using System;
using System.Collections.Generic;
using System.IO;
using System.Threading;
using System.Threading.Tasks;
using Xtremegaida.DataStructures;

namespace MediaContainers;

public class EBMLHeader
{
	public EBMLMasterElement OriginalElement { get; private set; }
	public int EBMLVersion { get; set; } = 1;
	public int EBMLReadVersion { get; set; } = 1;
	public int EBMLMaxIDLength { get; set; } = 4;
	public int EBMLMaxSizeLength { get; set; } = 8;
	public string DocType { get; set; }
	public int DocTypeVersion { get; set; } = 1;
	public int DocTypeReadVersion { get; set; } = 1;
	public List<KeyValuePair<string, ulong>> DocTypeExtensions { get; set; }

	public EBMLHeader() { }

	public EBMLHeader(EBMLMasterElement element)
	{
		if (element == null) { throw new ArgumentNullException(nameof(element)); }
		if (element.Definition != EBMLElementDefiniton.EBML) { throw new ArgumentException("Element must be an EBML header section", nameof(element)); }
		if (!element.IsFullyRead) { throw new ArgumentException("Element must be fully read", nameof(element)); }
		OriginalElement = element;
		foreach (var item in element.Children)
		{
			if (item.Definition == EBMLElementDefiniton.EBMLVersion) { EBMLVersion = (int)item.IntValue; }
			else if (item.Definition == EBMLElementDefiniton.EBMLReadVersion) { EBMLReadVersion = (int)item.IntValue; }
			else if (item.Definition == EBMLElementDefiniton.EBMLMaxIDLength) { EBMLMaxIDLength = (int)item.IntValue; }
			else if (item.Definition == EBMLElementDefiniton.EBMLMaxSizeLength) { EBMLMaxSizeLength = (int)item.IntValue; }
			else if (item.Definition == EBMLElementDefiniton.DocType) { DocType = item.StringValue; }
			else if (item.Definition == EBMLElementDefiniton.DocTypeVersion) { DocTypeVersion = (int)item.IntValue; }
			else if (item.Definition == EBMLElementDefiniton.DocTypeReadVersion) { DocTypeReadVersion = (int)item.IntValue; }
			else if (item.Definition == EBMLElementDefiniton.DocTypeExtension)
			{
				string name = string.Empty;
				ulong version = 0;
				foreach (var ext in ((EBMLMasterElement)item).Children)
				{
					if (item.Definition == EBMLElementDefiniton.DocTypeExtensionName) { name = item.StringValue ?? name; }
					else if (item.Definition == EBMLElementDefiniton.DocTypeExtensionVersion) { version = item.UIntValue; }
				}
				if (name.Length > 0 && version > 0)
				{
					if (DocTypeExtensions == null) { DocTypeExtensions = new List<KeyValuePair<string, ulong>>(); }
					DocTypeExtensions.Add(new KeyValuePair<string, ulong>(name, version));
				}
			}
		}
	}

	public static async ValueTask<EBMLHeader> Read(EBMLReader reader, CancellationToken cancellationToken = default)
	{
		var header = await reader.ReadNextElement(true, cancellationToken);
		if (header == null) { throw new Exception("Unexpected end of stream"); }
		if (header.Definition != EBMLElementDefiniton.EBML) { throw new Exception("Expected EBML header; read different element"); }
		while (!header.IsFullyRead) { if ((await reader.ReadNextElement(true, cancellationToken)) == null) { break; } }
		return new EBMLHeader(header as EBMLMasterElement);
	}

	public static async ValueTask<EBMLHeader> Read(IDataQueueReader reader, DataBufferCache cache = null, CancellationToken cancellationToken = default)
	{
		using (var ebml = new EBMLReader(reader, true, cache))
		{
			EBMLElementDefiniton.AddHeaderElements(ebml);
			return await Read(ebml, cancellationToken);
		}
	}

