;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2012, 2013 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 utils)
  #:use-module (guix config)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-9)
  #:use-module (srfi srfi-26)
  #:use-module (srfi srfi-39)
  #:use-module (srfi srfi-60)
  #:use-module (rnrs bytevectors)
  #:use-module ((rnrs io ports) #:select (put-bytevector))
  #:use-module ((guix build utils) #:select (dump-port))
  #:use-module (ice-9 vlist)
  #:use-module (ice-9 format)
  #:autoload   (ice-9 popen)  (open-pipe*)
  #:autoload   (ice-9 rdelim) (read-line)
  #:use-module (ice-9 regex)
  #:use-module (ice-9 match)
  #:use-module (ice-9 format)
  #:autoload   (system foreign) (pointer->procedure)
  #:export (bytevector->base16-string
            base16-string->bytevector
            sha256

            %nixpkgs-directory
            nixpkgs-derivation
            nixpkgs-derivation*

            compile-time-value
            memoize
            default-keyword-arguments
            substitute-keyword-arguments

            <location>
            location
            location?
            location-file
            location-line
            location-column
            source-properties->location

            gnu-triplet->nix-system
            %current-system
            version-compare
            version>?
            package-name->name+version
            string-tokenize*
            file-extension
            call-with-temporary-output-file
            fold2
            filtered-port))


;;;
;;; Compile-time computations.
;;;

(define-syntax compile-time-value
  (syntax-rules ()
    "Evaluate the given expression at compile time.  The expression must
evaluate to a simple datum."
    ((_ exp)
     (let-syntax ((v (lambda (s)
                       (let ((val exp))
                         (syntax-case s ()
                           (_ #`'#,(datum->syntax s val)))))))
       v))))


;;;
;;; Base 16.
;;;

(define (bytevector->base16-string bv)
  "Return the hexadecimal representation of BV's contents."
  (define len
    (bytevector-length bv))

  (let-syntax ((base16-chars (lambda (s)
                               (syntax-case s ()
                                 (_
                                  (let ((v (list->vector
                                            (unfold (cut > <> 255)
                                                    (lambda (n)
                                                      (format #f "~2,'0x" n))
                                                    1+
                                                    0))))
                                    v))))))
    (define chars base16-chars)
    (let loop ((i 0)
               (r '()))
      (if (= i len)
          (string-concatenate-reverse r)
          (loop (+ 1 i)
                (cons (vector-ref chars (bytevector-u8-ref bv i)) r))))))

(define base16-string->bytevector
  (let ((chars->value (fold (lambda (i r)
                              (vhash-consv (string-ref (number->string i 16)
                                                       0)
                                           i r))
                            vlist-null
                            (iota 16))))
    (lambda (s)
      "Return the bytevector whose hexadecimal representation is string S."
      (define bv
        (make-bytevector (quotient (string-length s) 2) 0))

      (string-fold (lambda (chr i)
                     (let ((j (quotient i 2))
                           (v (and=> (vhash-assv chr chars->value) cdr)))
                       (if v
                           (if (zero? (logand i 1))
                               (bytevector-u8-set! bv j
                                                   (arithmetic-shift v 4))
                               (let ((w (bytevector-u8-ref bv j)))
                                 (bytevector-u8-set! bv j (logior v w))))
                           (error "invalid hexadecimal character" chr)))
                     (+ i 1))
                   0
                   s)
      bv)))


;;;
;;; Hash.
;;;

(define sha256
  (let ((hash   (pointer->procedure void
                                    (dynamic-func "gcry_md_hash_buffer"
                                                  (dynamic-link %libgcrypt))
                                    `(,int * * ,size_t)))
        (sha256 8))                        ; GCRY_MD_SHA256, as of 1.5.0
    (lambda (bv)
      "Return the SHA256 of BV as a bytevector."
      (let ((digest (make-bytevector (/ 256 8))))
        (hash sha256 (bytevector->pointer digest)
              (bytevector->pointer bv) (bytevector-length bv))
        digest))))


;;;
;;; Filtering & pipes.
;;;

(define (filtered-port command input)
  "Return an input port where data drained from INPUT is filtered through
COMMAND (a list).  In addition, return a list of PIDs that the caller must
wait."
  (let loop ((input input)
             (pids '()))
    (if (file-port? input)
        (match (pipe)
          ((in . out)
           (match (primitive-fork)
             (0
              (close-port in)
              (close-port (current-input-port))
              (dup2 (fileno input) 0)
              (close-port (current-output-port))
              (dup2 (fileno out) 1)
              (apply execl (car command) command))
             (child
              (close-port out)
              (values in (cons child pids))))))

