(function (global) {
    'use strict';

    function nodeId(n) {
        return String(n.uuid || n._id || n.name || '');
    }

    /**
     * 先序遍历；fn 返回 false 时提前停止。
     * @param {*} node
     * @param {function(*):boolean|void} fn
     * @returns {boolean} false 表示被 fn 中止
     */
    function walk(node, fn) {
        if (!node) return true;
        if (fn(node) === false) return false;
        var ch = node.children;
        if (!ch) return true;
        for (var i = 0; i < ch.length; i++) {
            if (walk(ch[i], fn) === false) return false;
        }
        return true;
    }

    /** 按 uuid / _id / name 查找节点，命中即停。 */
    function findNodeByUuid(root, uuid) {
        if (!root || !uuid) return null;
        var found = null;
        walk(root, function (n) {
            if (nodeId(n) === uuid) {
                found = n;
                return false;
            }
            return true;
        });
        return found;
    }

    function serializeNode(node, depth, maxDepth) {
        if (!node || depth > maxDepth) return null;
        var children = [];
        var ch = node.children || [];
        for (var i = 0; i < ch.length; i++) {
            var c = serializeNode(ch[i], depth + 1, maxDepth);
            if (c) children.push(c);
        }
        var comps = [];
        if (node.components) {
            for (var j = 0; j < node.components.length; j++) {
                var comp = node.components[j];
                if (comp && comp.constructor) comps.push(comp.constructor.name || '');
            }
        }
        return {
            uuid: nodeId(node),
            name: node.name || '(未命名)',
            active: node.active !== false,
            comps: comps,
            children: children,
        };
    }

    function copySeries(series) {
        var out = {};
        for (var k in series) {
            if (Object.prototype.hasOwnProperty.call(series, k)) out[k] = series[k].slice();
        }
        return out;
    }

    function hierFingerprint(node) {
        if (!node) return '';
        var parts = [node.uuid, node.name, node.active ? 1 : 0, (node.comps || []).length];
        var ch = node.children || [];
        parts.push(ch.length);
        for (var i = 0; i < ch.length; i++) parts.push(hierFingerprint(ch[i]));
        return parts.join('/');
    }

    global.PWAgentUtil = {
        nodeId: nodeId,
        walk: walk,
        findNodeByUuid: findNodeByUuid,
        serializeNode: serializeNode,
        copySeries: copySeries,
        hierFingerprint: hierFingerprint,
    };
})(window);