import { StateHolder } from './state-holder';
import { StateKey } from "./state-key";
/**
 * The StateMachine and the Command are the two classes for interacting with the Simple State Machine.
 *
 * This is an abstract base class representing a command in the system which can modify state as part of execution.
 * The Command pattern allows you to encapsulate the business logic which modifies the state and
 * separate this logic out from the rest of the code.
 *
 * @template P The type for executionContext, the execution parameter passed to the command.
 */
export declare abstract class Command<P> {
    private stateHolder;
    private executionContext;
    /**
     * Initializes the command with the provided execution context.
     *
     * @param executionContext The parameter required for executing the command.
     */
    constructor(executionContext: P);
    /**
     * Retrieve the current execution context.
     *
     * @returns The execution context.
     */
    getExecutionContext(): P;
    /**
     * Sets the StateHolder instance that allows the command to interact with global state.
     * This is called by the StateMachine when the command is dispatched, before the execute method is called.
     *
     * @param stateHolder The StateHolder instance injected by the StateMachine.
     */
    setStateHolder(stateHolder: StateHolder): void;
    /**
     * This method allows a command to modify the state.  It stores a value in the global state and makes it "Observable".
     * Other parts of the application can observe the value stored against the key and reqct to changes to its value.
     * ######
     *
     * @example
     * // puts a key named "counter" in the global state with the value set to 0.
     * this.putState(new StateKey<number>('counter'), 0);
     *
     * // how a UI component will observe and react to the change in value
     * StateMachine.getInstance().onChange(key, newValue => doSomethingWithNewValue(newValue));
     *
     *
     * @template T The type of the value to store.
     * @param key The StateKey associated with the value.
     * @param value The value to store in the state.
     *
     */
    protected putState<T>(key: StateKey<T>, value: T): void;
    /**
     * This method allows commands to access the most recent value in the state instead of observing changes to it.
     *
     * #### Note:
     * The command should avoid calling {@link StateMachine.observe} or {@link StateMachine.subscribe}
     * to avoid accidentally creating large number run away subscriptions.
     * ######
     *
     * @example
     * // get the latest value for "counter" from the global state.
     * let counter:number = this.getLatest(new StateKey<number>('counter'));
     *
     * @template T The type of the value in the state.
     * @param key The StateKey associated with the state.
     * @returns The latest value from the state or undefined if the value does not exist.
     *
     */
    getLatest<T>(key: StateKey<T>): T | undefined;
    /**
     * Abstract method that must be implemented by subclasses. This allows encapsulation application logic and
     * modification of the application state as part of the logic.
     *
     * #### Note:
     * The command object has getLatest and putState methods which allows it to get and change the state as part of the logic.
     *
     * @example
     * execute(params) {
     *  let key = new StateKey<number>('counter');
     *  // get the latest value of "counter" from the global state
     *  let counter = this.getLatest(key);
     *  // change the value of key named "counter" in the global state, set to 0.
     *  this.putState(key, 0);
     * }
     *
     * @param executionContext The parameter required for executing the {@link Command}, the execution context.
     * The other way to get this in a subclass of the command class is by calling {@link getExecutionContext()}
     * This parameter provides convenient access to the execution context.
     *
     */
    abstract execute(executionContext: P): void;
}