;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2018, 2019 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 guile-build-system)
  #:use-module ((guix build gnu-build-system) #:prefix gnu:)
  #:use-module (guix build utils)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-26)
  #:use-module (ice-9 match)
  #:use-module (ice-9 popen)
  #:use-module (ice-9 rdelim)
  #:use-module (ice-9 regex)
  #:use-module (ice-9 format)
  #:use-module (guix build utils)
  #:export (target-guile-effective-version
            target-guile-scm+go
            %standard-phases
            guile-build))

(define* (target-guile-effective-version #:optional guile)
  "Return the effective version of GUILE or whichever 'guile' is in $PATH.
Return #false if it cannot be determined."
  (let* ((pipe (open-pipe* OPEN_READ
                           (if guile
                               (string-append guile "/bin/guile")
                               "guile")
                           "-c" "(display (effective-version))"))
         (line (read-line pipe)))
    (and (zero? (close-pipe pipe))
         (string? line)
         line)))

(define* (target-guile-scm+go output #:optional guile)
  "Return paths under `output' for scm and go files for effective version of
GUILE or whichever `guile' is in $PATH.  Raises an error if they cannot be
determined."
  (let* ((version (or (target-guile-effective-version guile)
                      (error "Cannot determine the effective target guile version.")))
         (scm (string-append output "/share/guile/site/" version))
         (go (string-append output "/lib/guile/" version "/site-ccache")))
    (values scm go)))

(define (file-sans-extension file)      ;TODO: factorize
  "Return the substring of FILE without its extension, if any."
  (let ((dot (string-rindex file #\.)))
    (if dot
        (substring file 0 dot)
        file)))

(define %scheme-file-regexp
  ;; Regexp to match Scheme files.
  "\\.(scm|sls)$")

(define %documentation-file-regexp
  ;; Regexp to match README files and the likes.
  "^(README.*|.*\\.html|.*\\.org|.*\\.md)$")

(define* (set-locale-path #:key inputs native-inputs
                          #:allow-other-keys)
  "Set 'GUIX_LOCPATH'."
  (match (assoc-ref (or native-inputs inputs) "locales")
    (#f #t)
    (locales
     (setenv "GUIX_LOCPATH" (string-append locales "/lib/locale"))
     #t)))

(define* (invoke-each commands
                      #:key (max-processes (current-processor-count))
                      report-progress)
  "Run each command in COMMANDS in a separate process, using up to
MAX-PROCESSES processes in parallel.  Call REPORT-PROGRESS at each step.
Raise an error if one of the processes exit with non-zero."
  (define total
    (length commands))

  (define processes
    (make-hash-table))

  (define (wait-for-one-process)
    (match (waitpid WAIT_ANY)
      ((pid . status)
       (let ((command (hashv-ref processes pid)))
         (hashv-remove! processes command)
         (unless (zero? (status:exit-val status))
           (format (current-error-port)
                   "process '~{~a ~}' failed with status ~a~%"
                   command status)
           (exit 1))))))

  (define (fork-and-run-command command)
    (match (primitive-fork)
      (0
       (dynamic-wind
         (const #t)
         (lambda ()
           (apply execlp command))
         (lambda ()
           (primitive-exit 127))))
      (pid
       (hashv-set! processes pid command)
       #t)))

  (let loop ((commands  commands)
             (running   0)
             (completed 0))
    (match commands
      (()
       (or (zero? running)
           (let ((running   (- running 1))
                 (completed (+ completed 1)))
             (wait-for-one-process)
             (report-progress total completed)
             (loop commands running completed))))
      ((command . rest)
       (if (< running max-processes)
           (let ((running (+ 1 running)))
             (fork-and-run-command command)
             (loop rest running completed))
           (let ((running   (- running 1))
                 (completed (+ completed 1)))
             (wait-for-one-process)
             (report-progress total completed)
             (loop commands running completed)))))))

(define* (report-build-progress total completed
                                #:optional (log-port (current-error-port)))
  "Report that COMPLETED out of TOTAL files have been completed."
  (format log-port "[~2d/~2d] Compiling...~%"
          completed total)
  (force-output log-port))

(define* (build #:key outputs inputs native-inputs
                (source-directory ".")
                (compile-flags '())
                (scheme-file-regexp %scheme-file-regexp)
                (not-compiled-file-regexp #f)
                target
                #:allow-other-keys)
  "Build files in SOURCE-DIRECTORY that match SCHEME-FILE-REGEXP.  Files
matching NOT-COMPILED-FILE-REGEXP, if true, are not compiled but are
installed; this is useful for files that are meant to be included."
  (let* ((out        (assoc-ref outputs "out"))
         (guile      (assoc-ref (or native-inputs inputs) "guile"))
         (effective  (target-guile-effective-version guile))
         (module-dir (string-append out "/share/guile/site/"
                                    effective))
         (go-dir     (string-append out "/lib/guile/"
                                    effective "/site-ccache/"))
         (guild      (string-append guile "/bin/guild"))
         (flags      (if target
                         (cons (string-append "--target=" target)
                               compile-flags)
                         compile-flags)))
    (if target
        (format #t "Cross-compiling for '~a' with Guile ~a...~%"
                target effective)
        (format #t "Compiling with Guile ~a...~%" effective))
    (format #t "compile flags: ~s~%" flags)

    ;; Make installation directories.
    (mkdir-p module-dir)
    (mkdir-p go-dir)

    ;; Compile .scm files and install.
    (setenv "GUILE_AUTO_COMPILE" "0")
    (setenv "GUILE_LOAD_COMPILED_PATH"
            (string-append go-dir
                           (match (getenv "GUILE_LOAD_COMPILED_PATH")
                             (#f "")
                             (path (string-append ":" path)))))

  (let ((source-files
           (with-directory-excursion source-directory
             (find-files "." scheme-file-regexp))))
    (invoke-each
     (filter-map (lambda (file)
                   (and (or (not not-compiled-file-regexp)
                            (not (string-match not-compiled-file-regexp
                                               file)))
                        (cons* guild
                               "guild" "compile"
                               "-L" source-directory
                               "-o" (string-append go-dir
                                                   (file-sans-extension file)
                                                   ".go")
                               (string-append source-directory "/" file)
                               flags)))
                 source-files)
     #:max-processes (parallel-job-count)
     #:report-progress report-build-progress)

    (for-each
     (lambda (file)
         (install-file (string-append source-directory "/" file)
                       (string-append module-dir
                                      "/" (dirname file))))
     source-files))
    #t))

(define* (install-documentation #:key outputs
                                (documentation-file-regexp
                                 %documentation-file-regexp)
                                #:allow-other-keys)
  "Install files that mactch DOCUMENTATION-FILE-REGEXP."
  (let* ((out (assoc-ref outputs "out"))
         (doc (string-append out "/share/doc/"
                             (strip-store-file-name out))))
    (for-each (cut install-file <> doc)
              (find-files "." documentation-file-regexp))
    #t))

(define %standard-phases
  (modify-phases gnu:%standard-phases
    (delete 'bootstrap)
    (delete 'configure)
    (add-before 'install-locale 'set-locale-path
      set-locale-path)
    (replace 'build build)
    (add-after 'build 'install-documentation
      install-documentation)
    (delete 'check)
    (delete 'strip)
    (delete 'validate-runpath)
    (delete 'install)))

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