;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2014, 2015 David Thompson <davet@gnu.org>
;;; Copyright © 2015 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 scripts environment)
  #:use-module (guix ui)
  #:use-module (guix store)
  #:use-module (guix derivations)
  #:use-module (guix packages)
  #:use-module (guix profiles)
  #:use-module (guix search-paths)
  #:use-module (guix utils)
  #:use-module (guix monads)
  #:use-module ((guix gexp) #:select (lower-inputs))
  #:use-module (guix scripts)
  #:use-module (guix scripts build)
  #:use-module (gnu packages)
  #:use-module (ice-9 format)
  #:use-module (ice-9 match)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-11)
  #:use-module (srfi srfi-26)
  #:use-module (srfi srfi-37)
  #:use-module (srfi srfi-98)
  #:export (guix-environment))

(define (evaluate-input-search-paths inputs search-paths)
  "Evaluate SEARCH-PATHS, a list of search-path specifications, for the
directories corresponding to INPUTS, a list of (DERIVATION) or (DERIVATION
OUTPUT) tuples."
  (let ((directories (map (match-lambda
                            (((? derivation? drv))
                             (derivation->output-path drv))
                            (((? derivation? drv) output)
                             (derivation->output-path drv output))
                            (((? string? item))
                             item))
                          inputs)))
    (evaluate-search-paths search-paths directories)))

;; Protect some env vars from purification.  Borrowed from nix-shell.
(define %precious-variables
  '("HOME" "USER" "LOGNAME" "DISPLAY" "TERM" "TZ" "PAGER"))

(define (purify-environment)
  "Unset almost all environment variables.  A small number of variables such
as 'HOME' and 'USER' are left untouched."
  (for-each unsetenv
            (remove (cut member <> %precious-variables)
                    (match (get-environment-variables)
                      (((names . _) ...)
                       names)))))

(define (create-environment inputs paths pure?)
  "Set the environment variables specified by PATHS for all the packages
within INPUTS.  When PURE? is #t, unset the variables in the current
environment.  Otherwise, augment existing enviroment variables with additional
search paths."
  (when pure? (purify-environment))
  (for-each (match-lambda
              ((($ <search-path-specification> variable _ separator) . value)
               (let ((current (getenv variable)))
                 (setenv variable
                         (if (and current (not pure?))
                             (string-append value separator current)
                             value)))))
            (evaluate-input-search-paths inputs paths))

  ;; Give users a way to know that they're in 'guix environment', so they can
  ;; adjust 'PS1' accordingly, for instance.
  (setenv "GUIX_ENVIRONMENT" "t"))

(define (show-search-paths inputs search-paths pure?)
  "Display SEARCH-PATHS applied to the packages specified by INPUTS, a list of
 (DERIVATION) or (DERIVATION OUTPUT) tuples.  When PURE? is #t, do not augment
existing environment variables with additional search paths."
  (for-each (match-lambda
              ((search-path . value)
               (display
                (search-path-definition search-path value
                                        #:kind (if pure? 'exact 'prefix)))
               (newline)))
            (evaluate-input-search-paths inputs search-paths)))

(define (package+propagated-inputs package output)
  "Return the union of PACKAGE's OUTPUT and its transitive propagated inputs."
  `((,(package-name package) ,package ,output)
    ,@(package-transitive-propagated-inputs package)))

(define (show-help)
  (display (_ "Usage: guix environment [OPTION]... PACKAGE...
Build an environment that includes the dependencies of PACKAGE and execute a
shell command in that environment.\n"))
  (display (_ "
  -e, --expression=EXPR  create environment for the package that EXPR
                         evaluates to"))
  (display (_ "
  -l, --load=FILE        create environment for the package that the code within
                         FILE evaluates to"))
  (display (_ "
  -E, --exec=COMMAND     execute COMMAND in new environment"))
  (display (_ "
      --ad-hoc           include all specified packages in the environment instead
                         of only their inputs"))
  (display (_ "
      --pure             unset existing environment variables"))
  (display (_ "
      --search-paths     display needed environment variable definitions"))
  (display (_ "
  -s, --system=SYSTEM    attempt to build for SYSTEM--e.g., \"i686-linux\""))
  (newline)
  (show-build-options-help)
  (newline)
  (display (_ "
  -h, --help             display this help and exit"))
  (display (_ "
  -V, --version          display version information and exit"))
  (newline)
  (show-bug-report-information))

(define %default-options
  ;; Default to opening a new shell.
  `((exec . ,(or (getenv "SHELL") "/bin/sh"))
    (system . ,(%current-system))
    (substitutes? . #t)
    (max-silent-time . 3600)
    (verbosity . 0)))

