;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2016, 2017 Mathieu Lirzin <mthl@gnu.org>
;;; Copyright © 2019 Caleb Ristvedt <caleb.ristvedt@cune.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 store derivations)
  #:use-module (ice-9 match)
  #:use-module (rnrs io ports)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-9)
  #:use-module (srfi srfi-9 gnu)
  #:use-module (srfi srfi-26)
  #:use-module (guix base16)
  #:use-module (guix memoization)
  #:export (<derivation>
            make-derivation
            derivation?
            derivation-outputs
            derivation-inputs
            derivation-sources
            derivation-system
            derivation-builder
            derivation-builder-arguments
            derivation-builder-environment-vars
            derivation-file-name

            <derivation-output>
            make-derivation-output
            derivation-output?
            derivation-output-path
            derivation-output-hash-algo
            derivation-output-hash
            derivation-output-recursive?

            <derivation-input>
            make-derivation-input
            derivation-input?
            derivation-input-path
            derivation-input-sub-derivations

            read-derivation
            read-derivation-from-file
            derivation->bytevector
            %derivation-cache
            write-derivation))

;;;
;;; Nix derivations, as implemented in Nix's `derivations.cc'.
;;;

(define-immutable-record-type <derivation>
  (make-derivation outputs inputs sources system builder args env-vars
                   file-name)
  derivation?
  (outputs  derivation-outputs)      ; list of name/<derivation-output> pairs
  (inputs   derivation-inputs)       ; list of <derivation-input>
  (sources  derivation-sources)      ; list of store paths
  (system   derivation-system)       ; string
  (builder  derivation-builder)      ; store path
  (args     derivation-builder-arguments)         ; list of strings
  (env-vars derivation-builder-environment-vars)  ; list of name/value pairs
  (file-name derivation-file-name))               ; the .drv file name

(define-immutable-record-type <derivation-output>
  (make-derivation-output path hash-algo hash recursive?)
  derivation-output?
  (path       derivation-output-path)             ; store path
  (hash-algo  derivation-output-hash-algo)        ; symbol | #f
  (hash       derivation-output-hash)             ; bytevector | #f
  (recursive? derivation-output-recursive?))      ; Boolean

(define-immutable-record-type <derivation-input>
  (make-derivation-input path sub-derivations)
  derivation-input?
  (path            derivation-input-path)             ; store path
  (sub-derivations derivation-input-sub-derivations)) ; list of strings

(set-record-type-printer! <derivation>
                          (lambda (drv port)
                            (format port "#<derivation ~a => ~a ~a>"
                                    (derivation-file-name drv)
                                    (string-join
                                     (map (match-lambda
                                           ((_ . output)
                                            (derivation-output-path output)))
                                          (derivation-outputs drv)))
                                    (number->string (object-address drv) 16))))

(define (read-derivation drv-port)
  "Read the derivation from DRV-PORT and return the corresponding <derivation>
object.  Most of the time you'll want to use 'read-derivation-from-file',
which caches things as appropriate and is thus more efficient."

  (define comma (string->symbol ","))

  (define (ununquote x)
    (match x
      (('unquote x) (ununquote x))
      ((x ...)      (map ununquote x))
      (_            x)))

  (define (outputs->alist x)
    (fold-right (lambda (output result)
                  (match output
                    ((name path "" "")
                     (alist-cons name
                                 (make-derivation-output path #f #f #f)
                                 result))
                    ((name path hash-algo hash)
                     ;; fixed-output
                     (let* ((rec? (string-prefix? "r:" hash-algo))
                            (algo (string->symbol
                                   (if rec?
                                       (string-drop hash-algo 2)
                                       hash-algo)))
                            (hash (base16-string->bytevector hash)))
                       (alist-cons name
                                   (make-derivation-output path algo
                                                           hash rec?)
                                   result)))))
                '()
                x))

  (define (make-input-drvs x)
    (fold-right (lambda (input result)
                  (match input
                    ((path (sub-drvs ...))
                     (cons (make-derivation-input path sub-drvs)
                           result))))
                '()
                x))

  ;; The contents of a derivation are typically ASCII, but choosing
  ;; UTF-8 allows us to take the fast path for Guile's `scm_getc'.
  (set-port-encoding! drv-port "UTF-8")

