;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2018, 2019 Mathieu Othacehe <m.othacehe@gmail.com>
;;; Copyright © 2020, 2021 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 (gnu installer steps)
  #:use-module (guix records)
  #:use-module (guix build utils)
  #:use-module (guix i18n)
  #:use-module (gnu installer utils)
  #:use-module (ice-9 match)
  #:use-module (ice-9 pretty-print)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-34)
  #:use-module (srfi srfi-35)
  #:use-module (rnrs io ports)
  #:export (<installer-step>
            installer-step
            make-installer-step
            installer-step?
            installer-step-id
            installer-step-description
            installer-step-compute
            installer-step-configuration-formatter

            run-installer-steps
            find-step-by-id
            result->step-ids
            result-step
            result-step-done?

            %installer-configuration-file
            %installer-target-dir
            format-configuration
            configuration->file

            %current-result))

;; Hash table storing the step results. Use it only for logging and debug
;; purposes.
(define %current-result (make-hash-table))

;; An installer-step record is basically an id associated to a compute
;; procedure. The COMPUTE procedure takes exactly one argument, an association
;; list containing the results of previously executed installer-steps (see
;; RUN-INSTALLER-STEPS description). The value returned by the COMPUTE
;; procedure will be stored in the results list passed to the next
;; installer-step and so on.
(define-record-type* <installer-step>
  installer-step make-installer-step
  installer-step?
  (id                         installer-step-id) ;symbol
  (description                installer-step-description ;string
                              (default #f)

                              ;; Make it thunked so that 'G_' is called at the
                              ;; right time, as opposed to being called once
                              ;; when the installer starts.
                              (thunked))
  (compute                    installer-step-compute) ;procedure
  (configuration-formatter    installer-step-configuration-formatter ;procedure
                              (default #f)))

(define* (run-installer-steps #:key
                              steps
                              (rewind-strategy 'previous)
                              (menu-proc (const #f)))
  "Run the COMPUTE procedure of all <installer-step> records in STEPS
sequentially, inside a the 'installer-step prompt.  When aborted to with a
parameter of 'abort, fallback to a previous install-step, accordingly to the
specified REWIND-STRATEGY.  When aborted to with a parameter of 'break, stop
the computation and return the accumalated result so far.

REWIND-STRATEGY possible values are 'previous, 'menu and 'start.  If 'previous
is selected, the execution will resume at the previous installer-step. If
'menu is selected, the MENU-PROC procedure will be called. Its return value
has to be an installer-step ID to jump to. The ID has to be the one of a
previously executed step. It is impossible to jump forward. Finally if 'start
is selected, the execution will resume at the first installer-step.

The result of every COMPUTE procedures is stored in an association list, under
the form:

		'((STEP-ID . COMPUTE-RESULT) ...)

where STEP-ID is the ID field of the installer-step and COMPUTE-RESULT the
result of the associated COMPUTE procedure. This result association list is
passed as argument of every COMPUTE procedure. It is finally returned when the
computation is over."
  (define (pop-result list)
    (cdr list))

  (define (first-step? steps step)
    (match steps
      ((first-step . rest-steps)
       (equal? first-step step))))

  (define* (skip-to-step step result
                         #:key todo-steps done-steps)
    (match todo-steps
      ((todo . rest-todo)
       (let ((found? (eq? (installer-step-id todo)
                          (installer-step-id step))))
         (cond
          (found?
           (run result
                #:todo-steps todo-steps
                #:done-steps done-steps))
          ((and (not found?)
                (null? done-steps))
           (error (format #f "Step ~a not found" (installer-step-id step))))
          (else
           (match done-steps
             ((prev-done ... last-done)
              (skip-to-step step (pop-result result)
                            #:todo-steps (cons last-done todo-steps)
                            #:done-steps prev-done)))))))))

