const signitures = `
## Usage
// single task
$(...args);
// managed task chains
e = new Extractor();
e.task(...args).task(...args).start();

## Task Call Signitures:
function(itemsSelector:string, fieldSelectors:string[]);
function(itemsSelector:string, fieldSelectors:string[], url:string, from:number, to:number, interval:number);
function(itemsSelector:string, fieldSelectors:string[], url:string, pages:number[]);
function(itemsSelector:string, fieldSelectors:string[], urls:string[]);

## Example:
// extract all links text & url under '.item' elements
// use 'selector@attr' to get attribute of the field elements
$(".item", ["a", "a@href"]);

## See Detailed Help:
https://git.jebbs.co/jebbs/data-extracter-extesion
`.trim();

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 ExtractResult
                    )
                );
        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);
    }
}

function argsToString(...args) {
    return args.map(v => (v instanceof Array ? `[${v.join(', ')}]` : v.toString())).join(', ');
}