// A local random guest key restores this browser's history, never customer order identity.
var VisitorSession = (function(){
    const storageName = 'baiyue-visitor-key';
    const nativeFetch = typeof window.fetch === 'function' ? window.fetch.bind(window) : fetch;
    let ready = null, established = false;
    function localKey(){
        try{
            const saved = localStorage.getItem(storageName);
            if(saved && /^[0-9a-f]{64}$/.test(saved)) return saved;
            const crypto = window.crypto;
            if(!crypto || !crypto.getRandomValues) return null;
            const bytes = crypto.getRandomValues(new Uint8Array(32));
            const key = Array.from(bytes, value => value.toString(16).padStart(2, '0')).join('');
            localStorage.setItem(storageName, key);
            return key;
        }catch(error){ return null; } // HttpOnly cookie can still retain this guest when storage is disabled.
    }
    function ensure(){
        if(ready) return ready;
        const controller = new AbortController();
        const timer = setTimeout(() => controller.abort(), 10000);
        ready = nativeFetch('/api/visitor/session', {method:'POST',credentials:'same-origin',
            headers:{'Content-Type':'application/json'},body:JSON.stringify({key:localKey()}),signal:controller.signal})
        .then(async response => {
            const data = await response.json();
            if(!response.ok || !data.ok || typeof data.key !== 'string' || !/^[0-9a-f]{64}$/.test(data.key)){
                throw new Error('访客会话暂时无法建立，请刷新后重试。');
            }
            try{ localStorage.setItem(storageName, data.key); }catch(error){}
            established = true;
        }).catch(error => { ready = null; established = false; throw error; }).finally(() => clearTimeout(timer));
        return ready;
    }
    function request(path, options){
        const init = Object.assign({}, options, {credentials:'same-origin'});
        function send(){
            if(init.signal && init.signal.aborted) return Promise.reject(Object.assign(new Error('Aborted'), {name:'AbortError'}));
            const session = ready;
            return nativeFetch(path, init).then(async response => {
                if(response.status !== 401) return response;
                if(ready === session){ ready = null; established = false; }
                await ensure();
                return nativeFetch(path, init);
            });
        }
        return established ? send() : ensure().then(send);
    }
    return {fetch:request};
})();