// Unity C# reference source
// Copyright (c) Unity Technologies. For terms of use, see
// https://unity3d.com/legal/licenses/Unity_Reference_Only_License

using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace UnityEngine
{
 public partial class TextAsset : Object
 {
 // Used by MonoScript constructor to avoid creating native TextAsset object.
 internal enum CreateOptions
 {
 None = 0,
 CreateNativeObject = 1
 }

 // The text contents of the .txt file as a string. (RO)
 public string text
 {
 get
 {
 return DecodeString(bytes);
 }
 }

 public override string ToString() { return text; }

 public TextAsset() : this(CreateOptions.CreateNativeObject, null)
 {
 }

 public TextAsset(string text) : this(CreateOptions.CreateNativeObject, text)
 {
 }

 internal TextAsset(CreateOptions options, string text)
 {
 if (options == CreateOptions.CreateNativeObject)
 {
 Internal_CreateInstance(this, text);
 }
 }

 static class EncodingUtility
 {
 internal static readonly KeyValuePair<byte[], Encoding>[] encodingLookup;

 internal static readonly Encoding targetEncoding =
 Encoding.GetEncoding(Encoding.UTF8.CodePage,
 new EncoderReplacementFallback("�"),
 new DecoderReplacementFallback("�"));

 static EncodingUtility()
 {
 Encoding utf32BE = new UTF32Encoding(true, true, true);
 Encoding utf32LE = new UTF32Encoding(false, true, true);
 Encoding utf16BE = new UnicodeEncoding(true, true, true);
 Encoding utf16LE = new UnicodeEncoding(false, true, true);
 Encoding utf8BOM = new UTF8Encoding(true, true);

 encodingLookup = new KeyValuePair<byte[], Encoding>[]
 {
 new KeyValuePair<byte[], Encoding>(utf32BE.GetPreamble(), utf32BE),
 new KeyValuePair<byte[], Encoding>(utf32LE.GetPreamble(), utf32LE),
 new KeyValuePair<byte[], Encoding>(utf16BE.GetPreamble(), utf16BE),
 new KeyValuePair<byte[], Encoding>(utf16LE.GetPreamble(), utf16LE),
 new KeyValuePair<byte[], Encoding>(utf8BOM.GetPreamble(), utf8BOM),
 };
 }
 }

 internal static string DecodeString(byte[] bytes)
 {
 Encoding encoding = null;
 int preambleLength = 0;
 int encodingLookupLength = EncodingUtility.encodingLookup.Length;

 for (int i = 0; i < encodingLookupLength; i++)
 {
 byte[] preamble = EncodingUtility.encodingLookup[i].Key;
 preambleLength = preamble.Length;
 if (bytes.Length >= preambleLength)
 {
 for (int j = 0; j < preambleLength; j++)
 {
 if (preamble[j] != bytes[j])
 {
 preambleLength = -1;
 }
 }

 if (preambleLength < 0) continue;

 try
 {
 Encoding tempEncoding = EncodingUtility.encodingLookup[i].Value;
 string text = tempEncoding.GetString(bytes, preambleLength, bytes.Length - preambleLength);
 encoding = tempEncoding;
 break;
 }
 catch {};
 }
 }

 if (encoding == null)
 {
 encoding = EncodingUtility.targetEncoding;
 preambleLength = 0;
 }

 return encoding.GetString(bytes, preambleLength, bytes.Length - preambleLength);
 }
 }
}