using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using Biff8Excel.Interfaces;

namespace Biff8Excel.Records
{
    [StructLayoutAttribute(LayoutKind.Sequential, CharSet = CharSet.Auto, Pack = 1)]
    struct StructExternSheet
    {
        public ushort tIndex;           // for our purposes will always be zero, index to first supbook record
        public ushort tFirstSheet;
        public ushort tLastSheet;
    }

    [StructLayoutAttribute(LayoutKind.Sequential, CharSet = CharSet.Auto, Pack = 1)]
    struct RecordExternSheet
    {
        public ushort opcode;
        public ushort length;
        public ushort num;
    }

    internal class ExternSheet : IRecords 
    {
        RecordExternSheet externsheet;
        StructExternSheet[] structs;

        public ExternSheet()
        {
            externsheet.opcode = 0x17;
        }

        public StructExternSheet[] ExternSheets
        {
            set
            {                
                try
                {
                    if (value == null)
                        externsheet.num = 0;
                    else
                        externsheet.num = (ushort)value.Length;
                    structs = value;
                }
                catch 
                {
                    throw;
                }
            }
        }

        #region IRecords ³ΙΤ±

        public byte[] GetByte()
        {
            byte[] b;
            ushort length;

            if (externsheet.num == 0)
                return null;

            length = (ushort)(6 + (6 & externsheet.num));
            b = new byte[length];

            externsheet.length = (ushort)(length - 4);
            Globals.GetStructToBytes(externsheet).CopyTo(b, 0);

            int pos = 6;
            for (int i = 0; i < structs.Length; i++, pos += 6)
            {
                Globals.GetStructToBytes(structs[i]).CopyTo(b, pos);
            }
            return b;

        }

        #endregion
    }
}