(define %options
  ;; Specification of the command-line options.
  (cons* (option '(#\h "help") #f #f
                 (lambda args
                   (show-help)
                   (exit 0)))
         (option '(#\V "version") #f #f
                 (lambda args
                   (show-version-and-exit "guix environment")))
         (option '("pure") #f #f
                 (lambda (opt name arg result)
                   (alist-cons 'pure #t result)))
         (option '(#\E "exec") #t #f
                 (lambda (opt name arg result)
                   (alist-cons 'exec arg result)))
         (option '("search-paths") #f #f
                 (lambda (opt name arg result)
                   (alist-cons 'search-paths #t result)))
         (option '(#\l "load") #t #f
                 (lambda (opt name arg result)
                   (alist-cons 'load arg result)))
         (option '(#\e "expression") #t #f
                 (lambda (opt name arg result)
                   (alist-cons 'expression arg result)))
         (option '("ad-hoc") #f #f
                 (lambda (opt name arg result)
                   (alist-cons 'ad-hoc? #t result)))
         (option '(#\n "dry-run") #f #f
                 (lambda (opt name arg result)
                   (alist-cons 'dry-run? #t result)))
         (option '(#\s "system") #t #f
                 (lambda (opt name arg result)
                   (alist-cons 'system arg
                               (alist-delete 'system result eq?))))
         %standard-build-options))

(define (pick-all alist key)
  "Return a list of values in ALIST associated with KEY."
  (define same-key? (cut eq? key <>))

  (fold (lambda (pair memo)
          (match pair
            (((? same-key? k) . v)
             (cons v memo))
            (_ memo)))
        '() alist))

(define (options/resolve-packages opts)
  "Return OPTS with package specification strings replaced by actual
packages."
  (append-map (match-lambda
                (('package . (? string? spec))
                 (let-values (((package output)
                               (specification->package+output spec)))
                   `((package ,package ,output))))
                (('expression . str)
                 ;; Add all the outputs of the package STR evaluates to.
                 (match (read/eval str)
                   ((? package? package)
                    (map (lambda (output)
                           `(package ,package ,output))
                         (package-outputs package)))))
                (('load . file)
                 ;; Add all the outputs of the package defined in FILE.
                 (let ((package (load* file (make-user-module '()))))
                   (map (lambda (output)
                          `(package ,package ,output))
                        (package-outputs package))))
                (opt (list opt)))
              opts))

(define (build-inputs inputs opts)
  "Build the derivations in INPUTS, a list of (DERIVATION) or (DERIVATION
OUTPUT) tuples, using the build options in OPTS."
  (let ((substitutes? (assoc-ref opts 'substitutes?))
        (dry-run?     (assoc-ref opts 'dry-run?)))
    (match inputs
      (((derivations _ ...) ...)
       (mbegin %store-monad
         (show-what-to-build* derivations
                              #:use-substitutes? substitutes?
                              #:dry-run? dry-run?)
         (if dry-run?
             (return #f)
             (mbegin %store-monad
               (set-build-options-from-command-line* opts)
               (built-derivations derivations)
               (return derivations))))))))

;; Entry point.
(define (guix-environment . args)
  (define (handle-argument arg result)
    (alist-cons 'package arg result))

  (with-error-handling
    (let* ((opts     (parse-command-line args %options (list %default-options)
                                         #:argument-handler handle-argument))
           (pure?    (assoc-ref opts 'pure))
           (ad-hoc?  (assoc-ref opts 'ad-hoc?))
           (command  (assoc-ref opts 'exec))
           (packages (pick-all (options/resolve-packages opts) 'package))
           (inputs   (if ad-hoc?
                         (append-map (match-lambda
                                       ((package output)
                                        (package+propagated-inputs package
                                                                   output)))
                                     packages)
                         (append-map (compose bag-transitive-inputs
                                              package->bag
                                              first)
                                     packages)))
           (paths    (delete-duplicates
                      (cons $PATH
                            (append-map (match-lambda
                                          ((label (? package? p) _ ...)
                                           (package-native-search-paths p))
                                          (_
                                           '()))
                                        inputs))
                      eq?)))
      (with-store store
        (run-with-store store
          (mlet %store-monad ((inputs (lower-inputs
                                       (map (match-lambda
                                              ((label item)
                                               (list item))
                                              ((label item output)
                                               (list item output)))
                                            inputs)
                                       #:system (assoc-ref opts 'system))))
            (mbegin %store-monad
              ;; First build INPUTS.  This is necessary even for
              ;; --search-paths.
              (build-inputs inputs opts)
              (cond ((assoc-ref opts 'dry-run?)
                     (return #t))
                    ((assoc-ref opts 'search-paths)
                     (show-search-paths inputs paths pure?)
                     (return #t))
                    (else
                     (create-environment inputs paths pure?)
                     (return (exit (status:exit-val (system command)))))))))))))
