Preserve inherited source origins and transfer evidence

internal/engine/inheritance_origin.go

@@ -0,0 +1,127 @@
+package engine
+
+import (
+	"slices"
+
+	"gitea.maximumdirect.net/eric/ConfigKit/internal/document"
+)
+
+func directInheritanceOrigins(node *document.Node, root Path, input map[string]Origin) map[string]Origin {
+	result := make(map[string]Origin)
+	walkDocument(node, root, func(path Path, value *document.Node) {
+		origin, found := input[path.String()]
+		if !found {
+			origin = Origin{Layer: LayerBase, Locations: []Location{publicLocation(value.Location)}}
+		}
+		origin = cloneOrigin(origin)
+		if len(origin.contributors) == 0 {
+			origin.contributors = make([]inheritanceContributor, len(origin.Locations))
+			for index, location := range origin.Locations {
+				origin.contributors[index] = inheritanceContributor{
+					source: path.clone(), location: location,
+				}
+			}
+		}
+		result[path.String()] = origin
+	})
+	return result
+}
+
+func transferredInheritanceOrigins(parent map[string]Origin, from, to Path, control inheritanceTransfer) map[string]Origin {
+	result := make(map[string]Origin, len(parent))
+	transfer := control // one immutable edge shared by every matching contributor
+	links := make(map[*inheritanceTrace]*inheritanceTrace)
+	for pointer, origin := range parent {
+		path, err := ParsePath(pointer)
+		if err != nil {
+			continue
+		}
+		relative, ok := relativeHistoryPath(from, path)
+		if !ok {
+			continue
+		}
+		destination := appendInheritancePath(to, relative)
+		origin = cloneOrigin(origin)
+		for index, contributor := range origin.contributors {
+			link, found := links[contributor.trace]
+			if !found {
+				link = &inheritanceTrace{previous: contributor.trace, transfer: &transfer}
+				links[contributor.trace] = link
+			}
+			origin.contributors[index].trace = link
+		}
+		result[destination.String()] = origin
+	}
+	return result
+}
+
+func appendInheritancePath(root, relative Path) Path {
+	return Path{segments: append(clonePathSegments(root.segments, len(relative.segments)), relative.segments...)}
+}
+
+func mergeInheritanceOrigin(origins map[string]Origin, path Path, incoming Origin) {
+	pointer := path.String()
+	current := origins[pointer]
+	current.Layer = incoming.Layer
+	current.Locations = append(current.Locations, incoming.Locations...)
+	current.contributors = append(current.contributors, incoming.contributors...)
+	origins[pointer] = current
+}
+
+func copyInheritanceSubtree(target, incoming map[string]Origin, node *document.Node, root Path) {
+	walkDocument(node, root, func(path Path, _ *document.Node) {
+		target[path.String()] = cloneOrigin(incoming[path.String()])
+	})
+}
+
+// Materialize concrete steps only for an inspection record. The linked private
+// traces remain compact when one parent supplies many descendant values.
+func projectInheritanceSteps(origin Origin) []InheritanceStep {
+	steps := cloneInheritanceSteps(origin.Inheritance)
+	for _, contributor := range origin.contributors {
+		var reverse []*inheritanceTrace
+		for link := contributor.trace; link != nil; link = link.previous {
+			reverse = append(reverse, link)
+		}
+		current := contributor.source
+		for index := len(reverse) - 1; index >= 0; index-- {
+			transfer := reverse[index].transfer
+			relative, ok := relativeHistoryPath(transfer.from, current)
+			if !ok {
+				continue
+			}
+			next := appendInheritancePath(transfer.to, relative)
+			step := InheritanceStep{
+				From: current.clone(), To: next.clone(), Reference: transfer.reference.clone(),
+				Locations: cloneLocations(transfer.locations),
+			}
+			if !slices.ContainsFunc(steps, func(existing InheritanceStep) bool {
+				return existing.From.String() == step.From.String() &&
+					existing.To.String() == step.To.String() &&
+					existing.Reference.String() == step.Reference.String() &&
+					slices.Equal(existing.Locations, step.Locations)
+			}) {
+				steps = append(steps, step)
+			}
+			current = next
+		}
+	}
+	return steps
+}
+
+func sameInheritanceTrace(left, right *inheritanceTrace) bool {
+	for left != nil && right != nil {
+		if left == right {
+			return true
+		}
+		l, r := left.transfer, right.transfer
+		if !slices.Equal(l.from.segments, r.from.segments) ||
+			!slices.Equal(l.to.segments, r.to.segments) ||
+			!slices.Equal(l.reference.segments, r.reference.segments) ||
+			!slices.Equal(l.locations, r.locations) {
+			return false
+		}
+		left, right = left.previous, right.previous
+	}
+	return left == nil && right == nil
+}