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indexer.go
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indexer.go
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package indexer
import (
"context"
"errors"
"math"
"strconv"
"sync"
"time"
"github.com/sschiz/indexer/collecter"
"github.com/sschiz/indexer/ticker"
"go.uber.org/atomic"
)
type Handler func(ticker.Price)
var (
ErrInvalidHandler = errors.New("invalid handler")
ErrInvalidCollecter = errors.New("invalid collecter")
)
// Indexer streaming price indexer.
type Indexer struct {
mu sync.Mutex
avgs map[ticker.Ticker]*avg
handle Handler
interval time.Duration
collecter collecter.Collecter
err error // last error from collecter
started *atomic.Bool
done chan struct{}
}
// NewIndexer returns new Indexer instance.
// Handle is called for each indexed TickerPrice.
// Interval is a period during which indexing will be carried out.
func NewIndexer(clctr collecter.Collecter, handle Handler, interval time.Duration) (*Indexer, error) {
if handle == nil {
return nil, ErrInvalidHandler
}
if clctr == nil {
return nil, ErrInvalidCollecter
}
return &Indexer{
collecter: clctr,
done: make(chan struct{}, 1),
started: atomic.NewBool(false),
avgs: make(map[ticker.Ticker]*avg),
handle: handle,
interval: interval,
}, nil
}
// Stop stops Indexer.
func (i *Indexer) Stop(ctx context.Context) error {
if !i.started.Load() {
return nil
}
select {
case i.done <- struct{}{}:
return nil
case <-ctx.Done():
return ctx.Err()
}
}
// Start starts Indexer.
func (i *Indexer) Start(ctx context.Context) {
if i.started.Load() {
return
}
go i.start(ctx)
i.started.Store(true)
}
// Err returns error
// if any of that returned while collecting.
func (i *Indexer) Err() error {
return i.err
}
func (i *Indexer) start(ctx context.Context) {
t := time.NewTicker(i.interval)
defer t.Stop()
defer i.started.Store(false)
errs := make(chan error)
for {
select {
case t := <-t.C:
go func() {
err := i.index(ctx, t)
if err != nil {
errs <- err
return
}
}()
case <-i.done:
return
case <-ctx.Done():
if i.err == nil {
i.err = ctx.Err()
}
return
case err := <-errs:
i.err = err
return
}
}
}
const bitSize = 64
func (i *Indexer) index(ctx context.Context, t time.Time) error {
i.mu.Lock()
defer i.mu.Unlock()
prices, err := i.collecter.Collect(ctx)
if err != nil {
return err
}
for _, price := range prices {
p, err := strconv.ParseFloat(price.Price, bitSize)
if err != nil {
return err
}
if _, ok := i.avgs[price.Ticker]; !ok {
i.avgs[price.Ticker] = &avg{
num: 1,
sum: p,
}
continue
}
i.avgs[price.Ticker] = i.avgs[price.Ticker].Add(p)
}
for k, v := range i.avgs {
i.handle(ticker.Price{
Ticker: k,
Time: t,
Price: strconv.FormatFloat(v.Average(), 'f', -1, bitSize),
})
}
return nil
}
type avg struct {
sum float64
num float64
}
func (a *avg) Add(b float64) *avg {
a.sum += math.Abs(b)
a.num++
return a
}
func (a avg) Average() float64 {
return a.sum / a.num
}