Make chunk validation a framework contract

internal/framework/pipeline/chunk_validation.go

@@ -0,0 +1,60 @@
+package pipeline
+
+import (
+	"fmt"
+	"strings"
+
+	"gitea.maximumdirect.net/eric/notarius/internal/core/source"
+	"gitea.maximumdirect.net/eric/notarius/internal/framework/contracts"
+)
+
+func validateChunkResult(doc *source.SourceDocument, chunks []contracts.SourceChunk) error {
+	sourceUnitIndexes := make(map[string]int, len(doc.Units))
+	for index, unit := range doc.Units {
+		sourceUnitIndexes[unit.ID] = index
+	}
+
+	seenChunkIDs := make(map[string]struct{}, len(chunks))
+	for chunkIndex, chunk := range chunks {
+		if strings.TrimSpace(chunk.ID) == "" {
+			return fmt.Errorf("chunk[%d].id must not be empty", chunkIndex)
+		}
+		if _, ok := seenChunkIDs[chunk.ID]; ok {
+			return fmt.Errorf("chunk id %q is duplicated", chunk.ID)
+		}
+		seenChunkIDs[chunk.ID] = struct{}{}
+
+		if chunk.SourceID != doc.ID {
+			return fmt.Errorf("chunk %q source_id %q does not match source document id %q", chunk.ID, chunk.SourceID, doc.ID)
+		}
+		if chunk.Index != chunkIndex {
+			return fmt.Errorf("chunk %q index %d does not match returned order %d", chunk.ID, chunk.Index, chunkIndex)
+		}
+		if len(chunk.Units) == 0 {
+			return fmt.Errorf("chunk %q units must not be empty", chunk.ID)
+		}
+
+		seenUnitIDs := make(map[string]struct{}, len(chunk.Units))
+		previousSourceIndex := -1
+		for unitIndex, unit := range chunk.Units {
+			if strings.TrimSpace(unit.ID) == "" {
+				return fmt.Errorf("chunk %q unit[%d].id must not be empty", chunk.ID, unitIndex)
+			}
+			if _, ok := seenUnitIDs[unit.ID]; ok {
+				return fmt.Errorf("chunk %q repeats source unit %q", chunk.ID, unit.ID)
+			}
+			seenUnitIDs[unit.ID] = struct{}{}
+
+			sourceIndex, ok := sourceUnitIndexes[unit.ID]
+			if !ok {
+				return fmt.Errorf("chunk %q source unit %q was not found in source document %q", chunk.ID, unit.ID, doc.ID)
+			}
+			if sourceIndex <= previousSourceIndex {
+				return fmt.Errorf("chunk %q source units must appear in source document order", chunk.ID)
+			}
+			previousSourceIndex = sourceIndex
+		}
+	}
+
+	return nil
+}