Let a process read the router's record of its module's own ask (issue 1189)

go/process/asks.go

@@ -0,0 +1,68 @@
+package process
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"strings"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+)
+
+// Ask reads the router's record of one of this process's module's own asks, under its own module and no
+// other's (novox/hq ADR 0436 clause 4, ADR 0259 §3): by direct get on bucket, the same subject the tool
+// runner reads (mesh-tools node-tools/internal/bus/seat.go ~300-345):
+//
+//	$JS.API.DIRECT.GET.KV_<bucket>.$KV.<bucket>.<module>.<id>
+//
+// bucket is the router's records bucket as the caller's own manifest names it (operator-channel's is
+// messenger_asks in the controller's own test fixtures) — never hard-coded to one bucket here, since a
+// process may read records of more than one seat's router. A missing, deleted or purged key is nil, not
+// an error.
+func (c *Conn) Ask(bucket, id string) (*stdio.StateEntry, error) {
+	if err := checkAskID(id); err != nil {
+		return nil, err
+	}
+	subject := "$JS.API.DIRECT.GET.KV_" + bucket + ".$KV." + bucket + "." + c.account.Module + "." + id
+	ctx, cancel := context.WithTimeout(context.Background(), StateTimeout)
+	defer cancel()
+	reply, err := c.nc.RequestWithContext(ctx, subject, nil)
+	if err != nil {
+		return nil, fmt.Errorf("reading %s's ask %s from %s: %w", c.account.Module, id, bucket, err)
+	}
+	if status := reply.Header.Get("Status"); status == "404" {
+		return nil, nil
+	} else if status != "" {
+		return nil, fmt.Errorf("the record %s.%s could not be read: %s %s", c.account.Module, id, status,
+			reply.Header.Get("Description"))
+	}
+	if op := reply.Header.Get("KV-Operation"); op == "DEL" || op == "PURGE" {
+		return nil, nil
+	}
+	var revision uint64
+	if _, err := fmt.Sscan(reply.Header.Get("Nats-Sequence"), &revision); err != nil {
+		return nil, fmt.Errorf("the record %s.%s carries no readable revision: %w", c.account.Module, id, err)
+	}
+	return &stdio.StateEntry{Key: c.account.Module + "." + id, Value: askValueOf(reply.Data), Revision: revision}, nil
+}
+
+// checkAskID refuses an id holding a dot or a wildcard before anything is sent: either would name a
+// different key under the direct-get subject's own dot-joined path, never this one (novox/hq issue 1189
+// AC2).
+func checkAskID(id string) error {
+	if id == "" || strings.ContainsAny(id, ".*>") {
+		return fmt.Errorf("%q is not an ask id: an ask id holds no dot and no wildcard, naming one key and "+
+			"no other", id)
+	}
+	return nil
+}
+
+// askValueOf is a record's raw bytes as JSON, quoting them when they are not already valid JSON
+// (mesh-tools node-tools/internal/bus/state.go:351-357, valueOf).
+func askValueOf(raw []byte) json.RawMessage {
+	if len(raw) == 0 || !json.Valid(raw) {
+		b, _ := json.Marshal(string(raw))
+		return b
+	}
+	return json.RawMessage(append([]byte(nil), raw...))
+}