;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2020 Edouard Klein <edk@beaver-labs.com>
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix is free software; you can redistribute it and/or modify it
;;; under the terms of the GNU General Public License as published by
;;; the Free Software Foundation; either version 3 of the License, or (at
;;; your option) any later version.
;;;
;;; GNU Guix 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 General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.

(define-module (guix build gerbil-build-system)
  #:use-module ((guix build gnu-build-system) #:prefix gnu:)
  #:use-module (guix build utils)
  #:use-module (ice-9 match)
  #:use-module (ice-9 ftw)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-26)
  #:export (%standard-phases
            gerbil-build))

;; Gerbil's build system and package management is documented at
;; https://cons.io/guide/package-manager.html
;; https://cons.io/guide/build.html
;; https://cons.io/guide/env-vars.html
;;
;; The compiler is writing its output in the directory
;; pointed to by GERBIL_PATH (or ~/.gerbil by default).
;;
;; Every package is supposed to have a build.ss script
;; whose default action (when called with no argument)
;; is to compile the package.
;;
;; The GERBIL_LOADPATH env variable tells gerbil's runtime
;; where it can find its loadable code.
;;
;; GERBIL_HOME tells gerbil where to find its runtime
;; and standard library
;;
;; This build system therefore just
;; - makes GERBIL_PATH point to the output directory in the store,
;; - makes GERBIL_LOADPATH point to the lib subdir
;; of all the gerbil inputs,
;; - calls ./build.ss,
;; - wrap any executable with GERBIL_LOADPATH set the the lib
;; subdir of all the gerbil inputs plus the lib subdir
;; of the current package's output, and with GERBIL_HOME
;; set to the lib directory of the 'gerbil' input

(define (loadpath inputs)
  (string-join (map (match-lambda
                      ((_ . path)
                       (string-append path "/lib")))
                    ;; Restrict to inputs beginning with "gerbil-".
                    (filter (match-lambda
                              ((name . _)
                               (string-prefix? "gerbil-" name)))
                            inputs))
               ":"))

(define (gerbil-home inputs)
  (assoc-ref inputs "gerbil"))

(define* (install #:key inputs outputs #:allow-other-keys)
  "Install a given Gerbil package."
  (let ((out (assoc-ref outputs "out"))
        (in (loadpath inputs)))
    (setenv "GERBIL_PATH" out)
    (setenv "GERBIL_LOADPATH" in)
    (invoke "./build.ss"))
  #t)

(define* (wrap #:key inputs outputs #:allow-other-keys)
  "Wrap any executable with a proper GERBIL_LOADPATH and GERBIL_HOME"
  (let* ((out (assoc-ref outputs "out"))
         (in (loadpath inputs))
         (gerbil-loadpath (string-append out "/lib:" in)))
    (for-each (cut wrap-program <>
                   `("GERBIL_LOADPATH" = (,gerbil-loadpath))
                   `("GERBIL_HOME" = (,(gerbil-home inputs))))
              (find-files (string-append out "/bin")))))

(define %standard-phases
  (modify-phases gnu:%standard-phases
    (delete 'bootstrap)
    (delete 'configure)                 ;not needed
    (delete 'build)                     ;build.ss does both build and install
    (delete 'check)                     ;no standard way of testing
    (replace 'install install)
    (add-after 'install 'wrap wrap)))

(define* (gerbil-build #:key inputs (phases %standard-phases)
                       #:allow-other-keys #:rest args)
  "Build the given Gerbil package, applying all of PHASES in order."
  (apply gnu:gnu-build #:inputs inputs #:phases phases args))