import {
	Container,
	type AbstractType,
	type ProviderDefinition,
	type Token,
	type Type,
} from "./container.ts";
import {
	getInjectableOptions,
	getModuleOptions,
} from "../decorators/Module.ts";

export interface ModuleContext {
	type: Type;
	container: Container;
	exports: Token[];
	controllers: Type[];
	imports: ModuleContext[];
}

/** Per request container graph, one scoped container per module. */
export class ScopeGraph {
	private readonly containers = new Map<ModuleContext, Container>();

	constructor(private readonly registry: ModuleRegistry) {
		for (const context of registry.all()) {
			const scope = context.container.createScope();
			scopeGraphs.set(scope, this);
			this.containers.set(context, scope);
		}
	}

	/** Scoped container of a module. */
	containerFor(context: ModuleContext): Container {
		const container = this.containers.get(context);
		if (!container)
			throw new Error(`Module ${context.type.name} is not registered`);
		return container;
	}
}

const scopeGraphs = new WeakMap<Container, ScopeGraph>();

export class ModuleRegistry {
	private readonly contexts = new Map<Type, ModuleContext>();
	private readonly order: ModuleContext[] = [];

	/** Every registered module, in registration order. */
	all(): ModuleContext[] {
		return [...this.order];
	}

	/** Registers a module and all of its imports. */
	register(moduleType: Type): ModuleContext {
		const existing = this.contexts.get(moduleType);
		if (existing) return existing;

		const options = getModuleOptions(moduleType);
		const context: ModuleContext = {
			type: moduleType,
			container: new Container(),
			exports: [],
			controllers: [...(options.controllers ?? [])],
			imports: [],
		};
		this.contexts.set(moduleType, context);

		for (const imported of options.imports ?? []) {
			context.imports.push(this.register(imported));
		}

		for (const provider of options.providers ?? []) {
			if (typeof provider === "function") {
				const scope = getInjectableOptions(provider).scope;
				context.container.registerClass(provider as AbstractType, { scope });
			} else {
				context.container.registerProvider(provider as ProviderDefinition);
			}
		}

		for (const controller of context.controllers) {
			context.container.registerClass(controller);
		}

		context.exports = [...(options.exports ?? [])];
		context.container.fallbackResolver = (token, scope) =>
			this.resolveFromImports(context, token, scope);

		this.order.push(context);
		return context;
	}

	/** Resolves a token from the exported providers of the imported modules. */
	resolveFromImports(
		context: ModuleContext,
		token: Token,
		scope?: Container,
	): unknown {
		for (const imported of context.imports) {
			const resolved = this.resolveExported(imported, token, scope);
			if (resolved !== undefined) return resolved;
		}
		return undefined;
	}

	/** Resolves a token that an imported module re-exports. */
	resolveExported(
		context: ModuleContext,
		token: Token,
		scope?: Container,
	): unknown {
		if (context.exports.includes(token)) {
			return context.container.resolve(token, scope);
		}
		for (const exported of context.exports) {
			if (typeof exported !== "function") continue;
			const exportedContext = this.contexts.get(exported as Type);
			if (!exportedContext) continue;
			const resolved = this.resolveExported(exportedContext, token, scope);
			if (resolved !== undefined) return resolved;
		}
		return undefined;
	}

	/** Controllers of every module together with the module they belong to. */
	controllers(): { context: ModuleContext; controller: Type }[] {
		const result: { context: ModuleContext; controller: Type }[] = [];
		for (const context of this.order) {
			for (const controller of context.controllers) {
				result.push({ context, controller });
			}
		}
		return result;
	}

	/** Instantiates every controller, surfacing dependency errors at boot time. */
	bootstrap(): void {
		for (const { context, controller } of this.controllers()) {
			context.container.resolve(controller);
		}
	}

	/** Instantiates every controller asynchronously. */
	async bootstrapAsync(): Promise<void> {
		for (const { context, controller } of this.controllers()) {
			await context.container.resolveAsync(controller);
		}
	}

	/** Creates the per request container graph. */
	createScope(): ScopeGraph {
		return new ScopeGraph(this);
	}
}