package util

import (
	"time"
	"unsafe"

	"github.com/prometheus/common/model"
	"github.com/prometheus/prometheus/model/labels"
)

// ModelLabelSetToMap convert a model.LabelSet to a map[string]string
func ModelLabelSetToMap(m model.LabelSet) map[string]string {
	if len(m) == 0 {
		return map[string]string{}
	}
	return *(*map[string]string)(unsafe.Pointer(&m))
}

// MapToModelLabelSet converts a map into a model.LabelSet
func MapToModelLabelSet(m map[string]string) model.LabelSet {
	if len(m) == 0 {
		return model.LabelSet{}
	}
	return *(*map[model.LabelName]model.LabelValue)(unsafe.Pointer(&m))
}

// RoundToMilliseconds returns milliseconds precision time from nanoseconds.
// from will be rounded down to the nearest milliseconds while through is rounded up.
func RoundToMilliseconds(from, through time.Time) (model.Time, model.Time) {
	fromMs := from.UnixNano() / int64(time.Millisecond)
	throughMs := through.UnixNano() / int64(time.Millisecond)

	// add a millisecond to the through time if the nanosecond offset within the second is not a multiple of milliseconds
	if int64(through.Nanosecond())%int64(time.Millisecond) != 0 {
		throughMs++
	}

	return model.Time(fromMs), model.Time(throughMs)
}

// LabelsToMetric converts a Labels to Metric
// Don't do this on any performance sensitive paths.
func LabelsToMetric(ls labels.Labels) model.Metric {
	m := make(model.Metric, len(ls))
	for _, l := range ls {
		m[model.LabelName(l.Name)] = model.LabelValue(l.Value)
	}
	return m
}