Add private input destination placement helpers

2026-10-14 13:09:06 +00:00
parent ea55ab43ce
commit 667a536ae7
3 changed files with 292 additions and 3 deletions
--- a/internal/engine/destination.go
+++ b/internal/engine/destination.go
@@ -0,0 +1,108 @@
+package engine
+
+import (
+	"errors"
+
+	"gitea.maximumdirect.net/eric/ConfigKit/internal/document"
+)
+
+var (
+	errInvalidDestination = errors.New("configkit: destination must contain only non-reserved mapping keys")
+	errDestinationLimit   = errors.New("configkit: destination exceeds document limits")
+)
+
+func normalizeDestination(path Path) (Path, error) {
+	if !path.valid() {
+		return Path{}, errInvalidDestination
+	}
+
+	segments := make([]pathSegment, 0, len(path.segments))
+	for _, segment := range path.segments {
+		if segment.kind != pathSegmentKey && segment.kind != pathSegmentParsed {
+			return Path{}, errInvalidDestination
+		}
+		if segment.key == "configkit" || segment.key == "extends" {
+			return Path{}, errInvalidDestination
+		}
+		segments = append(segments, pathSegment{kind: pathSegmentKey, key: segment.key})
+	}
+	return Path{segments: segments}, nil
+}
+
+// placeDocument checks all per-document bounds before allocating destination
+// wrappers. Aggregate accounting remains the caller's responsibility.
+func placeDocument(body *document.Node, destination Path, sourceRoot document.Location, maxDepth, maxNodes int) (Path, *document.Node, error) {
+	normalized, err := normalizeDestination(destination)
+	if err != nil {
+		return Path{}, nil, err
+	}
+	if body == nil {
+		return normalized, nil, nil
+	}
+	if !destinationWithinLimits(body, normalized, maxDepth, maxNodes) {
+		return normalized, nil, errDestinationLimit
+	}
+
+	placed := body
+	for index := len(normalized.segments) - 1; index >= 0; index-- {
+		key := normalized.segments[index].key
+		placed = &document.Node{
+			Kind:     document.Mapping,
+			Location: sourceRoot,
+			Mapping: []document.Entry{{
+				Key:           key,
+				KeyLocation:   sourceRoot,
+				ValueLocation: sourceRoot,
+				Value:         placed,
+			}},
+		}
+	}
+	return normalized, placed, nil
+}
+
+// destinationWithinLimits expects a normalized mapping-key destination.
+func destinationWithinLimits(body *document.Node, destination Path, maxDepth, maxNodes int) bool {
+	if body == nil {
+		return true
+	}
+	if maxDepth < 0 || maxNodes < 0 || !destination.valid() {
+		return false
+	}
+	segments := len(destination.segments)
+	if segments > maxDepth || segments > maxNodes/2 {
+		return false
+	}
+	for _, segment := range destination.segments {
+		if segment.kind != pathSegmentKey {
+			return false
+		}
+	}
+	if documentDepth(body) > maxDepth-segments {
+		return false
+	}
+	return countInputNodes(body) <= maxNodes-2*segments
+}
+
+func documentDepth(node *document.Node) int {
+	if node == nil {
+		return -1
+	}
+	depth := 0
+	var visit func(*document.Node, int)
+	visit = func(current *document.Node, currentDepth int) {
+		if current == nil {
+			return
+		}
+		if currentDepth > depth {
+			depth = currentDepth
+		}
+		for _, entry := range current.Mapping {
+			visit(entry.Value, currentDepth+1)
+		}
+		for _, child := range current.Sequence {
+			visit(child, currentDepth+1)
+		}
+	}
+	visit(node, 0)
+	return depth
+}