import { FactoryProvider, InjectionToken } from '@angular/core';
import { UniversalService                } from '@bespunky/angular-zen/universal';

import { GoogleMapsApiService            } from '../../api/google-maps-api.service';
import { Native, NativeOf, Wrapper       } from '../types/abstraction';
import { FactoryGeneratorConfig          } from './common';
import { NativeInstance, WrapperInstance } from './tokens';

type WrapperFactory<TWrapper extends Wrapper> = (api: GoogleMapsApiService, native: NativeOf<TWrapper>, ...deps: any[]) => TWrapper;

/**
 * Creates the factory that will be used in the provider created by `createWrapperFactoryProvider`.
 * See `createWrapperFactoryProvider` for more details.
 *
 * @template TWrapper The type of wrapper generated by the factory.
 * @param {WrapperFactory<TWrapper>} produceWrapper The function that will create the wrapper object. Receives the `GoogleMapsApiService`, the native object and the dependencies specified in `deps` when configuring the generator.
 * @returns A factory that receives the `GoogleMapsApiService`, `UniversalService`, and the native object to wrap along with any additional dependencies, then returns a new wrapper object on browsers and `null` on non-browsers.
 */
function createWrapperFactory<TWrapper extends Wrapper>(produceWrapper: WrapperFactory<TWrapper>)
{
    // Called by Angular's Dependency Injector
    return (api: GoogleMapsApiService, universal: UniversalService, native: NativeOf<TWrapper>, ...deps: any[]) =>
    {
        // TODO: Test with Angular Universal app and see if this doesn't break the chain of contained directives
        if (!universal.isPlatformBrowser) return null;
            
        return produceWrapper(api, native, ...deps);
    };
}

/**
 * Defines the configuration for a function that generates a `FactoryProvider` for wrapper objects.
 *
 * @export
 * @interface WrapperFactoryGeneratorConfig
 * @extends {FactoryGeneratorConfig<Wrapper>}
 */
export interface WrapperFactoryGeneratorConfig extends FactoryGeneratorConfig<Wrapper>
{
    /**
     * (Optional) The token to use when injecting the native object into the factory. Default is `NativeInstance`.
     *
     * @type {InjectionToken<Native>}
     */
    nativeToken?: InjectionToken<Native>;
}

/**
 * Applies default values for undefined values in the config object.
 *
 * @export
 * @param {WrapperFactoryGeneratorConfig} config The optional config.
 * @returns {Required<WrapperFactoryGeneratorConfig>} The filled config.
 */
export function configWrapperFactoryProviderGeneratorDefaults(config: WrapperFactoryGeneratorConfig): Required<WrapperFactoryGeneratorConfig>
{
    return {
        token      : config.token       || WrapperInstance,
        nativeToken: config.nativeToken || NativeInstance,
        deps       : config.deps        || []
    };
}

/**
 * Creates a factory provider for the a natve object injection token.
 * The factory runs the specified function and passes the `GoogleMapsApiService`, the native object to be wrapped and the specified dependencies to it.
 *
 * By default, the generator will create the factory provider for the `WrapperInstance` token, and inject `NativeInstance` as a dependency.
 * To change this behavior, specify the appropriate tokens in the config argument.
 * 
 * Note: The factory will detect non-browser platforms and return `null` instead of calling the function.
 * 
 * @export
 * @template TWrapper The type of wrapper generated by the factory.
 * @param {WrapperFactory<TWrapper>} produceWrapper The function that will create the wrapper object. Receives the `GoogleMapsApiService`, the native object and the dependencies specified in `deps`.
 * @param {WrapperFactoryGeneratorConfig} [config={}] (Optional) A configuration object for the generator.
 * @returns {FactoryProvider} A `FactoryProvider` object for the specified token.
 */
export function createWrapperFactoryProvider<TWrapper extends Wrapper>(produceWrapper: WrapperFactory<TWrapper>, config: WrapperFactoryGeneratorConfig = {}): FactoryProvider
{
    const { token, nativeToken, deps } = configWrapperFactoryProviderGeneratorDefaults(config);
    
    return {
        provide   : token,
        useFactory: createWrapperFactory(produceWrapper),
        deps      : [GoogleMapsApiService, UniversalService, nativeToken, ...deps]
    };
}