;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2012, 2013, 2014, 2020 Ludovic Courtès <ludo@gnu.org>
;;;
;;; 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-system)
  #:use-module (guix records)
  #:use-module (srfi srfi-1)
  #:use-module (ice-9 match)
  #:export (@*

            build-system
            build-system?
            build-system-name
            build-system-description
            build-system-lower

            bag
            bag?
            bag-name
            bag-system
            bag-target
            bag-build-inputs
            bag-host-inputs
            bag-target-inputs
            bag-outputs
            bag-arguments
            bag-build

            make-bag

            build-system-with-c-toolchain))

(define-syntax-rule (@* module name)
  "Like (@ MODULE NAME), but resolves at run time."
  (module-ref (resolve-interface 'module) 'name))

(define-record-type* <build-system> build-system make-build-system
  build-system?
  (name        build-system-name)         ; symbol
  (description build-system-description)  ; short description
  (lower       build-system-lower))       ; args ... -> bags

;; "Bags" are low-level representations of "packages".  The system and target
;; of a bag is fixed when it's created.  This is because build systems may
;; choose inputs as a function of the system and target.
(define-record-type* <bag> bag %make-bag
  bag?
  (name          bag-name)               ;string

  (system        bag-system)             ;string
  (target        bag-target              ;string | #f
                 (default #f))

  ;; Here we use build/host/target in the sense of the GNU tool chain (info
  ;; "(autoconf) Specifying Target Triplets").
  (build-inputs  bag-build-inputs        ;list of packages
                 (default '()))
  (host-inputs   bag-host-inputs         ;list of packages
                 (default '()))

  ;; "Target inputs" are packages that are built natively, but that are used
  ;; by target programs in a cross-compilation environment.  Thus, they act
  ;; like 'inputs' as far as search paths are concerned.  The only example of
  ;; that is the cross-libc: it is an input of 'cross-gcc', thus built
  ;; natively; yet, we want it to be considered as a target input for the
  ;; purposes of $CPATH, $LIBRARY_PATH, etc.
  (target-inputs bag-target-inputs
                 (default '()))

  (outputs       bag-outputs             ;list of strings
                 (default '("out")))
  (arguments     bag-arguments           ;list
                 (default '()))
  (build         bag-build))             ;bag -> derivation

(define* (make-bag build-system name
                   #:key source (inputs '()) (native-inputs '())
                   (outputs '()) (arguments '())
                   system target)
  "Ask BUILD-SYSTEM to return a 'bag' for NAME, with the given SOURCE,
INPUTS, NATIVE-INPUTS, OUTPUTS, and additional ARGUMENTS.  If TARGET is not
#f, it must be a string with the GNU triplet of a cross-compilation target.

This is the mechanism by which a package is \"lowered\" to a bag, which is the
intermediate representation just above derivations."
  (match build-system
    (($ <build-system> _ description lower)
     (apply lower name
            #:system system
            #:source source
            #:inputs inputs
            #:native-inputs native-inputs
            #:outputs outputs
            #:target target
            arguments))))

(define (build-system-with-c-toolchain bs toolchain)
  "Return a variant of BS, a build system, that uses TOOLCHAIN instead of the
default GNU C/C++ toolchain.  TOOLCHAIN must be a list of
inputs (label/package tuples) providing equivalent functionality, such as the
'gcc-toolchain' package."
  (define lower
    (build-system-lower bs))

  (define toolchain-packages
    ;; These are the GNU toolchain packages pulled in by GNU-BUILD-SYSTEM and
    ;; all the build systems that inherit from it.  Keep the list in sync with
    ;; 'standard-packages' in (guix build-system gnu).
    '("gcc" "binutils" "libc" "libc:static" "ld-wrapper"))

  (define (lower* . args)
    (let ((lowered (apply lower args)))
      (bag
        (inherit lowered)
        (build-inputs
         (append (fold alist-delete
                       (bag-build-inputs lowered)
                       toolchain-packages)
                 toolchain)))))

  (build-system
    (inherit bs)
    (lower lower*)))
