core/src/container/Container.ts

import "reflect-metadata";
import { CircularDependencyError, ProviderNotFoundError } from "../errors";
import { ContextualModuleRef, ModuleRef } from "../module/ModuleRef";
import type { Constructor } from "../types";
import {
	type BaseProvider,
	INJECT_METADATA_KEY,
	INJECTABLE_METADATA_KEY,
	MODULE_METADATA_KEY,
	type ModuleOptions,
	type Provider,
	type ProviderToken,
	type ResolvedProvider,
} from "./types";

interface ParamType {
	name?: string;
}

type LifecycleHook = "onModuleInit" | "onModuleDestroy";
type LifecycleHookFn = () => Promise<void> | void;
type LifecycleAware = Partial<Record<LifecycleHook, LifecycleHookFn>>;

export class Container {
	private readonly providers = new Map<
		string,
		Map<ProviderToken, ResolvedProvider>
	>();
	private readonly instances = new Map<string, Map<ProviderToken, unknown>>();
	private readonly moduleOptions = new Map<string, ModuleOptions>();
	private readonly resolving = new Set<ProviderToken>();
	private readonly proxies = new Map<string, Map<ProviderToken, unknown>>();
	private readonly pendingResolutions = new Map<
		string,
		Map<ProviderToken, Promise<unknown>>
	>();
	private rootModuleName?: string;

	constructor(private readonly globalContext = "global") {
		this.ensureScope(this.globalContext);
	}

	public registerRootModule(moduleClass: Constructor): void {
		this.rootModuleName = moduleClass.name;
		this.registerModule(moduleClass);
	}

	public getRootModuleName(): string | undefined {
		return this.rootModuleName;
	}

	public registerModule(moduleClass: Constructor): void {
		const options: ModuleOptions | undefined = Reflect.getMetadata(
			MODULE_METADATA_KEY,
			moduleClass,
		);
		if (!options) return;

		const moduleName = moduleClass.name;
		if (this.moduleOptions.has(moduleName)) return;

		this.moduleOptions.set(moduleName, options);
		this.ensureScope(moduleName);

		if (options.imports) {
			for (const imported of options.imports) {
				this.registerModule(
					this.unwrapToken(imported as ProviderToken<Constructor>),
				);
			}
		}

		if (options.providers) {
			for (const provider of options.providers) {
				const normalized = this.normalizeProvider(provider, moduleName);
				this.providers
					.get(moduleName)!
					.set(normalized.token, normalized);
			}
		}

		const moduleProvider = this.normalizeProvider(moduleClass, moduleName);
		this.providers.get(moduleName)!.set(moduleClass, moduleProvider);
	}

	public registerProvider(provider: Provider): void {
		const normalized = this.normalizeProvider(provider, this.globalContext);
		this.providers
			.get(this.globalContext)!
			.set(normalized.token, normalized);
	}

	public async get<T>(
		token: ProviderToken<T>,
		moduleName?: string,
	): Promise<T> {
		return this.resolve(token, moduleName);
	}

	public async resolveAll(): Promise<void> {
		for (const [scope] of this.providers) {
			for (const token of this.providers.get(scope)!.keys()) {
				await this.resolve(
					token,
					scope === this.globalContext ? undefined : scope,
				);
			}
		}
	}

	public async callLifecycleHook(
		hook: "onModuleInit" | "onModuleDestroy",
	): Promise<void> {
		for (const instances of this.instances.values()) {
			for (const instance of instances.values()) {
				if (!instance) continue;
				const lifecycleInstance = instance as LifecycleAware;
				const hookFn = lifecycleInstance[hook];
				if (typeof hookFn === "function") {
					await hookFn.call(lifecycleInstance);
				}
			}
		}
	}

	private async resolve<T>(
		token: ProviderToken<T>,
		moduleName?: string,
	): Promise<T> {
		const unwrappedToken = this.unwrapToken(token) as ProviderToken<T>;
		const context = moduleName ?? this.globalContext;

		if (unwrappedToken === ModuleRef) {
			return new ContextualModuleRef(this, context) as T;
		}

