Structure for ordering, need to implement for serde_json::Value.

src/renderer/parameters_context.rs

@@ -8,7 +8,7 @@ use crate::renderer::RenderError;
 use crate::renderer::Renderable;
 use crate::renderer::WalkError;
 use crate::renderer::Walkable;
-use std::collections::HashMap;
+use std::{cmp::Ordering, collections::HashMap};
 
 /// Copy the data from an RValue to an Owned struct
 ///
@@ -122,6 +122,11 @@ impl CompareContextElement for ParametersContext {
         // TODO: Does this ever happen? perhaps I should have a panic here.
         false
     }
+
+    fn partial_compare(&self, other: &dyn ContextElement) -> Option<Ordering> {
+        // TODO: Does this ever happen? perhaps I should have a panic here.
+        None
+    }
 }
 
 impl ContextElement for String {}
@@ -158,6 +163,23 @@ impl CompareContextElement for String {
             Some(other_string) => self == other_string,
         }
     }
+
+    fn partial_compare(&self, other: &dyn ContextElement) -> Option<Ordering> {
+        // If its a string then compare them directly, otherwise defer
+        // to the other type's implementation of CompareContextElement
+        // since the end user could add any type.
+        match other.to_any().downcast_ref::<Self>() {
+            None => match other.partial_compare(self) {
+                None => None,
+                Some(ord) => match ord {
+                    Ordering::Equal => Some(Ordering::Equal),
+                    Ordering::Greater => Some(Ordering::Less),
+                    Ordering::Less => Some(Ordering::Greater),
+                },
+            },
+            Some(other_string) => self.partial_cmp(other_string),
+        }
+    }
 }
 
 impl ContextElement for u64 {}
@@ -190,4 +212,21 @@ impl CompareContextElement for u64 {
             Some(other_num) => self == other_num,
         }
     }
+
+    fn partial_compare(&self, other: &dyn ContextElement) -> Option<Ordering> {
+        // If its a u64 then compare them directly, otherwise defer
+        // to the other type's implementation of CompareContextElement
+        // since the end user could add any type.
+        match other.to_any().downcast_ref::<Self>() {
+            None => match other.partial_compare(self) {
+                None => None,
+                Some(ord) => match ord {
+                    Ordering::Equal => Some(Ordering::Equal),
+                    Ordering::Greater => Some(Ordering::Less),
+                    Ordering::Less => Some(Ordering::Greater),
+                },
+            },
+            Some(other_num) => self.partial_cmp(other_num),
+        }
+    }
 }