        ;; INPUT is not a file port, so fork just for the sake of tunneling it
        ;; through a file port.
        (match (pipe)
          ((in . out)
           (match (primitive-fork)
             (0
              (dynamic-wind
                (const #t)
                (lambda ()
                  (close-port in)
                  (dump-port input out))
                (lambda ()
                  (false-if-exception (close out))
                  (primitive-exit 0))))
             (child
              (close-port out)
              (loop in (cons child pids)))))))))


;;;
;;; Nixpkgs.
;;;

(define %nixpkgs-directory
  (make-parameter
   ;; Capture the build-time value of $NIXPKGS.
   (or %nixpkgs
       (and=> (getenv "NIXPKGS")
              (lambda (val)
                ;; Bail out when passed an empty string, otherwise
                ;; `nix-instantiate' will sit there and attempt to read
                ;; from its standard input.
                (if (string=? val "")
                    #f
                    val))))))

(define* (nixpkgs-derivation attribute #:optional (system (%current-system)))
  "Return the derivation path of ATTRIBUTE in Nixpkgs."
  (let* ((p (open-pipe* OPEN_READ (or (getenv "NIX_INSTANTIATE")
                                      %nix-instantiate)
                        "-A" attribute (%nixpkgs-directory)
                        "--argstr" "system" system))
         (l (read-line p))
         (s (close-pipe p)))
    (and (zero? (status:exit-val s))
         (not (eof-object? l))
         l)))

(define-syntax-rule (nixpkgs-derivation* attribute)
  "Evaluate the given Nixpkgs derivation at compile-time."
  (compile-time-value (nixpkgs-derivation attribute)))


;;;
;;; Miscellaneous.
;;;

(define (memoize proc)
  "Return a memoizing version of PROC."
  (let ((cache (make-hash-table)))
    (lambda args
      (let ((results (hash-ref cache args)))
        (if results
            (apply values results)
            (let ((results (call-with-values (lambda ()
                                               (apply proc args))
                             list)))
              (hash-set! cache args results)
              (apply values results)))))))

(define (default-keyword-arguments args defaults)
  "Return ARGS augmented with any keyword/value from DEFAULTS for
keywords not already present in ARGS."
  (let loop ((defaults defaults)
             (args     args))
    (match defaults
      ((kw value rest ...)
       (loop rest
             (if (assoc-ref kw args)
                 args
                 (cons* kw value args))))
      (()
       args))))

(define-syntax substitute-keyword-arguments
  (syntax-rules ()
    "Return a new list of arguments where the value for keyword arg KW is
replaced by EXP.  EXP is evaluated in a context where VAR is boud to the
previous value of the keyword argument."
    ((_ original-args ((kw var) exp) ...)
     (let loop ((args    original-args)
                (before '()))
       (match args
         ((kw var rest (... ...))
          (loop rest (cons* exp kw before)))
         ...
         ((x rest (... ...))
          (loop rest (cons x before)))
         (()
          (reverse before)))))))

(define (gnu-triplet->nix-system triplet)
  "Return the Nix system type corresponding to TRIPLET, a GNU triplet as
returned by `config.guess'."
  (let ((triplet (cond ((string-match "^i[345]86-(.*)$" triplet)
                        =>
                        (lambda (m)
                          (string-append "i686-" (match:substring m 1))))
                       (else triplet))))
    (cond ((string-match "^([^-]+)-([^-]+-)?linux-gnu.*" triplet)
           =>
           (lambda (m)
             ;; Nix omits `-gnu' for GNU/Linux.
             (string-append (match:substring m 1) "-linux")))
          ((string-match "^([^-]+)-([^-]+-)?([[:alpha:]]+)([0-9]+\\.?)*$" triplet)
           =>
           (lambda (m)
             ;; Nix strip the version number from names such as `gnu0.3',
             ;; `darwin10.2.0', etc., and always strips the vendor part.
             (string-append (match:substring m 1) "-"
                            (match:substring m 3))))
          (else triplet))))

(define %current-system
  ;; System type as expected by Nix, usually ARCHITECTURE-KERNEL.
  ;; By default, this is equal to (gnu-triplet->nix-system %host-type).
  (make-parameter %system))

