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

namespace PriFileFormat
{
	public class PriFile: IDisposable
	{
		public string Version { get; private set; }
		public uint TotalFileSize { get; private set; }
		public IReadOnlyList <TocEntry> TableOfContents { get; private set; }
		public IReadOnlyList <Section> Sections { get; private set; }
		private bool _disposed = false;
		private Stream _internalStream; // 跟踪内部流
		private PriFile ()
		{
		}

		public static PriFile Parse (Stream stream)
		{
			PriFile priFile = new PriFile ();
			priFile.ParseInternal (stream, false);
			return priFile;
		}

		public static PriFile Parse (System.Runtime.InteropServices.ComTypes.IStream stream, out Stream output)
		{

			ComStreamWrapper csw = new ComStreamWrapper (stream);
			output = csw;
			PriFile priFile = new PriFile ();
			priFile.ParseInternal (csw, true);
			return priFile;
		}

		private void ParseInternal (Stream stream, bool ownStream)
		{
			if (ownStream) { _internalStream = stream; }
			using (BinaryReader binaryReader = new BinaryReader (stream, Encoding.ASCII, true))
			{
				long fileStartOffset = binaryReader.BaseStream.Position;

				string magic = new string (binaryReader.ReadChars (8));

				switch (magic)
				{
					case "mrm_pri0":
					case "mrm_pri1":
					case "mrm_pri2":
					case "mrm_prif":
						Version = magic;
						break;
					default:
						throw new InvalidDataException ("Data does not start with a PRI file header.");
				}

				binaryReader.ExpectUInt16 (0);
				binaryReader.ExpectUInt16 (1);
				TotalFileSize = binaryReader.ReadUInt32 ();
				uint tocOffset = binaryReader.ReadUInt32 ();
				uint sectionStartOffset = binaryReader.ReadUInt32 ();
				ushort numSections = binaryReader.ReadUInt16 ();

				binaryReader.ExpectUInt16 (0xFFFF);
				binaryReader.ExpectUInt32 (0);

				binaryReader.BaseStream.Seek (fileStartOffset + TotalFileSize - 16, SeekOrigin.Begin);

				binaryReader.ExpectUInt32 (0xDEFFFADE);
				binaryReader.ExpectUInt32 (TotalFileSize);
				binaryReader.ExpectString (magic);

				binaryReader.BaseStream.Seek (tocOffset, SeekOrigin.Begin);

				List<TocEntry> toc = new List<TocEntry> (numSections);

				for (int i = 0; i < numSections; i++)
					toc.Add (TocEntry.Parse (binaryReader));

				TableOfContents = toc;

				Section [] sections = new Section [numSections];

				Sections = sections;

				bool parseSuccess = false;
				bool parseFailure = false;

				do
				{
					for (int i = 0; i < sections.Length; i++)
						if (sections [i] == null)
						{
							binaryReader.BaseStream.Seek (sectionStartOffset + toc [i].SectionOffset, SeekOrigin.Begin);

							Section section = Section.CreateForIdentifier (toc [i].SectionIdentifier, this);

							if (section.Parse (binaryReader))
							{
								sections [i] = section;
								parseSuccess = true;
							}
							else
								parseFailure = true;
						}
				} while (parseFailure && parseSuccess);

				if (parseFailure)
					throw new InvalidDataException ();
			}
		}

		public void Dispose ()
		{
			Dispose (true);
			GC.SuppressFinalize (this);
		}
		protected virtual void Dispose (bool disposing)
		{
			if (_disposed) return;
			if (disposing)
			{
				// 释放托管资源
				if (_internalStream != null)
				{
					_internalStream.Dispose ();
					_internalStream = null;
				}

				// 释放 section 内容
				if (Sections != null)
				{
					foreach (var section in Sections)
					{
						var unknown = section as UnknownSection;
						if (unknown != null)
							unknown.ClearContent ();

						var dataSection = section as DataItemSection;
						if (dataSection != null)
							dataSection.ClearData ();
					}
					Sections = null;
				}
			}

			_disposed = true;
		}

		~PriFile ()
		{
			Dispose (false);
		}

		PriDescriptorSection priDescriptorSection;

		public PriDescriptorSection PriDescriptorSection
		{
			get
			{
				if (priDescriptorSection == null) priDescriptorSection = Sections.OfType<PriDescriptorSection> ().Single ();
				return priDescriptorSection;
			}
		}

		public T GetSectionByRef<T> (SectionRef<T> sectionRef) where T : Section
		{
			return (T)Sections [sectionRef.sectionIndex];
		}

		public ResourceMapItem GetResourceMapItemByRef (ResourceMapItemRef resourceMapItemRef)
		{
			return GetSectionByRef (resourceMapItemRef.schemaSection).Items [resourceMapItemRef.itemIndex];
		}

		public ByteSpan GetDataItemByRef (DataItemRef dataItemRef)
		{
			return GetSectionByRef (dataItemRef.dataItemSection).DataItems [dataItemRef.itemIndex];
		}

		public ReferencedFile GetReferencedFileByRef (ReferencedFileRef referencedFileRef)
		{
			return GetSectionByRef (PriDescriptorSection.ReferencedFileSections.First ()).ReferencedFiles [referencedFileRef.fileIndex];
		}
	}
}