// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
/*
 *******************************************************************************
 * Copyright (C) 1996-2015, International Business Machines Corporation and    *
 * others. All Rights Reserved.                                                *
 *******************************************************************************
 */
package com.ibm.icu.dev.util;

import java.util.Collection;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.SortedSet;
import java.util.TreeSet;
import java.util.regex.Matcher;

/**
 * Utilities that ought to be on collections, but aren't
 *
 * @internal CLDR
 */
public final class CollectionUtilities {

    /**
     * Join an array of items.
     * @param <T>
     * @param array
     * @param separator
     * @return string
     */
    public static <T> String join(T[] array, String separator) {
        StringBuffer result = new StringBuffer();
        for (int i = 0; i < array.length; ++i) {
            if (i != 0) result.append(separator);
            result.append(array[i]);
        }
        return result.toString();
    }

    /**
     * Join a collection of items.
     * @param <T>
     * @param collection 
     * @param <U> 
     * @param array
     * @param separator
     * @return string
     */
    public static <T, U extends Iterable<T>>String join(U collection, String separator) {
        StringBuffer result = new StringBuffer();
        boolean first = true;
        for (Iterator it = collection.iterator(); it.hasNext();) {
            if (first) first = false;
            else result.append(separator);
            result.append(it.next());
        }
        return result.toString();
    }

    /**
     * Utility like Arrays.asList()
     * @param source 
     * @param target 
     * @param reverse 
     * @param <T> 
     * @return 
     */
    public static <T> Map<T,T> asMap(T[][] source, Map<T,T> target, boolean reverse) {
        int from = 0, to = 1;
        if (reverse) {
            from = 1; to = 0;
        }
        for (int i = 0; i < source.length; ++i) {
            target.put(source[i][from], source[i][to]);
        }
        return target;
    }

    /**
     * Add all items in iterator to target collection
     * @param <T>
     * @param <U>
     * @param source
     * @param target
     * @return
     */
    public static <T, U extends Collection<T>> U addAll(Iterator<T> source, U target) {
        while (source.hasNext()) {
            target.add(source.next());
        }
        return target; // for chaining
    }

    /**
     * Get the size of an iterator (number of items in it).
     * @param source
     * @return
     */
    public static int size(Iterator source) {
        int result = 0;
        while (source.hasNext()) {
            source.next();
            ++result;
        }
        return result;
    }


    /**
     * @param <T>
     * @param source
     * @return
     */
    public static <T> Map<T,T> asMap(T[][] source) {
        return asMap(source, new HashMap<T,T>(), false);
    }

    /**
     * Utility that ought to be on Map
     * @param m 
     * @param itemsToRemove 
     * @param <K> 
     * @param <V> 
     * @return map passed in
     */
    public static <K,V> Map<K,V> removeAll(Map<K,V> m, Collection<K> itemsToRemove) {
        for (Iterator it = itemsToRemove.iterator(); it.hasNext();) {
            Object item = it.next();
            m.remove(item);
        }
        return m;
    }

    /**
     * Get first item in collection, or null if there is none.
     * @param <T>
     * @param <U>
     * @param c
     * @return first item
     */
    public <T, U extends Collection<T>> T getFirst(U c) {
        Iterator<T> it = c.iterator();
        if (!it.hasNext()) return null;
        return it.next();
    }

    /**
     * Get the "best" in collection. That is the least if direction is < 0, otherwise the greatest. The first is chosen if there are multiples.
     * @param <T>
     * @param <U>
     * @param c
     * @param comp
     * @param direction
     * @return
     */
    public static <T, U extends Collection<T>> T getBest(U c, Comparator<T> comp, int direction) {
        Iterator<T> it = c.iterator();
        if (!it.hasNext()) return null;
        T bestSoFar = it.next();
        if (direction < 0) {
            while (it.hasNext()) {
                T item = it.next();
                int compValue = comp.compare(item, bestSoFar);
                if (compValue < 0) {
                    bestSoFar = item;
                }
            }
        } else {
            while (it.hasNext()) {
                T item = it.next();
                int compValue = comp.compare(item, bestSoFar);
                if (compValue > 0) {
                    bestSoFar = item;
                }
            }
        }
        return bestSoFar;
    }

    /**
     * Matches item.
     * @param <T>
     */
    public interface ObjectMatcher<T> {
        /**
         * Must handle null, never throw exception
         * @param o 
         * @return 
         */
        boolean matches(T o);
    }

