// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

/*
 * Ordered String/String[] collection of name/value pairs with support for null key
 * Wraps NameObject collection
 *
 */

using System.ComponentModel;
using System.Diagnostics;
using System.Runtime.Serialization;
using System.Text;

namespace System.Collections.Specialized
{
    /// <devdoc>
    /// <para>Represents a sorted collection of associated <see cref='string' qualify='true'/> keys and <see cref='string' qualify='true'/> values that
    ///    can be accessed either with the hash code of the key or with the index.</para>
    /// </devdoc>
    public class NameValueCollection : NameObjectCollectionBase
    {
        private string?[]? _all; // Do not rename (binary serialization)
        private string?[]? _allKeys; // Do not rename (binary serialization)

        //
        // Constructors
        //

        /// <devdoc>
        /// <para>Creates an empty <see cref='System.Collections.Specialized.NameValueCollection'/> with the default initial capacity
        ///    and using the default case-insensitive hash code provider and the default
        ///    case-insensitive comparer.</para>
        /// </devdoc>
        public NameValueCollection() : base()
        {
        }

        /// <devdoc>
        /// <para>Copies the entries from the specified <see cref='System.Collections.Specialized.NameValueCollection'/> to a new <see cref='System.Collections.Specialized.NameValueCollection'/> with the same initial capacity as
        ///    the number of entries copied and using the default case-insensitive hash code
        ///    provider and the default case-insensitive comparer.</para>
        /// </devdoc>
        public NameValueCollection(NameValueCollection col)
            : base(col?.Comparer)
        {
            Add(col!);
        }

        [Obsolete("This constructor has been deprecated. Use NameValueCollection(IEqualityComparer) instead.")]
        public NameValueCollection(IHashCodeProvider? hashProvider, IComparer? comparer)
            : base(hashProvider, comparer)
        {
        }

        /// <devdoc>
        /// <para>Creates an empty <see cref='System.Collections.Specialized.NameValueCollection'/> with
        ///    the specified initial capacity and using the default case-insensitive hash code
        ///    provider and the default case-insensitive comparer.</para>
        /// </devdoc>
        public NameValueCollection(int capacity) : base(capacity)
        {
        }

        public NameValueCollection(IEqualityComparer? equalityComparer) : base(equalityComparer)
        {
        }

        public NameValueCollection(int capacity, IEqualityComparer? equalityComparer)
            : base(capacity, equalityComparer)
        {
        }

        /// <devdoc>
        /// <para>Copies the entries from the specified <see cref='System.Collections.Specialized.NameValueCollection'/> to a new <see cref='System.Collections.Specialized.NameValueCollection'/> with the specified initial capacity or the
        ///    same initial capacity as the number of entries copied, whichever is greater, and
        ///    using the default case-insensitive hash code provider and the default
        ///    case-insensitive comparer.</para>
        /// </devdoc>
        public NameValueCollection(int capacity, NameValueCollection col)
            : base(capacity, col != null ? col.Comparer : throw new ArgumentNullException(nameof(col)))
        {
            this.Comparer = col.Comparer;
            Add(col);
        }

        [Obsolete("This constructor has been deprecated. Use NameValueCollection(Int32, IEqualityComparer) instead.")]
        public NameValueCollection(int capacity, IHashCodeProvider? hashProvider, IComparer? comparer)
            : base(capacity, hashProvider, comparer)
        {
        }

        [Obsolete(Obsoletions.LegacyFormatterImplMessage, DiagnosticId = Obsoletions.LegacyFormatterImplDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
        [EditorBrowsable(EditorBrowsableState.Never)]
        protected NameValueCollection(SerializationInfo info, StreamingContext context) : base(info, context)
        {
        }

        //
        //  Helper methods
        //

        /// <devdoc>
        /// <para> Resets the cached arrays of the collection to <see langword='null'/>.</para>
        /// </devdoc>
        protected void InvalidateCachedArrays()
        {
            _all = null;
            _allKeys = null;
        }

        private static string? GetAsOneString(ArrayList? list)
        {
            int n = (list != null) ? list.Count : 0;

            if (n == 1)
            {
                Debug.Assert(list != null);
                return (string?)list[0];
            }
            else if (n > 1)
            {
                Debug.Assert(list != null);
                StringBuilder s = new StringBuilder((string?)list[0]);

                for (int i = 1; i < n; i++)
                {
                    s.Append(',');
                    s.Append((string?)list[i]);
                }

                return s.ToString();
            }
            else
            {
                return null;
            }
        }

        private static string[]? GetAsStringArray(ArrayList? list)
        {
            int n = (list != null) ? list.Count : 0;
            if (n == 0)
                return null;

            string[] array = new string[n];
            list!.CopyTo(0, array, 0, n);
            return array;
        }

        //
        // Misc public APIs
        //

        /// <devdoc>
        /// <para>Copies the entries in the specified <see cref='System.Collections.Specialized.NameValueCollection'/> to the current <see cref='System.Collections.Specialized.NameValueCollection'/>.</para>
        /// </devdoc>
        public void Add(NameValueCollection c)
        {
            ArgumentNullException.ThrowIfNull(c);

            InvalidateCachedArrays();

            int n = c.Count;

            for (int i = 0; i < n; i++)
            {
                string? key = c.GetKey(i);
                string[]? values = c.GetValues(i);

                if (values != null)
                {
                    for (int j = 0; j < values.Length; j++)
                        Add(key, values[j]);
                }
                else
                {
                    Add(key, null);
                }
            }
        }

        /// <devdoc>
        ///    <para>Invalidates the cached arrays and removes all entries
        ///       from the <see cref='System.Collections.Specialized.NameValueCollection'/>.</para>
        /// </devdoc>
        public virtual void Clear()
        {
            if (IsReadOnly)
                throw new NotSupportedException(SR.CollectionReadOnly);

