package me.patothebest.gamecore.util;

import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;

import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;

public class CacheCollection<E> implements Collection<E> {

    private final Cache<E, Byte> cacheMap;

    @SuppressWarnings("unchecked")
    public CacheCollection(CallableCallback<CacheBuilder> mapper) {
        CacheBuilder cacheBuilder = CacheBuilder.newBuilder();
        cacheBuilder = mapper.call(cacheBuilder);
        this.cacheMap = cacheBuilder.build();
    }

    /**
     * Returns the number of elements in this list.  If this list contains
     * more than <tt>Integer.MAX_VALUE</tt> elements, returns
     * <tt>Integer.MAX_VALUE</tt>.
     *
     * @return the number of elements in this list
     */
    @Override
    public int size() {
        return (int) cacheMap.size();
    }

    /**
     * Returns <tt>true</tt> if this list contains no elements.
     *
     * @return <tt>true</tt> if this list contains no elements
     */
    @Override
    public boolean isEmpty() {
        return cacheMap.size() == 0;
    }

    /**
     * Returns <tt>true</tt> if this list contains the specified element.
     * More formally, returns <tt>true</tt> if and only if this list contains
     * at least one element <tt>e</tt> such that
     * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>.
     *
     * @param o element whose presence in this list is to be tested
     *
     * @return <tt>true</tt> if this list contains the specified element
     *
     * @throws ClassCastException   if the type of the specified element
     *                              is incompatible with this list
     *                              (<a href="Collection.html#optional-restrictions">optional</a>)
     * @throws NullPointerException if the specified element is null and this
     *                              list does not permit null elements
     *                              (<a href="Collection.html#optional-restrictions">optional</a>)
     */
    @Override
    public boolean contains(Object o) {
        return cacheMap.asMap().containsKey(o);
    }

    /**
     * Returns an iterator over the elements in this list in proper sequence.
     *
     * @return an iterator over the elements in this list in proper sequence
     */
    @Override
    public Iterator<E> iterator() {
        return cacheMap.asMap().keySet().iterator();
    }

    /**
     * Returns an array containing all of the elements in this list in proper
     * sequence (from first to last element).
     * <p>
     * <p>The returned array will be "safe" in that no references to it are
     * maintained by this list.  (In other words, this method must
     * allocate a new array even if this list is backed by an array).
     * The caller is thus free to modify the returned array.
     * <p>
     * <p>This method acts as bridge between array-based and collection-based
     * APIs.
     *
     * @return an array containing all of the elements in this list in proper
     * sequence
     *
     * @see Arrays#asList(Object[])
     */
    @Override
    public Object[] toArray() {
        return cacheMap.asMap().keySet().toArray();
    }

    /**
     * Returns an array containing all of the elements in this list in
     * proper sequence (from first to last element); the runtime type of
     * the returned array is that of the specified array.  If the list fits
     * in the specified array, it is returned therein.  Otherwise, a new
     * array is allocated with the runtime type of the specified array and
     * the size of this list.
     * <p>
     * <p>If the list fits in the specified array with room to spare (i.e.,
     * the array has more elements than the list), the element in the array
     * immediately following the end of the list is set to <tt>null</tt>.
     * (This is useful in determining the length of the list <i>only</i> if
     * the caller knows that the list does not contain any null elements.)
     * <p>
     * <p>Like the {@link #toArray()} method, this method acts as bridge between
     * array-based and collection-based APIs.  Further, this method allows
     * precise control over the runtime type of the output array, and may,
     * under certain circumstances, be used to save allocation costs.
     * <p>
     * <p>Suppose <tt>x</tt> is a list known to contain only strings.
     * The following code can be used to dump the list into a newly
     * allocated array of <tt>String</tt>:
     * <p>
     * <pre>{@code
     *     String[] y = x.toArray(new String[0]);
     * }</pre>
     * <p>
     * Note that <tt>toArray(new Object[0])</tt> is identical in function to
     * <tt>toArray()</tt>.
     *
     * @param a the array into which the elements of this list are to
     *          be stored, if it is big enough; otherwise, a new array of the
     *          same runtime type is allocated for this purpose.
     *
     * @return an array containing the elements of this list
     *
     * @throws ArrayStoreException  if the runtime type of the specified array
     *                              is not a supertype of the runtime type of every element in
     *                              this list
     * @throws NullPointerException if the specified array is null
     */
    @Override
    public <T> T[] toArray(T[] a) {
        return cacheMap.asMap().keySet().toArray(a);
    }
    /**
     * Appends the specified element to the end of this list (optional
     * operation).
     * <p>
     * <p>Lists that support this operation may place limitations on what
     * elements may be added to this list.  In particular, some
     * lists will refuse to add null elements, and others will impose
     * restrictions on the type of elements that may be added.  List
     * classes should clearly specify in their documentation any restrictions
     * on what elements may be added.
     *
     * @param e element to be appended to this list
     *
     * @return <tt>true</tt> (as specified by {@link Collection#add})
     *
     * @throws UnsupportedOperationException if the <tt>add</tt> operation
     *                                       is not supported by this list
     * @throws ClassCastException            if the class of the specified element
     *                                       prevents it from being added to this list
     * @throws NullPointerException          if the specified element is null and this
     *                                       list does not permit null elements
     * @throws IllegalArgumentException      if some property of this element
     *                                       prevents it from being added to this list
     */
    @Override
    public boolean add(E e) {
        cacheMap.put(e, (byte) 0);
        return true;
    }

