// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Net.Mime;
using System.Text;
 
namespace System.Net.Mail
{
    public class MailAddressCollection : Collection<MailAddress>
    {
        public MailAddressCollection()
        {
        }
 
        public void Add(string addresses)
        {
            ArgumentException.ThrowIfNullOrEmpty(addresses);
 
            ParseValue(addresses);
        }
 
        protected override void SetItem(int index, MailAddress item)
        {
            ArgumentNullException.ThrowIfNull(item);
 
            base.SetItem(index, item);
        }
 
        protected override void InsertItem(int index, MailAddress item)
        {
            ArgumentNullException.ThrowIfNull(item);
 
            base.InsertItem(index, item);
        }
 
        internal void ParseValue(string addresses)
        {
            List<MailAddress> result = MailAddressParser.ParseMultipleAddresses(addresses);
 
            for (int i = 0; i < result.Count; i++)
            {
                Add(result[i]);
            }
        }
 
        public override string ToString() => string.Join(", ", this);
 
        internal string Encode(int charsConsumed, bool allowUnicode)
        {
            var encodedAddresses = new ValueStringBuilder(stackalloc char[256]);
 
            //encode each address individually (except the first), fold and separate with a comma
            foreach (MailAddress address in this)
            {
                if (encodedAddresses.Length == 0)
                {
                    //no need to append a comma to the first one because it may be the only one.
                    encodedAddresses.Append(address.Encode(charsConsumed, allowUnicode));
                }
                else
                {
                    //appending another one, append a comma to separate and then fold and add the encoded address
                    //the charsConsumed will be 1 because only the first line needs to account for the header itself for
                    //line length; subsequent lines have a single whitespace character because they are folded here
                    encodedAddresses.Append(", ");
                    encodedAddresses.Append(address.Encode(1, allowUnicode));
                }
            }
            return encodedAddresses.ToString();
        }
    }
}