package me.mrletsplay.scraperbot;

import java.net.URI;
import java.net.URISyntaxException;
import java.net.http.HttpClient;
import java.net.http.HttpClient.Redirect;
import java.net.http.HttpClient.Version;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse.BodyHandlers;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashSet;
import java.util.Objects;
import java.util.Random;
import java.util.Set;
import java.util.UUID;
import java.util.concurrent.Future;
import java.util.stream.Collectors;

import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;

import net.dv8tion.jda.api.entities.Message;
import net.dv8tion.jda.api.entities.channel.middleman.MessageChannel;

public class ScraperTask {

	private static final HttpClient CLIENT = HttpClient.newBuilder()
			.version(Version.HTTP_2)
			.followRedirects(Redirect.ALWAYS)
			.build();

	private String id;
	private String firstURL;
	private Strategy strategy;

	private String
		cookie, // For CF bypass, login etc.
		userAgent = "Mozilla/5.0 (X11; Linux x86_64; rv:109.0) Gecko/20100101 Firefox/119.0";

	private FilterList exclude;
	private FilterList include;
	private FilterList find;

	private Future<?> future;
	private long startTime;

	public ScraperTask(String firstURL) {
		this.id = UUID.randomUUID().toString();
		this.firstURL = firstURL;
		this.strategy = Strategy.RANDOM;
		this.exclude = new FilterList();
		this.include = new FilterList();
		this.find = new FilterList();

		this.include.getPrefix().add(firstURL);
	}

	public String getID() {
		return id;
	}

	public String getFirstURL() {
		return firstURL;
	}

	public void setStrategy(Strategy strategy) {
		this.strategy = strategy;
	}

	public Strategy getStrategy() {
		return strategy;
	}

	public void setCookie(String cookie) {
		this.cookie = cookie;
	}

	public String getCookie() {
		return cookie;
	}

	public void setUserAgent(String userAgent) {
		this.userAgent = userAgent;
	}

	public String getUserAgent() {
		return userAgent;
	}

	public FilterList getExclude() {
		return exclude;
	}

	public FilterList getInclude() {
		return include;
	}

	public FilterList getFind() {
		return find;
	}

	public long getStartTime() {
		return startTime;
	}

	public void start(MessageChannel channel) {
		if(future != null) return;

		this.startTime = System.currentTimeMillis();

		future = ScraperBot.EXECUTOR.submit(() -> {
			try {
				Set<String> visited = new HashSet<>();
				Set<String> toVisit = new HashSet<>();
				Set<String> found = new HashSet<>();

				toVisit.add(firstURL);

				Random r = new Random();

				while(!toVisit.isEmpty()) {
					String url;
					switch(strategy) {
						case BREADTH_FIRST:
							url = toVisit.iterator().next();
							break;
						case RANDOM:
						default:
							url = new ArrayList<>(toVisit).get(r.nextInt(toVisit.size()));
							break;
					}

					System.out.println(toVisit.size() + " " + url); // TODO: show in info command
					toVisit.remove(url);
					if(!visited.add(url)) {
						System.out.println("Deja vu, I've been in this place before");
						continue;
					}

					Set<String> links = getLinks(url);
					if(Thread.currentThread().isInterrupted()) break;
					links.removeAll(visited);
					links.stream().filter(l -> include.matches(url) && !exclude.matches(url)).forEach(toVisit::add);

					Set<String> newFound = links.stream().filter(l -> find.matches(l)).collect(Collectors.toSet());
					System.out.println("FOUND: " + newFound); // TODO: show in info command
					newFound.removeAll(found);
					found.addAll(newFound);
					if(!newFound.isEmpty()) {
						Utils.splitToLength(newFound.stream().collect(Collectors.joining("\n")), Message.MAX_CONTENT_LENGTH, Utils.SPLIT_NEWLINES).stream()
							.forEach(s -> channel.sendMessage(s).queue());
					}

					Thread.sleep(1000);
				}
			}catch(InterruptedException e) {
			}catch(Exception e) {
				channel.sendMessage("Failed: " + e.toString()).queue();
			}

			ScraperBot.TASKS.remove(this);
			channel.sendMessage("Done!").queue();
		});
	}

	public void cancel() {
		if(future != null) future.cancel(true);
	}

	private static String clean(String uri) throws URISyntaxException {
		URI u = URI.create(uri);
		return new URI(u.getScheme(), u.getSchemeSpecificPart(), null).toString();
	}

	private Set<String> getLinks(String url) throws Exception {
		for(int i = 0; i < 5; i++) {
			try {
				HttpRequest.Builder b = HttpRequest.newBuilder(URI.create(url))
					.header("User-Agent", userAgent);

				if(cookie != null) b.header("Cookie", cookie);

				var r = CLIENT.send(b.build(), BodyHandlers.ofString());

				if(r.statusCode() != 200) {
					if(r.statusCode() == 404) continue;

					System.out.println("RETRY");
					throw new RuntimeException("Failed");
				}

				Document d = Jsoup.parse(r.body(), url);
				Set<String> linksOnPage = d.getElementsByTag("a").stream().map(a -> {
					try {
						return clean(a.attr("abs:href"));
					} catch (URISyntaxException e) {
						e.printStackTrace();
						return null;
					}
				})
				.filter(Objects::nonNull)
				.collect(Collectors.toSet());
				return linksOnPage;
			}catch(InterruptedException e) {
				Thread.currentThread().interrupt();
				return Collections.emptySet();
			}catch(Exception e) {
				Thread.sleep(1000);
//				e.printStackTrace();
			}
		}

		return Collections.emptySet();
	}

	public static enum Strategy {
//		DEPTH_FIRST("Depth-First Search"), TODO: implement
		BREADTH_FIRST("Breadth-First Search"),
		RANDOM("Random"),
		;

		public final String friendlyName;

		private Strategy(String friendlyName) {
			this.friendlyName = friendlyName;
		}

		public String getFriendlyName() {
			return friendlyName;
		}
	}

}