    /**
     * Removes the first occurrence of the specified element from this list,
     * if it is present (optional operation).  If this list does not contain
     * the element, it is unchanged.  More formally, removes the element with
     * the lowest index <tt>i</tt> such that
     * <tt>(o==null&nbsp;?&nbsp;get(i)==null&nbsp;:&nbsp;o.equals(get(i)))</tt>
     * (if such an element exists).  Returns <tt>true</tt> if this list
     * contained the specified element (or equivalently, if this list changed
     * as a result of the call).
     *
     * @param o element to be removed from this list, if present
     *
     * @return <tt>true</tt> if this list contained the specified element
     *
     * @throws ClassCastException            if the type of the specified element
     *                                       is incompatible with this list
     *                                       (<a href="Collection.html#optional-restrictions">optional</a>)
     * @throws NullPointerException          if the specified element is null and this
     *                                       list does not permit null elements
     *                                       (<a href="Collection.html#optional-restrictions">optional</a>)
     * @throws UnsupportedOperationException if the <tt>remove</tt> operation
     *                                       is not supported by this list
     */
    @Override
    public boolean remove(Object o) {
        cacheMap.invalidate(o);
        return true;
    }

    /**
     * Returns <tt>true</tt> if this list contains all of the elements of the
     * specified collection.
     *
     * @param c collection to be checked for containment in this list
     *
     * @return <tt>true</tt> if this list contains all of the elements of the
     * specified collection
     *
     * @throws ClassCastException   if the types of one or more elements
     *                              in the specified collection are incompatible with this
     *                              list
     *                              (<a href="Collection.html#optional-restrictions">optional</a>)
     * @throws NullPointerException if the specified collection contains one
     *                              or more null elements and this list does not permit null
     *                              elements
     *                              (<a href="Collection.html#optional-restrictions">optional</a>),
     *                              or if the specified collection is null
     * @see #contains(Object)
     */
    @Override
    public boolean containsAll(Collection<?> c) {
        for (Object o : c) {
            if (!contains(o)) {
                return false;
            }
        }

        return true;
    }

    /**
     * Appends all of the elements in the specified collection to the end of
     * this list, in the order that they are returned by the specified
     * collection's iterator (optional operation).  The behavior of this
     * operation is undefined if the specified collection is modified while
     * the operation is in progress.  (Note that this will occur if the
     * specified collection is this list, and it's nonempty.)
     *
     * @param c collection containing elements to be added to this list
     *
     * @return <tt>true</tt> if this list changed as a result of the call
     *
     * @throws UnsupportedOperationException if the <tt>addAll</tt> operation
     *                                       is not supported by this list
     * @throws ClassCastException            if the class of an element of the specified
     *                                       collection prevents it from being added to this list
     * @throws NullPointerException          if the specified collection contains one
     *                                       or more null elements and this list does not permit null
     *                                       elements, or if the specified collection is null
     * @throws IllegalArgumentException      if some property of an element of the
     *                                       specified collection prevents it from being added to this list
     * @see #add(Object)
     */
    @Override
    public boolean addAll(Collection<? extends E> c) {
        for (E e : c) {
            add(e);
        }

        return true;
    }

    /**
     * Removes from this list all of its elements that are contained in the
     * specified collection (optional operation).
     *
     * @param c collection containing elements to be removed from this list
     *
     * @return <tt>true</tt> if this list changed as a result of the call
     *
     * @throws UnsupportedOperationException if the <tt>removeAll</tt> operation
     *                                       is not supported by this list
     * @throws ClassCastException            if the class of an element of this list
     *                                       is incompatible with the specified collection
     *                                       (<a href="Collection.html#optional-restrictions">optional</a>)
     * @throws NullPointerException          if this list contains a null element and the
     *                                       specified collection does not permit null elements
     *                                       (<a href="Collection.html#optional-restrictions">optional</a>),
     *                                       or if the specified collection is null
     * @see #remove(Object)
     * @see #contains(Object)
     */
    @Override
    public boolean removeAll(Collection<?> c) {
        for (Object o : c) {
            remove(o);
        }

        return true;
    }

    /**
     * Retains only the elements in this list that are contained in the
     * specified collection (optional operation).  In other words, removes
     * from this list all of its elements that are not contained in the
     * specified collection.
     *
     * @param c collection containing elements to be retained in this list
     *
     * @return <tt>true</tt> if this list changed as a result of the call
     *
     * @throws UnsupportedOperationException if the <tt>retainAll</tt> operation
     *                                       is not supported by this list
     * @throws ClassCastException            if the class of an element of this list
     *                                       is incompatible with the specified collection
     *                                       (<a href="Collection.html#optional-restrictions">optional</a>)
     * @throws NullPointerException          if this list contains a null element and the
     *                                       specified collection does not permit null elements
     *                                       (<a href="Collection.html#optional-restrictions">optional</a>),
     *                                       or if the specified collection is null
     * @see #remove(Object)
     * @see #contains(Object)
     */
    @Override
    public boolean retainAll(Collection<?> c) {
        removeIf(e -> !c.contains(e));
        return true;
    }

    /**
     * Removes all of the elements from this list (optional operation).
     * The list will be empty after this call returns.
     *
     * @throws UnsupportedOperationException if the <tt>clear</tt> operation
     *                                       is not supported by this list
     */
    @Override
    public void clear() {
        cacheMap.invalidateAll();
    }
}
