/*
 * Hunt - A refined core library for D programming language.
 *
 * Copyright (C) 2018-2019 HuntLabs
 *
 * Website: https://www.huntlabs.net/
 *
 * Licensed under the Apache-2.0 License.
 *
 */

module hunt.collection.AbstractCollection;

import hunt.collection.Collection;
import hunt.Exceptions;
import hunt.Functions;
import hunt.Object;

import std.array;
import std.conv;
import std.range;

import hunt.logging;

/**
 * This class provides a skeletal implementation of the {@code Collection}
 * interface, to minimize the effort required to implement this interface. <p>
 *
 * To implement an unmodifiable collection, the programmer needs only to
 * extend this class and provide implementations for the {@code iterator} and
 * {@code size} methods.  (The iterator returned by the {@code iterator}
 * method must implement {@code hasNext} and {@code next}.)<p>
 *
 * To implement a modifiable collection, the programmer must additionally
 * override this class's {@code add} method (which otherwise throws an
 * {@code UnsupportedOperationException}), and the iterator returned by the
 * {@code iterator} method must additionally implement its {@code remove}
 * method.<p>
 *
 * The programmer should generally provide a void (no argument) and
 * {@code Collection} constructor, as per the recommendation in the
 * {@code Collection} interface specification.<p>
 *
 * The documentation for each non-abstract method in this class describes its
 * implementation in detail.  Each of these methods may be overridden if
 * the collection being implemented admits a more efficient implementation.<p>
 *
 * This class is a member of the
 * <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
 * Java Collections Framework</a>.
 *
 * @author  Josh Bloch
 * @author  Neal Gafter
 * @see Collection
 */
abstract class AbstractCollection(E) : Collection!E {
    /**
     * Sole constructor.  (For invocation by subclass constructors, typically
     * implicit.)
     */
    protected this() {
    }

    // Query Operations

    /**
     * Returns an iterator over the elements contained in this collection.
     *
     * @return an iterator over the elements contained in this collection
     */
    InputRange!E iterator() {
        throw new NotImplementedException();
    }

    abstract int size();

    /**
     * {@inheritDoc}
     *
     * <p>This implementation returns <tt>size() == 0</tt>.
     */
    bool isEmpty() {
        return size() == 0;
    }

    /**
     * {@inheritDoc}
     *
     * <p>This implementation iterates over the elements in the collection,
     * checking each element in turn for equality with the specified element.
     *
     * @throws ClassCastException   {@inheritDoc}
     * @throws NullPointerException {@inheritDoc}
     */
    bool contains(E o) {
        // Iterator<E> it = iterator();
        // if (o==null) {
        //     while (it.hasNext())
        //         if (it.next()==null)
        //             return true;
        // } else {
        //     while (it.hasNext())
        //         if (o.equals(it.next()))
        //             return true;
        // }
        // return false;

        throw new NotImplementedException();
    }

    bool add(E e) {
        throw new NotImplementedException();
    }

    bool remove(E e) {
        throw new NotImplementedException();
    }

    // E get(int index) { throw new UnsupportedOperationException(); }

    // Bulk Operations

    /**
     * {@inheritDoc}
     *
     * <p>This implementation iterates over the specified collection,
     * checking each element returned by the iterator in turn to see
     * if it's contained in this collection.  If all elements are so
     * contained <tt>true</tt> is returned, otherwise <tt>false</tt>.
     *
     * @throws ClassCastException            {@inheritDoc}
     * @throws NullPointerException          {@inheritDoc}
     * @see #contains(Object)
     */
    bool containsAll(Collection!E c) {
        foreach (E e; c)
            if (!contains(e))
                return false;
        return true;
    }

    /**
     * {@inheritDoc}
     *
     * <p>This implementation iterates over the specified collection, and adds
     * each object returned by the iterator to this collection, in turn.
     *
     * <p>Note that this implementation will throw an
     * <tt>UnsupportedOperationException</tt> unless <tt>add</tt> is
     * overridden (assuming the specified collection is non-empty).
     *
     * @throws UnsupportedOperationException {@inheritDoc}
     * @throws ClassCastException            {@inheritDoc}
     * @throws NullPointerException          {@inheritDoc}
     * @throws IllegalArgumentException      {@inheritDoc}
     * @throws IllegalStateException         {@inheritDoc}
     *
     * @see #add(Object)
     */
    bool addAll(Collection!E c) {
        bool modified = false;
        foreach (E e; c) {
            if (add(e))
                modified = true;
        }
        return modified;
    }

    bool addAll(E[] c) {
        bool modified = false;
        foreach (E e; c) {
            if (add(e))
                modified = true;
        }
        return modified;
    }

