mtsatellite/cmd/mtredisalize/changetracker.go

package main

import (
	"encoding/json"
	"log"
	"net/http"
	"sync"

	"bytes"

	"bitbucket.org/s_l_teichmann/mtredisalize/common"
)

type quantizedXZ struct {
	X, Z int16
}

type ChangeTracker struct {
	changes map[quantizedXZ]bool
	mutex   sync.Mutex
}

func NewChangeTracker() *ChangeTracker {
	return &ChangeTracker{changes: make(map[quantizedXZ]bool)}
}

func (ct *ChangeTracker) BlockChanged(key []byte) {
	var err error
	var coord common.Coord
	if coord, err = common.DecodeStringBytesToCoord(key); err != nil {
		log.Printf("decoding key failed: %s", err)
		return
	}
	ct.mutex.Lock()
	ct.changes[quantizedXZ{X: coord.X / 16, Z: coord.Z / 16}] = true
	ct.mutex.Unlock()
}

func (ct *ChangeTracker) FlushChanges(url string) (err error) {
	log.Println("change flush triggered")
	var oldChanges map[quantizedXZ]bool
	var sendNotification bool
	ct.mutex.Lock()
	oldChanges = ct.changes
	if len(oldChanges) > 0 {
		sendNotification = true
		ct.changes = make(map[quantizedXZ]bool)
	}
	ct.mutex.Unlock()
	if !sendNotification {
		return
	}
	go func() {
		changes := make([]quantizedXZ, len(oldChanges))
		i := 0
		for change, _ := range oldChanges {
			changes[i] = change
			i++
		}
		var err error
		var encoded []byte
		if encoded, err = json.Marshal(changes); err != nil {
			log.Printf("WARN: encode changes to JSON failed: %s", err)
			return
		}
		var buf bytes.Buffer
		buf.Write(encoded)
		if _, err = http.Post(url, "application/json", &buf); err != nil {
			log.Printf("WARN: posting changes to %s failed: %s", url, err)
		}
	}()
	return
}