// Copyright (c) 2012, Matt T. Proud
// All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// gauge.go provides a scalar metric that one can monitor.  It is useful for
// certain cases, such as instantaneous temperature.

package metrics

import (
	"fmt"
	"sync"
)

// A gauge metric merely provides an instantaneous representation of a scalar
// value or an accumulation.  For instance, if one wants to expose the current
// temperature or the hitherto bandwidth used, this would be the metric for such
// circumstances.
type GaugeMetric struct {
	value float64
	mutex sync.RWMutex
}

func (metric *GaugeMetric) Humanize() string {
	formatString := "[GaugeMetric; value=%f]"

	metric.mutex.RLock()
	defer metric.mutex.RUnlock()

	return fmt.Sprintf(formatString, metric.value)
}

func (metric *GaugeMetric) Set(value float64) float64 {
	metric.mutex.Lock()
	defer metric.mutex.Unlock()

	metric.value = value

	return metric.value
}

func (metric *GaugeMetric) IncrementBy(value float64) float64 {
	metric.mutex.Lock()
	defer metric.mutex.Unlock()

	metric.value += value

	return metric.value
}

func (metric *GaugeMetric) Increment() float64 {
	return metric.IncrementBy(1)
}

func (metric *GaugeMetric) DecrementBy(value float64) float64 {
	metric.mutex.Lock()
	defer metric.mutex.Unlock()

	metric.value -= value

	return metric.value
}

func (metric *GaugeMetric) Decrement() float64 {
	return metric.DecrementBy(1)
}

func (metric *GaugeMetric) Get() float64 {
	metric.mutex.RLock()
	defer metric.mutex.RUnlock()

	return metric.value
}

func (metric *GaugeMetric) Marshallable() map[string]interface{} {
	metric.mutex.RLock()
	defer metric.mutex.RUnlock()

	v := make(map[string]interface{}, 2)

	v["value"] = metric.value
	v["type"] = "gauge"

	return v
}