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Event Handling

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The event handling mechanism offers a comprehensive approach to capture and process events across the entire lifecycle of a web page. The following concise program logs the sequence of all page events along with their respective names. Page event handlers are encapsulated within the PageEventHandlers class, categorized into three distinct groups to manage events at various phases:

  1. CrawlEventHandlers - Deals with events occurring within the crawling iteration.
  2. LoadEventHandlers - Manages events related to the loading and parsing of the page.
  3. BrowseEventHandlers - Controls events that happen during the interactive browsing phase, including actions that prompt the loading or display of associated elements.
/**
 * Print the call sequence and the event name of all page event handlers
 * */
class PrintFlowEventHandlers: DefaultPageEventHandlers() {
    private val sequencer = AtomicInteger()
    private val seq get() = sequencer.incrementAndGet()
    
    init {
        loadEventHandlers.apply {
            onNormalize.addLast { url ->
                println("$seq. load - onNormalize")
                url
            }
            onWillLoad.addLast { url ->
                println("$seq. load - onWillLoad")
                null
            }
            onWillFetch.addLast { page ->
                println("$seq. load - onWillFetch")
            }
            onFetched.addLast { page ->
                println("$seq. load - onFetched")
            }
            onWillParse.addLast { page ->
                println("$seq. load - onWillParse")
            }
            onWillParseHTMLDocument.addLast { page ->
                println("$seq. load - onWillParseHTMLDocument")
            }
            onHTMLDocumentParsed.addLast { page: WebPage, document: FeaturedDocument ->
                println("$seq. load - onHTMLDocumentParsed")
            }
            onParsed.addLast { page ->
                println("$seq. load - onParsed")
            }
            onLoaded.addLast { page ->
                println("$seq. load - onLoaded")
            }
        }
        
        browseEventHandlers.apply {
            onWillLaunchBrowser.addLast { page ->
                println("$seq. browse - onWillLaunchBrowser")
            }
            onBrowserLaunched.addLast { page, driver ->
                println("$seq. browse - onBrowserLaunched")
            }
            onWillNavigate.addLast { page, driver ->
                println("$seq. browse - onWillNavigate")
            }
            onNavigated.addLast { page, driver ->
                println("$seq. browse - onNavigated")
            }
            onWillInteract.addLast { page, driver ->
                println("$seq. browse - onWillInteract")
            }
            onWillCheckDocumentState.addLast { page: WebPage, driver: WebDriver ->
                println("$seq. browse - onWillCheckDocumentState")
            }
            onDocumentActuallyReady.addLast { page: WebPage, driver: WebDriver ->
                println("$seq. browse - onDocumentActuallyReady")
            }
            onWillScroll.addLast { page: WebPage, driver: WebDriver ->
                println("$seq. browse - onWillScroll")
            }
            onDidScroll.addLast { page: WebPage, driver: WebDriver ->
                println("$seq. browse - onDidScroll")
            }
            onDocumentSteady.addLast { page: WebPage, driver: WebDriver ->
                println("$seq. browse - onDocumentSteady")
            }
            onWillComputeFeature.addLast { page: WebPage, driver: WebDriver ->
                println("$seq. browse - onWillComputeFeature")
            }
            onFeatureComputed.addLast { page: WebPage, driver: WebDriver ->
                println("$seq. browse - onFeatureComputed")
            }
            onDidInteract.addLast { page, driver ->
                println("$seq. browse - onDidInteract")
            }
            onWillStopTab.addLast { page: WebPage, driver: WebDriver ->
                println("$seq. browse - onWillStopTab")
            }
            onTabStopped.addLast { page: WebPage, driver: WebDriver ->
                println("$seq. browse - onTabStopped")
            }
        }
        
        crawlEventHandlers.apply {
            onWillLoad.addLast { url: UrlAware ->
                println("$seq. crawl - onWillLoad")
                url
            }
            onLoaded.addLast { url, page ->
                println("$seq. crawl - onLoaded")
            }
        }
    }
}

The entry point for the call is as follows:

/**
 * Demonstrates how to use event handlers.
 * */
fun main() {
    BrowserSettings.withSystemDefaultBrowser()
    
    val url = "https://www.amazon.com/dp/B0C1H26C46"
    val session = PulsarContexts.createSession()
    val link = ListenableHyperlink(url, args = "-refresh -parse", event = PrintFlowEventHandlers())
    
    // submit the link to the fetch pool.
    session.submit(link)
    
    // wait until all done.
    PulsarContexts.await()
}

The example program outputs the following:

1. crawl - onWillLoad
2. load - onNormalize
3. load - onWillLoad
4. load - onWillFetch
5. browse - onWillLaunchBrowser
6. browse - onBrowserLaunched
7. browse - onWillNavigate
8. browse - onNavigated
9. browse - onWillNavigate
10. browse - onWillCheckDocumentState
11. browse - onDocumentActuallyReady
12. browse - onWillScroll
13. browse - onDidScroll
14. browse - onDocumentSteady
15. browse - onWillComputeFeature
16. browse - onFeatureComputed
17. browse - onDidInteract
18. browse - onWillStopTab
19. browse - onTabStopped
20. load - onFetched
21. load - onWillParse
22. load - onWillParseHTMLDocument
23. load - onHTMLDocumentParsed
24. load - onParsed
25. load - onLoaded
26. crawl - onLoaded

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