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/**
 * @module zrender/core/util
 */
define(function(require) {
    var Gradient = require('../graphic/Gradient');
    // 用于处理merge时无法遍历Date等对象的问题
    var BUILTIN_OBJECT = {
        '[object Function]': 1,
        '[object RegExp]': 1,
        '[object Date]': 1,
        '[object Error]': 1,
        '[object CanvasGradient]': 1
    };

    var objToString = Object.prototype.toString;

    var arrayProto = Array.prototype;
    var nativeForEach = arrayProto.forEach;
    var nativeFilter = arrayProto.filter;
    var nativeSlice = arrayProto.slice;
    var nativeMap = arrayProto.map;
    var nativeReduce = arrayProto.reduce;

    /**
     * @param {*} source
     * @return {*} 拷贝后的新对象
     */
    function clone(source) {
        if (typeof source == 'object' && source !== null) {
            var result = source;
            if (source instanceof Array) {
                result = [];
                for (var i = 0, len = source.length; i < len; i++) {
                    result[i] = clone(source[i]);
                }
            }
            else if (
                !isBuildInObject(source)
                // 是否为 dom 对象
                && !isDom(source)
            ) {
                result = {};
                for (var key in source) {
                    if (source.hasOwnProperty(key)) {
                        result[key] = clone(source[key]);
                    }
                }
            }

            return result;
        }

        return source;
    }

    /**
     * @memberOf module:zrender/core/util
     * @param {*} target
     * @param {*} source
     * @param {boolean} [overwrite=false]
     */
    function merge(target, source, overwrite) {
        // We should escapse that source is string
        // and enter for ... in ...
        if (!isObject(source) || !isObject(target)) {
            return overwrite ? clone(source) : target;
        }

        for (var key in source) {
            if (source.hasOwnProperty(key)) {
                var targetProp = target[key];
                var sourceProp = source[key];

                if (isObject(sourceProp)
                    && isObject(targetProp)
                    && !isArray(sourceProp)
                    && !isArray(targetProp)
                    && !isDom(sourceProp)
                    && !isDom(targetProp)
                    && !isBuildInObject(sourceProp)
                    && !isBuildInObject(targetProp)
                ) {
                    // 如果需要递归覆盖，就递归调用merge
                    merge(targetProp, sourceProp, overwrite);
                }
                else if (overwrite || !(key in target)) {
                    // 否则只处理overwrite为true，或者在目标对象中没有此属性的情况
                    // NOTE，在 target[key] 不存在的时候也是直接覆盖
                    target[key] = clone(source[key], true);
                }
            }
        }

        return target;
    }

    /**
     * @param {Array} targetAndSources The first item is target, and the rests are source.
     * @param {boolean} [overwrite=false]
     * @return {*} target
     */
    function mergeAll(targetAndSources, overwrite) {
        var result = targetAndSources[0];
        for (var i = 1, len = targetAndSources.length; i < len; i++) {
            result = merge(result, targetAndSources[i], overwrite);
        }
        return result;
    }

    /**
     * @param {*} target
     * @param {*} source
     * @memberOf module:zrender/core/util
     */
    function extend(target, source) {
        for (var key in source) {
            if (source.hasOwnProperty(key)) {
                target[key] = source[key];
            }
        }
        return target;
    }

    /**
     * @param {*} target
     * @param {*} source
     * @param {boolen} [overlay=false]
     * @memberOf module:zrender/core/util
     */
    function defaults(target, source, overlay) {
        for (var key in source) {
            if (source.hasOwnProperty(key)
                && (overlay ? source[key] != null : target[key] == null)
            ) {
                target[key] = source[key];
            }
        }
        return target;
    }

    function createCanvas() {
        return document.createElement('canvas');
    }
    // FIXME
    var _ctx;
    function getContext() {
        if (!_ctx) {
            // Use util.createCanvas instead of createCanvas
            // because createCanvas may be overwritten in different environment
            _ctx = util.createCanvas().getContext('2d');
        }
        return _ctx;
    }

