1 files changed, 72 insertions, 0 deletions
diff --git a/grammar/lexical/parser/fragment.go b/grammar/lexical/parser/fragment.go
new file mode 100644
index 0000000..fc6f16b
--- /dev/null
+++ b/grammar/lexical/parser/fragment.go
@@ -0,0 +1,72 @@
+package parser
+
+import (
+	"fmt"
+
+	spec "github.com/nihei9/vartan/spec/grammar"
+)
+
+type incompleteFragment struct {
+	kind spec.LexKindName
+	root *rootNode
+}
+
+func CompleteFragments(fragments map[spec.LexKindName]CPTree) error {
+	if len(fragments) == 0 {
+		return nil
+	}
+
+	completeFragments := map[spec.LexKindName]CPTree{}
+	incompleteFragments := []*incompleteFragment{}
+	for kind, tree := range fragments {
+		root, ok := tree.(*rootNode)
+		if !ok {
+			return fmt.Errorf("CompleteFragments can take only *rootNode: %T", tree)
+		}
+		if root.incomplete() {
+			incompleteFragments = append(incompleteFragments, &incompleteFragment{
+				kind: kind,
+				root: root,
+			})
+		} else {
+			completeFragments[kind] = root
+		}
+	}
+	for len(incompleteFragments) > 0 {
+		lastIncompCount := len(incompleteFragments)
+		remainingFragments := []*incompleteFragment{}
+		for _, e := range incompleteFragments {
+			complete, err := ApplyFragments(e.root, completeFragments)
+			if err != nil {
+				return err
+			}
+			if !complete {
+				remainingFragments = append(remainingFragments, e)
+			} else {
+				completeFragments[e.kind] = e.root
+			}
+		}
+		incompleteFragments = remainingFragments
+		if len(incompleteFragments) == lastIncompCount {
+			return ParseErr
+		}
+	}
+
+	return nil
+}
+
+func ApplyFragments(t CPTree, fragments map[spec.LexKindName]CPTree) (bool, error) {
+	root, ok := t.(*rootNode)
+	if !ok {
+		return false, fmt.Errorf("ApplyFragments can take only *rootNode type: %T", t)
+	}
+
+	for name, frag := range fragments {
+		err := root.applyFragment(name, frag)
+		if err != nil {
+			return false, err
+		}
+	}
+
+	return !root.incomplete(), nil
+}