/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.inputmethod.latin;

import android.text.TextUtils;

import java.util.ArrayList;
import java.util.Locale;

public final class StringUtils {
    public static final int CAPITALIZE_NONE = 0;  // No caps, or mixed case
    public static final int CAPITALIZE_FIRST = 1; // First only
    public static final int CAPITALIZE_ALL = 2;   // All caps

    private StringUtils() {
        // This utility class is not publicly instantiable.
    }

    public static int codePointCount(final String text) {
        if (TextUtils.isEmpty(text)) return 0;
        return text.codePointCount(0, text.length());
    }

    public static boolean containsInArray(final String key, final String[] array) {
        for (final String element : array) {
            if (key.equals(element)) return true;
        }
        return false;
    }

    public static boolean containsInCsv(final String key, final String csv) {
        if (TextUtils.isEmpty(csv)) return false;
        return containsInArray(key, csv.split(","));
    }

    public static String appendToCsvIfNotExists(final String key, final String csv) {
        if (TextUtils.isEmpty(csv)) return key;
        if (containsInCsv(key, csv)) return csv;
        return csv + "," + key;
    }

    public static String removeFromCsvIfExists(final String key, final String csv) {
        if (TextUtils.isEmpty(csv)) return "";
        final String[] elements = csv.split(",");
        if (!containsInArray(key, elements)) return csv;
        final ArrayList<String> result = CollectionUtils.newArrayList(elements.length - 1);
        for (final String element : elements) {
            if (!key.equals(element)) result.add(element);
        }
        return TextUtils.join(",", result);
    }

    /**
     * Remove duplicates from an array of strings.
     *
     * This method will always keep the first occurrence of all strings at their position
     * in the array, removing the subsequent ones.
     */
    public static void removeDupes(final ArrayList<String> suggestions) {
        if (suggestions.size() < 2) return;
        int i = 1;
        // Don't cache suggestions.size(), since we may be removing items
        while (i < suggestions.size()) {
            final String cur = suggestions.get(i);
            // Compare each suggestion with each previous suggestion
            for (int j = 0; j < i; j++) {
                final String previous = suggestions.get(j);
                if (TextUtils.equals(cur, previous)) {
                    suggestions.remove(i);
                    i--;
                    break;
                }
            }
            i++;
        }
    }

    public static String capitalizeFirstCodePoint(final String s, final Locale locale) {
        if (s.length() <= 1) {
            return s.toUpperCase(locale);
        }
        // Please refer to the comment below in
        // {@link #capitalizeFirstAndDowncaseRest(String,Locale)} as this has the same shortcomings
        final int cutoff = s.offsetByCodePoints(0, 1);
        return s.substring(0, cutoff).toUpperCase(locale) + s.substring(cutoff);
    }

    public static String capitalizeFirstAndDowncaseRest(final String s, final Locale locale) {
        if (s.length() <= 1) {
            return s.toUpperCase(locale);
        }
        // TODO: fix the bugs below
        // - This does not work for Greek, because it returns upper case instead of title case.
        // - It does not work for Serbian, because it fails to account for the "lj" character,
        // which should be "Lj" in title case and "LJ" in upper case.
        // - It does not work for Dutch, because it fails to account for the "ij" digraph when it's
        // written as two separate code points. They are two different characters but both should
        // be capitalized as "IJ" as if they were a single letter in most words (not all). If the
        // unicode char for the ligature is used however, it works.
        final int cutoff = s.offsetByCodePoints(0, 1);
        return s.substring(0, cutoff).toUpperCase(locale) + s.substring(cutoff).toLowerCase(locale);
    }

    private static final int[] EMPTY_CODEPOINTS = {};

    public static int[] toCodePointArray(final String string) {
        final int length = string.length();
        if (length <= 0) {
            return EMPTY_CODEPOINTS;
        }
        final int[] codePoints = new int[string.codePointCount(0, length)];
        int destIndex = 0;
        for (int index = 0; index < length; index = string.offsetByCodePoints(index, 1)) {
            codePoints[destIndex] = string.codePointAt(index);
            destIndex++;
        }
        return codePoints;
    }

    public static String[] parseCsvString(final String text) {
        final int size = text.length();
        if (size == 0) {
            return null;
        }
        if (codePointCount(text) == 1) {
            return text.codePointAt(0) == Constants.CSV_SEPARATOR ? null : new String[] { text };
        }

        ArrayList<String> list = null;
        int start = 0;
        for (int pos = 0; pos < size; pos++) {
            final char c = text.charAt(pos);
            if (c == Constants.CSV_SEPARATOR) {
                // Skip empty entry.
                if (pos - start > 0) {
                    if (list == null) {
                        list = CollectionUtils.newArrayList();
                    }
                    list.add(text.substring(start, pos));
                }
                // Skip comma
                start = pos + 1;
            } else if (c == Constants.CSV_ESCAPE) {
                // Skip escape character and escaped character.
                pos++;
            }
        }
        final String remain = (size - start > 0) ? text.substring(start) : null;
        if (list == null) {
            return remain != null ? new String[] { remain } : null;
        }
        if (remain != null) {
            list.add(remain);
        }
        return list.toArray(new String[list.size()]);
    }

