Replace evidence context with source unit excerpts

internal/framework/evidencecontext/codec.go

@@ -6,7 +6,6 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
-	"regexp"
 	"strings"
 	"sync"
 
@@ -18,8 +17,6 @@ import (
 //go:embed assets/schemas/source_evidence_context.v1.json
 var schemaAssets embed.FS
 
-var digestPattern = regexp.MustCompile(`^sha256:[0-9a-f]{64}$`)
-
 var (
 	loadSchemaOnce sync.Once
 	loadedSchema   []byte
@@ -78,24 +75,24 @@ func (c *Codec) Encode(value Document) ([]byte, error) {
 
 func (c *Codec) Decode(content []byte) (Document, error) {
 	if _, err := c.schemaBytes(); err != nil {
-		return Document{}, err
+		return nil, err
 	}
 	if err := validateSchemaInstance(content); err != nil {
-		return Document{}, fmt.Errorf("decode evidence context: %w", err)
+		return nil, fmt.Errorf("decode evidence context: %w", err)
 	}
 	decoder := json.NewDecoder(bytes.NewReader(content))
 	decoder.DisallowUnknownFields()
 	var value Document
 	if err := decoder.Decode(&value); err != nil {
-		return Document{}, fmt.Errorf("decode evidence context: %w", err)
+		return nil, fmt.Errorf("decode evidence context: %w", err)
 	}
 	var trailing any
 	if err := decoder.Decode(&trailing); err != io.EOF {
-		return Document{}, fmt.Errorf("decode evidence context: multiple JSON values")
+		return nil, fmt.Errorf("decode evidence context: multiple JSON values")
 	}
 	canonical, err := canonicalizeOwned(value)
 	if err != nil {
-		return Document{}, fmt.Errorf("decode evidence context: %w", err)
+		return nil, fmt.Errorf("decode evidence context: %w", err)
 	}
 	return canonical, nil
 }
@@ -115,17 +112,16 @@ func loadAndCompileSchema() {
 		return
 	}
 	var identity struct {
-		ID       string   `json:"$id"`
-		Title    string   `json:"title"`
-		Type     string   `json:"type"`
-		Required []string `json:"required"`
+		ID    string `json:"$id"`
+		Title string `json:"title"`
+		Type  string `json:"type"`
 	}
 	if err := json.Unmarshal(raw, &identity); err != nil {
 		loadSchemaErr = fmt.Errorf("decode source evidence context schema: %w", err)
 		return
 	}
-	if identity.ID != SchemaID || identity.Title != SchemaName || identity.Type != "object" || !hasRequiredFields(identity.Required) {
-		loadSchemaErr = fmt.Errorf("source evidence context schema identity or required fields are invalid")
+	if identity.ID != SchemaID || identity.Title != SchemaName || identity.Type != "array" {
+		loadSchemaErr = fmt.Errorf("source evidence context schema identity is invalid")
 		return
 	}
 	schemaDocument, err := jsonschema.UnmarshalJSON(bytes.NewReader(raw))
@@ -158,164 +154,59 @@ func validateSchemaInstance(content []byte) error {
 	return nil
 }
 
-func hasRequiredFields(required []string) bool {
-	want := map[string]bool{"source_id": true, "source_digest": true, "window_units": true, "selected_lanes": true, "contexts": true}
-	for _, field := range required {
-		delete(want, field)
-	}
-	return len(want) == 0
-}
-
 func canonicalize(value Document) (Document, error) {
 	owned, err := clone(value)
 	if err != nil {
-		return Document{}, err
+		return nil, err
 	}
 	return canonicalizeOwned(owned)
 }
 
