;;; Multi-language support

;; Copyright (C) 2001,2005,2008-2011,2013,2020 Free Software Foundation, Inc.

;; This library is free software; you can redistribute it and/or
;; modify it under the terms of the GNU Lesser General Public
;; License as published by the Free Software Foundation; either
;; version 3 of the License, or (at your option) any later version.
;; 
;; This library is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
;; Lesser General Public License for more details.
;; 
;; You should have received a copy of the GNU Lesser General Public
;; License along with this library; if not, write to the Free Software
;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
;; 02110-1301 USA

;;; Code:

(define-module (system base language)
  #:use-module (system base syntax)
  #:export (define-language language? lookup-language make-language
            language-name language-title language-reader
            language-printer language-parser 
            language-compilers language-decompilers language-evaluator
            language-joiner language-for-humans?
            language-make-default-environment
            language-lowerer language-analyzer
            language-compiler-chooser

            lookup-compilation-order lookup-decompilation-order
            default-environment)

  #:re-export (current-language))


;;;
;;; Language class
;;;

(define-record/keywords <language>
  name
  title
  reader
  printer
  (parser #f)
  (compilers '())
  (decompilers '())
  (evaluator #f)
  (joiner #f)
  (for-humans? #t)
  (make-default-environment make-fresh-user-module)
  (lowerer #f)
  (analyzer #f)
  (compiler-chooser #f))

(define-syntax-rule (define-language name . spec)
  (define name (make-language #:name 'name . spec)))

(define (lookup-language name)
  (let ((m (resolve-module `(language ,name spec))))
    (if (module-bound? m name)
	(module-ref m name)
	(error "no such language" name))))

(begin-deprecated
 (define-public (invalidate-compilation-cache!)
   (issue-deprecation-warning
    "invalidate-compilation-cache is deprecated; recompile your modules")
   (values)))

(define (compute-translation-order from to language-translators)
  (cond
   ((not (language? to))
    (compute-translation-order from (lookup-language to) language-translators))
   (else
    (let lp ((from from) (seen '()))
      (cond
       ((not (language? from))
        (lp (lookup-language from) seen))
       ((eq? from to) (reverse! seen))
       ((memq from seen) #f)
       (else (or-map (lambda (pair)
                       (lp (car pair) (acons from (cdr pair) seen)))
                     (language-translators from))))))))

(define (lookup-compilation-order from to)
  (compute-translation-order from to language-compilers))

(define (lookup-decompilation-order from to)
  (and=> (compute-translation-order to from language-decompilers)
         reverse!))

(define (default-environment lang)
  "Return the default compilation environment for source language LANG."
  ((language-make-default-environment
    (if (language? lang) lang (lookup-language lang)))))



;;;
;;; Current language
;;;

;; Deprecated; use current-language instead.
(begin-deprecated
 (define-public *current-language* (parameter-fluid current-language)))