(define-record-type module-store
  (make-module-store* root)
  module-store?
  (root module-store-root))

(define-record-type namespace
  (make-namespace* root)
  namespace?
  (root namespace-root))

(define-record-type module-definition
  (make-module-definition direct-requires direct-requires-for-syntax bindings syntax-bindings)
  module-definition?
  (direct-requires module-definition-direct-requires)
  (direct-requires-for-syntax module-definition-direct-requires-for-syntax)
  (bindings module-definition-bindings)
  (syntax-bindings module-definition-syntax-bindings))

(define kernel-url "http://srfi.schemers.org/srfi-N/kernel-language.scm")
;; ^^ is this a good idea?

(define (make-module-store)
  (make-module-store* (make-hash-table 'equal)))

(define (make-kernel-module-store)
  ;; %%% this needs lots more thought
  (let ((store (make-module-store)))
    (hash-table-put! (module-store-root store)
		     'srfi-N-kernel
		     (make-module-definition '()
					     '()
					     '() ;; should include stx-manipulation procs?
					     (initial-eenv))) ;; ??
    store))

(define (make-namespace)
  (make-namespace* (make-hash-table)))

(define (compile-named-module-form! module-store module-name module-form)
  ...)

(define lookup-or-compile-module-definition!
  (let ()
    (define (compile-module-by-url! module-store module-url)
      ;; Future: support proper URLs here, deal with relative URLs, all that muck
      (let ((module-form (with-input-from-file module-url
			   (lambda ()
			     (let ((form (read)))
			       (cond
				((eof-object? form) (error "Could not read module" module-url))
				((not (eof-object? (read)))
				 (error "Expected a single form in module source file" module-url))
				(else form)))))))
	(if (not (and (pair? module-form) (eq? 'module (car module-form))
		      (pair? (cdr module-form)) (symbol? (cadr module-form))
		      (pair? (cddr module-form)) (or (symbol? (caddr module-form))
						     (string? (caddr module-form))
						     (list? (caddr module-form)))))
	    (error "Illegal module definition syntax in module source file" module-url)
	    (compile-named-module-form! module-store module-url module-form))))

    (lambda (module-store module-url)
      (let ((definition (hash-table-get (module-store-root module-store)
					module-url
					(lambda ()
					  (compile-module-by-url! module-store module-url)))))
	(if (module-definition? definition)
	    definition
	    (error "Could not find module" module-url definition))))))

(define invoke-module!
  (let ()
    (define (visit-module! module-url phase module-store namespace)
      (let ((module-definition (lookup-or-compile-module-definition! module-store module-url)))
	(for-each (lambda (required-url)
		    (visit-module! required-url phase module-store namespace))
		  (module-definition-direct-requires module-definition))
	(for-each (lambda (required-url)
		    (visit-module! required-url (+ phase 1) module-store namespace)
		    (invoke-module! required-url (+ phase 1) module-store namespace))
		  (module-definition-direct-requires-for-syntax module-definition))
	(for-each (lambda (binding-name parsed-exp)
		    (install-module-binding! namespace module-url binding-name phase
					     (parsed-exp-eval parsed-exp phase namespace)))
		  (module-definition-syntax-bindings module-definition))))

    (define (invoke-module! module-url phase module-store namespace)
      (let ((module-definition (lookup-or-compile-module-definition! module-store module-url)))
	(for-each (lambda (required-url)
		    (invoke-module! required-url phase module-store namespace))
		  (module-definition-direct-requires module-definition))
	(for-each (lambda (binding-name parsed-exp)
		    (install-module-binding! namespace module-url binding-name phase
					     (parsed-exp-eval parsed-exp namespace)))
		  (module-definition-bindings module-definition))))

    (lambda (module-store module-url namespace)
      (invoke-module! module-url 0 module-store namespace)
      namespace)))