;;; 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 build utils)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-11)
  #:use-module (ice-9 ftw)
  #:use-module (ice-9 match)
  #:use-module (ice-9 regex)
  #:use-module (ice-9 rdelim)
  #:use-module (rnrs bytevectors)
  #:use-module (rnrs io ports)
  #:export (directory-exists?
            executable-file?
            call-with-ascii-input-file
            with-directory-excursion
            mkdir-p
            copy-recursively
            find-files

            set-path-environment-variable
            search-path-as-string->list
            list->search-path-as-string
            which

            alist-cons-before
            alist-cons-after
            alist-replace
            with-atomic-file-replacement
            substitute
            substitute*
            dump-port
            set-file-time
            patch-shebang
            patch-makefile-SHELL
            fold-port-matches
            remove-store-references))


;;;
;;; Directories.
;;;

(define (directory-exists? dir)
  "Return #t if DIR exists and is a directory."
  (let ((s (stat dir #f)))
    (and s
         (eq? 'directory (stat:type s)))))

(define (executable-file? file)
  "Return #t if FILE exists and is executable."
  (let ((s (stat file #f)))
    (and s
         (not (zero? (logand (stat:mode s) #o100))))))

(define (call-with-ascii-input-file file proc)
  "Open FILE as an ASCII or binary file, and pass the resulting port to
PROC.  FILE is closed when PROC's dynamic extent is left.  Return the
return values of applying PROC to the port."
  (let ((port (with-fluids ((%default-port-encoding #f))
                ;; Use "b" so that `open-file' ignores `coding:' cookies.
                (open-file file "rb"))))
    (dynamic-wind
      (lambda ()
        #t)
      (lambda ()
        (proc port))
      (lambda ()
        (close-input-port port)))))

(define-syntax-rule (with-directory-excursion dir body ...)
  "Run BODY with DIR as the process's current directory."
  (let ((init (getcwd)))
   (dynamic-wind
     (lambda ()
       (chdir dir))
     (lambda ()
       body ...)
     (lambda ()
       (chdir init)))))

(define (mkdir-p dir)
  "Create directory DIR and all its ancestors."
  (define absolute?
    (string-prefix? "/" dir))

  (define not-slash
    (char-set-complement (char-set #\/)))

  (let loop ((components (string-tokenize dir not-slash))
             (root       (if absolute?
                             ""
                             ".")))
    (match components
      ((head tail ...)
       (let ((path (string-append root "/" head)))
         (catch 'system-error
           (lambda ()
             (mkdir path)
             (loop tail path))
           (lambda args
             (if (= EEXIST (system-error-errno args))
                 (loop tail path)
                 (apply throw args))))))
      (() #t))))

(define* (copy-recursively source destination
                           #:optional (log (current-output-port)))
  "Copy SOURCE directory to DESTINATION."
  (define strip-source
    (let ((len (string-length source)))
      (lambda (file)
        (substring file len))))

  (file-system-fold (const #t)                    ; enter?
                    (lambda (file stat result)    ; leaf
                      (let ((dest (string-append destination
                                                 (strip-source file))))
                        (format log "`~a' -> `~a'~%" file dest)
                        (copy-file file dest)))
                    (lambda (dir stat result)     ; down
                      (mkdir-p (string-append destination
                                              (strip-source dir))))
                    (lambda (dir stat result)     ; up
                      result)
                    (const #t)                    ; skip
                    (lambda (file stat errno result)
                      (format (current-error-port) "i/o error: ~a: ~a~%"
                              file (strerror errno))
                      #f)
                    #t
                    source))

(define (find-files dir regexp)
  "Return the list of files under DIR whose basename matches REGEXP."
  (define file-rx
    (if (regexp? regexp)
        regexp
        (make-regexp regexp)))

