// Copyright 2016 by Sascha L. Teichmann
// Use of this source code is governed by the MIT license
// that can be found in the LICENSE file.

package common

import (
	"bytes"
	"image"
	"sync"
)

type BaseTileHash struct {
	// XXX: Maybe use some kind of LRU cache instead?
	hashes map[struct{ x, y int }][]byte
	sync.Mutex
}

func NewBaseTileHash() *BaseTileHash {
	return &BaseTileHash{hashes: map[struct{ x, y int }][]byte{}}
}

func (bth *BaseTileHash) Update(x, y int, img image.Image) bool {
	hash := SHA1Image(img)
	key := struct{ x, y int }{x, y}
	bth.Lock()
	defer bth.Unlock()
	if old, found := bth.hashes[key]; found {
		if !bytes.Equal(old, hash) {
			bth.hashes[key] = hash
			return true
		}
		return false
	}
	bth.hashes[key] = hash
	return true
}