Introducing Traversing with a IWktTraverseHandler interface

WktToProjConverter is an implementation example of this interface.

ParseAllWKTs unittest succeeds.

src/ProjNet/Wkt/Tree/IWktObject.cs

@@ -12,25 +12,11 @@ public interface IWktObject
         string Keyword { get; }
 
 
-        /// <summary>
-        /// Set Left Delimiter. (For semantic checking).
-        /// </summary>
-        /// <param name="leftDelimiter"></param>
-        /// <returns></returns>
-        IWktObject SetLeftDelimiter(char leftDelimiter);
-
-        /// <summary>
-        /// Set Right Delimiter. (For semantic checking).
-        /// </summary>
-        /// <param name="rightDelimiter"></param>
-        /// <returns></returns>
-        IWktObject SetRightDelimiter(char rightDelimiter);
 
         /// <summary>
-        /// Cast function to reach the "lower" interfaces.
+        /// Traverse this object and its descendants calling the handler as we go down.
         /// </summary>
-        /// <typeparam name="T"></typeparam>
-        /// <returns></returns>
-        T As<T>() where T : IWktObject;
+        /// <param name="handler"></param>
+        void Traverse(IWktTraverseHandler handler);
     }
 }

src/ProjNet/Wkt/Tree/IWktTraverseHandler.cs

@@ -0,0 +1,41 @@
+using System.Collections.Generic;
+
+namespace ProjNet.Wkt.Tree
+{
+    /// <summary>
+    /// IWktTraverseHandler interface for traveling a WktObject tree.
+    /// </summary>
+    public interface IWktTraverseHandler
+    {
+
+        /// <summary>
+        /// Handle method for WktAuthority.
+        /// </summary>
+        /// <param name="authority"></param>
+        void Handle(WktAuthority authority);
+
+        void Handle(WktAxis axis);
+
+        void Handle(WktDatum datum);
+
+        void Handle(WktEllipsoid ellipsoid);
+
+        void Handle(WktSpheroid spheroid);
+
+        void Handle(WktExtension extension);
+
+        void Handle(WktUnit unit);
+
+        void Handle(WktParameter parameter);
+
+        void Handle(WktPrimeMeridian meridian);
+
+        void Handle(WktProjection projection);
+
+        void Handle(WktToWgs84 toWgs84);
+
+        void Handle(WktGeocentricCoordinateSystem cs);
+        void Handle(WktGeographicCoordinateSystem cs);
+        void Handle(WktProjectedCoordinateSystem cs);
+    }
+}

src/ProjNet/Wkt/Tree/WktAuthority.cs

@@ -86,5 +86,11 @@ public override int GetHashCode()
                 return ((Name != null ? Name.GetHashCode() : 0) * 397) ^ Code.GetHashCode();
             }
         }
+
+        /// <inheritdoc/>>
+        public override void Traverse(IWktTraverseHandler handler)
+        {
+            handler.Handle(this);
+        }
     }
 }

src/ProjNet/Wkt/Tree/WktAxis.cs

@@ -90,5 +90,12 @@ public override int GetHashCode()
                 return ((Name != null ? Name.GetHashCode() : 0) * 397) ^ (int) Direction;
             }
         }
+
+
+        /// <inheritdoc/>>
+        public override void Traverse(IWktTraverseHandler handler)
+        {
+            handler.Handle(this);
+        }
     }
 }

src/ProjNet/Wkt/Tree/WktBaseObject.cs

@@ -5,7 +5,7 @@ namespace ProjNet.Wkt.Tree
     /// <summary>
     /// Base class for all WKT Objects.
     /// </summary>
-    public class WktBaseObject : IWktObject
+    public abstract class WktBaseObject : IWktObject
     {
         /// <inheritdoc/>
         public string Keyword { get; internal set; }
@@ -21,21 +21,6 @@ public class WktBaseObject : IWktObject
         public char RightDelimiter { get; set; }
 
 
-        /// <inheritdoc/>
-        public virtual IWktObject SetLeftDelimiter(char leftDelimiter)
-        {
-            LeftDelimiter = leftDelimiter;
-            return this;
-        }
-
-        /// <inheritdoc/>
-        public virtual IWktObject SetRightDelimiter(char rightDelimiter)
-        {
-            RightDelimiter = rightDelimiter;
-            return this;
-        }
-
-
         /// <summary>
         /// Constructor for all Wkt Object's.
         /// </summary>
@@ -57,17 +42,8 @@ public WktBaseObject(string keyword = null, char left = '[', char right = ']')
         }
 
