nakedobjects.spa/lib/app/simple-lru-cache.js

Single Page Application client for a Naked Objects application.

var LruNode = (function () {
    function LruNode(key, value) {
        this.key = key;
        this.value = value;
        this.next = null;
        this.previous = null;
    }
    return LruNode;
}());
var SimpleLruCache = (function () {
    function SimpleLruCache(depth) {
        this.depth = depth;
        this.cache = {};
        this.count = 0;
        this.head = null;
        this.tail = null;
    }
    SimpleLruCache.prototype.unlinkNode = function (node) {
        var nodePrevious = node.previous;
        var nodeNext = node.next;
        if (nodePrevious) {
            nodePrevious.next = nodeNext;
        }
        else {
            // was head
            this.head = nodeNext;
        }
        if (nodeNext) {
            nodeNext.previous = nodePrevious;
        }
        else {
            //was tail
            this.tail = nodePrevious;
        }
        this.count--;
    };
    SimpleLruCache.prototype.moveNodeToHead = function (node) {
        var existingHead = this.head;
        node.previous = null;
        node.next = existingHead;
        if (existingHead) {
            existingHead.previous = node;
        }
        else {
            // no existing head so this is also tail
            this.tail = node;
        }
        this.head = node;
        this.count++;
    };
    SimpleLruCache.prototype.add = function (key, value) {
        if (this.cache[key]) {
            this.updateExistingEntry(key, value);
        }
        else {
            this.addNewEntry(key, value);
        }
    };
    SimpleLruCache.prototype.remove = function (key) {
        var node = this.cache[key];
        if (node) {
            this.unlinkNode(node);
            delete this.cache[key];
        }
    };
    SimpleLruCache.prototype.removeAll = function () {
        this.head = this.tail = null;
        this.cache = {};
        this.count = 0;
    };
    SimpleLruCache.prototype.getNode = function (key) {
        var node = this.cache[key];
        if (node) {
            this.unlinkNode(node);
            this.moveNodeToHead(node);
        }
        return node;
    };
    SimpleLruCache.prototype.get = function (key) {
        var node = this.getNode(key);
        return node ? node.value : null;
    };
    SimpleLruCache.prototype.updateExistingEntry = function (key, value) {
        var node = this.getNode(key);
        node.value = value;
    };
    SimpleLruCache.prototype.addNewEntry = function (key, value) {
        var newNode = new LruNode(key, value);
        this.cache[key] = newNode;
        this.moveNodeToHead(newNode);
        this.trimCache();
    };
    SimpleLruCache.prototype.trimCache = function () {
        while (this.count > this.depth) {
            var tail = this.tail;
            if (tail) {
                this.unlinkNode(tail);
                delete this.cache[tail.key];
            }
        }
    };
    return SimpleLruCache;
}());
export { SimpleLruCache };
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