(function (root, factory) {
    if (typeof exports === 'object') {
        module.exports = factory(root);
    } else if (typeof define === "function" && define.amd) {
        define([], factory);
    } else {
        root.IdiomSolitaire = factory(root);
    }
})(typeof global !== 'undefined' ? global : this.window || this.global, function (root) {

class IdiomSolitaire {
    constructor() {
        this.idioms = null;
    }

    load() {
        return this.idioms ? Promise.resolve(this) : fetch('https://cdn.jsdelivr.net/gh/pwxcoo/chinese-xinhua/data/idiom.json')
            .then(res => res.json())
            .then(res => {
                this.idioms = Object.freeze(res.map(e => {
                    const pinyin = e.pinyin.replace(/[　，?]/, '').split(' ');
                    e.start = pinyin[0];
                    e.end = pinyin[pinyin.length - 1];
                    return Object.freeze(e);
                }));
                return this;
            });
    }

    solve(start, end) {
        if (!this.idioms) {
            throw new Error('Idioms not ready');
        }

        console.time('Solve');

        const startIdiom = this.idioms.find(e => e.word === start);
        const endIdiom = this.idioms.find(e => e.word === end);
        if (!startIdiom || !endIdiom) {
            throw new Error('Invalid idiom');
        }

        const set = new Set;
        const queue = [{
            parent: null,
            idiom: startIdiom,
        }];
        let found;
        let nodeCount = 0;
        while (queue.length) {
            const node = queue.shift();
            nodeCount++;
            const children = this.idioms
                .filter((e, i) => e.start === node.idiom.end && !set.has(i) && set.add(i))
                .map(e => ({
                    parent: node,
                    idiom: e,
                }));
                if (found = children.find(e => e.idiom.end === endIdiom.start)) {
                    break;
                }
            children.forEach(e => queue.push(e));
        }

        console.info('Node count:', nodeCount);
        console.timeEnd('Solve');

        if (found) {
            const result = [endIdiom];
            while (found) {
                result.unshift(found.idiom);
                found = found.parent;
            }
            return result;
        } else {
            throw new Error('No solution');
        }
    }
}

return IdiomSolitaire;

});

// 使用例：
const solitaire = new IdiomSolitaire;
solitaire.load().then(solitaire => console.log(solitaire.solve('身经百战', '谈笑风生').map(e => e.word).join(' -> ')));