package acr.browser.lightning;

import android.content.Context;
import android.content.res.AssetManager;
import android.util.Log;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.HashSet;
import java.util.Locale;
import java.util.Set;

public class AdBlock {

	private static final String TAG = "AdBlock";
	private static final String BLOCKED_DOMAINS_LIST_FILE_NAME = "hosts.txt";
	private static final Set<String> mBlockedDomainsList = new HashSet<String>();
	private boolean mBlockAds;
	private static final Locale mLocale = Locale.getDefault();
	private static AdBlock mInstance;

	public static AdBlock getInstance(Context context) {
		if (mInstance == null) {
			mInstance = new AdBlock(context);
		}
		return mInstance;
	}

	private AdBlock(Context context) {
		if (mBlockedDomainsList.isEmpty() && Constants.FULL_VERSION) {
			loadBlockedDomainsList(context);
		}
		mBlockAds = PreferenceManager.getInstance().getAdBlockEnabled();
	}

	public void updatePreference() {
		mBlockAds = PreferenceManager.getInstance().getAdBlockEnabled();
	}

	private void loadBlockedDomainsList(final Context context) {
		Thread thread = new Thread(new Runnable() {

			@Override
			public void run() {
				AssetManager asset = context.getAssets();
				try {
					BufferedReader reader = new BufferedReader(new InputStreamReader(
							asset.open(BLOCKED_DOMAINS_LIST_FILE_NAME)));
					String line;
					while ((line = reader.readLine()) != null) {
						mBlockedDomainsList.add(line.trim().toLowerCase(mLocale));
					}
				} catch (IOException e) {
					Log.wtf(TAG, "Reading blocked domains list from file '"
							+ BLOCKED_DOMAINS_LIST_FILE_NAME + "' failed.", e);
				}
			}
		});
		thread.start();
	}

	public boolean isAd(String url) {
		if (!mBlockAds || url == null) {
			return false;
		}

		String domain;
		try {
			domain = getDomainName(url);
		} catch (URISyntaxException e) {
			Log.d(TAG, "URL '" + url + "' is invalid", e);
			return false;
		}

		boolean isOnBlacklist = mBlockedDomainsList.contains(domain.toLowerCase(mLocale));
		if (isOnBlacklist) {
			Log.d(TAG, "URL '" + url + "' is an ad");
		}
		return isOnBlacklist;
	}

	private static String getDomainName(String url) throws URISyntaxException {
		int index = url.indexOf('/', 8);
		if (index != -1) {
			url = url.substring(0, index);
		}

		URI uri = new URI(url);
		String domain = uri.getHost();
		if (domain == null) {
			return url;
		}

		return domain.startsWith("www.") ? domain.substring(4) : domain;
	}
}