namespace System.Web.UI.WebControls {
    using System;
    using System.Collections;
    using System.Collections.Generic;
    using System.ComponentModel;
    using System.Globalization;
    using System.Text;
    using System.Web.UI;

    public sealed class MenuItemCollection : ICollection, IStateManager {
        private List<MenuItem> _list;
        private MenuItem _owner;
        private int _version;

        private bool _isTrackingViewState;

        private List<LogItem> _log;


        public MenuItemCollection() : this(null) {
        }


        public MenuItemCollection(MenuItem owner) {
            _owner = owner;
            _list = new List<MenuItem>();
        }


        public int Count {
            get {
                return _list.Count;
            }
        }


        public bool IsSynchronized {
            get {
                return ((ICollection)_list).IsSynchronized;
            }
        }

        private List<LogItem> Log {
            get {
                if (_log == null) {
                    _log = new List<LogItem>();
                }
                return _log;
            }
        }


        public object SyncRoot {
            get {
                return ((ICollection)_list).SyncRoot;
            }
        }


        public MenuItem this[int index] {
            get {
                return _list[index];
            }
        }


        public void Add(MenuItem child) {
            AddAt(_list.Count, child);
        }


        public void AddAt(int index, MenuItem child) {
            if (child == null) {
                throw new ArgumentNullException("child");
            }

            if (child.Owner != null && child.Parent == null) {
                child.Owner.Items.Remove(child);
            }
            if (child.Parent != null) {
                child.Parent.ChildItems.Remove(child);
            }

            if (_owner != null) {
                child.SetParent(_owner);
                child.SetOwner(_owner.Owner);
            }

            _list.Insert(index, child);
            _version++;

            if (_isTrackingViewState) {
                ((IStateManager)child).TrackViewState();
                child.SetDirty();
            }
            Log.Add(new LogItem(LogItemType.Insert, index, _isTrackingViewState));
        }


        public void Clear() {
            if (this.Count == 0) return;
            if (_owner != null) {
                Menu owner = _owner.Owner;
                if (owner != null) {
                    MenuItem current = owner.SelectedItem;
                    // Check if the selected item is under this collection
                    while (current != null) {
                        if (this.Contains(current)) {
                            owner.SetSelectedItem(null);
                            break;
                        }
                        current = current.Parent;
                    }
                }
            }
            foreach (MenuItem item in _list) {
                item.SetParent(null);
            }
            _list.Clear();
            _version++;
            if (_isTrackingViewState) {
                // Clearing invalidates all previous log entries, so we can just clear them out and save some space
                Log.Clear();
            }
            Log.Add(new LogItem(LogItemType.Clear, 0, _isTrackingViewState));
        }


        public void CopyTo(Array array, int index) {
            if (!(array is MenuItem[])) {
                throw new ArgumentException(SR.GetString(SR.MenuItemCollection_InvalidArrayType), "array");
            }
            _list.CopyTo((MenuItem[])array, index);
        }


        public void CopyTo(MenuItem[] array, int index) {
            _list.CopyTo(array, index);
        }


        public bool Contains(MenuItem c) {
            return _list.Contains(c);
        }

        internal MenuItem FindItem(string[] path, int pos) {
            if (pos == path.Length) {
                return _owner;
            }

            string pathPart = TreeView.UnEscape(path[pos]);
            for (int i = 0; i < Count; i++) {
                MenuItem node = _list[i];
                if (node.Value == pathPart) {
                    return node.ChildItems.FindItem(path, pos + 1);
                }
            }

            return null;
        }


        public IEnumerator GetEnumerator() {
            return new MenuItemCollectionEnumerator(this);
        }


        public int IndexOf(MenuItem value) {
            return _list.IndexOf(value);
        }


        public void Remove(MenuItem value) {
            if (value == null) {
                throw new ArgumentNullException("value");
            }

            int index = _list.IndexOf(value);
            if (index != -1) {
                RemoveAt(index);
            }
        }


        public void RemoveAt(int index) {
            MenuItem item = _list[index];
            Menu owner = item.Owner;
            if (owner != null) {
                MenuItem current = owner.SelectedItem;
                // Check if the selected item is under this item
                while (current != null) {
                    if (current == item) {
                        owner.SetSelectedItem(null);
                        break;
                    }
                    current = current.Parent;
                }
            }
            item.SetParent(null);

            _list.RemoveAt(index);
            _version++;
            Log.Add(new LogItem(LogItemType.Remove, index, _isTrackingViewState));
        }

        internal void SetDirty() {
            foreach (LogItem item in Log) {
                item.Tracked = true;
            }
            for (int i = 0; i < Count; i++) {
                this[i].SetDirty();
            }
        }

