// 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 btPos struct {
	x int
	y int
}

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

func NewBaseTileHash() *BaseTileHash {
	return &BaseTileHash{hashes: map[btPos][]byte{}}
}

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