            InvalidateCachedArrays();
            BaseClear();
        }

        public void CopyTo(Array dest, int index)
        {
            ArgumentNullException.ThrowIfNull(dest);

            if (dest.Rank != 1)
            {
                throw new ArgumentException(SR.Arg_MultiRank, nameof(dest));
            }

            ArgumentOutOfRangeException.ThrowIfNegative(index);

            if (dest.Length - index < Count)
            {
                throw new ArgumentException(SR.Arg_InsufficientSpace);
            }

            int n = Count;
            if (_all == null)
            {
                string?[] all = new string[n];
                for (int i = 0; i < n; i++)
                {
                    all[i] = Get(i);
                    dest.SetValue(all[i], i + index);
                }
                _all = all; // wait until end of loop to set _all reference in case Get throws
            }
            else
            {
                for (int i = 0; i < n; i++)
                {
                    dest.SetValue(_all[i], i + index);
                }
            }
        }

        /// <devdoc>
        /// <para>Gets a value indicating whether the <see cref='System.Collections.Specialized.NameValueCollection'/> contains entries whose keys are not <see langword='null'/>.</para>
        /// </devdoc>
        public bool HasKeys()
        {
            return InternalHasKeys();
        }

        /// <devdoc>
        /// <para>Allows derived classes to alter HasKeys().</para>
        /// </devdoc>
        internal virtual bool InternalHasKeys()
        {
            return BaseHasKeys();
        }

        //
        // Access by name
        //

        /// <devdoc>
        ///    <para>Adds an entry with the specified name and value into the
        ///    <see cref='System.Collections.Specialized.NameValueCollection'/>.</para>
        /// </devdoc>
        public virtual void Add(string? name, string? value)
        {
            if (IsReadOnly)
                throw new NotSupportedException(SR.CollectionReadOnly);

            InvalidateCachedArrays();

            ArrayList? values = (ArrayList?)BaseGet(name);

            if (values == null)
            {
                // new key - add new key with single value
                values = new ArrayList(1);
                if (value != null)
                    values.Add(value);
                BaseAdd(name, values);
            }
            else
            {
                // old key -- append value to the list of values
                if (value != null)
                    values.Add(value);
            }
        }

        /// <devdoc>
        /// <para> Gets the values associated with the specified key from the <see cref='System.Collections.Specialized.NameValueCollection'/> combined into one comma-separated list.</para>
        /// </devdoc>
        public virtual string? Get(string? name)
        {
            ArrayList? values = (ArrayList?)BaseGet(name);
            return GetAsOneString(values);
        }

        /// <devdoc>
        /// <para>Gets the values associated with the specified key from the <see cref='System.Collections.Specialized.NameValueCollection'/>.</para>
        /// </devdoc>
        public virtual string[]? GetValues(string? name)
        {
            ArrayList? values = (ArrayList?)BaseGet(name);
            return GetAsStringArray(values);
        }

        /// <devdoc>
        /// <para>Adds a value to an entry in the <see cref='System.Collections.Specialized.NameValueCollection'/>.</para>
        /// </devdoc>
        public virtual void Set(string? name, string? value)
        {
            if (IsReadOnly)
                throw new NotSupportedException(SR.CollectionReadOnly);

            InvalidateCachedArrays();

            ArrayList values = new ArrayList(1);
            values.Add(value);
            BaseSet(name, values);
        }

        /// <devdoc>
        /// <para>Removes the entries with the specified key from the <see cref='System.Collections.Specialized.NameObjectCollectionBase'/> instance.</para>
        /// </devdoc>
        public virtual void Remove(string? name)
        {
            InvalidateCachedArrays();
            BaseRemove(name);
        }

        /// <devdoc>
        ///    <para> Represents the entry with the specified key in the
        ///    <see cref='System.Collections.Specialized.NameValueCollection'/>.</para>
        /// </devdoc>
        public string? this[string? name]
        {
            get
            {
                return Get(name);
            }

            set
            {
                Set(name, value);
            }
        }

        //
        // Indexed access
        //

        /// <devdoc>
        ///    <para>
        ///       Gets the values at the specified index of the <see cref='System.Collections.Specialized.NameValueCollection'/> combined into one
        ///       comma-separated list.</para>
        /// </devdoc>
        public virtual string? Get(int index)
        {
            ArrayList? values = (ArrayList?)BaseGet(index);
            return GetAsOneString(values);
        }

        /// <devdoc>
        ///    <para> Gets the values at the specified index of the <see cref='System.Collections.Specialized.NameValueCollection'/>.</para>
        /// </devdoc>
        public virtual string[]? GetValues(int index)
        {
            ArrayList? values = (ArrayList?)BaseGet(index);
            return GetAsStringArray(values);
        }

        /// <devdoc>
        /// <para>Gets the key at the specified index of the <see cref='System.Collections.Specialized.NameValueCollection'/>.</para>
        /// </devdoc>
        public virtual string? GetKey(int index)
        {
            return BaseGetKey(index);
        }

        /// <devdoc>
        /// <para>Represents the entry at the specified index of the <see cref='System.Collections.Specialized.NameValueCollection'/>.</para>
        /// </devdoc>
        public string? this[int index]
        {
            get
            {
                return Get(index);
            }
        }

        //
        // Access to keys and values as arrays
        //

        /// <devdoc>
        /// <para>Gets all the keys in the <see cref='System.Collections.Specialized.NameValueCollection'/>. </para>
        /// </devdoc>
        public virtual string?[] AllKeys => _allKeys ??= BaseGetAllKeys();
    }
}