/*
 * Copyright (c) 2018-2019, Daniel Gultsch All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation and/or
 * other materials provided with the distribution.
 *
 * 3. Neither the name of the copyright holder nor the names of its contributors
 * may be used to endorse or promote products derived from this software without
 * specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package eu.siacs.conversations.utils;

import android.annotation.TargetApi;
import android.content.Context;
import android.os.Build;
import android.support.annotation.ColorInt;
import android.text.Spannable;
import android.text.SpannableString;
import android.text.SpannableStringBuilder;
import android.text.style.ForegroundColorSpan;
import android.util.LruCache;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import eu.siacs.conversations.R;
import eu.siacs.conversations.ui.util.StyledAttributes;
import eu.siacs.conversations.xmpp.Jid;

public class IrregularUnicodeDetector {

	private static final Map<Character.UnicodeBlock, Character.UnicodeBlock> NORMALIZATION_MAP;
	private static final LruCache<Jid, PatternTuple> CACHE = new LruCache<>(4096);
	private static final List<String> AMBIGUOUS_CYRILLIC = Arrays.asList("а","г","е","ѕ","і","q","о","р","с","у");

	static {
		Map<Character.UnicodeBlock, Character.UnicodeBlock> temp = new HashMap<>();
		temp.put(Character.UnicodeBlock.LATIN_1_SUPPLEMENT, Character.UnicodeBlock.BASIC_LATIN);
		NORMALIZATION_MAP = Collections.unmodifiableMap(temp);
	}

	private static Character.UnicodeBlock normalize(Character.UnicodeBlock in) {
		if (NORMALIZATION_MAP.containsKey(in)) {
			return NORMALIZATION_MAP.get(in);
		} else {
			return in;
		}
	}

	public static Spannable style(Context context, Jid jid) {
		return style(jid, StyledAttributes.getColor(context, R.attr.color_warning));
	}

	private static Spannable style(Jid jid, @ColorInt int color) {
		PatternTuple patternTuple = find(jid);
		SpannableStringBuilder builder = new SpannableStringBuilder();
		if (jid.getEscapedLocal() != null && patternTuple.local != null) {
			SpannableString local = new SpannableString(jid.getEscapedLocal());
			colorize(local, patternTuple.local, color);
			builder.append(local);
			builder.append('@');
		}
		if (jid.getDomain() != null) {
			String[] labels = jid.getDomain().split("\\.");
			for (int i = 0; i < labels.length; ++i) {
				SpannableString spannableString = new SpannableString(labels[i]);
				colorize(spannableString, patternTuple.domain.get(i), color);
				if (i != 0) {
					builder.append('.');
				}
				builder.append(spannableString);
			}
		}
		if (builder.length() != 0 && jid.getResource() != null) {
			builder.append('/');
			builder.append(jid.getResource());
		}
		return builder;
	}

	private static void colorize(SpannableString spannableString, Pattern pattern, @ColorInt int color) {
		Matcher matcher = pattern.matcher(spannableString);
		while (matcher.find()) {
			if (matcher.start() < matcher.end()) {
				spannableString.setSpan(new ForegroundColorSpan(color), matcher.start(), matcher.end(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
			}
		}
	}

	private static Map<Character.UnicodeBlock, List<String>> mapCompat(String word) {
		Map<Character.UnicodeBlock, List<String>> map = new HashMap<>();
		final int length = word.length();
		for (int offset = 0; offset < length; ) {
			final int codePoint = word.codePointAt(offset);
			offset += Character.charCount(codePoint);
			if (!Character.isLetter(codePoint)) {
				continue;
			}
			Character.UnicodeBlock block = normalize(Character.UnicodeBlock.of(codePoint));
			List<String> codePoints;
			if (map.containsKey(block)) {
				codePoints = map.get(block);
			} else {
				codePoints = new ArrayList<>();
				map.put(block, codePoints);
			}
			codePoints.add(String.copyValueOf(Character.toChars(codePoint)));
		}
		return map;
	}

