/** Why a command refused: `reason` is a stable machine code; `message`, when set, is shown to the player. */
export interface CommandRejection {
    reason: string;
    /** Player-facing text ("Needs 40 more gold"). The shell shows it in the notice feed with the deny cue. */
    message?: string;
}
export type CommandDecodeResult<TInput> = {
    ok: true;
    value: TInput;
} | {
    ok: false;
    reason: string;
};
/** Parses raw `unknown` transport input into `TInput`, rejecting anything that doesn't match the command's declared shape. Runs before `validate`/`apply`, so a malformed payload never reaches game logic. */
export type CommandDecoder<TInput> = (input: unknown) => CommandDecodeResult<TInput>;
export interface CommandDefinition<TState, TInput> {
    /** Runtime codec for this command's input. Declaring one turns the boundary strict: a payload that fails to decode is rejected before `validate`/`apply` ever see it. Omit to keep passing raw input through unchanged (existing behavior). */
    decode?: CommandDecoder<TInput>;
    validate?(state: TState, input: TInput): CommandRejection | null;
    apply(state: TState, input: TInput): TState | void;
}
export type CommandResult<TState> = {
    status: "applied";
    state: TState;
} | {
    status: "rejected";
    reason: string;
    message?: string;
} | {
    status: "unknown-command";
};
export interface CommandRegistry<TState> {
    define<TInput>(name: string, definition: CommandDefinition<TState, TInput>): void;
    has(name: string): boolean;
    names(): string[];
    run(state: TState, name: string, input: unknown): CommandResult<TState>;
}
export declare function createCommandRegistry<TState>(): CommandRegistry<TState>;