 
-
-        /// <summary>
-        /// Cast function for all IWktObject"s.
-        /// </summary>
-        /// <typeparam name="T"></typeparam>
-        /// <returns></returns>
-        public virtual T As<T>() where T : IWktObject
-        {
-            return (T) Convert.ChangeType(this, typeof(T));
-        }
-
+        /// <inheritdoc/>
+        public abstract void Traverse(IWktTraverseHandler handler);
 
     }
 }

src/ProjNet/Wkt/Tree/WktCoordinateSystem.cs

@@ -30,5 +30,15 @@ public WktCoordinateSystem(string name,
             Name = name;
         }
 
+        /// <inheritdoc/>>
+        public override void Traverse(IWktTraverseHandler handler)
+        {
+            if (this is WktProjectedCoordinateSystem projcs)
+                projcs.Traverse(handler);
+            else if (this is WktGeographicCoordinateSystem geogcs)
+                geogcs.Traverse(handler);
+            else if (this is WktGeocentricCoordinateSystem geoccs)
+                geoccs.Traverse(handler);
+        }
     }
 }

src/ProjNet/Wkt/Tree/WktDatum.cs

@@ -83,5 +83,18 @@ public override int GetHashCode()
                 return hashCode;
             }
         }
+
+        /// <inheritdoc/>
+        public override void Traverse(IWktTraverseHandler handler)
+        {
+            if (Spheroid!=null)
+                this.Spheroid.Traverse(handler);
+            if (ToWgs84!=null)
+                this.ToWgs84.Traverse(handler);
+            if (Authority!=null)
+                this.Authority.Traverse(handler);
+
+            handler.Handle(this);
+        }
     }
 }

src/ProjNet/Wkt/Tree/WktEllipsoid.cs

@@ -87,5 +87,15 @@ public override int GetHashCode()
                 return hashCode;
             }
         }
+
+
+        /// <inheritdoc/>
+        public override void Traverse(IWktTraverseHandler handler)
+        {
+            if (Authority!=null)
+                Authority.Traverse(handler);
+
+            handler.Handle(this);
+        }
     }
 }

src/ProjNet/Wkt/Tree/WktExtension.cs

@@ -71,5 +71,11 @@ public override int GetHashCode()
                 return ((Name != null ? Name.GetHashCode() : 0) * 397) ^ Value.GetHashCode();
             }
         }
+
+        /// <inheritdoc/>
+        public override void Traverse(IWktTraverseHandler handler)
+        {
+            handler.Handle(this);
+        }
     }
 }

src/ProjNet/Wkt/Tree/WktGeocentricCoordinateSystem.cs

@@ -102,5 +102,19 @@ public override int GetHashCode()
                 return hashCode;
             }
         }
+
+        /// <inheritdoc/>
+        public override void Traverse(IWktTraverseHandler handler)
+        {
+            Datum.Traverse(handler);
+            PrimeMeridian.Traverse(handler);
+            Unit.Traverse(handler);
+            Authority.Traverse(handler);
+
+            foreach (var axis in Axes)
+                axis.Traverse(handler);
+
+            handler.Handle(this);
+        }
     }
 }

src/ProjNet/Wkt/Tree/WktGeographicCoordinateSystem.cs

@@ -125,5 +125,28 @@ public override int GetHashCode()
                 return hashCode;
             }
         }
+
+
+        /// <inheritdoc/>
+        public override void Traverse(IWktTraverseHandler handler)
+        {
+            if (AngularUnit!=null)
+                AngularUnit.Traverse(handler);
+            if (Unit!=null)
+                Unit.Traverse(handler);
+            if (HorizontalDatum!=null)
+                HorizontalDatum.Traverse(handler);
+            if (PrimeMeridian!=null)
+                PrimeMeridian.Traverse(handler);
+
+            foreach (var axis in Axes)
+                if (axis!=null)
+                    axis.Traverse(handler);
+
+            if (Authority!=null)
+                Authority.Traverse(handler);
+
+            handler.Handle(this);
+        }
     }
 }

