Bound external result file reads

internal/contracts/bounds.go

@@ -4,12 +4,17 @@ import (
 	"encoding/json"
 	"fmt"
 	"math"
-	"os"
 	"strconv"
 	"strings"
+
+	"gitea.maximumdirect.net/eric/narratio/internal/fileops"
 )
 
 const (
+	// MaxSessionBoundsFileBytes bounds one Scriptorium bounds JSON result.
+	MaxSessionBoundsFileBytes int64 = 1 * 1024 * 1024
+	// MaxTranscriptFileBytes bounds a transcript JSON handoff used for bounds validation.
+	MaxTranscriptFileBytes int64 = 64 * 1024 * 1024
 	// BoundsTrimActionTrim keeps only a selected segment range.
 	BoundsTrimActionTrim = "trim"
 	// BoundsTrimActionNone indicates no trimming should be applied.
@@ -36,9 +41,9 @@ type SessionBounds struct {
 
 // ParseSessionBoundsFile reads and parses one Scriptorium bounds output JSON file.
 func ParseSessionBoundsFile(path string) (SessionBounds, error) {
-	data, err := os.ReadFile(path)
+	data, err := readContractResult(path, MaxSessionBoundsFileBytes, "scriptorium bounds result")
 	if err != nil {
-		return SessionBounds{}, fmt.Errorf("read bounds file: %w", err)
+		return SessionBounds{}, err
 	}
 	var bounds SessionBounds
 	if err := json.Unmarshal(data, &bounds); err != nil {
@@ -119,9 +124,9 @@ func normalizeBoundsTrimAction(raw string) (string, error) {
 }
 
 func loadTranscriptSegmentIDs(path string) (map[int]struct{}, error) {
-	data, err := os.ReadFile(path)
+	data, err := readContractResult(path, MaxTranscriptFileBytes, "transcript result")
 	if err != nil {
-		return nil, fmt.Errorf("read transcript file: %w", err)
+		return nil, err
 	}
 
 	var payload map[string]any
@@ -158,6 +163,14 @@ func loadTranscriptSegmentIDs(path string) (map[int]struct{}, error) {
 	return ids, nil
 }
 
+func readContractResult(path string, limit int64, category string) ([]byte, error) {
+	data, err := fileops.ReadRegularFile(path, limit)
+	if err != nil {
+		return nil, fmt.Errorf("%s exceeds or cannot be read within %d-byte limit: %w", category, limit, err)
+	}
+	return data, nil
+}
+
 func parseJSONSegmentID(v any) (int, error) {
 	n, ok := v.(float64)
 	if !ok {