 func canonicalizeOwned(value Document) (Document, error) {
-	if err := requireIdentity("source_id", value.SourceID); err != nil {
-		return Document{}, err
+	if value == nil {
+		return nil, fmt.Errorf("document must be a JSON array")
 	}
-	if !digestPattern.MatchString(value.SourceDigest) {
-		return Document{}, fmt.Errorf("source_digest must be a sha256 digest")
-	}
-	if value.WindowUnits < 0 {
-		return Document{}, fmt.Errorf("window_units must not be negative")
-	}
-	if err := validateSelectedLanes(value.SelectedLanes); err != nil {
-		return Document{}, err
-	}
-	if value.Contexts == nil {
-		value.Contexts = make([]Context, 0)
-	}
-	selected := make(map[string]struct{}, len(value.SelectedLanes))
-	for _, laneID := range value.SelectedLanes {
-		selected[laneID] = struct{}{}
-	}
-	seenUnits := make(map[int]struct{})
-	for contextIndex := range value.Contexts {
-		context, err := canonicalizeContext(value.SourceID, selected, seenUnits, value.Contexts[contextIndex], contextIndex)
-		if err != nil {
-			return Document{}, err
-		}
-		value.Contexts[contextIndex] = context
-	}
-	return value, nil
-}
-
-func validateSelectedLanes(lanes []string) error {
-	if len(lanes) == 0 {
-		return fmt.Errorf("selected_lanes must not be empty")
-	}
-	for index, laneID := range lanes {
-		if err := requireIdentity(fmt.Sprintf("selected_lanes[%d]", index), laneID); err != nil {
-			return err
-		}
-		if index > 0 && lanes[index-1] >= laneID {
-			return fmt.Errorf("selected_lanes must be unique and in lexical order")
-		}
-	}
-	return nil
-}
-
-func canonicalizeContext(sourceID string, selected map[string]struct{}, seenUnits map[int]struct{}, value Context, contextIndex int) (Context, error) {
-	prefix := fmt.Sprintf("contexts[%d]", contextIndex)
-	if len(value.EvidenceRefs) == 0 {
-		return Context{}, fmt.Errorf("%s.evidence_refs must not be empty", prefix)
-	}
-	if len(value.Units) == 0 {
-		return Context{}, fmt.Errorf("%s.units must not be empty", prefix)
-	}
-	if err := validateRefIdentity(sourceID, value.ContextRef, prefix+".context_ref"); err != nil {
-		return Context{}, err
-	}
-	positions := make(map[int]int, len(value.Units))
-	for unitIndex := range value.Units {
-		unit := value.Units[unitIndex]
+	seenUnitIDs := make(map[int]struct{}, len(value))
+	for unitIndex := range value {
+		unit := value[unitIndex]
 		if unit.ID <= 0 || strings.TrimSpace(unit.Kind) == "" || strings.TrimSpace(unit.Text) == "" {
-			return Context{}, fmt.Errorf("%s.units[%d] has invalid required fields", prefix, unitIndex)
+			return nil, fmt.Errorf("units[%d] has invalid required fields", unitIndex)
 		}
-		if err := validateRefIdentity(sourceID, unit.Ref, fmt.Sprintf("%s.units[%d].ref", prefix, unitIndex)); err != nil {
-			return Context{}, err
+		if err := validateUnitRef(unit, unitIndex); err != nil {
+			return nil, err
 		}
-		if unit.Ref.StartUnitID != unit.ID || unit.Ref.EndUnitID != unit.ID {
-			return Context{}, fmt.Errorf("%s.units[%d].ref must identify unit id %d", prefix, unitIndex, unit.ID)
-		}
-		if _, exists := positions[unit.ID]; exists {
-			return Context{}, fmt.Errorf("%s.units contains duplicate unit id %d", prefix, unit.ID)
-		}
-		if _, exists := seenUnits[unit.ID]; exists {
-			return Context{}, fmt.Errorf("contexts contain duplicate unit id %d", unit.ID)
-		}
-		positions[unit.ID] = unitIndex
-		seenUnits[unit.ID] = struct{}{}
-	}
-	if value.ContextRef.StartUnitID != value.Units[0].ID || value.ContextRef.EndUnitID != value.Units[len(value.Units)-1].ID {
-		return Context{}, fmt.Errorf("%s.context_ref must identify the first and last units", prefix)
-	}
-	for evidenceIndex := range value.EvidenceRefs {
-		evidence := value.EvidenceRefs[evidenceIndex]
-		if _, ok := selected[evidence.LaneID]; !ok {
-			return Context{}, fmt.Errorf("%s.evidence_refs[%d].lane_id is not selected", prefix, evidenceIndex)
-		}
-		if err := requireIdentity(fmt.Sprintf("%s.evidence_refs[%d].lane_id", prefix, evidenceIndex), evidence.LaneID); err != nil {
-			return Context{}, err
-		}
-		if err := validateRefIdentity(sourceID, evidence.SourceRef, fmt.Sprintf("%s.evidence_refs[%d].source_ref", prefix, evidenceIndex)); err != nil {
-			return Context{}, err
-		}
-		start, startOK := positions[evidence.SourceRef.StartUnitID]
-		end, endOK := positions[evidence.SourceRef.EndUnitID]
-		if !startOK || !endOK || start > end {
-			return Context{}, fmt.Errorf("%s.evidence_refs[%d].source_ref is outside context units", prefix, evidenceIndex)
-		}
-		if evidenceIndex > 0 && !lessEvidenceRef(value.EvidenceRefs[evidenceIndex-1], evidence) {
-			return Context{}, fmt.Errorf("%s.evidence_refs must be unique and in deterministic order", prefix)
+		if _, exists := seenUnitIDs[unit.ID]; exists {
+			return nil, fmt.Errorf("units contains duplicate unit id %d", unit.ID)
 		}
+		seenUnitIDs[unit.ID] = struct{}{}
 	}
 	return value, nil
 }
 
