#region PDFsharp - A .NET library for processing PDF
//
// Authors:
//   Stefan Lange
//
// Copyright (c) 2005-2017 empira Software GmbH, Cologne Area (Germany)
//
// http://www.pdfsharp.com
// http://sourceforge.net/projects/pdfsharp
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
// DEALINGS IN THE SOFTWARE.
#endregion

using System;
using Fixed = System.Int32;
using FWord = System.Int16;
using UFWord = System.UInt16;

namespace PdfSharp.Fonts.OpenType
{
    /// <summary>
    /// Represents an indirect reference to an existing font table in a font image.
    /// Used to create binary copies of an existing font table that is not modified.
    /// </summary>
    // ReSharper disable once InconsistentNaming - "I" stands for "indirect", not "interface".
    internal class IRefFontTable : OpenTypeFontTable
    {
        public IRefFontTable(OpenTypeFontface fontData, OpenTypeFontTable fontTable)
            : base(null, fontTable.DirectoryEntry.Tag)
        {
            _fontData = fontData;
            _irefDirectoryEntry = fontTable.DirectoryEntry;
        }

        readonly TableDirectoryEntry _irefDirectoryEntry;

        /// <summary>
        /// Prepares the font table to be compiled into its binary representation.
        /// </summary>
        public override void PrepareForCompilation()
        {
            base.PrepareForCompilation();
            DirectoryEntry.Length = _irefDirectoryEntry.Length;
            DirectoryEntry.CheckSum = _irefDirectoryEntry.CheckSum;
#if DEBUG
            // Check the checksum algorithm
            if (DirectoryEntry.Tag != TableTagNames.Head)
            {
                byte[] bytes = new byte[DirectoryEntry.PaddedLength];
                Buffer.BlockCopy(_irefDirectoryEntry.FontTable._fontData.FontSource.Bytes, _irefDirectoryEntry.Offset, bytes, 0, DirectoryEntry.PaddedLength);
                uint checkSum1 = DirectoryEntry.CheckSum;
                uint checkSum2 = CalcChecksum(bytes);
                // TODO: Sometimes this Assert fails,
                //Debug.Assert(checkSum1 == checkSum2, "Bug in checksum algorithm.");
            }
#endif
        }

        /// <summary>
        /// Converts the font into its binary representation.
        /// </summary>
        public override void Write(OpenTypeFontWriter writer)
        {
            writer.Write(_irefDirectoryEntry.FontTable._fontData.FontSource.Bytes, _irefDirectoryEntry.Offset, _irefDirectoryEntry.PaddedLength);
        }
    }
}