  (file-system-fold (const #t)
                    (lambda (file stat result)    ; leaf
                      (if (regexp-exec file-rx (basename file))
                          (cons file result)
                          result))
                    (lambda (dir stat result)     ; down
                      result)
                    (lambda (dir stat result)     ; up
                      result)
                    (lambda (file stat result)    ; skip
                      result)
                    (lambda (file stat errno result)
                      (format (current-error-port) "find-files: ~a: ~a~%"
                              file (strerror errno))
                      #f)
                    '()
                    dir))


;;;
;;; Search paths.
;;;

(define (search-path-as-list sub-directories input-dirs)
  "Return the list of directories among SUB-DIRECTORIES that exist in
INPUT-DIRS.  Example:

  (search-path-as-list '(\"share/emacs/site-lisp\" \"share/emacs/24.1\")
                       (list \"/package1\" \"/package2\" \"/package3\"))
  => (\"/package1/share/emacs/site-lisp\"
      \"/package3/share/emacs/site-lisp\")

"
  (append-map (lambda (input)
                (filter-map (lambda (dir)
                              (let ((dir (string-append input "/"
                                                        dir)))
                                (and (directory-exists? dir)
                                     dir)))
                            sub-directories))
              input-dirs))

(define (list->search-path-as-string lst separator)
  (string-join lst separator))

(define* (search-path-as-string->list path #:optional (separator #\:))
  (string-tokenize path (char-set-complement (char-set separator))))

(define* (set-path-environment-variable env-var sub-directories input-dirs
                                        #:key (separator ":"))
  "Look for each of SUB-DIRECTORIES in INPUT-DIRS.  Set ENV-VAR to a
SEPARATOR-separated path accordingly.  Example:

  (set-path-environment-variable \"PKG_CONFIG\"
                                 '(\"lib/pkgconfig\")
                                 (list package1 package2))
"
  (let* ((path  (search-path-as-list sub-directories input-dirs))
         (value (list->search-path-as-string path separator)))
   (setenv env-var value)
   (format #t "environment variable `~a' set to `~a'~%"
           env-var value)))

(define (which program)
  "Return the complete file name for PROGRAM as found in $PATH, or #f if
PROGRAM could not be found."
  (search-path (search-path-as-string->list (getenv "PATH"))
               program))


;;;
;;; Phases.
;;;
;;; In (guix build gnu-build-system), there are separate phases (configure,
;;; build, test, install).  They are represented as a list of name/procedure
;;; pairs.  The following procedures make it easy to change the list of
;;; phases.
;;;

(define* (alist-cons-before reference key value alist
                            #:optional (key=? equal?))
  "Insert the KEY/VALUE pair before the first occurrence of a pair whose key
is REFERENCE in ALIST.  Use KEY=? to compare keys."
  (let-values (((before after)
                (break (match-lambda
                        ((k . _)
                         (key=? k reference)))
                       alist)))
    (append before (alist-cons key value after))))

(define* (alist-cons-after reference key value alist
                           #:optional (key=? equal?))
  "Insert the KEY/VALUE pair after the first occurrence of a pair whose key
is REFERENCE in ALIST.  Use KEY=? to compare keys."
  (let-values (((before after)
                (break (match-lambda
                        ((k . _)
                         (key=? k reference)))
                       alist)))
    (match after
      ((reference after ...)
       (append before (cons* reference `(,key . ,value) after)))
      (()
       (append before `((,key . ,value)))))))

(define* (alist-replace key value alist #:optional (key=? equal?))
  "Replace the first pair in ALIST whose car is KEY with the KEY/VALUE pair.
An error is raised when no such pair exists."
  (let-values (((before after)
                (break (match-lambda
                        ((k . _)
                         (key=? k key)))
                       alist)))
    (match after
      ((_ after ...)
       (append before (alist-cons key value after))))))


;;;
;;; Text substitution (aka. sed).
;;;