    /**
     * Reverse a match
     * @param <T>
     */
    public static class InverseMatcher<T> implements ObjectMatcher<T> {
        ObjectMatcher<T> other;
        /**
         * @param toInverse
         * @return
         */
        public ObjectMatcher set(ObjectMatcher toInverse) {
            other = toInverse;
            return this;
        }
        public boolean matches(T value) {
            return !other.matches(value);
        }
    }

    /**
     * Remove matching items
     * @param <T>
     * @param <U>
     * @param c
     * @param f
     * @return
     */
    public static <T, U extends Collection<T>> U removeAll(U c, ObjectMatcher<T> f) {
        for (Iterator<T> it = c.iterator(); it.hasNext();) {
            T item = it.next();
            if (f.matches(item)) it.remove();
        }
        return c;
    }

    /**
     * Retain matching items
     * @param <T>
     * @param <U>
     * @param c
     * @param f
     * @return
     */
    public static <T, U extends Collection<T>> U retainAll(U c, ObjectMatcher<T> f) {
        for (Iterator<T> it = c.iterator(); it.hasNext();) {
            T item = it.next();
            if (!f.matches(item)) it.remove();
        }
        return c;
    }

    /**
     * @param a
     * @param b
     * @return
     */
    public static boolean containsSome(Collection a, Collection b) {
        // fast paths
        if (a.size() == 0 || b.size() == 0) return false;
        if (a == b) return true; // must test after size test.

        if (a instanceof SortedSet && b instanceof SortedSet) {
            SortedSet aa = (SortedSet) a;
            SortedSet bb = (SortedSet) b;
            Comparator bbc = bb.comparator();
            Comparator aac = aa.comparator();
            if (bbc == null && aac == null) {
                Iterator ai = aa.iterator();
                Iterator bi = bb.iterator();
                Comparable ao = (Comparable) ai.next(); // these are ok, since the sizes are != 0
                Comparable bo = (Comparable) bi.next();
                while (true) {
                    int rel = ao.compareTo(bo);
                    if (rel < 0) {
                        if (!ai.hasNext()) return false;
                        ao = (Comparable) ai.next();
                    } else if (rel > 0) {
                        if (!bi.hasNext()) return false;
                        bo = (Comparable) bi.next();
                    } else {
                        return true;  
                    }
                }
            } else if (bbc.equals(a)) {
                Iterator ai = aa.iterator();
                Iterator bi = bb.iterator();
                Object ao = ai.next(); // these are ok, since the sizes are != 0
                Object bo = bi.next();
                while (true) {
                    int rel = aac.compare(ao, bo);
                    if (rel < 0) {
                        if (!ai.hasNext()) return false;
                        ao = ai.next();
                    } else if (rel > 0)  {
                        if (!bi.hasNext()) return false;
                        bo = bi.next();
                    } else {
                        return true;  
                    }
                }
            }           
        }
        for (Iterator it = a.iterator(); it.hasNext();) {
            if (b.contains(it.next())) return true;
        }
        return false;
    }

    public static boolean containsAll(Collection a, Collection b) {
        // fast paths
        if (a == b) return true;
        if (b.size() == 0) return true;
        if (a.size() < b.size()) return false;

        if (a instanceof SortedSet && b instanceof SortedSet) {
            SortedSet aa = (SortedSet) a;
            SortedSet bb = (SortedSet) b;
            Comparator bbc = bb.comparator();
            Comparator aac = aa.comparator();
            if (bbc == null && aac == null) {
                Iterator ai = aa.iterator();
                Iterator bi = bb.iterator();
                Comparable ao = (Comparable) ai.next(); // these are ok, since the sizes are != 0
                Comparable bo = (Comparable) bi.next();
                while (true) {
                    int rel = ao.compareTo(bo);
                    if (rel == 0) {
                        if (!bi.hasNext()) return true;
                        if (!ai.hasNext()) return false;
                        bo = (Comparable) bi.next();
                        ao = (Comparable) ai.next();
                    } else if (rel < 0) {
                        if (!ai.hasNext()) return false;
                        ao = (Comparable) ai.next();
                    } else {
                        return false;  
                    }
                }
            } else if (bbc.equals(aac)) {
                Iterator ai = aa.iterator();
                Iterator bi = bb.iterator();
                Object ao = ai.next(); // these are ok, since the sizes are != 0
                Object bo = bi.next();
                while (true) {
                    int rel = aac.compare(ao, bo);
                    if (rel == 0) {
                        if (!bi.hasNext()) return true;
                        if (!ai.hasNext()) return false;
                        bo = bi.next();
                        ao = ai.next();
                    } else if (rel < 0) {
                        if (!ai.hasNext()) return false;
                        ao = ai.next();
                    } else {
                        return false;  
                    }
                }
            }           
        }
        return a.containsAll(b);
    }

    public static boolean containsNone(Collection a, Collection b) {
        return !containsSome(a, b);
    }

