package stats

import (
	"encoding/json"
	"fmt"
	"sync"
	"time"
)

type timeseries struct {
	sync.Mutex
	now      time.Time
	size     int
	interval time.Duration
	total    metric
	samples  []metric
}

func (ts *timeseries) Reset() {
	ts.total.Reset()
	for _, s := range ts.samples {
		s.Reset()
	}
}

func (ts *timeseries) roll() {
	t := time.Now()
	roll := int((t.Round(ts.interval).Sub(ts.now.Round(ts.interval))) / ts.interval)
	ts.now = t
	n := len(ts.samples)
	if roll <= 0 {
		return
	}
	if roll >= len(ts.samples) {
		ts.Reset()
	} else {
		for i := 0; i < roll; i++ {
			tmp := ts.samples[n-1]
			for j := n - 1; j > 0; j-- {
				ts.samples[j] = ts.samples[j-1]
			}
			ts.samples[0] = tmp
			ts.samples[0].Reset()
		}
		ts.total.Aggregate(roll, ts.samples)
	}
}

func (ts *timeseries) Add(n float64) {
	ts.Lock()
	defer ts.Unlock()
	ts.roll()
	ts.total.Add(n)
	ts.samples[0].Add(n)
}

func (ts *timeseries) MarshalJSON() ([]byte, error) {
	ts.Lock()
	defer ts.Unlock()
	ts.roll()
	return json.Marshal(struct {
		Interval float64  `json:"interval"`
		Total    Metric   `json:"total"`
		Samples  []metric `json:"samples"`
	}{float64(ts.interval) / float64(time.Second), ts.total, ts.samples})
}

func (ts *timeseries) String() string {
	ts.Lock()
	defer ts.Unlock()
	ts.roll()
	return ts.total.String()
}

func newTimeseries(builder func() metric, frame string) *timeseries {
	var (
		totalNum, intervalNum   int
		totalUnit, intervalUnit rune
	)
	units := map[rune]time.Duration{
		's': time.Second,
		'm': time.Minute,
		'h': time.Hour,
		'd': time.Hour * 24,
		'w': time.Hour * 24 * 7,
		'M': time.Hour * 24 * 30,
		'y': time.Hour * 24 * 365,
	}
	fmt.Sscanf(frame, "%d%c%d%c", &totalNum, &totalUnit, &intervalNum, &intervalUnit)
	interval := units[intervalUnit] * time.Duration(intervalNum)
	if interval == 0 {
		interval = time.Minute
	}
	totalDuration := units[totalUnit] * time.Duration(totalNum)
	if totalDuration == 0 {
		totalDuration = interval * 15
	}
	n := int(totalDuration / interval)
	samples := make([]metric, n, n)
	for i := 0; i < n; i++ {
		samples[i] = builder()
	}
	totalMetric := builder()
	return &timeseries{interval: interval, total: totalMetric, samples: samples}
}