(define (with-atomic-file-replacement file proc)
  "Call PROC with two arguments: an input port for FILE, and an output
port for the file that is going to replace FILE.  Upon success, FILE is
atomically replaced by what has been written to the output port, and
PROC's result is returned."
  (let* ((template (string-append file ".XXXXXX"))
         (out      (mkstemp! template))
         (mode     (stat:mode (stat file))))
    (with-throw-handler #t
      (lambda ()
        (call-with-input-file file
          (lambda (in)
            (let ((result (proc in out)))
              (close out)
              (chmod template mode)
              (rename-file template file)
              result))))
      (lambda (key . args)
        (false-if-exception (delete-file template))))))

(define (substitute file pattern+procs)
  "PATTERN+PROCS is a list of regexp/two-argument procedure.  For each line
of FILE, and for each PATTERN that it matches, call the corresponding PROC
as (PROC LINE MATCHES); PROC must return the line that will be written as a
substitution of the original line."
  (let ((rx+proc  (map (match-lambda
                        (((? regexp? pattern) . proc)
                         (cons pattern proc))
                        ((pattern . proc)
                         (cons (make-regexp pattern regexp/extended)
                               proc)))
                       pattern+procs)))
    (with-atomic-file-replacement file
      (lambda (in out)
        (let loop ((line (read-line in 'concat)))
          (if (eof-object? line)
              #t
              (let ((line (fold (lambda (r+p line)
                                  (match r+p
                                    ((regexp . proc)
                                     (match (list-matches regexp line)
                                       ((and m+ (_ _ ...))
                                        (proc line m+))
                                       (_ line)))))
                                line
                                rx+proc)))
                (display line out)
                (loop (read-line in 'concat)))))))))


(define-syntax let-matches
  ;; Helper macro for `substitute*'.
  (syntax-rules (_)
    ((let-matches index match (_ vars ...) body ...)
     (let-matches (+ 1 index) match (vars ...)
                  body ...))
    ((let-matches index match (var vars ...) body ...)
     (let ((var (match:substring match index)))
       (let-matches (+ 1 index) match (vars ...)
                    body ...)))
    ((let-matches index match () body ...)
     (begin body ...))))

(define-syntax substitute*
  (syntax-rules ()
    "Substitute REGEXP in FILE by the string returned by BODY.  BODY is
evaluated with each MATCH-VAR bound to the corresponding positional regexp
sub-expression.  For example:

  (substitute* file
     ((\"hello\")
      \"good morning\\n\")
     ((\"foo([a-z]+)bar(.*)$\" all letters end)
      (string-append \"baz\" letter end)))

Here, anytime a line of FILE contains \"hello\", it is replaced by \"good
morning\".  Anytime a line of FILE matches the second regexp, ALL is bound to
the complete match, LETTERS is bound to the first sub-expression, and END is
bound to the last one.

When one of the MATCH-VAR is `_', no variable is bound to the corresponding
match substring.

Alternatively, FILE may be a list of file names, in which case they are
all subject to the substitutions."
    ((substitute* file ((regexp match-var ...) body ...) ...)
     (let ()
       (define (substitute-one-file file-name)
         (substitute
          file-name
          (list (cons regexp
                      (lambda (l m+)
                        ;; Iterate over matches M+ and return the
                        ;; modified line based on L.
                        (let loop ((m* m+)  ; matches
                                   (o  0)   ; offset in L
                                   (r  '())) ; result
                          (match m*
                            (()
                             (let ((r (cons (substring l o) r)))
                               (string-concatenate-reverse r)))
                            ((m . rest)
                             (let-matches 0 m (match-var ...)
                               (loop rest
                                     (match:end m)
                                     (cons*
                                      (begin body ...)
                                      (substring l o (match:start m))
                                      r))))))))
                ...)))