    /**
     * 查询数组中元素的index
     * @memberOf module:zrender/core/util
     */
    function indexOf(array, value) {
        if (array) {
            if (array.indexOf) {
                return array.indexOf(value);
            }
            for (var i = 0, len = array.length; i < len; i++) {
                if (array[i] === value) {
                    return i;
                }
            }
        }
        return -1;
    }

    /**
     * 构造类继承关系
     *
     * @memberOf module:zrender/core/util
     * @param {Function} clazz 源类
     * @param {Function} baseClazz 基类
     */
    function inherits(clazz, baseClazz) {
        var clazzPrototype = clazz.prototype;
        function F() {}
        F.prototype = baseClazz.prototype;
        clazz.prototype = new F();

        for (var prop in clazzPrototype) {
            clazz.prototype[prop] = clazzPrototype[prop];
        }
        clazz.prototype.constructor = clazz;
        clazz.superClass = baseClazz;
    }

    /**
     * @memberOf module:zrender/core/util
     * @param {Object|Function} target
     * @param {Object|Function} sorce
     * @param {boolean} overlay
     */
    function mixin(target, source, overlay) {
        target = 'prototype' in target ? target.prototype : target;
        source = 'prototype' in source ? source.prototype : source;

        defaults(target, source, overlay);
    }

    /**
     * @param {Array|TypedArray} data
     */
    function isArrayLike(data) {
        if (! data) {
            return;
        }
        if (typeof data == 'string') {
            return false;
        }
        return typeof data.length == 'number';
    }

    /**
     * 数组或对象遍历
     * @memberOf module:zrender/core/util
     * @param {Object|Array} obj
     * @param {Function} cb
     * @param {*} [context]
     */
    function each(obj, cb, context) {
        if (!(obj && cb)) {
            return;
        }
        if (obj.forEach && obj.forEach === nativeForEach) {
            obj.forEach(cb, context);
        }
        else if (obj.length === +obj.length) {
            for (var i = 0, len = obj.length; i < len; i++) {
                cb.call(context, obj[i], i, obj);
            }
        }
        else {
            for (var key in obj) {
                if (obj.hasOwnProperty(key)) {
                    cb.call(context, obj[key], key, obj);
                }
            }
        }
    }

    /**
     * 数组映射
     * @memberOf module:zrender/core/util
     * @param {Array} obj
     * @param {Function} cb
     * @param {*} [context]
     * @return {Array}
     */
    function map(obj, cb, context) {
        if (!(obj && cb)) {
            return;
        }
        if (obj.map && obj.map === nativeMap) {
            return obj.map(cb, context);
        }
        else {
            var result = [];
            for (var i = 0, len = obj.length; i < len; i++) {
                result.push(cb.call(context, obj[i], i, obj));
            }
            return result;
        }
    }

    /**
     * @memberOf module:zrender/core/util
     * @param {Array} obj
     * @param {Function} cb
     * @param {Object} [memo]
     * @param {*} [context]
     * @return {Array}
     */
    function reduce(obj, cb, memo, context) {
        if (!(obj && cb)) {
            return;
        }
        if (obj.reduce && obj.reduce === nativeReduce) {
            return obj.reduce(cb, memo, context);
        }
        else {
            for (var i = 0, len = obj.length; i < len; i++) {
                memo = cb.call(context, memo, obj[i], i, obj);
            }
            return memo;
        }
    }

    /**
     * 数组过滤
     * @memberOf module:zrender/core/util
     * @param {Array} obj
     * @param {Function} cb
     * @param {*} [context]
     * @return {Array}
     */
    function filter(obj, cb, context) {
        if (!(obj && cb)) {
            return;
        }
        if (obj.filter && obj.filter === nativeFilter) {
            return obj.filter(cb, context);
        }
        else {
            var result = [];
            for (var i = 0, len = obj.length; i < len; i++) {
                if (cb.call(context, obj[i], i, obj)) {
                    result.push(obj[i]);
                }
            }
            return result;
        }
    }