		let provider = this.findProvider(unwrappedToken, context);

		if (
			!provider &&
			context === this.globalContext &&
			this.rootModuleName
		) {
			provider = this.findProvider(unwrappedToken, this.rootModuleName);
		}

		if (!provider) {
			throw new ProviderNotFoundError(
				typeof unwrappedToken === "function"
					? unwrappedToken.name
					: String(unwrappedToken),
				context,
			);
		}

		if (provider.scope === "singleton") {
			const scopeName = provider.moduleName ?? context;
			const proxy = this.proxies.get(scopeName)?.get(unwrappedToken);
			if (proxy !== undefined) {
				return proxy as T;
			}

			const existing = this.instances.get(scopeName)?.get(unwrappedToken);
			if (existing !== undefined) {
				return existing as T;
			}

			const pending = this.pendingResolutions
				.get(scopeName)
				?.get(unwrappedToken);
			if (pending) {
				return pending as Promise<T>;
			}
		}

		if (this.resolving.has(unwrappedToken)) {
			if (
				typeof token === "object" &&
				token !== null &&
				"forwardRef" in token
			) {
				const scopeName = provider.moduleName ?? context;
				const proxy = this.createProxy(unwrappedToken, scopeName);
				this.ensureScope(scopeName);
				this.proxies.get(scopeName)!.set(unwrappedToken, proxy);
				return proxy as T;
			}
			const stack = [...this.resolving].map((item) =>
				typeof item === "function" ? item.name : String(item),
			);
			stack.push(
				typeof unwrappedToken === "function"
					? unwrappedToken.name
					: String(unwrappedToken),
			);
			throw new CircularDependencyError(stack);
		}

		const performResolution = async (): Promise<T> => {
			this.resolving.add(unwrappedToken);

			try {
				let instance: T;

				if (provider.useValue !== undefined) {
					instance = provider.useValue as T;
				} else if (provider.useFactory) {
					const dependencies = await Promise.all(
						(provider.inject ?? []).map((dep) =>
							this.resolve(dep, provider.moduleName ?? context),
						),
					);
					instance = (await provider.useFactory(
						...dependencies,
					)) as T;
				} else if (provider.useExisting) {
					instance = await this.resolve<T>(
						provider.useExisting as ProviderToken<T>,
						provider.moduleName ?? context,
					);
				} else if (provider.useClass) {
					const targetClass = provider.useClass;
					const paramTypes: ParamType[] =
						Reflect.getMetadata("design:paramtypes", targetClass) ||
						[];
					const injectTokens: ProviderToken[] =
						Reflect.getMetadata(INJECT_METADATA_KEY, targetClass) ||
						[];

					const dependencies = await Promise.all(
						paramTypes.map(async (paramType, index) => {
							const depToken =
								injectTokens[index] ||
								(paramType as ProviderToken);
							return this.resolve(
								depToken as ProviderToken<unknown>,
								provider.moduleName ?? context,
							);
						}),
					);

					instance = new targetClass(...dependencies) as T;
				} else {
					throw new Error(
						`Invalid provider configuration for token ${String(token)}`,
					);
				}

				if (provider.scope === "singleton") {
					const scopeName = provider.moduleName ?? context;
					this.ensureScope(scopeName);
					this.instances
						.get(scopeName)!
						.set(unwrappedToken, instance);
				}

				return instance;
			} finally {
				this.resolving.delete(unwrappedToken);
				if (provider.scope === "singleton") {
					const scopeName = provider.moduleName ?? context;
					this.pendingResolutions
						.get(scopeName)
						?.delete(unwrappedToken);
				}
			}
		};

		if (provider.scope === "singleton") {
			const scopeName = provider.moduleName ?? context;
			this.ensureScope(scopeName);
			const promise = performResolution();
			this.pendingResolutions
				.get(scopeName)!
				.set(unwrappedToken, promise);
			return promise;
		}

