/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsISupports.idl"

interface nsISimpleEnumerator;

/**
 * nsIArray
 *
 * An indexed collection of elements. Provides basic functionality for
 * retrieving elements at a specific position, searching for
 * elements. Indexes are zero-based, such that the last element in the
 * array is stored at the index length-1.
 *
 * For an array which can be modified, see nsIMutableArray below.
 *
 * Neither interface makes any attempt to protect the individual
 * elements from modification. The convention is that the elements of
 * the array should not be modified. Documentation within a specific
 * interface should describe variations from this convention.
 *
 * It is also convention that if an interface provides access to an
 * nsIArray, that the array should not be QueryInterfaced to an
 * nsIMutableArray for modification. If the interface in question had
 * intended the array to be modified, it would have returned an
 * nsIMutableArray!
 *
 * null is a valid entry in the array, and as such any nsISupports
 * parameters may be null, except where noted.
 */
[scriptable, uuid(114744d9-c369-456e-b55a-52fe52880d2d)]
interface nsIArray : nsISupports
{
    /**
     * length
     *
     * number of elements in the array.
     */
    readonly attribute unsigned long length;

    /**
     * queryElementAt()
     *
     * Retrieve a specific element of the array, and QueryInterface it
     * to the specified interface. null is a valid result for
     * this method, but exceptions are thrown in other circumstances
     * 
     * @param index position of element
     * @param uuid the IID of the requested interface
     * @param result the object, QI'd to the requested interface
     *
     * @throws NS_ERROR_NO_INTERFACE when an entry exists at the
     *         specified index, but the requested interface is not
     *         available.
     * @throws NS_ERROR_ILLEGAL_VALUE when index > length-1
     *
     */
    void queryElementAt(in unsigned long index,
                        in nsIIDRef uuid,
                        [iid_is(uuid), retval] out nsQIResult result);
    
    /**
     * indexOf()
     * 
     * Get the position of a specific element. Note that since null is
     * a valid input, exceptions are used to indicate that an element
     * is not found.
     * 
     * @param startIndex The initial element to search in the array
     *                   To start at the beginning, use 0 as the
     *                   startIndex
     * @param element    The element you are looking for
     * @returns a number >= startIndex which is the position of the
     *          element in the array.
     * @throws NS_ERROR_FAILURE if the element was not in the array.
     */
    unsigned long indexOf(in unsigned long startIndex,
                          in nsISupports element);

    /**
     * enumerate the array
     *
     * @returns a new enumerator positioned at the start of the array
     * @throws NS_ERROR_FAILURE if the array is empty (to make it easy
     *         to detect errors), or NS_ERROR_OUT_OF_MEMORY if out of memory.
     */
    nsISimpleEnumerator enumerate();
};
