feat: persist and transfer script command payloads

internal/server/store/dispatch.go

@@ -3,6 +3,7 @@ package store
 import (
 	"bytes"
 	"context"
+	"crypto/sha256"
 	"database/sql"
 	"errors"
 	"fmt"
@@ -10,7 +11,9 @@ import (
 	"time"
 
 	"github.com/klauspost/compress/zstd"
+	rvboxv1 "github.com/rvbox/rvbox/gen/go/rvbox/v1"
 	"github.com/rvbox/rvbox/internal/domain"
+	"google.golang.org/protobuf/proto"
 )
 
 const maxStoredExecutionSpecBytes = 1 << 20
@@ -25,6 +28,19 @@ type DispatchCandidate struct {
 	QueueExpiryTime *time.Time
 	ImmutableSHA256 [32]byte
 	ExecutionSpec   []byte
+	ScriptPresent   bool
+	ScriptContent   []byte
+}
+
+// PendingScript is the server-owned immutable script body for a command that
+// has already crossed the queued boundary. It is used to reconstruct the
+// session-local transfer window after a daemon or server reconnect; the
+// command row remains the source of truth for whether the work is still
+// non-terminal.
+type PendingScript struct {
+	IssueUUID domain.UUID
+	Body      []byte
+	Digest    [sha256.Size]byte
 }
 
 // ClaimNextDispatch expires old queued rows and atomically assigns the oldest
@@ -79,6 +95,10 @@ FROM commands WHERE client_id = ? AND lifecycle = 1 ORDER BY issue_time, issue_u
 	if err != nil {
 		return nil, err
 	}
+	script, scriptPresent, err := loadDispatchScript(ctx, tx, issue, spec)
+	if err != nil {
+		return nil, err
+	}
 	result, err := tx.ExecContext(ctx, `UPDATE commands SET lifecycle = 2, target_session_generation = ? WHERE issue_uuid = ? AND client_id = ? AND lifecycle = 1`, generation, issue[:], clientID)
 	if err != nil {
 		return nil, err
@@ -93,7 +113,7 @@ FROM commands WHERE client_id = ? AND lifecycle = 1 ORDER BY issue_time, issue_u
 	if err := tx.Commit(); err != nil {
 		return nil, err
 	}
-	candidate := &DispatchCandidate{IssueUUID: issue, Revision: revision, IssueTime: time.Unix(0, issueTime).UTC(), ImmutableSHA256: immutable, ExecutionSpec: spec}
+	candidate := &DispatchCandidate{IssueUUID: issue, Revision: revision, IssueTime: time.Unix(0, issueTime).UTC(), ImmutableSHA256: immutable, ExecutionSpec: spec, ScriptPresent: scriptPresent, ScriptContent: script}
 	if expiry.Valid {
 		value := time.Unix(0, expiry.Int64).UTC()
 		candidate.QueueExpiryTime = &value
@@ -101,6 +121,116 @@ FROM commands WHERE client_id = ? AND lifecycle = 1 ORDER BY issue_time, issue_u
 	return candidate, nil
 }
 
