//  2018-2019 Darcy Rayner
//  2019 Labidi Aymen (labidi@aymen.co)

import {
  Provider,
  isClassProvider,
  ClassProvider,
  ValueProvider,
  FactoryProvider,
  isValueProvider,
  Token,
  InjectionToken,
} from './provider';
import {Type} from './type';
import {isInjectable} from './injectable';
import 'reflect-metadata';
import {getInjectionToken} from './inject';

type InjectableParam = Type<any>;

const REFLECT_PARAMS = 'design:paramtypes';

export class Container {
  private providers = new Map<Token<any>, Provider<any>>();

  addProvider<T>(provider: Provider<T>) {
    this.assertInjectableIfClassProvider(provider);
    this.providers.set(provider.provide, provider);
  }

  inject<T>(type: Token<T>): T {
    let provider = this.providers.get(type);
    if (provider === undefined && !(type instanceof InjectionToken)) {
      provider = {provide: type, useClass: type};
      this.assertInjectableIfClassProvider(provider);
    }
    return this.injectWithProvider(type, provider);
  }
  get(type: any): any {
    return this.providers.get(type).provide;
  }

  private injectWithProvider<T>(type: Token<T>, provider?: Provider<T>): T {
    if (provider === undefined) {
      throw new Error(`No provider for type ${this.getTokenName(type)}`);
    }
    if (isClassProvider(provider)) {
      return this.injectClass(provider);
    } else if (isValueProvider(provider)) {
      return this.injectValue(provider);
    } else {
      // Factory provider by process of elimination
      return this.injectFactory(provider);
    }
  }

  private assertInjectableIfClassProvider<T>(provider: Provider<T>) {
    if (isClassProvider(provider) && !isInjectable(provider.useClass)) {
      throw new Error(
        `Cannot provide ${this.getTokenName(provider.provide)} using class ${this.getTokenName(
          provider.useClass
        )}, ${this.getTokenName(provider.useClass)} isn't injectable`
      );
    }
  }

  private injectClass<T>(classProvider: ClassProvider<T>): T {
    const target = classProvider.useClass;
    const params = this.getInjectedParams(target);
    return Reflect.construct(target, params);
  }

  private injectValue<T>(valueProvider: ValueProvider<T>): T {
    return valueProvider.useValue;
  }

  private injectFactory<T>(valueProvider: FactoryProvider<T>): T {
    return valueProvider.useFactory();
  }

  private getInjectedParams<T>(target: Type<T>) {
    const argTypes = Reflect.getMetadata(REFLECT_PARAMS, target) as (InjectableParam | undefined)[];
    if (argTypes === undefined) {
      return [];
    }
    return argTypes.map((argType, index) => {
      // The reflect-metadata API fails on circular dependencies, and will return undefined
      // for the argument instead.
      if (argType === undefined) {
        throw new Error(
          `Injection error. Recursive dependency detected in constructor for type ${target.name} with parameter at index ${index}`
        );
      }
      const overrideToken = getInjectionToken(target, index);
      const actualToken = overrideToken === undefined ? argType : overrideToken;
      let provider = this.providers.get(actualToken);
      return this.injectWithProvider(actualToken, provider);
    });
  }

  private getTokenName<T>(token: Token<T>) {
    return token instanceof InjectionToken ? token.injectionIdentifier : token.name;
  }
}