WithLabelValues(string(event.Result)).Inc()
	if event.Requested > 0 && collector.requested != nil {
		collector.requested.Add(float64(event.Requested))
	}
	if event.Returned > 0 && collector.returned != nil {
		collector.returned.Add(float64(event.Returned))
	}
}

func validExtractionMetricResult(result controllerExtraction.MetricResult) bool {
	switch result {
	case controllerExtraction.MetricComplete, controllerExtraction.MetricPartial, controllerExtraction.MetricEmpty,
		controllerExtraction.MetricInsufficient, controllerExtraction.MetricIdempotencyConflict,
		controllerExtraction.MetricRateLimited, controllerExtraction.MetricUnavailable,
		controllerExtraction.MetricInvalid, controllerExtraction.MetricError:
		return true
	default:
		return false
	}
}