Fleshing out what-changed functionality.

Starting at the bottom again with low levels and sketching out how to consume it.

what-changed/extensions.go

@@ -0,0 +1,89 @@
+// Copyright 2022 Princess B33f Heavy Industries / Dave Shanley
+// SPDX-License-Identifier: MIT
+
+package what_changed
+
+import (
+	"fmt"
+	"github.com/pb33f/libopenapi/datamodel/low"
+	"strings"
+)
+
+type ExtensionChanges struct {
+	PropertyChanges
+}
+
+func CompareExtensions(l, r map[low.KeyReference[string]]low.ValueReference[any]) *ExtensionChanges {
+
+	// look at the original and then look through the new.
+	seenLeft := make(map[string]*low.ValueReference[any])
+	seenRight := make(map[string]*low.ValueReference[any])
+	for i := range l {
+		h := l[i]
+		seenLeft[strings.ToLower(i.Value)] = &h
+	}
+	for i := range r {
+		h := r[i]
+		seenRight[strings.ToLower(i.Value)] = &h
+	}
+
+	var changes []*Change
+	var changeType int
+	for i := range seenLeft {
+		changeType = 0
+		if seenRight[i] == nil {
+			// deleted
+			changeType = PropertyRemoved
+			ctx := CreateContext(seenLeft[i].ValueNode, nil)
+			changes = append(changes, &Change{
+				Context:    ctx,
+				ChangeType: changeType,
+				Property:   i,
+				Original:   fmt.Sprintf("%v", seenLeft[i].Value),
+			})
+
+		}
+		if seenRight[i] != nil {
+			// potentially modified and or moved
+			ctx := CreateContext(seenLeft[i].ValueNode, seenRight[i].ValueNode)
+			if seenLeft[i].Value != seenRight[i].Value {
+				changeType = Modified
+			}
+			if ctx.HasChanged() {
+				if changeType == Modified {
+					changeType = ModifiedAndMoved
+				} else {
+					changeType = Moved
+				}
+			}
+			if changeType != 0 {
+				changes = append(changes, &Change{
+					Context:    ctx,
+					ChangeType: changeType,
+					Property:   i,
+					Original:   fmt.Sprintf("%v", seenLeft[i].Value),
+					New:        fmt.Sprintf("%v", seenRight[i].Value),
+				})
+			}
+		}
+	}
+	for i := range seenRight {
+		if seenLeft[i] == nil {
+			// added
+			ctx := CreateContext(nil, seenRight[i].ValueNode)
+			changes = append(changes, &Change{
+				Context:    ctx,
+				ChangeType: PropertyAdded,
+				Property:   i,
+				New:        fmt.Sprintf("%v", seenRight[i].Value),
+			})
+		}
+	}
+
+	if len(changes) <= 0 {
+		return nil
+	}
+	ex := new(ExtensionChanges)
+	ex.Changes = changes
+	return ex
+}