  (let loop ((exp    (read drv-port))
             (result '()))
    (match exp
      ((? eof-object?)
       (let ((result (reverse result)))
         (match result
           (('Derive ((outputs ...) (input-drvs ...)
                      (input-srcs ...)
                      (? string? system)
                      (? string? builder)
                      ((? string? args) ...)
                      ((var value) ...)))
            (make-derivation (outputs->alist outputs)
                             (make-input-drvs input-drvs)
                             input-srcs
                             system builder args
                             (fold-right alist-cons '() var value)
                             (port-filename drv-port)))
           (_
            (error "failed to parse derivation" drv-port result)))))
      ((? (cut eq? <> comma))
       (loop (read drv-port) result))
      (_
       (loop (read drv-port)
             (cons (ununquote exp) result))))))

(define %derivation-cache
  ;; Maps derivation file names to <derivation> objects.
  ;; XXX: This is redundant with 'atts-cache' in the store.
  (make-weak-value-hash-table 200))

(define (read-derivation-from-file file)
  "Read the derivation in FILE, a '.drv' file, and return the corresponding
<derivation> object."
  ;; Memoize that operation because 'read-derivation' is quite expensive,
  ;; and because the same argument is read more than 15 times on average
  ;; during something like (package-derivation s gdb).
  (or (and file (hash-ref %derivation-cache file))
      (let ((drv (call-with-input-file file read-derivation)))
        (hash-set! %derivation-cache file drv)
        drv)))

(define-inlinable (write-sequence lst write-item port)
  ;; Write each element of LST with WRITE-ITEM to PORT, separating them with a
  ;; comma.
  (match lst
    (()
     #t)
    ((prefix (... ...) last)
     (for-each (lambda (item)
                 (write-item item port)
                 (display "," port))
               prefix)
     (write-item last port))))

(define-inlinable (write-list lst write-item port)
  ;; Write LST as a derivation list to PORT, using WRITE-ITEM to write each
  ;; element.
  (display "[" port)
  (write-sequence lst write-item port)
  (display "]" port))

(define-inlinable (write-tuple lst write-item port)
  ;; Same, but write LST as a tuple.
  (display "(" port)
  (write-sequence lst write-item port)
  (display ")" port))

(define (write-derivation drv port)
  "Write the ATerm-like serialization of DRV to PORT.  See Section 2.4 of
Eelco Dolstra's PhD dissertation for an overview of a previous version of
that form."

  ;; Make sure we're using the faster implementation.
  (define format simple-format)

  (define (write-string-list lst)
    (write-list lst write port))

  (define (write-output output port)
    (match output
     ((name . ($ <derivation-output> path hash-algo hash recursive?))
      (write-tuple (list name path
                         (if hash-algo
                             (string-append (if recursive? "r:" "")
                                            (symbol->string hash-algo))
                             "")
                         (or (and=> hash bytevector->base16-string)
                             ""))
                   write
                   port))))

  (define (write-input input port)
    (match input
      (($ <derivation-input> path sub-drvs)
       (display "(\"" port)
       (display path port)
       (display "\"," port)
       (write-string-list sub-drvs)
       (display ")" port))))

  (define (write-env-var env-var port)
    (match env-var
      ((name . value)
       (display "(" port)
       (write name port)
       (display "," port)
       (write value port)
       (display ")" port))))

  ;; Assume all the lists we are writing are already sorted.
  (match drv
    (($ <derivation> outputs inputs sources
        system builder args env-vars)
     (display "Derive(" port)
     (write-list outputs write-output port)
     (display "," port)
     (write-list inputs write-input port)
     (display "," port)
     (write-string-list sources)
     (simple-format port ",\"~a\",\"~a\"," system builder)
     (write-string-list args)
     (display "," port)
     (write-list env-vars write-env-var port)
     (display ")" port))))

(define derivation->bytevector
  (mlambda (drv)
    "Return the external representation of DRV as a UTF-8-encoded string."
    (with-fluids ((%default-port-encoding "UTF-8"))
      (call-with-values open-bytevector-output-port
        (lambda (port get-bytevector)
          (write-derivation drv port)
          (get-bytevector))))))