// ==++==
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--==
namespace System.Text
{
    using System;
    using System.Collections;
    using System.Collections.Generic;
 
    [System.Runtime.InteropServices.ComVisible(true)]
    public abstract class EncodingProvider
    {
        public EncodingProvider() { }
        public abstract Encoding GetEncoding(string name);
        public abstract Encoding GetEncoding(int codepage);
 
        // GetEncoding should return either valid encoding or null. shouldn't throw any exception except on null name
        public virtual Encoding GetEncoding(string name, EncoderFallback encoderFallback, DecoderFallback decoderFallback)
        {
            Encoding enc = GetEncoding(name);
            if (enc != null)
            {
                enc = (Encoding)GetEncoding(name).Clone();
                enc.EncoderFallback = encoderFallback;
                enc.DecoderFallback = decoderFallback;
            }
 
            return enc;
        }
 
        public virtual Encoding GetEncoding(int codepage, EncoderFallback encoderFallback, DecoderFallback decoderFallback)
        {
            Encoding enc = GetEncoding(codepage);
            if (enc != null)
            {
                enc = (Encoding)GetEncoding(codepage).Clone();
                enc.EncoderFallback = encoderFallback;
                enc.DecoderFallback = decoderFallback;
            }
 
            return enc;
        }
 
        internal static void AddProvider(EncodingProvider provider)
        {
            if (provider == null)
                throw new ArgumentNullException("provider");
 
            lock (s_InternalSyncObject)
            {
                if (s_providers == null)
                {
                    s_providers = new EncodingProvider[1] { provider };
                    return;
                }
 
                if (Array.IndexOf(s_providers, provider) >= 0)
                {
                    return;
                }
 
                var providers = new EncodingProvider[s_providers.Length + 1];
                Array.Copy(s_providers, providers, s_providers.Length);
                providers[providers.Length - 1] = provider;
                s_providers = providers;
            }
        }
 
        internal static Encoding GetEncodingFromProvider(int codepage)
        {
            if (s_providers == null)
                return null;
 
            var providers = s_providers;
            foreach (EncodingProvider provider in providers)
            {
                Encoding enc = provider.GetEncoding(codepage);
                if (enc != null)
                    return enc;
            }
 
            return null;
        }
 
        internal static Encoding GetEncodingFromProvider(string encodingName)
        {
            if (s_providers == null)
                return null;
 
            var providers = s_providers;
            foreach (EncodingProvider provider in providers)
            {
                Encoding enc = provider.GetEncoding(encodingName);
                if (enc != null)
                    return enc;
            }
 
            return null;
        }
 
        internal static Encoding GetEncodingFromProvider(int codepage, EncoderFallback enc, DecoderFallback dec)
        {
            if (s_providers == null)
                return null;
 
            var providers = s_providers;
            foreach (EncodingProvider provider in providers)
            {
                Encoding encing = provider.GetEncoding(codepage, enc, dec);
                if (encing != null)
                    return encing;
            }
 
            return null;
        }
 
        internal static Encoding GetEncodingFromProvider(string encodingName, EncoderFallback enc, DecoderFallback dec)
        {
            if (s_providers == null)
                return null;
 
            var providers = s_providers;
            foreach (EncodingProvider provider in providers)
            {
                Encoding encoding = provider.GetEncoding(encodingName, enc, dec);
                if (encoding != null)
                    return encoding;
            }
 
            return null;
        }
 
        private static Object s_InternalSyncObject = new Object();
        private static volatile EncodingProvider[] s_providers;
    }
}