        #region IStateManager implementation

        /// <internalonly/>
        bool IStateManager.IsTrackingViewState {
            get {
                return _isTrackingViewState;
            }
        }


        /// <internalonly/>
        void IStateManager.LoadViewState(object state) {
            object[] nodeState = (object[])state;
            if (nodeState != null) {
                if (nodeState[0] != null) {
                    string logString = (string)nodeState[0];
                    // Process each log entry
                    string[] items = logString.Split(',');
                    for (int i = 0; i < items.Length; i++) {
                        string[] parts = items[i].Split(':');
                        LogItemType type = (LogItemType)Int32.Parse(parts[0], CultureInfo.InvariantCulture);
                        int index = Int32.Parse(parts[1], CultureInfo.InvariantCulture);

                        if (type == LogItemType.Insert) {
                            AddAt(index, new MenuItem());
                        }
                        else if (type == LogItemType.Remove) {
                            RemoveAt(index);
                        }
                        else if (type == LogItemType.Clear) {
                            Clear();
                        }
                    }
                }

                for (int i = 0; i < nodeState.Length - 1; i++) {
                    if ((nodeState[i + 1] != null) && (this[i] != null)) {
                        ((IStateManager)this[i]).LoadViewState(nodeState[i + 1]);
                    }
                }
            }
        }


        /// <internalonly/>
        object IStateManager.SaveViewState() {
            object[] nodes = new object[Count + 1];

            bool hasViewState = false;

            if ((_log != null) && (_log.Count > 0)) {
                // Construct a string representation of the log, delimiting entries with commas
                // and seperator command and index with a colon
                StringBuilder builder = new StringBuilder();
                int realLogCount = 0;
                for (int i = 0; i < _log.Count; i++) {
                    LogItem item = (LogItem)_log[i];
                    if (item.Tracked) {
                        builder.Append((int)item.Type);
                        builder.Append(":");
                        builder.Append(item.Index);
                        if (i < (_log.Count - 1)) {
                            builder.Append(",");
                        }

                        realLogCount++;
                    }
                }

                if (realLogCount > 0) {
                    nodes[0] = builder.ToString();
                    hasViewState = true;
                }
            }

            for (int i = 0; i < Count; i++) {
                nodes[i + 1] = ((IStateManager)this[i]).SaveViewState();
                if (nodes[i + 1] != null) {
                    hasViewState = true;
                }
            }

            return (hasViewState ? nodes : null);
        }


        /// <internalonly/>
        void IStateManager.TrackViewState() {
            _isTrackingViewState = true;
            for (int i = 0; i < Count; i++) {
                ((IStateManager)this[i]).TrackViewState();
            }
        }
        #endregion

        /// <devdoc>
        ///     Convenience class for storing and using log entries.
        /// </devdoc>
        private class LogItem {
            private LogItemType _type;
            private int _index;
            private bool _tracked;

            public LogItem(LogItemType type, int index, bool tracked) {
                _type = type;
                _index = index;
                _tracked = tracked;
            }

            public int Index {
                get {
                    return _index;
                }
            }

            public bool Tracked {
                get {
                    return _tracked;
                }
                set {
                    _tracked = value;
                }
            }

            public LogItemType Type {
                get {
                    return _type;
                }
            }

        }

        /// <devdoc>
        ///     Convenience enumeration for identifying log commands
        /// </devdoc>
        private enum LogItemType {
            Insert = 0,
            Remove = 1,
            Clear = 2
        }

        // This is a copy of the ArrayListEnumeratorSimple in ArrayList.cs
        private class MenuItemCollectionEnumerator : IEnumerator {
            private MenuItemCollection list;
            private int index;
            private int version;
            private MenuItem currentElement;

            internal MenuItemCollectionEnumerator(MenuItemCollection list) {
                this.list = list;
                this.index = -1;
                version = list._version;
            }

            public bool MoveNext() {
                if (version != list._version)
                    throw new InvalidOperationException(SR.GetString(SR.ListEnumVersionMismatch));

                if (index < (list.Count - 1)) {
                    index++;
                    currentElement = list[index];
                    return true;
                }
                else
                    index = list.Count;
                return false;
            }

            object IEnumerator.Current {
                get {
                    return Current;
                }
            }

            public MenuItem Current {
                get {
                    if (index == -1)
                        throw new InvalidOperationException(SR.GetString(SR.ListEnumCurrentOutOfRange));
                    if (index >= list.Count)
                        throw new InvalidOperationException(SR.GetString(SR.ListEnumCurrentOutOfRange));
                    return currentElement;
                }
            }

            public void Reset() {
                if (version != list._version)
                    throw new InvalidOperationException(SR.GetString(SR.ListEnumVersionMismatch));
                currentElement = null;
                index = -1;
            }
        }
    }
}