-func validateRefIdentity(sourceID string, ref source.SourceRef, field string) error {
-	if ref.SourceID != sourceID {
-		return fmt.Errorf("%s.source_id does not match source_id", field)
+func validateUnitRef(unit source.SourceUnit, unitIndex int) error {
+	prefix := fmt.Sprintf("units[%d].ref", unitIndex)
+	if strings.TrimSpace(unit.Ref.SourceID) == "" || strings.TrimSpace(unit.Ref.SourceID) != unit.Ref.SourceID {
+		return fmt.Errorf("%s.source_id must be a non-empty trimmed string", prefix)
 	}
-	if ref.StartUnitID <= 0 || ref.EndUnitID <= 0 {
-		return fmt.Errorf("%s endpoints must be positive", field)
-	}
-	return nil
-}
-
-func requireIdentity(field, value string) error {
-	if strings.TrimSpace(value) == "" || strings.TrimSpace(value) != value {
-		return fmt.Errorf("%s must be a non-empty trimmed string", field)
+	if unit.Ref.StartUnitID != unit.ID || unit.Ref.EndUnitID != unit.ID {
+		return fmt.Errorf("%s must identify unit id %d", prefix, unit.ID)
 	}
 	return nil
 }
 
 func clone(value Document) (Document, error) {
-	value.SelectedLanes = append([]string(nil), value.SelectedLanes...)
-	if value.Contexts == nil {
-		value.Contexts = make([]Context, 0)
-	} else {
-		contexts := make([]Context, len(value.Contexts))
-		for contextIndex, context := range value.Contexts {
-			contexts[contextIndex].ContextRef = context.ContextRef
-			contexts[contextIndex].EvidenceRefs = append([]EvidenceRef(nil), context.EvidenceRefs...)
-			contexts[contextIndex].Units = make([]source.SourceUnit, len(context.Units))
-			for unitIndex, unit := range context.Units {
-				cloned, err := cloneSourceUnit(unit)
-				if err != nil {
-					return Document{}, fmt.Errorf("clone contexts[%d].units[%d]: %w", contextIndex, unitIndex, err)
-				}
-				contexts[contextIndex].Units[unitIndex] = cloned
-			}
-		}
-		value.Contexts = contexts
+	if value == nil {
+		return nil, nil
 	}
-	return value, nil
+	cloned := make(Document, len(value))
+	for unitIndex, unit := range value {
+		owned, err := cloneSourceUnit(unit)
+		if err != nil {
+			return nil, fmt.Errorf("clone units[%d]: %w", unitIndex, err)
+		}
+		cloned[unitIndex] = owned
+	}
+	return cloned, nil
 }
 
 func cloneSourceUnit(unit source.SourceUnit) (source.SourceUnit, error) {