using System;
using System.Xml;
using System.Diagnostics;
using System.Text.Json;
using System.Xml.Linq;
using System.Xml.Serialization;


public class Message {
    public Message(int from, int to, string msg)
    {
        Debug.Assert( !string.IsNullOrEmpty( msg ) );
        
        this.From = from;
        this.To = to;
        this.Msg = msg;
    }
    
    public int From { get; }
    public int To { get; }
    public string Msg { get; }

    public override string ToString()
    {
        return $"From: {From} -> To: {To}: \"{Msg}\"";
    }
}


// ## JSON
public class JsonMessage {
    public JsonMessage(Message m)
    {
        this.Message = m;
    }

    public void Save(string fn)
    {
        File.WriteAllText( fn, JsonSerializer.Serialize( this.Message ) );
    }

    public static Message Load(string fn)
    {
        return JsonSerializer.Deserialize<Message>(
                                        File.ReadAllText( fn )
                            ?? throw new IOException( "error reading file: " + fn ) )
                        ?? throw new JsonException( "error reading JSON from: " + fn );
    }
    
    public Message Message { get; }
}


// ## XML 1 (doesn't work, no parameterless constructor in Message)
public class XmlMessage {
    public XmlMessage(Message m)
    {
        this.Message = m;
    }
    
    public Message Message { get; }

    public void Save(string fn)
    {
        using ( var f = File.OpenWrite( fn ) ) {
        	new XmlSerializer( this.Message.GetType() )
                	.Serialize( f, this.Message );
        }
    }

    public static Message Load(string fn)
    {
    	using ( var f = File.OpenRead( fn ) ) {
    		return (Message) new XmlSerializer( typeof( Message ) )
                .Deserialize( f )
                    ?? throw new XmlException( "error reading XML from: " + fn );
    	}
    }
}


// ## XML 2 (bespoken XML) 
public class XmlMessage2 {
    public XmlMessage2(Message m)
    {
        this.Message = m;
    }
    
    public Message Message { get; }

    public void Save(string fn)
    {
        new XElement("Message",
        	new XAttribute( "from", this.Message.From ),
        	new XAttribute( "to", this.Message.To ),
        	this.Message.Msg ).Save( fn );
    }

    public static Message Load(string fn)
    {
        var msgElem = XElement.Load( fn ) ?? throw new IOException( "reading " + fn );
        int from = (int?) msgElem.Attribute( "from" ) ?? throw new XmlException( "missing from" );
        int to = (int?) msgElem.Attribute( "to" ) ?? throw new XmlException( "missing to" );

        return new Message( from, to, msgElem.Value );
    }
}


// ## XML 3 (using a DTO class)
public class MessageDTO {
	public int From { get; set; }
    public int To { get; set; }
    public string Msg { get; set; }

    public override string ToString()
    {
        return $"[MessageDTO [From: {From}][To: {To}]: \"{Msg}\"]";
    }
    
    public Message ToMessage()
    {
    	return new Message( this.From, this.To, this.Msg );
    }
    
    public static MessageDTO FromMessage(Message m)
    {
    	return new MessageDTO { From = m.From, To = m.To, Msg = m.Msg };
    }
}


public class XmlMessage3 {
    public XmlMessage3(Message m)
    {
        this.Message = m;
    }
    
    public Message Message { get; }

    public void Save(string fn)
    {
    	using ( var f = File.OpenWrite( fn ) ) {
        	new XmlSerializer( typeof( MessageDTO ) )
                .Serialize(
                    f, MessageDTO.FromMessage( this.Message ) );
        }
    }

    public static Message Load(string fn)
    {
    	using ( var f = File.OpenRead( fn ) ) {
    		return ( (MessageDTO) new XmlSerializer( typeof( MessageDTO ) )
                .Deserialize( f ) ).ToMessage()
                    ?? throw new XmlException( "error reading XML from: " + fn );
    	}
    }
}


public class TestSerialization
{
	public static void Main()
	{
		var m1 = new Message( 455123132, 555789789, "¿Peli y manta esta noche?" );

		new JsonMessage( m1 ).Save( "msg.json" );
		Console.WriteLine( JsonMessage.Load( "msg.json" ) );

		new XmlMessage2( m1 ).Save( "msg.xml" );
		Console.WriteLine( XmlMessage2.Load( "msg.xml" ) );
		
		new XmlMessage3( m1 ).Save( "msg.xml" );
		Console.WriteLine( XmlMessage3.Load( "msg.xml" ) );
	}
}