/**
 * attachments.ts — W4: File attachment helpers for @oxpulse/chat-sdk.
 *
 * E2EE-friendly: client encrypts the blob with the room SFrame key before
 * uploading; server stores ciphertext and never decrypts.
 *
 * Flow:
 *   1. presignAttachment — POST /api/sdk/attachments/presign
 *   2. PUT uploadUrl — upload the (encrypted) blob.
 *   3. client.send — send a sealed message referencing the attachment.
 *
 * sendFile() is a convenience wrapper that runs all three steps.
 */
/** Maximum attachment blob size enforced client-side before calling presign. */
export declare const MAX_ATTACHMENT_BYTES: number;
export interface PresignArgs {
    /** MIME type of the blob (e.g. "image/png"). */
    mimeType: string;
    /** Byte size of the (encrypted) blob. */
    byteSize: number;
    /** SHA-256 hex digest of the plaintext (for deduplication). */
    sha256: string;
    /** Optional ThumbHash preview, base64-encoded. */
    thumbhashB64?: string;
}
export interface PresignResult {
    /** Server-assigned attachment UUID. */
    attachmentId: string;
    /** PUT-able URL (relative, 5-min TTL). */
    uploadUrl: string;
}
export interface SendFileArgs {
    /** Caller-assigned stable user identifier (passed through to send). */
    senderUid: string;
    /** E2EE-sealed ciphertext to include in the message payload. */
    sealed: ArrayBuffer;
    /** MIME type for the presign request. Falls back to blob.type. */
    mimeType?: string;
    /** SHA-256 hex of the plaintext. Required for deduplication metadata. */
    sha256: string;
    /** Optional ThumbHash preview, base64-encoded. */
    thumbhashB64?: string;
}
/** Duck-typed interface satisfied by SDKChatClient. */
interface AttachmentClient {
    readonly baseUrl: string;
    readonly jwt: string;
    send(roomId: string, args: {
        senderUid: string;
        sealed: ArrayBuffer;
        msgId?: string;
    }): Promise<{
        seq: number;
        msgId: string;
    }>;
}
/**
 * POST /api/sdk/attachments/presign
 *
 * Returns a signed PUT URL and attachment_id.
 * Throws SDKChatError on network or server error.
 */
export declare function presignAttachment(client: AttachmentClient, args: PresignArgs): Promise<PresignResult>;
/**
 * sendFile — presign → PUT → send sealed reference.
 *
 * Validates blob size client-side before touching the network.
 *
 * @param client   Object satisfying AttachmentClient interface.
 * @param roomId   Room to post the attachment message to.
 * @param blob     The (encrypted) blob to upload.
 * @param args     senderUid + sealed ciphertext + sha256.
 */
export declare function sendFile(client: AttachmentClient, roomId: string, blob: Blob, args: SendFileArgs): Promise<{
    seq: number;
    msgId: string;
}>;
export {};
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