#nullable enable


using System;
using System.Collections.Generic;
using System.Collections.Immutable;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Runtime.Serialization;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using lib;

namespace imm;

/*
T O D O :
T O D O :
T O D O :
x) Add unit tests for all this.  This will definitely benefit from them
*/

static public class Util
{
	//This can handle both Timed and Recorded
	static public T Process<T>( ref T obj, Func<T, T> fn, string reason = "",
													[CallerMemberName] string dbgName = "",
													[CallerFilePath] string dbgPath = "",
													[CallerLineNumber] int dbgLine = 0,
													[CallerArgumentExpression("fn")]
													string dbgExp = "" )
		where T : Recorded<T>
	{
		obj = obj.Process( fn, reason, dbgName, dbgPath, dbgLine, dbgExp );
		return obj;
	}

	static public T LightProcess<T>( ref T obj, Func<T, T> fn,
													string reason = "",
													[CallerMemberName] string dbgName = "",
													[CallerFilePath] string dbgPath = "",
													[CallerLineNumber] int dbgLine = 0,
													[CallerArgumentExpression("fn")]
													string dbgExp = ""
													)
		where T : Versioned<T>
	{
		obj = obj.Process( fn, reason );
		return obj;
	}
}

public interface Meta
{
		public uint   Version => 0;
		public string Reason => "";
		public string Expression => "";
		public string MemberName => "";
		public string FilePath => "";
		public int    LineNumber => -1;
		public DateTime CreatedAt => DateTime.MinValue;
		public DateTime TouchedAt => DateTime.MinValue;

}

public interface Imm
{
	public Meta Meta { get; }
	public object Record(			string reason = "",
													[CallerMemberName] string dbgName = "",
													[CallerFilePath] string dbgPath = "",
													[CallerLineNumber] int dbgLine = 0
	);

	public Imm Process( Imm next,
													string reason = "",
													[CallerMemberName] string dbgName = "",
													[CallerFilePath] string dbgPath = "",
													[CallerLineNumber] int dbgLine = 0,
													[CallerArgumentExpression("next")]
													string dbgExp = ""
													)
	{
		return next;
	}

}


//[lib.Ser( Types = lib.Types.None )]
public record class Versioned<T> : Imm
	where T : Versioned<T>
{

	public delegate void ChangeDelegate( T ZZOld, T next );

	public record class MetaData : Meta
	{
		public uint Version { get; internal set; } = 0;
		public string Reason { get; internal set; } = "";

		public MetaData() { }
	}

	protected Versioned( )
	: this( new MetaData { Version = 1, Reason = $"Versioned.cons" } )
	{
	}

	internal Versioned( MetaData meta )
	{
		MetaStorage = meta;
	}

	virtual public T Record(
													string reason = "",
													[CallerMemberName] string dbgName = "",
													[CallerFilePath] string dbgPath = "",
													[CallerLineNumber] int dbgLine = 0
													)
	{
		return Process( t => t, reason );
	}



	protected MetaData MetaStorage = new();

	[DebuggerBrowsable(DebuggerBrowsableState.Never)]
	public MetaData Meta => MetaStorage;

	Meta Imm.Meta => MetaStorage;

	[lib.Dont]
	[DebuggerBrowsable(DebuggerBrowsableState.Never)]
	public ChangeDelegate OnChange = (old, cur) => {};

	/*
	public void AddOnChange( ChangeDelegate fn,
													string reason,
													[CallerMemberName] string dbgName = "",
													[CallerFilePath] string dbgPath = "",
													[CallerLineNumber] int dbgLine = 0`
	)
	{
		log.debug( $"ADD {log.whatFile(dbgPath)}({dbgLine}): {dbgName} added OnChange bcs {reason}" );
		OnChange += fn;
	}

	public void RemOnChange( ChangeDelegate fn,
													[CallerMemberName] string dbgName = "",
													[CallerFilePath] string dbgPath = "",
													[CallerLineNumber] int dbgLine = 0
	)
	{
		log.debug( $"REM {log.whatFile(dbgPath)}({dbgLine}): {dbgName} removing OnChange" );
		OnChange -= fn;
	}
	*/


	public T Process( Func<T, T> fn, string reason = "" )
	{
		var newT = fn( ( T )this );

		return newT with
		{
			MetaStorage = Meta with
			{
				Version = newT.Meta.Version + 1,
				Reason = reason,
			}
		};
	}

	object Imm.Record( string reason, string dbgName, string dbgPath, int dbgLine ) => Record( reason, dbgName, dbgPath, dbgLine );

	//public object Record( string reason = "", [CallerMemberName] string dbgName = "", [CallerFilePath] string dbgPath = "", [CallerLineNumber] int dbgLine = 0 ) => Recorded( );
}

