import type { IncomingMessage as HttpRequest, ServerResponse } from "node:http";
/**
 * The concurrency precondition every Todo edit carries: the version the caller
 * believes it is editing, supplied either as `expectedVersion` in the body or
 * as an `If-Match` ETag. An edit with neither is refused before it is read —
 * blind writes are how two agents overwrite each other silently.
 *
 * Also the two request-framing checks the edit route makes before parsing:
 * a well-formed `Content-Length` and an uncompressed body.
 */
export type TodoEditPrecondition = {
    ok: true;
    expectedVersion: number;
} | {
    ok: false;
    status: 400 | 428;
    body: {
        error: string;
        code: 'todo_precondition_required' | 'todo_invalid_version';
    };
};
export declare function readTodoEditPrecondition(req: HttpRequest, body: Record<string, unknown>): TodoEditPrecondition;
type TodoEditValidationCode = 'todo_invalid_patch' | 'todo_invalid_assignee';
export declare function todoEditValidationError(res: ServerResponse, error: string, code?: TodoEditValidationCode): void;
/** `undefined` when the header is absent, `null` when it is unusable. */
export declare function todoEditContentLength(value: string | string[] | undefined): number | undefined | null;
export declare function hasSupportedTodoEditContentEncoding(value: string | string[] | undefined): boolean;
export {};
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