    /**
     * {@inheritDoc}
     *
     * <p>This implementation iterates over this collection, checking each
     * element returned by the iterator in turn to see if it's contained
     * in the specified collection.  If it's so contained, it's removed from
     * this collection with the iterator's <tt>remove</tt> method.
     *
     * <p>Note that this implementation will throw an
     * <tt>UnsupportedOperationException</tt> if the iterator returned by the
     * <tt>iterator</tt> method does not implement the <tt>remove</tt> method
     * and this collection contains one or more elements in common with the
     * specified collection.
     *
     * @throws UnsupportedOperationException {@inheritDoc}
     * @throws ClassCastException            {@inheritDoc}
     * @throws NullPointerException          {@inheritDoc}
     *
     * @see #remove(Object)
     * @see #contains(Object)
     */
    bool removeAll(Collection!E c) {
        assert(c !is null);
        bool modified = false;
        foreach (E k; c) {
            if (this.contains(k)) {
                this.remove(k);
                modified = true;
            }
        }

        return modified;
    }

    bool removeIf(Predicate!E filter) {
        assert(filter !is null);
        E[] items;
        foreach (E item; this) {
            if (filter(item))
                items ~= item;
        }

        foreach (E item; items) {
            remove(item);
        }

        return items.length > 0;
    }

    /**
     * {@inheritDoc}
     *
     * <p>This implementation iterates over this collection, checking each
     * element returned by the iterator in turn to see if it's contained
     * in the specified collection.  If it's not so contained, it's removed
     * from this collection with the iterator's <tt>remove</tt> method.
     *
     * <p>Note that this implementation will throw an
     * <tt>UnsupportedOperationException</tt> if the iterator returned by the
     * <tt>iterator</tt> method does not implement the <tt>remove</tt> method
     * and this collection contains one or more elements not present in the
     * specified collection.
     *
     * @throws UnsupportedOperationException {@inheritDoc}
     * @throws ClassCastException            {@inheritDoc}
     * @throws NullPointerException          {@inheritDoc}
     *
     * @see #remove(Object)
     * @see #contains(Object)
     */
    bool retainAll(Collection!E c) {
        assert(c !is null);
        bool modified = false;

        // InputRange!E it = iterator();
        // while (!it.empty) {
        //     E current = it.front();
        //     it.popFront();

        //     if (!c.contains(current)) {
        //         // it.remove();
        //         this.remove(current);
        //         modified = true;
        //     }
        // }
        import std.container.slist;

        SList!E list;

        foreach (E k; this) {
            if (!c.contains(k)) {
                // this.remove(k);
                list.insert(k);
            }
        }

        modified = !list.empty();
        foreach (E e; list)
            this.remove(e);

        return modified;
    }

    void clear() {
        throw new NotImplementedException();
    }

    int opApply(scope int delegate(ref E) dg) {
        throw new NotImplementedException();
        // return 0;
    }

    // int opApply(scope int delegate(MapEntry!(E) entry) dg) {
    //     throw new NotImplementedException();
    // }

    /**
     * {@inheritDoc}
     *
     * <p>This implementation returns an array containing all the elements
     * returned by this collection's iterator, in the same order, stored in
     * consecutive elements of the array, starting with index {@code 0}.
     * The length of the returned array is equal to the number of elements
     * returned by the iterator, even if the size of this collection changes
     * during iteration, as might happen if the collection permits
     * concurrent modification during iteration.  The {@code size} method is
     * called only as an optimization hint; the correct result is returned
     * even if the iterator returns a different number of elements.
     *
     * <p>This method is equivalent to:
     *
     *  <pre> {@code
     * List<E> list = new ArrayList<E>(size());
     * for (E e : this)
     *     list.add(e);
     * return list.toArray();
     * }</pre>
     */
    E[] toArray() {
        int s = size();
        if (s == 0)
            return [];

        E[] r = new E[s];
        int i = 0;
        foreach (E e; this) {
            r[i++] = e;
        }
        return r;
    }

    override bool opEquals(IObject o) {
        return opEquals(cast(Object) o);
    }

    override bool opEquals(Object o) {
        return super.opEquals(o);
    }

    override size_t toHash() @trusted nothrow {
        return super.toHash();
    }

    //  string conversion

    /**
     * Returns a string representation of this collection.  The string
     * representation consists of a list of the collection's elements in the
     * order they are returned by its iterator, enclosed in square brackets
     * ({@code "[]"}).  Adjacent elements are separated by the characters
     * {@code ", "} (comma and space).  Elements are converted to strings as
     * by {@link string#valueOf(Object)}.
     *
     * @return a string representation of this collection
     */
    override string toString() {
        if (size() == 0)
            return "[]";

        Appender!string sb;
        sb.put("[");
        bool isFirst = true;
        foreach (E e; this) {
            if (!isFirst)
                sb.put(", ");
            static if (is(E == class))
                sb.put(e is this ? "(this Collection)" : e.toString());
            else
                sb.put(e.to!string());
            isFirst = false;
        }
        sb.put(']');
        return sb.data;
    }
}