	public static async ValueTask<EBMLHeader> Read(Stream stream, DataBufferCache cache = null, CancellationToken cancellationToken = default)
	{
		using (var ebml = new EBMLReader(stream, true, cache))
		{
			EBMLElementDefiniton.AddHeaderElements(ebml);
			return await Read(ebml, cancellationToken);
		}
	}

	public async ValueTask Write(EBMLWriter writer, CancellationToken cancellationToken = default)
	{
		await writer.BeginMasterElement(EBMLElementDefiniton.EBML, cancellationToken);
		await writer.WriteUnsignedInteger(EBMLElementDefiniton.EBMLVersion, (ulong)EBMLVersion, cancellationToken);
		await writer.WriteUnsignedInteger(EBMLElementDefiniton.EBMLReadVersion, (ulong)EBMLReadVersion, cancellationToken);
		await writer.WriteUnsignedInteger(EBMLElementDefiniton.EBMLMaxIDLength, (ulong)EBMLMaxIDLength, cancellationToken);
		await writer.WriteUnsignedInteger(EBMLElementDefiniton.EBMLMaxSizeLength, (ulong)EBMLMaxSizeLength, cancellationToken);
		await writer.WriteString(EBMLElementDefiniton.DocType, DocType, cancellationToken);
		await writer.WriteUnsignedInteger(EBMLElementDefiniton.DocTypeVersion, (ulong)DocTypeVersion, cancellationToken);
		await writer.WriteUnsignedInteger(EBMLElementDefiniton.DocTypeReadVersion, (ulong)DocTypeReadVersion, cancellationToken);
		if (DocTypeExtensions != null)
		{
			foreach (var ext in DocTypeExtensions)
			{
				await writer.BeginMasterElement(EBMLElementDefiniton.DocTypeExtension, cancellationToken);
				await writer.WriteString(EBMLElementDefiniton.DocTypeExtensionName, ext.Key, cancellationToken);
				await writer.WriteUnsignedInteger(EBMLElementDefiniton.DocTypeExtensionVersion, ext.Value, cancellationToken);
				await writer.EndMasterElement(cancellationToken);
			}
		}
		await writer.EndMasterElement(cancellationToken);
	}

	public EBMLMasterElement ToElement()
	{
		var header = new EBMLMasterElement(EBMLElementDefiniton.EBML);
		header.AddChild(new EBMLUnsignedIntegerElement(EBMLElementDefiniton.EBMLVersion, (ulong)EBMLVersion));
		header.AddChild(new EBMLUnsignedIntegerElement(EBMLElementDefiniton.EBMLReadVersion, (ulong)EBMLReadVersion));
		header.AddChild(new EBMLUnsignedIntegerElement(EBMLElementDefiniton.EBMLMaxIDLength, (ulong)EBMLMaxIDLength));
		header.AddChild(new EBMLUnsignedIntegerElement(EBMLElementDefiniton.EBMLMaxSizeLength, (ulong)EBMLMaxSizeLength));
		header.AddChild(new EBMLStringElement(EBMLElementDefiniton.DocType, DocType));
		header.AddChild(new EBMLUnsignedIntegerElement(EBMLElementDefiniton.DocTypeVersion, (ulong)DocTypeVersion));
		header.AddChild(new EBMLUnsignedIntegerElement(EBMLElementDefiniton.DocTypeReadVersion, (ulong)DocTypeReadVersion));
		if (DocTypeExtensions != null)
		{
			var extMaster = new EBMLMasterElement(EBMLElementDefiniton.DocTypeExtension);
			foreach (var ext in DocTypeExtensions)
			{
				extMaster.AddChild(new EBMLStringElement(EBMLElementDefiniton.DocTypeExtensionName, ext.Key));
				extMaster.AddChild(new EBMLUnsignedIntegerElement(EBMLElementDefiniton.DocTypeExtensionVersion, ext.Value));
			}
			header.AddChild(extMaster);
		}
		return header;
	}

	public override string ToString()
	{
		return (DocType ?? string.Empty) + " " + DocTypeVersion;
	}
}