using System;
using System.IO;
using System.Text;
using System.Runtime.InteropServices;
namespace PriFileFormat
{
	public abstract class Section
	{
		protected PriFile PriFile { get; private set; }
		public string SectionIdentifier { get; private set; }
		public uint SectionQualifier { get; private set; }
		public uint Flags { get; private set; }
		public uint SectionFlags { get; private set; }
		public uint SectionLength { get; private set; }

		protected Section (string sectionIdentifier, PriFile priFile)
		{
			if (sectionIdentifier.Length != 16)
				throw new ArgumentException ("Section identifiers need to be exactly 16 characters long.", nameof (sectionIdentifier));

			SectionIdentifier = sectionIdentifier;
			PriFile = priFile;
		}

		internal bool Parse (BinaryReader binaryReader)
		{
			if (new string (binaryReader.ReadChars (16)) != SectionIdentifier)
				throw new InvalidDataException ("Unexpected section identifier.");

			SectionQualifier = binaryReader.ReadUInt32 ();
			Flags = binaryReader.ReadUInt16 ();
			SectionFlags = binaryReader.ReadUInt16 ();
			SectionLength = binaryReader.ReadUInt32 ();
			binaryReader.ExpectUInt32 (0);

			binaryReader.BaseStream.Seek (SectionLength - 16 - 24, SeekOrigin.Current);

			binaryReader.ExpectUInt32 (0xDEF5FADE);
			binaryReader.ExpectUInt32 (SectionLength);

			binaryReader.BaseStream.Seek (-8 - (SectionLength - 16 - 24), SeekOrigin.Current);

			using (SubStream subStream = new SubStream (binaryReader.BaseStream, binaryReader.BaseStream.Position, (int)SectionLength - 16 - 24))
			using (BinaryReader subBinaryReader = new BinaryReader (subStream, Encoding.ASCII))
			{
				return ParseSectionContent (subBinaryReader);
			}
		}

		protected abstract bool ParseSectionContent (BinaryReader binaryReader);

		public override string ToString ()
		{
			return $"{SectionIdentifier.TrimEnd ('\0', ' ')} length: {SectionLength}";
		}

		internal static Section CreateForIdentifier (string sectionIdentifier, PriFile priFile)
		{
			switch (sectionIdentifier)
			{
				case PriDescriptorSection.Identifier:
					return new PriDescriptorSection (priFile);
				case HierarchicalSchemaSection.Identifier1:
					return new HierarchicalSchemaSection (priFile, false);
				case HierarchicalSchemaSection.Identifier2:
					return new HierarchicalSchemaSection (priFile, true);
				case DecisionInfoSection.Identifier:
					return new DecisionInfoSection (priFile);
				case ResourceMapSection.Identifier1:
					return new ResourceMapSection (priFile, false);
				case ResourceMapSection.Identifier2:
					return new ResourceMapSection (priFile, true);
				case DataItemSection.Identifier:
					return new DataItemSection (priFile);
				case ReverseMapSection.Identifier:
					return new ReverseMapSection (priFile);
				case ReferencedFileSection.Identifier:
					return new ReferencedFileSection (priFile);
				default:
					return new UnknownSection (sectionIdentifier, priFile);
			}
		}

	}
}