       (match file
         ((files (... ...))
          (for-each substitute-one-file files))
         ((? string? f)
          (substitute-one-file f)))))))


;;;
;;; Patching shebangs---e.g., /bin/sh -> /nix/store/xyz...-bash/bin/sh.
;;;

(define* (dump-port in out
                    #:key (buffer-size 16384)
                    (progress (lambda (t k) (k))))
  "Read as much data as possible from IN and write it to OUT, using
chunks of BUFFER-SIZE bytes.  Call PROGRESS after each successful
transfer of BUFFER-SIZE bytes or less, passing it the total number of
bytes transferred and the continuation of the transfer as a thunk."
  (define buffer
    (make-bytevector buffer-size))

  (let loop ((total 0)
             (bytes (get-bytevector-n! in buffer 0 buffer-size)))
    (or (eof-object? bytes)
        (let ((total (+ total bytes)))
          (put-bytevector out buffer 0 bytes)
          (progress total
                    (lambda ()
                      (loop total
                            (get-bytevector-n! in buffer 0 buffer-size))))))))

(define (set-file-time file stat)
  "Set the atime/mtime of FILE to that specified by STAT."
  (utime file
         (stat:atime stat)
         (stat:mtime stat)
         (stat:atimensec stat)
         (stat:mtimensec stat)))

(define patch-shebang
  (let ((shebang-rx (make-regexp "^[[:blank:]]*([[:graph:]]+)(.*)$")))
    (lambda* (file
              #:optional
              (path (search-path-as-string->list (getenv "PATH")))
              #:key (keep-mtime? #t))
      "Replace the #! interpreter file name in FILE by a valid one found in
PATH, when FILE actually starts with a shebang.  Return #t when FILE was
patched, #f otherwise.  When KEEP-MTIME? is true, the atime/mtime of
FILE are kept unchanged."
      (define (patch p interpreter rest-of-line)
        (let* ((template (string-append file ".XXXXXX"))
               (out      (mkstemp! template))
               (st       (stat file))
               (mode     (stat:mode st)))
          (with-throw-handler #t
            (lambda ()
              (format out "#!~a~a~%"
                      interpreter rest-of-line)
              (dump-port p out)
              (close out)
              (chmod template mode)
              (rename-file template file)
              (when keep-mtime?
                (set-file-time file st))
              #t)
            (lambda (key . args)
              (format (current-error-port)
                      "patch-shebang: ~a: error: ~a ~s~%"
                      file key args)
              (false-if-exception (delete-file template))
              #f))))

      (call-with-ascii-input-file file
        (lambda (p)
          (and (eq? #\# (read-char p))
               (eq? #\! (read-char p))
               (let ((line (false-if-exception (read-line p))))
                 (and=> (and line (regexp-exec shebang-rx line))
                        (lambda (m)
                          (let* ((cmd (match:substring m 1))
                                 (bin (search-path path (basename cmd))))
                            (if bin
                                (if (string=? bin cmd)
                                    #f            ; nothing to do
                                    (begin
                                      (format (current-error-port)
                                              "patch-shebang: ~a: changing `~a' to `~a'~%"
                                              file cmd bin)
                                      (patch p bin (match:substring m 2))))
                                (begin
                                  (format (current-error-port)
                                          "patch-shebang: ~a: warning: no binary for interpreter `~a' found in $PATH~%"
                                          file (basename cmd))
                                  #f))))))))))))

(define* (patch-makefile-SHELL file #:key (keep-mtime? #t))
  "Patch the `SHELL' variable in FILE, which is supposedly a makefile.
When KEEP-MTIME? is true, the atime/mtime of FILE are kept unchanged."

  ;; For instance, Gettext-generated po/Makefile.in.in do not honor $SHELL.

  ;; XXX: Unlike with `patch-shebang', FILE is always touched.

