alexandrajs/amule

/**
 * @author Michał Żaloudik <ponury.kostek@gmail.com>
 */
"use strict";

/**
 *
 * @constructor
 */
class Layer {
    constructor() {
        /**
         *
         * @type {Layer|null}
         */
        this.next = null;
        this.clearStats();
    }

    _next(err, name, args, callback) {
        const next = this.next;
        if (next !== null) {
            return next[name].apply(next, args.concat(callback));
        }
        callback(err, null);
    }

    /**
     *
     * @param {string} key
     * @param {string} field
     * @param {function} callback
     */
    has(key, field, callback) {
        this._has(key, field, callback);
    }

    /**
     *
     * @param {string} key
     * @param {string} field
     * @param {function} callback
     */
    get(key, field, callback) {
        this._get(key, field, (err, value) => {
            if (!err && value !== null) {
                this.stats.hits += 1;
                return callback(null, value);
            }
            this.stats.misses += 1;
            this._next(err, "get", [
                key,
                field
            ], (err, value) => {
                if (err) {
                    return callback(err, value);
                }
                this._set(key, field, value, () => {
                    callback(null, value);
                });
            });
        });
    }

    /**
     *
     * @param {string} key
     * @param {string} field
     * @param {*} value
     * @param {function} callback
     */
    set(key, field, value, callback) {
        this._set(key, field, value, (err) => {
            this._next(err, "set", [
                key,
                field,
                value
            ], callback);
        });
    }

    /**
     *
     * @param {string} key
     * @param {string} field
     * @param {function} callback
     */
    delete(key, field, callback) {
        this._delete(key, field, (err) => {
            this._next(err, "delete", [
                key,
                field
            ], callback);
        });
    }

    /**
     * @param {function} callback
     */
    clear(callback) {
        this._clear((err) => {
            this._next(err, "clear", [], callback);
        });
    }

    /**
     * @param [clear]
     * @returns {{hits: number, misses: number}}
     */
    getStats(clear) {
        const stats = this.stats;
        stats.ratio = stats.hits / (stats.misses + stats.hits);
        if (clear) {
            this.clearStats();
        }
        return stats;
    }

    /**
     *
     */
    clearStats() {
        this.stats = {
            hits: 0,
            misses: 0,
            ratio: 0
        };
    }
}

module.exports = Layer;