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/*
 * Copyright (C) 2016 HaiYang Li
 *
 * 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.landawn.abacus.util;

import java.util.NoSuchElementException;

import com.landawn.abacus.util.function.BooleanSupplier;
import com.landawn.abacus.util.function.LongSupplier;
import com.landawn.abacus.util.function.Supplier;

/**
 *
 * @author Haiyang Li
 * @since 0.8
 */
public abstract class LongIterator extends ImmutableIterator {

    public static final LongIterator EMPTY = new LongIterator() {
        @Override
        public boolean hasNext() {
            return false;
        }

        @Override
        public long nextLong() {
            throw new NoSuchElementException();
        }
    };

    public static LongIterator empty() {
        return EMPTY;
    }

    /**
     *
     * @param a
     * @return
     */
    @SafeVarargs
    public static LongIterator of(final long... a) {
        return N.isNullOrEmpty(a) ? EMPTY : of(a, 0, a.length);
    }

    /**
     *
     * @param a
     * @param fromIndex
     * @param toIndex
     * @return
     */
    public static LongIterator of(final long[] a, final int fromIndex, final int toIndex) {
        N.checkFromToIndex(fromIndex, toIndex, a == null ? 0 : a.length);

        if (fromIndex == toIndex) {
            return EMPTY;
        }

        return new LongIterator() {
            private int cursor = fromIndex;

            @Override
            public boolean hasNext() {
                return cursor < toIndex;
            }

            @Override
            public long nextLong() {
                if (cursor >= toIndex) {
                    throw new NoSuchElementException();
                }

                return a[cursor++];
            }
        };
    }

    /**
     * Lazy evaluation.
     *
     * @param iteratorSupplier
     * @return
     */
    public static LongIterator of(final Supplier iteratorSupplier) {
        N.checkArgNotNull(iteratorSupplier, "iteratorSupplier");

        return new LongIterator() {
            private LongIterator iter = null;
            private boolean isInitialized = false;

            @Override
            public boolean hasNext() {
                if (isInitialized == false) {
                    init();
                }

                return iter.hasNext();
            }

            @Override
            public long nextLong() {
                if (isInitialized == false) {
                    init();
                }

                return iter.nextLong();
            }

            private void init() {
                if (isInitialized == false) {
                    isInitialized = true;
                    iter = iteratorSupplier.get();
                }
            }
        };
    }

    /**
     * Lazy evaluation.
     *
     * @param arraySupplier
     * @return
     */
    public static LongIterator oF(final Supplier arraySupplier) {
        N.checkArgNotNull(arraySupplier, "arraySupplier");

        return new LongIterator() {
            private long[] aar = null;
            private int len = 0;
            private int cur = 0;
            private boolean isInitialized = false;

            @Override
            public boolean hasNext() {
                if (isInitialized == false) {
                    init();
                }

                return cur < len;
            }

            @Override
            public long nextLong() {
                if (isInitialized == false) {
                    init();
                }

                if (cur >= len) {
                    throw new NoSuchElementException();
                }

                return aar[cur++];
            }

            private void init() {
                if (isInitialized == false) {
                    isInitialized = true;
                    aar = arraySupplier.get();
                    len = N.len(aar);
                }
            }
        };
    }

    /**
     * Returns an infinite {@code LongIterator}.
     *
     * @param supplier
     * @return
     */
    public static LongIterator generate(final LongSupplier supplier) {
        N.checkArgNotNull(supplier);

        return new LongIterator() {
            @Override
            public boolean hasNext() {
                return true;
            }

            @Override
            public long nextLong() {
                return supplier.getAsLong();
            }
        };
    }

    /**
     *
     * @param hasNext
     * @param supplier
     * @return
     */
    public static LongIterator generate(final BooleanSupplier hasNext, final LongSupplier supplier) {
        N.checkArgNotNull(hasNext);
        N.checkArgNotNull(supplier);

        return new LongIterator() {
            @Override
            public boolean hasNext() {
                return hasNext.getAsBoolean();
            }

            @Override
            public long nextLong() {
                if (hasNext() == false) {
                    throw new NoSuchElementException();
                }

                return supplier.getAsLong();
            }
        };
    }

    /**
     *
     * @return
     * @Deprecated use nextLong() instead.
     */
    @Deprecated
    @Override
    public Long next() {
        return nextLong();
    }

    public abstract long nextLong();

    /**
     * For each remaining.
     *
     * @param action
     */
    @Override
    @Deprecated
    public void forEachRemaining(java.util.function.Consumer action) {
        super.forEachRemaining(action);
    }

    /**
     *
     * @param 
     * @param action
     * @throws E the e
     */
    public  void foreachRemaining(Throwables.LongConsumer action) throws E {
        N.checkArgNotNull(action);

        while (hasNext()) {
            action.accept(nextLong());
        }
    }

    /**
     *
     * @param 
     * @param action
     * @throws E the e
     */
    public  void foreachIndexed(Throwables.IndexedLongConsumer action) throws E {
        N.checkArgNotNull(action);

        int idx = 0;

        while (hasNext()) {
            action.accept(idx++, nextLong());
        }
    }
}