(define version-compare
  (let ((strverscmp
         (let ((sym (or (dynamic-func "strverscmp" (dynamic-link))
                        (error "could not find `strverscmp' (from GNU libc)"))))
           (pointer->procedure int sym (list '* '*)))))
    (lambda (a b)
      "Return '> when A denotes a newer version than B,
'< when A denotes a older version than B,
or '= when they denote equal versions."
      (let ((result (strverscmp (string->pointer a) (string->pointer b))))
        (cond ((positive? result) '>)
              ((negative? result) '<)
              (else '=))))))

(define (version>? a b)
  "Return #t when A denotes a newer version than B."
  (eq? '> (version-compare a b)))

(define (package-name->name+version name)
  "Given NAME, a package name like \"foo-0.9.1b\", return two values:
\"foo\" and \"0.9.1b\".  When the version part is unavailable, NAME and
#f are returned.  The first hyphen followed by a digit is considered to
introduce the version part."
  ;; See also `DrvName' in Nix.

  (define number?
    (cut char-set-contains? char-set:digit <>))

  (let loop ((chars   (string->list name))
             (prefix '()))
    (match chars
      (()
       (values name #f))
      ((#\- (? number? n) rest ...)
       (values (list->string (reverse prefix))
               (list->string (cons n rest))))
      ((head tail ...)
       (loop tail (cons head prefix))))))

(define (file-extension file)
  "Return the extension of FILE or #f if there is none."
  (let ((dot (string-rindex file #\.)))
    (and dot (substring file (+ 1 dot) (string-length file)))))

(define (string-tokenize* string separator)
  "Return the list of substrings of STRING separated by SEPARATOR.  This is
like `string-tokenize', but SEPARATOR is a string."
  (define (index string what)
    (let loop ((string string)
               (offset 0))
      (cond ((string-null? string)
             #f)
            ((string-prefix? what string)
             offset)
            (else
             (loop (string-drop string 1) (+ 1 offset))))))

  (define len
    (string-length separator))

  (let loop ((string string)
             (result  '()))
    (cond ((index string separator)
           =>
           (lambda (offset)
             (loop (string-drop string (+ offset len))
                   (cons (substring string 0 offset)
                         result))))
          (else
           (reverse (cons string result))))))

(define (call-with-temporary-output-file proc)
  "Call PROC with a name of a temporary file and open output port to that
file; close the file and delete it when leaving the dynamic extent of this
call."
  (let* ((template (string-copy "guix-file.XXXXXX"))
         (out      (mkstemp! template)))
    (dynamic-wind
      (lambda ()
        #t)
      (lambda ()
        (proc template out))
      (lambda ()
        (false-if-exception (close out))
        (false-if-exception (delete-file template))))))

(define fold2
  (case-lambda
    ((proc seed1 seed2 lst)
     "Like `fold', but with a single list and two seeds."
     (let loop ((result1 seed1)
                (result2 seed2)
                (lst     lst))
       (if (null? lst)
           (values result1 result2)
           (call-with-values
               (lambda () (proc (car lst) result1 result2))
             (lambda (result1 result2)
               (loop result1 result2 (cdr lst)))))))
    ((proc seed1 seed2 lst1 lst2)
     "Like `fold', but with a two lists and two seeds."
     (let loop ((result1 seed1)
                (result2 seed2)
                (lst1    lst1)
                (lst2    lst2))
       (if (or (null? lst1) (null? lst2))
           (values result1 result2)
           (call-with-values
               (lambda () (proc (car lst1) (car lst2) result1 result2))
             (lambda (result1 result2)
               (fold2 proc result1 result2 (cdr lst1) (cdr lst2)))))))))


;;;
;;; Source location.
;;;

;; A source location.
(define-record-type <location>
  (make-location file line column)
  location?
  (file          location-file)                   ; file name
  (line          location-line)                   ; 1-indexed line
  (column        location-column))                ; 0-indexed column

(define location
  (memoize
   (lambda (file line column)
     "Return the <location> object for the given FILE, LINE, and COLUMN."
     (and line column file
          (make-location file line column)))))

(define (source-properties->location loc)
  "Return a location object based on the info in LOC, an alist as returned
by Guile's `source-properties', `frame-source', `current-source-location',
etc."
  (let ((file (assq-ref loc 'filename))
        (line (assq-ref loc 'line))
        (col  (assq-ref loc 'column)))
    ;; In accordance with the GCS, start line and column numbers at 1.  Note
    ;; that unlike LINE and `port-column', COL is actually 1-indexed here...
    (location file (and line (+ line 1)) col)))