package client

import (
	"math"
	_ "net/http/pprof"
	"sync/atomic"
	"unsafe"

	"github.com/prometheus/client_golang/prometheus"
	"repositories.action2quare.com/ayo/gocommon/metric"
)

type metricDesc struct {
	*prometheus.Desc
	val       *uint64
	valueType prometheus.ValueType
}

type exporterForPrometheus struct {
	metricPtr unsafe.Pointer // []metricDesc
}

func newExporterForPrometheus() *exporterForPrometheus {
	return &exporterForPrometheus{
		metricPtr: unsafe.Pointer(new([]metricDesc)),
	}
}

type metricValueAccessor struct {
	ptr *uint64
}

func (va *metricValueAccessor) set(val float64) {
	atomic.StoreUint64(va.ptr, math.Float64bits(val))
}

func convertValueType(in metric.MetricType) prometheus.ValueType {
	switch in {
	case metric.MetricCounter:
		return prometheus.CounterValue

	case metric.MetricGuage:
		return prometheus.GaugeValue
	}

	return prometheus.UntypedValue
}

func (e *exporterForPrometheus) registMetric(namespace string, desc metric.MetricDescription) metricValueAccessor {
	ptr := atomic.LoadPointer(&e.metricPtr)
	container := *(*[]metricDesc)(ptr)

	newcont := make([]metricDesc, len(container)+1)
	copy(newcont, container)

	newval := new(uint64)
	newcont[len(container)] = metricDesc{
		Desc:      prometheus.NewDesc(prometheus.BuildFQName(namespace, "", desc.Name), desc.Help, nil, desc.ConstLabels),
		val:       newval,
		valueType: convertValueType(desc.Type),
	}

	atomic.StorePointer(&e.metricPtr, unsafe.Pointer(&newcont))
	return metricValueAccessor{
		ptr: newval,
	}
}

func (e *exporterForPrometheus) Describe(ch chan<- *prometheus.Desc) {
	ptr := atomic.LoadPointer(&e.metricPtr)
	container := *(*[]metricDesc)(ptr)

	for _, v := range container {
		ch <- v.Desc
	}
}

func (e *exporterForPrometheus) Collect(ch chan<- prometheus.Metric) {
	ptr := atomic.LoadPointer(&e.metricPtr)
	container := *(*[]metricDesc)(ptr)

	for _, v := range container {
		ch <- prometheus.MustNewConstMetric(v.Desc, v.valueType, math.Float64frombits(atomic.LoadUint64(v.val)))
	}
}