// function extract(itemsSelector, fieldSelectors, url, from, to, interval)
// function extract(itemsSelector, fieldSelectors, url, pages)
function extract(itemsSelector, fieldSelectors, url, ...args) {
    let urls = [];
    if (url) {
        if (args[0] instanceof Array) {
            urls = args[0].map(p => url.replace("${page}", p));
        } else if (args.length >= 3) {
            let from = args.shift();
            let to = args.shift();
            let interval = args.shift();
            for (let i = from; i <= to; i += interval) {
                urls.push(url.replace("${page}", i));
            }
        }
    }
    let data = [];
    return new Promise((resolve, reject) => {
        chrome.tabs.query({
            active: true,
            currentWindow: true
        }, function (tabs) {
            let pms;
            let tab = tabs[0];
            if (urls.length) {
                pms = urls.reduce((p, url) => p.then(
                    results => {
                        data.push(...results);
                        return redirectTab(tab, url).then(
                            tab => extractTabData(tab, itemsSelector, fieldSelectors)
                        );
                    },
                    () => p
                ), Promise.resolve([]));
            } else {
                pms = extractTabData(tab, itemsSelector, fieldSelectors);
            }
            pms.then(
                results => {
                    data.push(...results);
                    data.unshift(fieldSelectors);
                    saveFileAsk(data);
                    resolve("save done.")
                },
                err => reject(err)
            );
        });
    });
}

function extractTabData(tab, itemsSelector, fieldSelectors) {
    let done = false;
    return new Promise((resolve, reject) => {
        chrome.tabs.sendMessage(
            tab.id, {
                from: "doExtractRequest",
                itemsSelector: itemsSelector,
                fieldSelectors: fieldSelectors
            },
            response => {
                done = true;
                resolve(response);
            }
        );
        setTimeout(() => {
            if (!done) reject(`extractTabData failed after 2 second.`);
        }, 2000);
    });
}

function redirectTab(tab, url) {
    let done = false;
    let timeOut;
    return new Promise((resolve, reject) => {
        let req = {
            from: "doExtractGotoUrl",
            url: url
        }
        chrome.tabs.sendMessage(tab.id, req, r => {
            // if (r != req.from) return;
            // detectLoop();
            setTimeout(() => {
                detectLoop();
            }, 500);
        });
        setTimeout(() => {
            if (!done) {
                reject(`redirectTab failed after 10 second.`);
                clearTimeout(timeOut);
            }
        }, 10000);

        function detectLoop() {
            let req = {
                from: "doExtractReportIn"
            }
            chrome.tabs.sendMessage(tab.id, req, r => {
                if (r != req.from) return;
                resolve(tab)
                done = true;
            });
            if (!done) {
                clearTimeout(timeOut);
                timeOut = setTimeout(() => {
                    detectLoop();
                }, 100);
            }
        }
    });
}

function createTab(url) {
    return new Promise((resolve, reject) => {
        chrome.tabs.create({
            active: true,
            url: url
        }, function (tab) {
            resolve(tab);
        });
    });
}