Project sequence evidence through item mappings

internal/engine/compose.go

@@ -83,6 +83,48 @@ type sequenceRange struct {
 	path        Path
 	start       int
 	end         int
+	items       []sequenceItemProjection
+	projection  sequenceItemProjectionIndex
+}
+
+func (assigned sequenceRange) projections() []sequenceItemProjection {
+	if assigned.items != nil {
+		return append([]sequenceItemProjection{}, assigned.items...)
+	}
+	return sequenceItemProjections(assigned.end-assigned.start, assigned.start)
+}
+
+func (assigned sequenceRange) outputForInput(inputIndex int) (int, bool) {
+	if assigned.projection.outputByInput != nil {
+		return assigned.projection.outputForInput(inputIndex)
+	}
+	if assigned.items != nil {
+		return newSequenceItemProjectionIndex(assigned.items).outputForInput(inputIndex)
+	}
+	if inputIndex < 0 || inputIndex >= assigned.end-assigned.start {
+		return 0, false
+	}
+	return assigned.start + inputIndex, true
+}
+
+func (assigned sequenceRange) inputForOutput(outputIndex int) (int, bool) {
+	if assigned.projection.inputByOutput != nil {
+		return assigned.projection.inputForOutput(outputIndex)
+	}
+	if assigned.items != nil {
+		return newSequenceItemProjectionIndex(assigned.items).inputForOutput(outputIndex)
+	}
+	if outputIndex < assigned.start || outputIndex >= assigned.end {
+		return 0, false
+	}
+	return outputIndex - assigned.start, true
+}
+
+func indexSequenceRange(assigned sequenceRange) sequenceRange {
+	if assigned.projection.outputByInput == nil && assigned.projection.inputByOutput == nil {
+		assigned.projection = newSequenceItemProjectionIndex(assigned.projections())
+	}
+	return assigned
 }
 
 // composeDocuments recursively joins disjoint mapping entries. Source order
@@ -371,6 +413,11 @@ func cloneSequenceRanges(ranges []sequenceRange) []sequenceRange {
 	for i, assigned := range ranges {
 		cloned[i] = assigned
 		cloned[i].path = assigned.path.clone()
+		if assigned.items != nil {
+			cloned[i].items = append([]sequenceItemProjection{}, assigned.items...)
+		}
+		cloned[i].projection.outputByInput = append([]int(nil), assigned.projection.outputByInput...)
+		cloned[i].projection.inputByOutput = append([]int(nil), assigned.projection.inputByOutput...)
 	}
 	return cloned
 }
@@ -410,12 +457,22 @@ func documentEntryIndex(entries []document.Entry, key string) int {
 
 func projectedCompositionOrigins(inputs []*document.Node, ranges []sequenceRange) map[string]Origin {
 	origins := make(map[string]Origin)
-	rangeBySourcePath := make(map[sequenceRangeKey]int, len(ranges))
-	for index, assigned := range ranges {
-		rangeBySourcePath[sequenceRangeKey{sourceIndex: assigned.sourceIndex, path: assigned.path.String()}] = index
+	sequencesBySource := make([][]sequenceHistoryContribution, len(inputs))
+	for _, assigned := range ranges {
+		sequencesBySource[assigned.sourceIndex] = append(sequencesBySource[assigned.sourceIndex], sequenceHistoryContribution{
+			path: assigned.path.clone(), mode: sequenceHistoryMapped, items: assigned.projections(),
+		})
 	}
 	for sourceIndex, input := range inputs {
-		collectProjectedCompositionOrigins(input, Path{}, Path{}, sourceIndex, ranges, rangeBySourcePath, origins)
+		application := historyApplication{value: input, sequences: sequencesBySource[sourceIndex]}
+		application.sequencesByPath = indexSequenceHistoryContributions(application.sequences)
+		walkHistoryApplication(application, func(_, effective Path, node *document.Node) {
+			pointer := effective.String()
+			origin := origins[pointer]
+			origin.Layer = LayerBase
+			origin.Locations = append(origin.Locations, publicLocation(node.Location))
+			origins[pointer] = origin
+		})
 	}
 	return origins
 }
@@ -433,39 +490,12 @@ func indexSequenceRanges(ranges []sequenceRange) sequenceRangeIndex {
 	}
 	index := make(sequenceRangeIndex, len(ranges))
 	for _, assigned := range ranges {
+		assigned = indexSequenceRange(assigned)
 		index[sequenceRangeKey{sourceIndex: assigned.sourceIndex, path: assigned.path.String()}] = assigned
 	}
 	return index
 }
 
-// Keep local paths for matching Stage 2 ranges and effective paths for emitted
-// evidence. The paths are transformed segment by segment; pointer strings are
-// only used as map keys after projection is complete.
-func collectProjectedCompositionOrigins(node *document.Node, localPath, effectivePath Path, sourceIndex int, ranges []sequenceRange, rangeBySourcePath map[sequenceRangeKey]int, origins map[string]Origin) {
-	pointer := effectivePath.String()
-	origin := origins[pointer]
-	origin.Layer = LayerBase
-	origin.Locations = append(origin.Locations, publicLocation(node.Location))
-	origins[pointer] = origin
-
-	switch node.Kind {
-	case document.Mapping:
-		for _, entry := range node.Mapping {
-			collectProjectedCompositionOrigins(entry.Value, localPath.Key(entry.Key), effectivePath.Key(entry.Key), sourceIndex, ranges, rangeBySourcePath, origins)
-		}
-	case document.Sequence:
-		start := 0
-		if rangeIndex, ok := rangeBySourcePath[sequenceRangeKey{sourceIndex: sourceIndex, path: localPath.String()}]; ok {
-			start = ranges[rangeIndex].start
-		}
-		for index, child := range node.Sequence {
-			localChild := localPath.Index(index)
-			effectiveChild := effectivePath.Index(start + index)
-			collectProjectedCompositionOrigins(child, localChild, effectiveChild, sourceIndex, ranges, rangeBySourcePath, origins)
-		}
-	}
-}
-
 func applyCompositionOrigins(decoded *decodedConfiguration, origins map[string]Origin) {
 	for pointer, origin := range origins {
 		if _, present := decoded.presence[pointer]; present {