	@TargetApi(Build.VERSION_CODES.N)
	private static Map<Character.UnicodeScript, List<String>> map(String word) {
		Map<Character.UnicodeScript, List<String>> map = new HashMap<>();
		final int length = word.length();
		for (int offset = 0; offset < length; ) {
			final int codePoint = word.codePointAt(offset);
			Character.UnicodeScript script = Character.UnicodeScript.of(codePoint);
			if (script != Character.UnicodeScript.COMMON) {
				List<String> codePoints;
				if (map.containsKey(script)) {
					codePoints = map.get(script);
				} else {
					codePoints = new ArrayList<>();
					map.put(script, codePoints);
				}
				codePoints.add(String.copyValueOf(Character.toChars(codePoint)));
			}
			offset += Character.charCount(codePoint);
		}
		return map;
	}

	private static Set<String> eliminateFirstAndGetCodePointsCompat(Map<Character.UnicodeBlock, List<String>> map) {
		return eliminateFirstAndGetCodePoints(map, Character.UnicodeBlock.BASIC_LATIN);
	}

	@TargetApi(Build.VERSION_CODES.N)
	private static Set<String> eliminateFirstAndGetCodePoints(Map<Character.UnicodeScript, List<String>> map) {
		return eliminateFirstAndGetCodePoints(map, Character.UnicodeScript.COMMON);
	}

	private static <T> Set<String> eliminateFirstAndGetCodePoints(Map<T, List<String>> map, T defaultPick) {
		T pick = defaultPick;
		int size = 0;
		for (Map.Entry<T, List<String>> entry : map.entrySet()) {
			if (entry.getValue().size() > size) {
				size = entry.getValue().size();
				pick = entry.getKey();
			}
		}
		map.remove(pick);
		Set<String> all = new HashSet<>();
		for (List<String> codePoints : map.values()) {
			all.addAll(codePoints);
		}
		return all;
	}

	private static Set<String> findIrregularCodePoints(String word) {
		Set<String> codePoints;
		if (Build.VERSION.SDK_INT < Build.VERSION_CODES.N) {
			final Map<Character.UnicodeBlock, List<String>> map = mapCompat(word);
			final Set<String> set = asSet(map);
			if (containsOnlyAmbiguousCyrillic(set)) {
				return set;
			}
			codePoints = eliminateFirstAndGetCodePointsCompat(map);
		} else {
			final Map<Character.UnicodeScript, List<String>> map = map(word);
			final Set<String> set = asSet(map);
			if (containsOnlyAmbiguousCyrillic(set)) {
				return set;
			}
			codePoints = eliminateFirstAndGetCodePoints(map);
		}
		return codePoints;
	}

	private static Set<String> asSet(Map<?, List<String>> map) {
		final Set<String> flat = new HashSet<>();
		for(List<String> value : map.values()) {
			flat.addAll(value);
		}
		return flat;
	}


	private static boolean containsOnlyAmbiguousCyrillic(Collection<String> codePoints) {
		for (String codePoint : codePoints) {
			if (!AMBIGUOUS_CYRILLIC.contains(codePoint)) {
				return false;
			}
		}
		return true;
	}

	private static PatternTuple find(Jid jid) {
		synchronized (CACHE) {
			PatternTuple pattern = CACHE.get(jid);
			if (pattern != null) {
				return pattern;
			}
			;
			pattern = PatternTuple.of(jid);
			CACHE.put(jid, pattern);
			return pattern;
		}
	}

	private static Pattern create(Set<String> codePoints) {
		final StringBuilder pattern = new StringBuilder();
		for (String codePoint : codePoints) {
			if (pattern.length() != 0) {
				pattern.append('|');
			}
			pattern.append(Pattern.quote(codePoint));
		}
		return Pattern.compile(pattern.toString());
	}

	private static class PatternTuple {
		private final Pattern local;
		private final List<Pattern> domain;

		private PatternTuple(Pattern local, List<Pattern> domain) {
			this.local = local;
			this.domain = domain;
		}

		private static PatternTuple of(Jid jid) {
			final Pattern localPattern;
			if (jid.getEscapedLocal() != null) {
				localPattern = create(findIrregularCodePoints(jid.getEscapedLocal()));
			} else {
				localPattern = null;
			}
			String domain = jid.getDomain();
			final List<Pattern> domainPatterns = new ArrayList<>();
			if (domain != null) {
				for (String label : domain.split("\\.")) {
					domainPatterns.add(create(findIrregularCodePoints(label)));
				}
			}
			return new PatternTuple(localPattern, domainPatterns);
		}
	}
}