const signitures = `
# DataExtracter Help
----------------------------

## Signitures:
----------------------------

function extract(itemsSelector:string, fieldSelectors:string[])
function extract(itemsSelector:string, fieldSelectors:string[], url:string, from:number, to:number, interval:number)
function extract(itemsSelector:string, fieldSelectors:string, url:string, pages:number[])
function extract(itemsSelector:string, fieldSelectors:string[], urls:string[])
function extract(itemsSelector:string, fieldSelectors:string[], urls:ExractResult)

## Examples:
----------------------------

### Extract current page
extract(".list-item", ["a.title", "p.content"])

### Extract multiple pages (1-10, interval 1)
extract(".list-item", ["a.title", "p.content"],"http://sample.com/?pn=\${page}", 1, 10, 1)

### Extract multiple urls (list)
extract(".list-item", ["a.title", "p.content"],["http://sample.com/abc","http://sample.com/xyz"])

### Extract specified pages (1,3,5)
extract(".list-item", ["a.title", "p.content"], "http://sample.com/?pn=\${page}", [1, 3, 5])

## Advanced Examples:
----------------------------

### Extract link text and target (use 'selector@attribute')
extract('.list-item', ['a.title', 'a.title@href'])

### Collect links from page(s) & Extract data of each link
>> (Available only in console of extension background page)

extract('body',["a.title", "p.content"], await getData('.list-item', ['.item a@href'],["http://sample.com/abc"]))
`.trim();


function saveFile(data, mimeType, fileName) {
    fileName = fileName || document.title || "result";
    var blob;
    if (typeof window.Blob == "function") {
        blob = new Blob([data], {
            type: mimeType
        })
    } else {
        var BlobBuiler = window.BlobBuilder || window.MozBlobBuilder || window.WebKitBlobBuilder || window.MSBlobBuilder;
        var builer = new BlobBuiler();
        builer.append(data);
        blob = builer.getBlob(mimeType)
    }
    var URL = window.URL || window.webkitURL;
    var url = URL.createObjectURL(blob);
    var link = document.createElement("a");
    if ('download' in link) {
        link.style.visibility = "hidden";
        link.href = url;
        link.download = fileName;
        document.body.appendChild(link);
        var j = document.createEvent("MouseEvents");
        j.initEvent("click", true, true);
        link.dispatchEvent(j);
        document.body.removeChild(link)
    } else if (navigator.msSaveBlob) {
        navigator.msSaveBlob(blob, fileName)
    } else {
        location.href = url
    }
}

function testArgs(...args) {
    switch (args.length) {
        case 0, 1:
            return false;
        case 2:
            return args[0] && args[1] &&
                (typeof args[0] == "string") &&
                (args[1] instanceof Array) &&
                testArrayVals(args[1], v => typeof v == "string");
        case 3:
            return args[0] && args[1] &&
                typeof args[0] == "string" &&
                args[1] instanceof Array &&
                testArrayVals(args[1], v => typeof v == "string") &&
                (
                    (
                        args[2] instanceof Array &&
                        testArrayVals(args[2], v => typeof v == "string")
                    ) || (
                        args[2] instanceof ExractResult
                    )
                );
        case 4:
            return args[0] && args[1] &&
                typeof args[0] == "string" &&
                args[1] instanceof Array &&
                testArrayVals(args[1], v => typeof v == "string") &&
                typeof args[2] == "string" &&
                args[3] instanceof Array &&
                testArrayVals(args[3], v => typeof v == "number");
        case 6:
            return args[0] && args[1] &&
                typeof args[0] == "string" &&
                args[1] instanceof Array &&
                testArrayVals(args[1], v => typeof v == "string") &&
                typeof args[2] == "string" &&
                !isNaN(args[3]) && !isNaN(args[4]) && !isNaN(args[5]);
        default:
            return false;
    }

    function testArrayVals(arr, tester) {
        return arr.reduce((p, c) => p && tester(c), true);
    }
}