    // This method assumes the text is not null. For the empty string, it returns CAPITALIZE_NONE.
    public static int getCapitalizationType(final String text) {
        // If the first char is not uppercase, then the word is either all lower case or
        // camel case, and in either case we return CAPITALIZE_NONE.
        final int len = text.length();
        int index = 0;
        for (; index < len; index = text.offsetByCodePoints(index, 1)) {
            if (Character.isLetter(text.codePointAt(index))) {
                break;
            }
        }
        if (index == len) return CAPITALIZE_NONE;
        if (!Character.isUpperCase(text.codePointAt(index))) {
            return CAPITALIZE_NONE;
        }
        int capsCount = 1;
        int letterCount = 1;
        for (index = text.offsetByCodePoints(index, 1); index < len;
                index = text.offsetByCodePoints(index, 1)) {
            if (1 != capsCount && letterCount != capsCount) break;
            final int codePoint = text.codePointAt(index);
            if (Character.isUpperCase(codePoint)) {
                ++capsCount;
                ++letterCount;
            } else if (Character.isLetter(codePoint)) {
                // We need to discount non-letters since they may not be upper-case, but may
                // still be part of a word (e.g. single quote or dash, as in "IT'S" or "FULL-TIME")
                ++letterCount;
            }
        }
        // We know the first char is upper case. So we want to test if either every letter other
        // than the first is lower case, or if they are all upper case. If the string is exactly
        // one char long, then we will arrive here with letterCount 1, and this is correct, too.
        if (1 == capsCount) return CAPITALIZE_FIRST;
        return (letterCount == capsCount ? CAPITALIZE_ALL : CAPITALIZE_NONE);
    }

    public static boolean isIdenticalAfterUpcase(final String text) {
        final int len = text.length();
        for (int i = 0; i < len; i = text.offsetByCodePoints(i, 1)) {
            final int codePoint = text.codePointAt(i);
            if (Character.isLetter(codePoint) && !Character.isUpperCase(codePoint)) {
                return false;
            }
        }
        return true;
    }

    public static boolean isIdenticalAfterDowncase(final String text) {
        final int len = text.length();
        for (int i = 0; i < len; i = text.offsetByCodePoints(i, 1)) {
            final int codePoint = text.codePointAt(i);
            if (Character.isLetter(codePoint) && !Character.isLowerCase(codePoint)) {
                return false;
            }
        }
        return true;
    }

    public static boolean isIdenticalAfterCapitalizeEachWord(final String text,
            final String separators) {
        boolean needCapsNext = true;
        final int len = text.length();
        for (int i = 0; i < len; i = text.offsetByCodePoints(i, 1)) {
            final int codePoint = text.codePointAt(i);
            if (Character.isLetter(codePoint)) {
                if ((needCapsNext && !Character.isUpperCase(codePoint))
                        || (!needCapsNext && !Character.isLowerCase(codePoint))) {
                    return false;
                }
            }
            // We need a capital letter next if this is a separator.
            needCapsNext = (-1 != separators.indexOf(codePoint));
        }
        return true;
    }

    // TODO: like capitalizeFirst*, this does not work perfectly for Dutch because of the IJ digraph
    // which should be capitalized together in *some* cases.
    public static String capitalizeEachWord(final String text, final String separators,
            final Locale locale) {
        final StringBuilder builder = new StringBuilder();
        boolean needCapsNext = true;
        final int len = text.length();
        for (int i = 0; i < len; i = text.offsetByCodePoints(i, 1)) {
            final String nextChar = text.substring(i, text.offsetByCodePoints(i, 1));
            if (needCapsNext) {
                builder.append(nextChar.toUpperCase(locale));
            } else {
                builder.append(nextChar.toLowerCase(locale));
            }
            // We need a capital letter next if this is a separator.
            needCapsNext = (-1 != separators.indexOf(nextChar.codePointAt(0)));
        }
        return builder.toString();
    }

    /**
     * Approximates whether the text before the cursor looks like a URL.
     *
     * This is not foolproof, but it should work well in the practice.
     * Essentially it walks backward from the cursor until it finds something that's not a letter,
     * digit, or common URL symbol like underscore. If it hasn't found a period yet, then it
     * does not look like a URL.
     * If the text:
     * - starts with www and contains a period
     * - starts with a slash preceded by either a slash, whitespace, or start-of-string
     * Then it looks like a URL and we return true. Otherwise, we return false.
     *
     * Note: this method is called quite often, and should be fast.
     *
     * TODO: This will return that "abc./def" and ".abc/def" look like URLs to keep down the
     * code complexity, but ideally it should not. It's acceptable for now.
     */
    public static boolean lastPartLooksLikeURL(final CharSequence text) {
        int i = text.length();
        if (0 == i) return false;
        int wCount = 0;
        int slashCount = 0;
        boolean hasSlash = false;
        boolean hasPeriod = false;
        int codePoint = 0;
        while (i > 0) {
            codePoint =  Character.codePointBefore(text, i);
            if (codePoint < Constants.CODE_PERIOD || codePoint > 'z') {
                // Handwavy heuristic to see if that's a URL character. Anything between period
                // and z. This includes all lower- and upper-case ascii letters, period,
                // underscore, arrobase, question mark, equal sign. It excludes spaces, exclamation
                // marks, double quotes...
                // Anything that's not a URL-like character causes us to break from here and
                // evaluate normally.
                break;
            }
            if (Constants.CODE_PERIOD == codePoint) {
                hasPeriod = true;
            }
            if (Constants.CODE_SLASH == codePoint) {
                hasSlash = true;
                if (2 == ++slashCount) {
                    return true;
                }
            } else {
                slashCount = 0;
            }
            if ('w' == codePoint) {
                ++wCount;
            } else {
                wCount = 0;
            }
            i = Character.offsetByCodePoints(text, i, -1);
        }
        // End of the text run.
        // If it starts with www and includes a period, then it looks like a URL.
        if (wCount >= 3 && hasPeriod) return true;
        // If it starts with a slash, and the code point before is whitespace, it looks like an URL.
        if (1 == slashCount && (0 == i || Character.isWhitespace(codePoint))) return true;
        // If it has both a period and a slash, it looks like an URL.
        if (hasPeriod && hasSlash) return true;
        // Otherwise, it doesn't look like an URL.
        return false;
    }
}