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

namespace Nikse.SubtitleEdit.Core.SubtitleFormats
{
    public class TSB4 : SubtitleFormat
    {
        public override string Extension
        {
            get { return ".sub"; }
        }

        public override string Name
        {
            get { return "TSB4"; }
        }

        public override bool IsTimeBased
        {
            get { return true; }
        }

        public override bool IsMine(List<string> lines, string fileName)
        {
            var subtitle = new Subtitle();
            LoadSubtitle(subtitle, lines, fileName);
            return subtitle.Paragraphs.Count > _errorCount;
        }

        public override string ToText(Subtitle subtitle, string title)
        {
            return "Not supported!";
        }

        public override void LoadSubtitle(Subtitle subtitle, List<string> lines, string fileName)
        {
            _errorCount = 0;
            subtitle.Paragraphs.Clear();
            if (string.IsNullOrEmpty(fileName))
            {
                return;
            }
            byte[] array;
            try
            {
                array = FileUtil.ReadAllBytesShared(fileName);
            }
            catch
            {
                _errorCount++;
                return;
            }
            if (array.Length < 100 || array[0] != 84 || array[1] != 83 || array[2] != 66 || array[3] != 52)
            {
                return;
            }
            
            int CodePage = 0; // use default code page if not found
            
            for (int i = 0; i < array.Length - 20; i++)
            {
                if (array[i] == 67 && array[i + 1] == 80 && array[i + 2] == 65 && array[i + 3] == 71 && array[i + 4] == 4 && array[i + 5] == 0 && array[i + 6] == 0 && array[i + 7] == 0) // CPAG
                {
                  CodePage = array[i+8] + array[i+9]*256;
                  i += 12;
                }
                if (array[i] == 84 && array[i + 1] == 73 && array[i + 2] == 84 && array[i + 3] == 76 && array[i + 8] == 84 && array[i + 9] == 73 && array[i + 10] == 77 && array[i + 11] == 69) // TITL + TIME
                {
                    int endOfText = array[i + 4] + array[i+5]*256; // get only first two bytes of size

                    int start = array[i + 16] + array[i + 17] * 256;
                    // if (array[i + 18] != 32)
                        start += array[i + 18] * 256 * 256;

                    int end = array[i + 20] + array[i + 21] * 256;
                    // if (array[i + 22] != 32)
                        end += array[i + 22] * 256 * 256;

                    int textStart = i;
                    while (textStart < i + endOfText - 8 && !(array[textStart] == 0x4C && array[textStart + 1] == 0x49 && array[textStart + 2] == 0x4E && array[textStart + 3] == 0x45)) // LINE
                    {
                        textStart++;
                    }
                    // int length = i + endOfText - textStart - 2;
                    int length = array[textStart+4] + array[textStart+5]*256;
                    textStart += 8;

                    // string text = Encoding.Default.GetString(array, textStart, length);
                    string text = Encoding.GetEncoding(CodePage).GetString(array, textStart, length);
                    // text = Encoding.Default.GetString(array, i + 53, endOfText - 47);
                    text = text.Trim('\0').Replace("\0", " ").Trim();
                    text = text.Replace("\r\n", "\n").Replace("\r", "\n").Replace("\n", "\r\n"); //conform to CRLF
                    var item = new Paragraph(text, FramesToMilliseconds(start), FramesToMilliseconds(end));
                    subtitle.Paragraphs.Add(item);
                    i += endOfText + 5;
                }
            }
            subtitle.RemoveEmptyLines();
            subtitle.Renumber();
        }

    }
}