Cut metadata history over to shared model

internal/engine/metadata.go

@@ -5,12 +5,12 @@ import "gitea.maximumdirect.net/eric/ConfigKit/internal/document"
 // Metadata provides detached effective presence/origin and chronological history
 // queries for a load. Its zero value contains no paths.
 type Metadata struct {
-	effectivePaths   map[string]Path
-	fields           map[string]FieldInfo
-	history          map[string][]Change
-	inheritance      []inheritanceOperation
-	inheritanceIndex *inheritanceHistoryIndex
-	historyModel     *historyModel
+	effectivePaths map[string]Path
+	fields         map[string]FieldInfo
+	history        map[string][]Change
+	inheritance    []inheritanceOperation
+	historyBuilder *historyBuilder
+	historyModel   *historyModel
 }
 
 // Lookup returns information for an effective path. Unknown and invalid paths
@@ -50,15 +50,38 @@ func (m Metadata) effectiveField(path Path) (FieldInfo, bool) {
 // Removed historical paths can have history even though Lookup returns false.
 // Unknown and invalid paths return nil.
 func (m Metadata) History(path Path) []Change {
-	if !m.hasHistoricalPath(path) {
+	model := m.historyEvidence()
+	if model == nil || !model.hasObservedShape(path) {
 		return nil
 	}
-	history := m.history[path.String()]
-	operations := m.inheritance
-	if m.inheritanceIndex != nil {
-		operations = m.inheritanceIndex.matchingOperations(path, m.inheritance)
+	selections := model.selectHistory(path)
+	if len(selections) == 0 {
+		return nil
 	}
-	return historyWithInheritance(path, history, operations)
+	changes := make([]Change, 0, len(selections))
+	for _, selection := range selections {
+		if !metadataHistoryRole(selection.role) || !selection.hasAttribution {
+			continue
+		}
+		var previous []Origin
+		if len(selection.previous) != 0 {
+			previous = make([]Origin, len(selection.previous))
+			for index, origin := range selection.previous {
+				previous[index] = cloneOrigin(origin)
+			}
+		}
+		changes = append(changes, Change{
+			Path:         selection.reportedPath.clone(),
+			Origin:       cloneOrigin(selection.attribution.origin),
+			Previous:     previous,
+			Reasons:      append([]string(nil), selection.attribution.reasons...),
+			Dependencies: clonePaths(selection.attribution.dependencies),
+		})
+	}
+	if len(changes) == 0 {
+		return nil
+	}
+	return changes
 }
 
 // HistoricalPaths returns the paths observed during loading, including effective
@@ -73,7 +96,17 @@ func (m Metadata) History(path Path) []Change {
 // a path remains effective. Enumeration exposes no configuration values and does
 // not perform another load or resolve secrets.
 func (m Metadata) HistoricalPaths() []Path {
-	return m.historyModel.historicalPaths()
+	return m.historyEvidence().historicalPaths()
+}
+
+func (m Metadata) historyEvidence() *historyModel {
+	if m.historyModel != nil {
+		return m.historyModel
+	}
+	if m.historyBuilder != nil {
+		return m.historyBuilder.model
+	}
+	return nil
 }
 
 // Textual pointers are lookup keys, but explicit key/index kinds remain part of
@@ -100,7 +133,7 @@ func matchesPathShape(query, candidate Path) bool {
 }
 
 func (m Metadata) hasHistoricalPath(path Path) bool {
-	return m.historyModel.hasObservedShape(path)
+	return m.historyEvidence().hasObservedShape(path)
 }
 
 func finalizeMetadataPaths(m *Metadata, final *document.Node, applications []historyApplication, earlier ...*document.Node) {
@@ -109,7 +142,10 @@ func finalizeMetadataPaths(m *Metadata, final *document.Node, applications []his
 
 func finalizeMetadataPathsWithResolution(m *Metadata, final *document.Node, applications []historyApplication, snapshots []resolutionSnapshot, earlier ...*document.Node) {
 	finalizeEffectiveMetadataPaths(m, final)
-	builder := newHistoryBuilder()
+	builder := m.historyBuilder
+	if builder == nil {
+		builder = newHistoryBuilder()
+	}
 	if len(earlier) != 0 {
 		builder.model.baseline = earlier[0]
 	}
@@ -164,12 +200,11 @@ func finalizeMetadataPathsWithResolution(m *Metadata, final *document.Node, appl
 		builder.observeResolutionEvidence(snapshots)
 	}
 	m.historyModel = builder.freeze()
-	m.inheritanceIndex = newInheritanceHistoryIndex(m.inheritance)
+	m.historyBuilder = nil
 }
 
 func finalizeEffectiveMetadataPaths(m *Metadata, final *document.Node) {
 	m.effectivePaths = effectivePathIndex(final)
-	m.inheritanceIndex = newInheritanceHistoryIndex(m.inheritance)
 }
 
 // effectivePathIndex records document-derived paths with their contextual segment