export const DEPENDENCY_KEYS_METADATA_KEY = 'extollo:di:dependencies:ctor';
export const DEPENDENCY_KEYS_PROPERTY_METADATA_KEY = 'extollo:di:dependencies:properties';
export const DEPENDENCY_KEYS_SERVICE_TYPE_KEY = 'extollo:di:service_type';

/**
 * Interface that designates a particular value as able to be constructed.
 */
export interface Instantiable<T> {
    new(...args: any[]): T
}

/**
 * Returns true if the given value is instantiable.
 * @param what
 */
export function isInstantiable<T>(what: any): what is Instantiable<T> {
    return (typeof what === 'object' || typeof what === 'function') && 'constructor' in what && typeof what.constructor === 'function'
}

/**
 * Type that identifies a value as a static class, even if it is not instantiable.
 */
export type StaticClass<T, T2> = Function & {prototype: T} & T2

/**
 * Returns true if the parameter is a static class.
 * @param something
 */
export function isStaticClass<T, T2>(something: any): something is StaticClass<T, T2> {
    return typeof something === 'function' && typeof something.prototype !== 'undefined'
}

/**
 * Type used to represent a value that can identify a factory in the container.
 */
export type DependencyKey = Instantiable<any> | StaticClass<any, any> | string

/**
 * Interface used to store dependency requirements by their place in the injectable
 * target's parameters.
 */
export interface DependencyRequirement {
    paramIndex: number,
    key: DependencyKey,
    overridden: boolean,
}

/**
 * Interface used to store dependency requirements by the class property they should
 * be injected into.
 */
export interface PropertyDependency {
    key: DependencyKey,
    property: string | symbol,
}

/**
 * Interface used to keep track of singleton factory values, by their dependency key.
 */
export interface InstanceRef {
    key: DependencyKey,
    value: any,
}

/**
 * Interface used to keep track of the injection type of a class.
 */
export interface InjectionType {
    type: 'named' | 'singleton',
    name?: string,
}