Can Kanna be used for scraping websites with pagination?

Yes, Kanna, a Swift library for parsing HTML and XML, can be used for scraping websites with pagination. However, since Kanna itself is just a parsing library, you'll need to handle the networking part (i.e., making HTTP requests to retrieve the paginated content) separately.

In a typical pagination scenario, a website will have a series of pages or a mechanism to load more content dynamically. You will need to:

1. Make an HTTP request to the initial page to retrieve the content.
2. Parse the HTML content to extract the data you're interested in.
3. Find the link or mechanism used for pagination (e.g., a "next" button, numbered page links, or a load more button).
4. Make subsequent HTTP requests to the URLs corresponding to the paginated content.
5. Repeat the parsing and data extraction for each page.

Below is a simplified example using Swift with Kanna and URLSession to scrape a hypothetical website with pagination. Please note that this example does not include error handling and is for demonstration purposes only.

import Kanna

// Function to fetch HTML content from a URL
func fetchHTML(from urlString: String, completion: @escaping (String?) -> Void) {
    guard let url = URL(string: urlString) else {
        completion(nil)
        return
    }

    let task = URLSession.shared.dataTask(with: url) { data, response, error in
        guard let data = data, error == nil else {
            completion(nil)
            return
        }
        let htmlString = String(data: data, encoding: .utf8)
        completion(htmlString)
    }
    task.resume()
}

// Function to scrape a website with pagination
func scrapeWebsiteWithPagination(baseURL: String, startPage: Int, endPage: Int) {
    for pageNumber in startPage...endPage {
        let pageURL = "\(baseURL)?page=\(pageNumber)"

        fetchHTML(from: pageURL) { htmlString in
            guard let html = htmlString else {
                print("Error fetching HTML from \(pageURL)")
                return
            }

            do {
                let doc = try Kanna.HTML(html: html, encoding: .utf8)
                // Parse the document to find the elements you need, e.g., product details
                for product in doc.xpath("//div[@class='product']") {
                    // Extract the data you want, e.g., product name and price
                    let productName = product.at_xpath(".//h3")?.text?.trimmingCharacters(in: .whitespacesAndNewlines)
                    let productPrice = product.at_xpath(".//span[@class='price']")?.text?.trimmingCharacters(in: .whitespacesAndNewlines)
                    print("Product Name: \(productName ?? "unknown"), Price: \(productPrice ?? "unknown")")
                }
            } catch {
                print("Error parsing HTML for \(pageURL)")
            }
        }
    }
}

// Example usage
let baseURL = "https://example.com/products"
scrapeWebsiteWithPagination(baseURL: baseURL, startPage: 1, endPage: 5)

In this example, fetchHTML is a function that takes a URL string as input and fetches the HTML content of the page using URLSession. The scrapeWebsiteWithPagination function constructs the URL for each page by appending a page query parameter and then calls fetchHTML for each page. Once the HTML content is fetched, it uses Kanna to parse it and extract the necessary information.

This example assumes that pages are accessed via a simple query parameter ?page=, which is common in pagination. However, real-world scenarios may require handling more complex pagination mechanisms, including JavaScript-generated content, which Kanna alone cannot handle since it does not execute JavaScript.

For JavaScript-heavy websites or when pages are loaded dynamically (such as through AJAX), you might need to use a tool like Puppeteer or Selenium, which can control a browser and simulate user interactions to retrieve and scrape content.