    /**
     * 数组项查找
     * @memberOf module:zrender/core/util
     * @param {Array} obj
     * @param {Function} cb
     * @param {*} [context]
     * @return {Array}
     */
    function find(obj, cb, context) {
        if (!(obj && cb)) {
            return;
        }
        for (var i = 0, len = obj.length; i < len; i++) {
            if (cb.call(context, obj[i], i, obj)) {
                return obj[i];
            }
        }
    }

    /**
     * @memberOf module:zrender/core/util
     * @param {Function} func
     * @param {*} context
     * @return {Function}
     */
    function bind(func, context) {
        var args = nativeSlice.call(arguments, 2);
        return function () {
            return func.apply(context, args.concat(nativeSlice.call(arguments)));
        };
    }

    /**
     * @memberOf module:zrender/core/util
     * @param {Function} func
     * @return {Function}
     */
    function curry(func) {
        var args = nativeSlice.call(arguments, 1);
        return function () {
            return func.apply(this, args.concat(nativeSlice.call(arguments)));
        };
    }

    /**
     * @memberOf module:zrender/core/util
     * @param {*} value
     * @return {boolean}
     */
    function isArray(value) {
        return objToString.call(value) === '[object Array]';
    }

    /**
     * @memberOf module:zrender/core/util
     * @param {*} value
     * @return {boolean}
     */
    function isFunction(value) {
        return typeof value === 'function';
    }

    /**
     * @memberOf module:zrender/core/util
     * @param {*} value
     * @return {boolean}
     */
    function isString(value) {
        return objToString.call(value) === '[object String]';
    }

    /**
     * @memberOf module:zrender/core/util
     * @param {*} value
     * @return {boolean}
     */
    function isObject(value) {
        // Avoid a V8 JIT bug in Chrome 19-20.
        // See https://code.google.com/p/v8/issues/detail?id=2291 for more details.
        var type = typeof value;
        return type === 'function' || (!!value && type == 'object');
    }

    /**
     * @memberOf module:zrender/core/util
     * @param {*} value
     * @return {boolean}
     */
    function isBuildInObject(value) {
        return !!BUILTIN_OBJECT[objToString.call(value)]
            || (value instanceof Gradient);
    }

    /**
     * @memberOf module:zrender/core/util
     * @param {*} value
     * @return {boolean}
     */
    function isDom(value) {
        return value && value.nodeType === 1
               && typeof(value.nodeName) == 'string';
    }

    /**
     * If value1 is not null, then return value1, otherwise judget rest of values.
     * @memberOf module:zrender/core/util
     * @return {*} Final value
     */
    function retrieve(values) {
        for (var i = 0, len = arguments.length; i < len; i++) {
            if (arguments[i] != null) {
                return arguments[i];
            }
        }
    }

    /**
     * @memberOf module:zrender/core/util
     * @param {Array} arr
     * @param {number} startIndex
     * @param {number} endIndex
     * @return {Array}
     */
    function slice() {
        return Function.call.apply(nativeSlice, arguments);
    }

    /**
     * @memberOf module:zrender/core/util
     * @param {boolean} condition
     * @param {string} message
     */
    function assert(condition, message) {
        if (!condition) {
            throw new Error(message);
        }
    }

    var util = {
        inherits: inherits,
        mixin: mixin,
        clone: clone,
        merge: merge,
        mergeAll: mergeAll,
        extend: extend,
        defaults: defaults,
        getContext: getContext,
        createCanvas: createCanvas,
        indexOf: indexOf,
        slice: slice,
        find: find,
        isArrayLike: isArrayLike,
        each: each,
        map: map,
        reduce: reduce,
        filter: filter,
        bind: bind,
        curry: curry,
        isArray: isArray,
        isString: isString,
        isObject: isObject,
        isFunction: isFunction,
        isBuildInObject: isBuildInObject,
        isDom: isDom,
        retrieve: retrieve,
        assert: assert,
        noop: function () {}
    };
    return util;
});