    /**
     * Used for results of getContainmentRelation
     */
    public static final int
    ALL_EMPTY = 0,
    NOT_A_SUPERSET_B = 1,
    NOT_A_DISJOINT_B = 2,
    NOT_A_SUBSET_B = 4,
    NOT_A_EQUALS_B = NOT_A_SUBSET_B | NOT_A_SUPERSET_B,
    A_PROPER_SUBSET_OF_B = NOT_A_DISJOINT_B | NOT_A_SUPERSET_B,
    A_PROPER_SUPERSET_B = NOT_A_SUBSET_B | NOT_A_DISJOINT_B,
    A_PROPER_OVERLAPS_B = NOT_A_SUBSET_B | NOT_A_DISJOINT_B | NOT_A_SUPERSET_B;

    /**
     * Assesses all the possible containment relations between collections A and B with one call.<br>
     * Returns an int with bits set, according to a "Venn Diagram" view of A vs B.<br>
     * NOT_A_SUPERSET_B: a - b != {}<br>
     * NOT_A_DISJOINT_B: a * b != {}  // * is intersects<br>
     * NOT_A_SUBSET_B: b - a != {}<br>
     * Thus the bits can be used to get the following relations:<br>
     * for A_SUPERSET_B, use (x & CollectionUtilities.NOT_A_SUPERSET_B) == 0<br>
     * for A_SUBSET_B, use (x & CollectionUtilities.NOT_A_SUBSET_B) == 0<br>
     * for A_EQUALS_B, use (x & CollectionUtilities.NOT_A_EQUALS_B) == 0<br>
     * for A_DISJOINT_B, use (x & CollectionUtilities.NOT_A_DISJOINT_B) == 0<br>
     * for A_OVERLAPS_B, use (x & CollectionUtilities.NOT_A_DISJOINT_B) != 0<br>
     */
    public static int getContainmentRelation(Collection a, Collection b) {
        if (a.size() == 0) {
            return (b.size() == 0) ? ALL_EMPTY : NOT_A_SUPERSET_B;
        } else if (b.size() == 0) {
            return NOT_A_SUBSET_B;
        }
        int result = 0;
        // WARNING: one might think that the following can be short-circuited, by looking at
        // the sizes of a and b. However, this would fail in general, where a different comparator is being
        // used in the two collections. Unfortunately, there is no failsafe way to test for that.
        for (Iterator it = a.iterator(); result != 6 && it.hasNext();) {
            result |= (b.contains(it.next())) ? NOT_A_DISJOINT_B : NOT_A_SUBSET_B;
        }
        for (Iterator it = b.iterator(); (result & 3) != 3 && it.hasNext();) {
            result |= (a.contains(it.next())) ? NOT_A_DISJOINT_B : NOT_A_SUPERSET_B;
        }
        return result;
    }

    /**
     * Does one string contain another, starting at a specific offset?
     * @param text
     * @param offset
     * @param other
     * @return
     */
    public static int matchesAt(CharSequence text, int offset, CharSequence other) {
        int len = other.length();
        int i = 0;
        int j = offset;
        for (; i < len; ++i, ++j) {
            char pc = other.charAt(i);
            char tc = text.charAt(j);
            if (pc != tc) return -1;
        }
        return i;
    }

    /**
     * For producing filtered iterators
     */
    public static abstract class FilteredIterator implements Iterator {
        private Iterator baseIterator;
        private static final Object EMPTY = new Object();
        private static final Object DONE = new Object();
        private Object nextObject = EMPTY;
        public FilteredIterator set(Iterator baseIterator) {
            this.baseIterator = baseIterator;
            return this;
        }
        public void remove() {
            throw new UnsupportedOperationException("Doesn't support removal");
        }
        public Object next() {
            Object result = nextObject;
            nextObject = EMPTY;
            return result;
        }       
        public boolean hasNext() {
            if (nextObject == DONE) return false;
            if (nextObject != EMPTY) return true;
            while (baseIterator.hasNext()) {
                nextObject = baseIterator.next();
                if (isIncluded(nextObject)) {
                    return true;
                }
            }
            nextObject = DONE;
            return false;
        }
        abstract public boolean isIncluded(Object item);
    }

    public static class PrefixIterator extends FilteredIterator {
        private String prefix;
        public PrefixIterator set(Iterator baseIterator, String prefix) {
            super.set(baseIterator);
            this.prefix = prefix;
            return this;
        }
        public boolean isIncluded(Object item) {
            return ((String)item).startsWith(prefix);
        }
    }

    public static class RegexIterator extends FilteredIterator {
        private Matcher matcher;
        public RegexIterator set(Iterator baseIterator, Matcher matcher) {
            super.set(baseIterator);
            this.matcher = matcher;
            return this;
        }
        public boolean isIncluded(Object item) {
            return matcher.reset((String)item).matches();
        }
    }