		return performResolution();
	}

	private findProvider(
		token: ProviderToken,
		context: string,
	): ResolvedProvider | undefined {
		const unwrappedToken = this.unwrapToken(token) as ProviderToken;
		const moduleProviders = this.providers.get(context);
		if (moduleProviders?.has(unwrappedToken)) {
			return moduleProviders.get(unwrappedToken);
		}

		const options = this.moduleOptions.get(context);
		if (options?.imports) {
			for (const imported of options.imports) {
				const unwrappedImport = this.unwrapToken(
					imported as ProviderToken<Constructor>,
				);
				const importedProviders = this.providers.get(
					unwrappedImport.name,
				);
				const importedOptions = this.moduleOptions.get(
					unwrappedImport.name,
				);
				if (
					importedProviders?.has(unwrappedToken) &&
					importedOptions?.exports?.some(
						(exportToken) =>
							this.unwrapToken(exportToken) === unwrappedToken,
					)
				) {
					return importedProviders.get(unwrappedToken);
				}
				if (unwrappedToken === unwrappedImport) {
					return importedProviders?.get(unwrappedToken);
				}
			}
		}

		if (context !== this.globalContext) {
			const globalProviders = this.providers.get(this.globalContext);
			if (globalProviders?.has(unwrappedToken)) {
				return globalProviders.get(unwrappedToken);
			}
		}

		if (context === this.globalContext && this.rootModuleName) {
			const rootProviders = this.providers.get(this.rootModuleName);
			if (rootProviders?.has(unwrappedToken)) {
				return rootProviders.get(unwrappedToken);
			}
		}

		return undefined;
	}

	private normalizeProvider(
		provider: Provider,
		moduleName?: string,
	): ResolvedProvider {
		if (typeof provider === "function") {
			const metadata = Reflect.getMetadata(
				INJECTABLE_METADATA_KEY,
				provider,
			);
			return {
				token: provider,
				scope: metadata?.scope ?? "singleton",
				useClass: provider,
				moduleName,
			};
		}

		const base = {
			token: this.unwrapToken(provider.provide) as ProviderToken,
			scope: provider.scope ?? "singleton",
			moduleName,
		};

		if ("useClass" in provider) {
			return { ...base, useClass: provider.useClass };
		}
		if ("useValue" in provider) {
			return { ...base, useValue: provider.useValue };
		}
		if ("useFactory" in provider) {
			return {
				...base,
				useFactory: provider.useFactory,
				inject: provider.inject,
			};
		}
		if ("useExisting" in provider) {
			return { ...base, useExisting: provider.useExisting };
		}

		const exhaustiveCheck: never = provider;
		throw new Error(
			`Invalid provider definition for token ${String((exhaustiveCheck as BaseProvider).provide)}`,
		);
	}

	private ensureScope(name: string): void {
		if (!this.providers.has(name)) {
			this.providers.set(name, new Map());
		}
		if (!this.instances.has(name)) {
			this.instances.set(name, new Map());
		}
		if (!this.proxies.has(name)) {
			this.proxies.set(name, new Map());
		}
		if (!this.pendingResolutions.has(name)) {
			this.pendingResolutions.set(name, new Map());
		}
	}

	private unwrapToken<T>(token: ProviderToken<T>): T {
		if (
			typeof token === "object" &&
			token !== null &&
			"forwardRef" in token
		) {
			return (token as { forwardRef: () => T }).forwardRef();
		}
		return token as T;
	}

	private createProxy<T>(token: ProviderToken<T>, context: string): T {
		const self = this;
		return new Proxy({} as object, {
			get(_target, prop, receiver) {
				if (prop === "then") return undefined;
				const instance = self.instances.get(context)?.get(token);
				if (!instance) {
					throw new Error(
						`Circular dependency instance for ${
							typeof token === "function"
								? token.name
								: String(token)
						} is not yet available. It might be accessed too early (e.g. in a constructor or during static initialization).`,
					);
				}
				const value = Reflect.get(instance as object, prop, receiver);
				return typeof value === "function"
					? value.bind(instance)
					: value;
			},
			has(_target, prop) {
				const instance = self.instances.get(context)?.get(token);
				return instance ? Reflect.has(instance as object, prop) : false;
			},
		}) as T;
	}
}