// TODO: add more comments.

/**
 * The dumbest possible implementation of AMD to handle only the code that
 * `tsc -m amd` produces.
 */
class Registry {
    private readonly modules = new Map<string, Module>();
    private readonly reified = new Map<string, {}>();

    define(name: string, deps: string[], factory: FactoryFunction) {
        this.modules.set(name, {deps, factory, exports: {}});
    }

    require(dep: string, srcMod?: Module): {} {
        if (dep === 'require') {
            return (child: string) => this.require(child, srcMod);
        }
        if (dep === 'exports') {
            if (!srcMod) throw new Error('Invalid package name.');
            return srcMod.exports;
        }
        const exp = this.reified.get(dep);
        if (exp) return exp;
        const mod = this.modules.get(dep);
        if (!mod) throw new Error('Undefined module.');
        this.reified.set(dep, mod.exports);
        const deps = mod.deps.map(child => this.require(child, mod));
        mod.factory(...deps);
        return mod.exports;
    }

    install() {
        self.define =
            (name: string, deps: string[], factory: FactoryFunction) =>
                this.define(name, deps, factory);
        self.require = (dep: string) => this.require(dep);
    }
}

(() => new Registry().install())();