Does Kanna provide any utilities to help with web scraping, such as user-agent rotation?

Kanna is a Swift library for parsing XML and HTML, commonly used with iOS and macOS applications. It is not designed specifically for web scraping, and as such, does not include utilities like user-agent rotation, which is a technique often used in web scraping to avoid detection and blocking by web servers.

User-agent rotation involves changing the user-agent string in the HTTP request headers to mimic different devices and browsers, thereby making the traffic seem like it's coming from multiple users. This can help prevent the scraper from being identified and blocked by the target website's anti-scraping mechanisms.

Since Kanna doesn't provide user-agent rotation out of the box, you would need to implement this feature yourself. In a Swift application where you might be using Kanna, you would typically make network requests using URLSession or a third-party library like Alamofire. You can set the user-agent header manually for each request.

Here's an example of how you might rotate user-agents using URLSession in Swift:

import Foundation

let userAgents = [
    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.183 Safari/537.36",
    "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.183 Safari/537.36",
    "Mozilla/5.0 (iPhone; CPU iPhone OS 14_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/14.0.1 Mobile/15E148 Safari/604.1"
    // Add more user-agent strings as necessary
]

func scrapeURLWithRandomUserAgent(url: URL) {
    let randomUserAgent = userAgents.randomElement()!
    var request = URLRequest(url: url)
    request.setValue(randomUserAgent, forHTTPHeaderField: "User-Agent")

    let task = URLSession.shared.dataTask(with: request) { data, response, error in
        guard let data = data, error == nil else {
            print(error ?? "Unknown error")
            return
        }

        // Use Kanna to parse the HTML content here
        // ...

        print(String(decoding: data, as: UTF8.self))
    }

    task.resume()
}

let url = URL(string: "https://example.com")!
scrapeURLWithRandomUserAgent(url: url)

In the above code, we have an array of user-agent strings that the scrapeURLWithRandomUserAgent function uses to set a random user-agent each time it's called. The URLRequest is then configured with this user-agent before the request is made.

Please remember that web scraping can be legally and ethically contentious, and you should always follow the robots.txt guidelines of the target website and respect their terms of service. Moreover, scraping can put a load on the website's servers, so it should be done responsibly. If you're scraping at scale, consider using a professional web scraping service or build a more robust system that includes proxy rotation, request throttling, and more sophisticated user-agent rotation to minimize the impact on the target server and reduce the chance of being blocked.