    /**
     * Compare, allowing nulls
     * @param a
     * @param b
     * @return
     */
    public static <T> boolean equals(T a, T b) {
        return a == null 
                ? b == null 
                : b == null ? false : a.equals(b);
    }

    /**
     * Compare, allowing nulls and putting them first
     * @param a
     * @param b
     * @return
     */
    public static <T extends Comparable> int compare(T a, T b) {
        return a == null 
                ? b == null ? 0 : -1 
                        : b == null ? 1 : a.compareTo(b);
    }

    /**
     * Compare iterators
     * @param iterator1
     * @param iterator2
     * @return
     */
    public static <T extends Comparable> int compare(Iterator<T> iterator1, Iterator<T> iterator2) {
        int diff;
        while (true) {
            if (!iterator1.hasNext()) {
                return iterator2.hasNext() ? -1 : 0;
            } else if (!iterator2.hasNext()) {
                return 1;
            }
            diff = CollectionUtilities.compare(iterator1.next(), iterator2.next());
            if (diff != 0) {
                return diff;
            }
        }
    }

    /**
     * Compare, with shortest first, and otherwise lexicographically
     * @param a
     * @param b
     * @return
     */
    public static <T extends Comparable, U extends Collection<T>> int compare(U o1, U o2) {
        int diff = o1.size() - o2.size();
        if (diff != 0) {
            return diff;
        }
        Iterator<T> iterator1 = o1.iterator();
        Iterator<T> iterator2 = o2.iterator();
        return compare(iterator1, iterator2);
    }

    /**
     * Compare, with shortest first, and otherwise lexicographically
     * @param a
     * @param b
     * @return
     */
    public static <T extends Comparable, U extends Set<T>> int compare(U o1, U o2) {
        int diff = o1.size() - o2.size();
        if (diff != 0) {
            return diff;
        }
        Collection<T> x1 = SortedSet.class.isInstance(o1) ? o1 : new TreeSet<T>(o1);
        Collection<T> x2 = SortedSet.class.isInstance(o2) ? o2 : new TreeSet<T>(o2);
        return compare(x1, x2);
    }

    public static class SetComparator<T extends Comparable> 
    implements Comparator<Set<T>> {
        public int compare(Set<T> o1, Set<T> o2) {
            return CollectionUtilities.compare(o1, o2);
        }
    };


    public static class CollectionComparator<T extends Comparable> 
    implements Comparator<Collection<T>> {
        public int compare(Collection<T> o1, Collection<T> o2) {
            return CollectionUtilities.compare(o1, o2);
        }
    };

    /**
     * Compare, allowing nulls and putting them first
     * @param a
     * @param b
     * @return
     */
    public static <K extends Comparable, V extends Comparable, T extends Entry<K, V>> int compare(T a, T b) {
        if (a == null) {
            return b == null ? 0 : -1;
        } else if (b == null) {
            return 1;
        }
        int diff = compare(a.getKey(), b.getKey());
        if (diff != 0) {
            return diff;
        }
        return compare(a.getValue(), b.getValue());
    }

    public static <K extends Comparable, V extends Comparable, T extends Entry<K, V>> int compareEntrySets(Collection<T> o1, Collection<T> o2) {
        int diff = o1.size() - o2.size();
        if (diff != 0) {
            return diff;
        }
        Iterator<T> iterator1 = o1.iterator();
        Iterator<T> iterator2 = o2.iterator();
        while (true) {
            if (!iterator1.hasNext()) {
                return iterator2.hasNext() ? -1 : 0;
            } else if (!iterator2.hasNext()) {
                return 1;
            }
            T item1 = iterator1.next();
            T item2 = iterator2.next();
            diff = CollectionUtilities.compare(item1, item2);
            if (diff != 0) {
                return diff;
            }
        }
    }

    public static class MapComparator<K extends Comparable, V extends Comparable> implements Comparator<Map<K,V>> {
        public int compare(Map<K, V> o1, Map<K, V> o2) {
            return CollectionUtilities.compareEntrySets(o1.entrySet(), o2.entrySet());
        }
    };
    
    public static class ComparableComparator<T extends Comparable> implements Comparator<T> {
        public int compare(T arg0, T arg1) {
            return CollectionUtilities.compare(arg0, arg1);
        }
    }
}
