using System;

using System.Collections.Generic;

using System.IO;

using System.Text;

​

public class MainClass {

  public static void Main()

  {

    var str = @"{

    books{

      isbn

      name

      author{

        id

        name

        birthdate

      }

    }

  }";

    GraphObject.Read(str).Dump();

  }

}

​

​

​

// A object can have to kinds of properties, simple values or sub-objects

public enum GraphElementType {

    @Object,    

    Value

}

​

// To make it easy to keep all values and objects in order, we define a single base class for both

// We define all elements to have a name, and set a static name for the root element

public abstract class GraphElement

{

    public static readonly string ROOT_NAME = "<ROOT>";

    public GraphElementType ElementType { get; }

    public string Name {get;}

    protected GraphElement(GraphElementType type, string name) {

        ElementType = type;

        Name = name;

    }

}

​

public class GraphValue : GraphElement

{

    public GraphValue(string name) : base(GraphElementType.Value, name) { }

}

​

public class GraphObject : GraphElement {   

    public List<GraphElement> Properties {get;} = new List<GraphElement>();

​

    public GraphObject(string name) : base(GraphElementType.Object, name) { }

    public static GraphObject Read(string graphString)

    {

        return Read(new StringReader(graphString));

    }

    public static GraphObject Read(TextReader reader) {

        return Read(GraphElement.ROOT_NAME, reader);

    }

    // Read an object with the given name from the given reader.

    // The reader must be positioned at the opening brace of the object.

    protected static GraphObject Read(string name, TextReader reader)

    {

        // Consume opening '{'

        if (reader.Read() != '{') throw new ApplicationException("Invalid object start");

        var o = new GraphObject(name);      

        while(true)

        {

            var next = ConsumeWhitespaceAndPeek(reader);

            if (next == -1) throw new ApplicationException("Unexpected end of input, unclosed object");

            if (next == '}')  {

                reader.Read(); // consume closing '}'

                return o;

            }

​

            var str = ConsumeUntilWhitespaceOrBrace(reader);

            next = ConsumeWhitespaceAndPeek(reader);         

​

            if (str.Length > 0 && next  == '{')

            {

                o.Properties.Add(Read(str, reader));

            }

            else if (str.Length > 0)

            {

                o.Properties.Add(new GraphValue(str));

            }

        }

    }

    // Helper method: Collect all non-whitespace, non-brace characters into a string

    private static string ConsumeUntilWhitespaceOrBrace(TextReader reader) {

        var b = new StringBuilder();

​

        var next = reader.Peek();

        while (next != -1 && !Char.IsWhiteSpace((char)next) && next != '}' && next != '{') {

            b.Append((char)next);

            reader.Read();

            next = reader.Peek();

        }

        return b.ToString();

    }

    // Helper method: Advance reader past any whitespace

    private static int ConsumeWhitespaceAndPeek(TextReader reader) {

        var next = reader.Peek();

        while(next != -1 && Char.IsWhiteSpace((char)next)) {

            reader.Read();

            next = reader.Peek();

        }

        return next;

    }

}