import { getContext, hasContext, setContext } from "svelte";
export class Context {
    #name;
    #key;
    /**
     * @param name The name of the context.
     * This is used for generating the context key and error messages.
     */
    constructor(name) {
        this.#name = name;
        this.#key = Symbol(name);
    }
    /**
     * The key used to get and set the context.
     *
     * It is not recommended to use this value directly.
     * Instead, use the methods provided by this class.
     */
    get key() {
        return this.#key;
    }
    /**
     * Checks whether this has been set in the context of a parent component.
     *
     * Must be called during component initialisation.
     */
    exists() {
        return hasContext(this.#key);
    }
    /**
     * Retrieves the context that belongs to the closest parent component.
     *
     * Must be called during component initialisation.
     *
     * @throws An error if the context does not exist.
     */
    get() {
        const context = getContext(this.#key);
        if (context === undefined) {
            throw new Error(`Context "${this.#name}" not found`);
        }
        return context;
    }
    /**
     * Retrieves the context that belongs to the closest parent component,
     * or the given fallback value if the context does not exist.
     *
     * Must be called during component initialisation.
     */
    getOr(fallback) {
        const context = getContext(this.#key);
        if (context === undefined) {
            return fallback;
        }
        return context;
    }
    /**
     * Associates the given value with the current component and returns it.
     *
     * Must be called during component initialisation.
     */
    set(context) {
        return setContext(this.#key, context);
    }
}