  (define* (run result #:key todo-steps done-steps)
    (match todo-steps
      (() (reverse result))
      ((step . rest-steps)
       (call-with-prompt 'installer-step
         (lambda ()
           (installer-log-line "running step '~a'" (installer-step-id step))
           (let* ((id (installer-step-id step))
                  (compute (installer-step-compute step))
                  (res (compute result done-steps)))
             (hash-set! %current-result id res)
             (run (alist-cons id res result)
                  #:todo-steps rest-steps
                  #:done-steps (append done-steps (list step)))))
         (lambda (k action)
           (match action
             ('abort
              (case rewind-strategy
                ((previous)
                 (match done-steps
                   (()
                    ;; We cannot go previous the first step. Abort again to
                    ;; 'installer-step prompt. It might be useful in the case
                    ;; of nested run-installer-steps.
                    (abort-to-prompt 'installer-step action))
                   ((prev-done ... last-done)
                    (run (pop-result result)
                         #:todo-steps (cons last-done todo-steps)
                         #:done-steps prev-done))))
                ((menu)
                 (let ((goto-step (menu-proc
                                   (append done-steps (list step)))))
                   (if (eq? goto-step step)
                       (run result
                            #:todo-steps todo-steps
                            #:done-steps done-steps)
                       (skip-to-step goto-step result
                                     #:todo-steps todo-steps
                                     #:done-steps done-steps))))
                ((start)
                 (if (null? done-steps)
                     ;; Same as above, it makes no sense to jump to start
                     ;; when we are at the first installer-step. Abort to
                     ;; 'installer-step prompt again.
                     (abort-to-prompt 'installer-step action)
                     (run '()
                          #:todo-steps steps
                          #:done-steps '())))))
             ('break
              (reverse result))))))))

  ;; Ignore SIGPIPE so that we don't die if a client closes the connection
  ;; prematurely.
  (sigaction SIGPIPE SIG_IGN)

  (with-server-socket
    (run '()
         #:todo-steps steps
         #:done-steps '())))

(define (find-step-by-id steps id)
  "Find and return the step in STEPS whose id is equal to ID."
  (find (lambda (step)
          (eq? (installer-step-id step) id))
        steps))

(define (result-step results step-id)
  "Return the result of the installer-step specified by STEP-ID in
RESULTS."
  (assoc-ref results step-id))

(define (result-step-done? results step-id)
  "Return #t if the installer-step specified by STEP-ID has a COMPUTE value
stored in RESULTS. Return #f otherwise."
  (and (assoc step-id results) #t))

(define %installer-configuration-file (make-parameter "/mnt/etc/config.scm"))
(define %installer-target-dir (make-parameter "/mnt"))

(define (format-configuration steps results)
  "Return the list resulting from the application of the procedure defined in
CONFIGURATION-FORMATTER field of <installer-step> on the associated result
found in RESULTS."
  (let ((configuration
         (append-map
          (lambda (step)
            (let* ((step-id (installer-step-id step))
                   (conf-formatter
                    (installer-step-configuration-formatter step))
                   (result-step (result-step results step-id)))
              (if (and result-step conf-formatter)
                  (conf-formatter result-step)
                  '())))
          steps))
        (modules '((use-modules (gnu))
                   (use-service-modules cups desktop networking ssh xorg))))
    `(,@modules
      ()
      (operating-system ,@configuration))))

(define* (configuration->file configuration
                              #:key (filename (%installer-configuration-file)))
  "Write the given CONFIGURATION to FILENAME."
  (mkdir-p (dirname filename))
  (call-with-output-file filename
    (lambda (port)
      ;; TRANSLATORS: This is a comment within a Scheme file.  Each line must
      ;; start with ";; " (two semicolons and a space).  Please keep line
      ;; length below 60 characters.
      (display (G_ "\
;; This is an operating system configuration generated
;; by the graphical installer.\n")
               port)
      (newline port)
      (for-each (lambda (part)
                  (if (null? part)
                      (newline port)
                      (pretty-print part port)))
                configuration)
      (flush-output-port port))))

;;; Local Variables:
;;; eval: (put 'with-server-socket 'scheme-indent-function 0)
;;; End: