feat: persist and dispatch client command input

internal/server/store/stdin.go

@@ -1,6 +1,7 @@
 package store
 
 import (
+	"bytes"
 	"context"
 	"crypto/sha256"
 	"database/sql"
@@ -9,6 +10,7 @@ import (
 	"math"
 	"time"
 
+	"github.com/klauspost/compress/zstd"
 	"github.com/rvbox/rvbox/internal/domain"
 )
 
@@ -33,6 +35,84 @@ type StdinWriteResult struct {
 	Duplicate bool
 }
 
+// StdinIntent is a server-owned input record ready for delivery to a live
+// client session. It is returned in command/write order and contains a copy of
+// the decompressed payload; callers must not mutate storage-owned buffers.
+type StdinIntent struct {
+	IssueUUID     domain.UUID
+	WriteSeq      uint64
+	Data          []byte
+	AppendNewline bool
+	Close         bool
+}
+
+// PendingStdin returns unacknowledged input intents for one client. Delivery is
+// intentionally tracked by the session dispatcher, not by this durable query:
+// a lost connection simply causes the next session to replay the same write
+// sequence, which the client acknowledges idempotently.
+func (store *Store) PendingStdin(ctx context.Context, clientID string) ([]StdinIntent, 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 w.issue_uuid, w.write_seq, w.payload, w.raw_bytes, w.stored_bytes, w.compression, w.sha256, w.append_newline, w.close_intent
+FROM stdin_writes w JOIN commands c ON c.issue_uuid = w.issue_uuid
+WHERE c.client_id = ? AND c.lifecycle BETWEEN 1 AND 4 AND w.acknowledged = 0
+ORDER BY c.issue_time, c.issue_uuid, w.write_seq`, clientID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var result []StdinIntent
+	for rows.Next() {
+		var encodedIssue, stored, digest []byte
+		var writeSeq, rawBytes, storedBytes uint64
+		var compression uint32
+		var appendNewline, closeIntent bool
+		if err := rows.Scan(&encodedIssue, &writeSeq, &stored, &rawBytes, &storedBytes, &compression, &digest, &appendNewline, &closeIntent); err != nil {
+			return nil, err
+		}
+		if len(encodedIssue) != len(domain.UUID{}) || writeSeq == 0 || compression != 2 || storedBytes != uint64(len(stored)) || len(digest) != sha256.Size || rawBytes > maxStoredExecutionSpecBytes {
+			return nil, ErrInvalidSegmentRecord
+		}
+		var data []byte
+		data, err = decompressStdinPayload(stored, rawBytes)
+		if err != nil || (!closeIntent && rawBytes == 0) || (closeIntent && rawBytes != 0) {
+			return nil, ErrInvalidSegmentRecord
+		}
+		computed := sha256.Sum256(data)
+		if string(computed[:]) != string(digest) {
+			return nil, ErrInvalidSegmentRecord
+		}
+		var issue domain.UUID
+		copy(issue[:], encodedIssue)
+		result = append(result, StdinIntent{IssueUUID: issue, WriteSeq: writeSeq, Data: data, AppendNewline: appendNewline, Close: closeIntent})
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return result, nil
+}
+
+func decompressStdinPayload(stored []byte, expected uint64) ([]byte, error) {
+	if expected > maxStoredExecutionSpecBytes {
+		return nil, ErrInvalidSegmentRecord
+	}
+	decoder, err := zstd.NewReader(bytes.NewReader(stored), zstd.WithDecoderConcurrency(1), zstd.WithDecoderMaxMemory(maxStoredExecutionSpecBytes+1))
+	if err != nil {
+		return nil, ErrInvalidSegmentRecord
+	}
+	defer decoder.Close()
+	data, err := decoder.DecodeAll(stored, nil)
+	if err != nil || uint64(len(data)) != expected {
+		return nil, ErrInvalidSegmentRecord
+	}
+	return data, nil
+}
+
 // AppendStdin durably records one ordered stdin intent. It does not claim
 // delivery to a process; an agent acknowledgement is a later protocol event.
 // Reusing RequestUUID with the same immutable hash returns the original write