//[lib.Ser( Types = lib.Types.None )]
public record class Recorded<T> : Versioned<T>, imm.Imm
	where T : Recorded<T>
{

	new public record class MetaData : Versioned<T>.MetaData
	{
		[lib.Dont]
		public T? ZZOld { get; internal set; }
		public T? Old => ZZOld;
		public string DbgName { get; internal set; } = "";
		public string DbgPath { get; internal set; } = "";
		public int    DbgLine { get; internal set; } = -1;
		public string DbgExp  { get; internal set; } = "";

		public MetaData() { }
	}

	public Recorded() : this( new MetaData() )
	{
	}

	public Recorded(MetaData meta) : base( meta )
	{
	}

	[DebuggerBrowsable(DebuggerBrowsableState.Never)]
	new public MetaData Meta => MetaStorage as MetaData ?? new MetaData();


	override public T Record(
													string reason = "",
													[CallerMemberName] string dbgName = "",
													[CallerFilePath] string dbgPath = "",
													[CallerLineNumber] int dbgLine = 0
													)
	{
		return Process( t => t, reason, dbgName, dbgPath, dbgLine );
	}

	virtual public T Process( T next,
													string reason = "",
													[CallerMemberName] string dbgName = "",
													[CallerFilePath] string dbgPath = "",
													[CallerLineNumber] int dbgLine = 0,
													[CallerArgumentExpression("next")]
													string dbgExp = ""
													)
	{
		return ProcessWork( ( old ) => next, reason, dbgName, dbgPath, dbgLine, dbgExp );
	}


	virtual public T Process( Func<T, T> fn,
													string reason = "",
													[CallerMemberName] string dbgName = "",
													[CallerFilePath] string dbgPath = "",
													[CallerLineNumber] int dbgLine = 0,
													[CallerArgumentExpression("fn")]
													string dbgExp = ""
													)
	{
		return ProcessWork( fn, reason, dbgName, dbgPath, dbgLine, dbgExp );
	}

	virtual public T ProcessWork( Func<T, T> fn,
													string reason,
													string dbgName,
													string dbgPath,
													int dbgLine,
													string dbgExp
													)
	{
		var orig = ( T )this;

		var next = fn( orig );

		if( object.ReferenceEquals( orig, next) )
			return next;

		var ret = next with
		{
			//Do the Versioned code here
			MetaStorage = Meta with
			{
				Version = orig.Meta.Version + 1,
				Reason = !string.IsNullOrWhiteSpace( reason ) ? reason : next.Meta.Reason,

				ZZOld = orig,
				DbgName = dbgName,
				DbgPath = dbgPath,
				DbgLine = dbgLine,
				DbgExp  = dbgExp
			}
		};

		OnChange( orig, ret );

		return ret;
	}
}

public record class Timed<T> : Recorded<T>, imm.Imm
	where T : Timed<T>
{

	new public record class MetaData : Recorded<T>.MetaData
	{
		public readonly DateTime CreatedAt = DateTime.Now;
		public DateTime TouchedAt { get; internal set; } = DateTime.Now;
	}

	public Timed() : this( new MetaData() )
	{
	}

	public Timed( MetaData meta ) : base( meta )
	{
	}

	[DebuggerBrowsable(DebuggerBrowsableState.Never)]
	new public MetaData Meta => MetaStorage as MetaData ?? new MetaData();

	public TimeSpan Since => Meta.TouchedAt - Meta.Old?.Meta.TouchedAt ?? TimeSpan.MaxValue;

	public void CallOnChange()
	{
		OnChange( Meta.Old, (T)this );
	}

	override public T Record(
													string reason = "",
													[CallerMemberName] string dbgName = "",
													[CallerFilePath] string dbgPath = "",
													[CallerLineNumber] int dbgLine = 0
													)
	{
		return Process( t => t with { MetaStorage = t.Meta with { Reason = $"Record {reason}" }}, reason, dbgName, dbgPath, dbgLine );
	}

	override public T Process( T next,
													string reason = "",
													[CallerMemberName] string dbgName = "",
													[CallerFilePath] string dbgPath = "",
													[CallerLineNumber] int dbgLine = 0,
													[CallerArgumentExpression("next")]
													string dbgExp = ""
													)
	{
		return ProcessWork( ( old ) => next, reason, dbgName, dbgPath, dbgLine, dbgExp );
	}

	public U ProcessFn<U>( Func<U, U> fn,
													string reason = "",
													[CallerMemberName] string dbgName = "",
													[CallerFilePath] string dbgPath = "",
													[CallerLineNumber] int dbgLine = 0,
													[CallerArgumentExpression("next")]
													string dbgExp = ""
													)
													where U : T
	{
		return (U)ProcessWork( fn as Func<T, T>, reason, dbgName, dbgPath, dbgLine, dbgExp );
	}

	override public T Process( Func<T, T> fn,
													string reason = "",
													[CallerMemberName] string dbgName = "",
													[CallerFilePath] string dbgPath = "",
													[CallerLineNumber] int dbgLine = 0,
													[CallerArgumentExpression("fn")]
													string dbgExp = ""
													)
													=> ProcessWork( fn, reason, dbgName, dbgPath, dbgLine, dbgExp );

	virtual public T ProcessWork( Func<T, T> fn,
													string reason,
													string dbgName,
													string dbgPath,
													int dbgLine,
													string dbgExp
													)
	{
		var orig = ( T )this;

		var next = fn( orig );

		if( object.ReferenceEquals( orig, next) )
			return next;

		var ret = next with
		{
			MetaStorage = Meta with
			{
				//Versioned
				Version = orig.Meta.Version + 1,
				Reason = !string.IsNullOrWhiteSpace( reason ) ? reason : next.Meta.Reason,

				//Recorded
				DbgName = dbgName,
				DbgPath = dbgPath,
				DbgLine = dbgLine,
				DbgExp = dbgExp,
				ZZOld = orig,

				//Timed
				TouchedAt = DateTime.Now,
			}

		};

		if( OnChange != null)
			OnChange( orig, ret );

		return ret;
	}


}