+func (store *Store) PendingScriptDispatches(ctx context.Context, clientID string) ([]PendingScript, error) {
+	if clientID == "" {
+		return nil, errors.New("client ID is required")
+	}
+	database, err := store.openDatabase()
+	if err != nil {
+		return nil, err
+	}
+	rows, err := database.QueryContext(ctx, `SELECT issue_uuid, execution_spec, execution_spec_raw_bytes
+FROM commands WHERE client_id = ? AND lifecycle BETWEEN 2 AND 4 ORDER BY issue_time, issue_uuid`, clientID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	type pendingRow struct {
+		issue       domain.UUID
+		storedSpec  []byte
+		rawSpecSize uint64
+	}
+	var candidates []pendingRow
+	for rows.Next() {
+		var encodedIssue, stored []byte
+		var rawBytes uint64
+		if err := rows.Scan(&encodedIssue, &stored, &rawBytes); err != nil {
+			return nil, err
+		}
+		if len(encodedIssue) != 16 {
+			return nil, ErrInvalidSegmentRecord
+		}
+		var issue domain.UUID
+		copy(issue[:], encodedIssue)
+		candidates = append(candidates, pendingRow{issue: issue, storedSpec: bytes.Clone(stored), rawSpecSize: rawBytes})
+	}
+	if err := rows.Close(); err != nil {
+		return nil, err
+	}
+	var pending []PendingScript
+	for _, candidate := range candidates {
+		spec, err := decompressCommandSpec(candidate.storedSpec, candidate.rawSpecSize)
+		if err != nil {
+			return nil, err
+		}
+		body, present, err := loadDispatchScript(ctx, database, candidate.issue, spec)
+		if err != nil {
+			return nil, err
+		}
+		if !present {
+			continue
+		}
+		pending = append(pending, PendingScript{IssueUUID: candidate.issue, Body: body, Digest: sha256.Sum256(body)})
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return pending, nil
+}
+
+type queryRower interface {
+	QueryRowContext(context.Context, string, ...any) *sql.Row
+}
+
+func loadDispatchScript(ctx context.Context, tx queryRower, issue domain.UUID, encodedSpec []byte) ([]byte, bool, error) {
+	var spec rvboxv1.ExecutionSpec
+	if err := proto.Unmarshal(encodedSpec, &spec); err != nil {
+		// Existing store callers may use opaque test bytes. They cannot carry a
+		// script descriptor, so there is no payload to load.
+		return nil, false, nil
+	}
+	descriptor := spec.GetScript()
+	if descriptor == nil {
+		return nil, false, nil
+	}
+	var stored []byte
+	var rawBytes, storedBytes uint64
+	var compression uint32
+	var digest []byte
+	if err := tx.QueryRowContext(ctx, `SELECT inline_data, raw_bytes, stored_bytes, compression, sha256
+FROM command_payloads WHERE issue_uuid = ? AND kind = 'script'`, issue[:]).Scan(&stored, &rawBytes, &storedBytes, &compression, &digest); err != nil {
+		return nil, false, fmt.Errorf("load persisted script payload: %w", err)
+	}
+	if compression != 2 || storedBytes != uint64(len(stored)) || rawBytes != descriptor.GetSizeBytes() || len(digest) != 32 || !bytes.Equal(digest, descriptor.GetSha256()) {
+		return nil, false, ErrInvalidSegmentRecord
+	}
+	body, err := decompressStoredPayload(stored, rawBytes, maxStoredScriptBytes)
+	if err != nil {
+		return nil, false, err
+	}
+	computed := sha256.Sum256(body)
+	if !bytes.Equal(computed[:], descriptor.GetSha256()) {
+		return nil, false, ErrInvalidSegmentRecord
+	}
+	return body, true, nil
+}
+
+func decompressStoredPayload(stored []byte, rawBytes, maximum uint64) ([]byte, error) {
+	if rawBytes > maximum || rawBytes > uint64(math.MaxInt) {
+		return nil, ErrInvalidSegmentRecord
+	}
+	decoder, err := zstd.NewReader(nil, zstd.WithDecoderConcurrency(1), zstd.WithDecoderMaxMemory(maximum+1))
+	if err != nil {
+		return nil, ErrInvalidSegmentRecord
+	}
+	defer decoder.Close()
+	decoded, err := decoder.DecodeAll(stored, nil)
+	if err != nil || uint64(len(decoded)) != rawBytes || uint64(len(decoded)) > maximum {
+		return nil, ErrInvalidSegmentRecord
+	}
+	return bytes.Clone(decoded), nil
+}
+
 // RequeueDispatch reverses only a known pre-acceptance write failure. A later
 // session generation, acceptance, or reconciliation decision cannot be rolled
 // back by a stale writer.