  (define (find-shell name)
    (let ((shell
           (search-path (search-path-as-string->list (getenv "PATH"))
                        name)))
      (unless shell
        (format (current-error-port)
                "patch-makefile-SHELL: warning: no binary for shell `~a' found in $PATH~%"
                name))
      shell))

  (let ((st (stat file)))
   (substitute* file
     (("^ *SHELL[[:blank:]]*=[[:blank:]]*([[:graph:]]*/)([[:graph:]]+)[[:blank:]]*" _ dir shell)
      (let* ((old (string-append dir shell))
             (new (or (find-shell shell) old)))
        (unless (string=? new old)
          (format (current-error-port)
                  "patch-makefile-SHELL: ~a: changing `SHELL' from `~a' to `~a'~%"
                  file old new))
        (string-append "SHELL = " new "\n"))))

   (when keep-mtime?
     (set-file-time file st))))

(define* (fold-port-matches proc init pattern port
                            #:optional (unmatched (lambda (_ r) r)))
  "Read from PORT character-by-character; for each match against
PATTERN, call (PROC MATCH RESULT), where RESULT is seeded with INIT.
PATTERN is a list of SRFI-14 char-sets.  Call (UNMATCHED CHAR RESULT)
for each unmatched character."
  (define initial-pattern
    ;; The poor developer's regexp.
    (if (string? pattern)
        (map char-set (string->list pattern))
        pattern))

  (define (get-char p)
    ;; We call it `get-char', but that's really a binary version
    ;; thereof.  (The real `get-char' cannot be used here because our
    ;; bootstrap Guile is hacked to always use UTF-8.)
    (match (get-u8 p)
      ((? integer? x) (integer->char x))
      (x x)))

  ;; Note: we're not really striving for performance here...
  (let loop ((chars   '())
             (pattern initial-pattern)
             (matched '())
             (result  init))
    (cond ((null? chars)
           (loop (list (get-char port))
                 pattern
                 matched
                 result))
          ((null? pattern)
           (loop chars
                 initial-pattern
                 '()
                 (proc (list->string (reverse matched)) result)))
          ((eof-object? (car chars))
           (fold-right unmatched result matched))
          ((char-set-contains? (car pattern) (car chars))
           (loop (cdr chars)
                 (cdr pattern)
                 (cons (car chars) matched)
                 result))
          ((null? matched)                        ; common case
           (loop (cdr chars)
                 pattern
                 matched
                 (unmatched (car chars) result)))
          (else
           (let ((matched (reverse matched)))
             (loop (append (cdr matched) chars)
                   initial-pattern
                   '()
                   (unmatched (car matched) result)))))))

(define* (remove-store-references file
                                  #:optional (store (or (getenv "NIX_STORE")
                                                        "/nix/store")))
  "Remove from FILE occurrences of file names in STORE; return #t when
store paths were encountered in FILE, #f otherwise.  This procedure is
known as `nuke-refs' in Nixpkgs."
  (define pattern
    (let ((nix-base32-chars
           '(#\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9
             #\a #\b #\c #\d #\f #\g #\h #\i #\j #\k #\l #\m #\n
             #\p #\q #\r #\s #\v #\w #\x #\y #\z)))
      `(,@(map char-set (string->list store))
        ,(char-set #\/)
        ,@(make-list 32 (list->char-set nix-base32-chars))
        ,(char-set #\-))))

  (with-fluids ((%default-port-encoding #f))
    (with-atomic-file-replacement file
      (lambda (in out)
        ;; We cannot use `regexp-exec' here because it cannot deal with
        ;; strings containing NUL characters.
        (format #t "removing store references from `~a'...~%" file)
        (setvbuf in _IOFBF 65536)
        (setvbuf out _IOFBF 65536)
        (fold-port-matches (lambda (match result)
                             (put-bytevector out (string->utf8 store))
                             (put-u8 out (char->integer #\/))
                             (put-bytevector out
                                             (string->utf8
                                              "eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee-"))
                             #t)
                           #f
                           pattern
                           in
                           (lambda (char result)
                             (put-u8 out (char->integer char))
                             result))))))

;;; Local Variables:
;;; eval: (put 'call-with-output-file/atomic 'scheme-indent-function 1)
;;; eval: (put 'with-throw-handler 'scheme-indent-function 1)
;;; eval: (put 'let-matches 'scheme-indent-function 3)
;;; eval: (put 'with-atomic-file-replacement 'scheme-indent-function 1)
;;; End:
