;;; GNU Guix --- Check load average on a remote computer via SSH.
;;; Copyright © Oleg Pykhalov <go.wigust@gmail.com>

(use-modules ((guix licenses) #:prefix license:)
             (gnu packages autotools)
             (gnu packages bash)
             (gnu packages gnupg)
             (gnu packages guile)
             (gnu packages package-management)
             (gnu packages pkg-config)
             (gnu packages ssh)
             (gnu packages tls)
             (guix build utils)
             (guix build-system gnu)
             (guix build-system python)
             (guix gexp)
             (guix git-download)
             (guix packages)
             (ice-9 popen)
             (ice-9 rdelim))

(define %source-dir (dirname (current-filename)))

(define (git-output . args)
  "Execute 'git ARGS ...' command and return its output without trailing
newspace."
  (with-directory-excursion %source-dir
    (let* ((port   (apply open-pipe* OPEN_READ "git" args))
           (output (read-string port)))
      (close-port port)
      (string-trim-right output #\newline))))

(define (current-commit)
  (git-output "log" "-n" "1" "--pretty=format:%H"))

(let ((commit (current-commit)))
  (package
    (home-page "https://gitlab.com/wigust/guile-loadavg/")
    (name "guile-loadavg")
    (version (string-append "0.0.1" "-" (string-take commit 7)))
    (source (local-file %source-dir
                        #:recursive? #t
                        #:select? (git-predicate %source-dir)))
    (build-system gnu-build-system)
    (arguments
     `(#:tests? #f
                #:modules ((guix build gnu-build-system)
                           (guix build utils)
                           (srfi srfi-26)
                           (ice-9 popen)
                           (ice-9 rdelim))
                #:phases
                (modify-phases %standard-phases
                  (add-after 'install 'wrap-program
                    (lambda* (#:key inputs outputs #:allow-other-keys)
                      (let* ((out    (assoc-ref outputs "out"))
                             (guile  (assoc-ref inputs "guile"))
                             (gcrypt (assoc-ref inputs "guile-gcrypt"))
                             (gnutls (assoc-ref inputs "gnutls"))
                             (guix   (assoc-ref inputs "guix"))
                             (ssh    (assoc-ref inputs "guile-ssh"))
                             (deps   (list gcrypt gnutls guix ssh out))
                             (effective
                              (read-line
                               (open-pipe* OPEN_READ
                                           (string-append guile "/bin/guile")
                                           "-c" "(display (effective-version))")))
                             (path   (string-join
                                      (map (cut string-append <>
                                                "/share/guile/site/"
                                                effective)
                                           deps)
                                      ":"))
                             (gopath (string-join
                                      (map (cut string-append <>
                                                "/lib/guile/" effective
                                                "/site-ccache")
                                           deps)
                                      ":")))

                        (wrap-program (string-append out "/bin/loadavg")
                          `("GUILE_LOAD_PATH" ":" prefix (,path))
                          `("GUILE_LOAD_COMPILED_PATH" ":" prefix (,gopath)))

                        #t)
                      (let* ((guile  (assoc-ref inputs "guile"))
                             (effective
                              (read-line
                               (open-pipe* OPEN_READ
                                           (string-append guile "/bin/guile")
                                           "-c" "(display (effective-version))")))
                             (path (cut string-append <>
                                        "/share/guile/site/"
                                        effective
                                        "/loadavg")))
                        (with-directory-excursion "loadavg"
                          (copy-file "config.scm.in" "config.scm")
                          (substitute* "config.scm"
                            (("@PACKAGE_NAME@") ,name)
                            (("@PACKAGE_VERSION@") ,version)
                            (("@PACKAGE_URL@") ,home-page))
                          (install-file "config.scm"
                                        (path (assoc-ref outputs "out"))))
                        #t))))))
    (native-inputs
     `(("autoconf" ,autoconf)
       ("automake" ,automake)
       ("pkg-config" ,pkg-config)))
    (inputs
     `(("gnutls" ,gnutls)
       ("guile" ,guile-2.2)
       ("guile-gcrypt" ,guile-gcrypt)
       ("guile-ssh" ,guile-ssh)
       ("guix" ,guix)))
    (synopsis "Guile interface to Linux loadavg")
    (description
     "This package provides a Guile interface to Linux loadavg")
    (license license:gpl3+)))