src/ProjNet/Wkt/Tree/WktParameter.cs

@@ -72,5 +72,12 @@ public override int GetHashCode()
                 return ((Name != null ? Name.GetHashCode() : 0) * 397) ^ Value.GetHashCode();
             }
         }
+
+
+        /// <inheritdoc/>
+        public override void Traverse(IWktTraverseHandler handler)
+        {
+            handler.Handle(this);
+        }
     }
 }

src/ProjNet/Wkt/Tree/WktPrimeMeridian.cs

@@ -81,5 +81,15 @@ public override int GetHashCode()
                 return hashCode;
             }
         }
+
+
+        /// <inheritdoc/>
+        public override void Traverse(IWktTraverseHandler handler)
+        {
+            if (Authority!=null)
+                Authority.Traverse(handler);
+
+            handler.Handle(this);
+        }
     }
 }

src/ProjNet/Wkt/Tree/WktProjectedCoordinateSystem.cs

@@ -124,5 +124,37 @@ public override int GetHashCode()
                 return hashCode;
             }
         }
+
+
+        /// <inheritdoc/>
+        public override void Traverse(IWktTraverseHandler handler)
+        {
+            if (GeographicCoordinateSystem!=null)
+                GeographicCoordinateSystem.Traverse(handler);
+            if (Projection!=null)
+                Projection.Traverse(handler);
+
+            if (Parameters != null)
+            {
+                foreach (var p in Parameters)
+                    p.Traverse(handler);
+            }
+
+            if (Unit!=null)
+                Unit.Traverse(handler);
+
+            if (Axes != null)
+            {
+                foreach (var axis in Axes)
+                    axis.Traverse(handler);
+            }
+
+            if (Authority!=null)
+                Authority.Traverse(handler);
+            if (Extension!=null)
+                Extension.Traverse(handler);
+
+            handler.Handle(this);
+        }
     }
 }

src/ProjNet/Wkt/Tree/WktProjection.cs

@@ -71,5 +71,15 @@ public override int GetHashCode()
                 return ((Name != null ? Name.GetHashCode() : 0) * 397) ^ (Authority != null ? Authority.GetHashCode() : 0);
             }
         }
+
+
+        /// <inheritdoc/>
+        public override void Traverse(IWktTraverseHandler handler)
+        {
+            if (Authority!=null)
+                Authority.Traverse(handler);
+
+            handler.Handle(this);
+        }
     }
 }

src/ProjNet/Wkt/Tree/WktSpheroid.cs

@@ -5,25 +5,8 @@ namespace ProjNet.Wkt.Tree
     /// <summary>
     /// WktSpheroid class.
     /// </summary>
-    public class WktSpheroid : WktBaseObject, IEquatable<WktSpheroid>
+    public class WktSpheroid : WktEllipsoid, IEquatable<WktSpheroid>
     {
-        /// <summary>
-        /// Name property.
-        /// </summary>
-        public string Name { get; internal set; }
-        /// <summary>
-        /// SemiMajorAxis property.
-        /// </summary>
-        public double SemiMajorAxis { get; internal set; }
-        /// <summary>
-        /// InverseFlattening property.
-        /// </summary>
-        public double InverseFlattening { get; internal set; }
-        /// <summary>
-        /// Authority property.
-        /// </summary>
-        public WktAuthority Authority { get; internal set; }
-
         /// <summary>
         /// Constructor for a WktSpheroid.
         /// </summary>
@@ -36,12 +19,8 @@ public class WktSpheroid : WktBaseObject, IEquatable<WktSpheroid>
         /// <param name="rightDelimiter"></param>
         public WktSpheroid(string name, double semiMajorAxis, double inverseFlattening, WktAuthority authority,
                             string keyword = "SPHEROID", char leftDelimiter = '[', char rightDelimiter = ']')
-            : base(keyword, leftDelimiter, rightDelimiter)
+            : base(name, semiMajorAxis, inverseFlattening, authority, keyword, leftDelimiter, rightDelimiter)
         {
-            Name = name;
-            SemiMajorAxis = semiMajorAxis;
-            InverseFlattening = inverseFlattening;
-            Authority = authority;
         }
 
 
@@ -87,5 +66,14 @@ public override int GetHashCode()
                 return hashCode;
             }
         }
+
+        /// <inheritdoc/>
+        public override void Traverse(IWktTraverseHandler handler)
+        {
+            if (Authority!=null)
+                Authority.Traverse(handler);
+
+            handler.Handle(this);
+        }
     }
 }