;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2014-2021, 2023 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2017 Mathieu Lirzin <mthl@gnu.org>
;;; Copyright © 2017 Christopher Baines <mail@cbaines.net>
;;; Copyright © 2020 Jakub Kądziołka <kuba@kadziolka.net>
;;; Copyright © 2023 Simon Tournier <zimon.toutoune@gmail.com>
;;; Copyright © 2023 Maxim Cournoyer <maxim.cournoyer@gmail.com>
;;;
;;; 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 git-download)
  #:use-module (guix gexp)
  #:use-module (guix store)
  #:use-module (guix monads)
  #:use-module (guix records)
  #:use-module (guix packages)
  #:use-module (guix modules)
  #:use-module ((guix derivations) #:select (raw-derivation))
  #:autoload   (guix build-system gnu) (standard-packages)
  #:autoload   (guix download) (%download-fallback-test)
  #:autoload   (git bindings)   (libgit2-init!)
  #:autoload   (git repository) (repository-open
                                 repository-close!
                                 repository-discover
                                 repository-head
                                 repository-working-directory)
  #:autoload   (git submodule)  (repository-submodules
                                 submodule-lookup
                                 submodule-path)
  #:autoload   (git commit)     (commit-lookup commit-tree)
  #:autoload   (git reference)  (reference-target)
  #:autoload   (git tree)       (tree-list)
  #:use-module (ice-9 match)
  #:use-module (ice-9 vlist)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-34)
  #:use-module (srfi srfi-35)
  #:export (git-reference
            git-reference?
            git-reference-url
            git-reference-commit
            git-reference-recursive?

            git-fetch
            git-fetch/lfs
            git-version
            git-file-name
            git-predicate))

;;; Commentary:
;;;
;;; An <origin> method that fetches a specific commit from a Git repository.
;;; The repository URL and commit hash are specified with a <git-reference>
;;; object.
;;;
;;; Code:

(define-record-type* <git-reference>
  git-reference make-git-reference
  git-reference?
  (url        git-reference-url)
  (commit     git-reference-commit)
  (recursive? git-reference-recursive?   ; whether to recurse into sub-modules
              (default #f)))

(define (git-package)
  "Return the default Git package."
  (let ((distro (resolve-interface '(gnu packages version-control))))
    (module-ref distro 'git-minimal)))

(define (git-lfs-package)
  "Return the default 'git-lfs' package."
  (let ((distro (resolve-interface '(gnu packages version-control))))
    (module-ref distro 'git-lfs)))

(define* (git-fetch/in-band* ref hash-algo hash
                             #:optional name
                             #:key (system (%current-system))
                             (guile (default-guile))
                             (git (git-package))
                             git-lfs)
  "Shared implementation code for git-fetch/in-band & friends.  Refer to their
respective documentation."
  (define inputs
    `(,(or git (git-package))
      ,@(if git-lfs
            (list git-lfs)
            '())
      ,@(if (git-reference-recursive? ref)
            ;; TODO: remove (standard-packages) after
            ;; 48e528a26f9c019eeaccf5e3de3126aa02c98d3b is merged into master;
            ;; currently when doing 'git clone --recursive', we need sed, grep,
            ;; etc. to be available so that 'git submodule' works.
            (map second (standard-packages))

            ;; The 'swh-download' procedure requires tar and gzip.
            (list (module-ref (resolve-interface '(gnu packages compression))
                              'gzip)
                  (module-ref (resolve-interface '(gnu packages base))
                              'tar)))))

  (define guile-json
    (module-ref (resolve-interface '(gnu packages guile)) 'guile-json-4))

  (define guile-lzlib
    (module-ref (resolve-interface '(gnu packages guile)) 'guile-lzlib))

  (define gnutls
    (module-ref (resolve-interface '(gnu packages tls)) 'guile-gnutls))

  (define glibc-locales
    ;; Note: pick the '-final' variant to avoid circular dependency on
    ;; i586-gnu, where 'glibc-utf8-locales' indirectly depends on Git.
    (module-ref (resolve-interface '(gnu packages commencement))
                'glibc-utf8-locales-final))

  (define modules
    (delete '(guix config)
            (source-module-closure '((guix build git)
                                     (guix build utils)))))

  (define build
    (with-imported-modules modules
      (with-extensions (list guile-json gnutls ;for (guix swh)
                             guile-lzlib)
        #~(begin
            (use-modules (guix build git)
                         ((guix build utils)
                          #:select (set-path-environment-variable))
                         (ice-9 match))

            (define lfs?
              (call-with-input-string (getenv "git lfs?") read))

            (define recursive?
              (call-with-input-string (getenv "git recursive?") read))

            ;; Let Guile interpret file names as UTF-8, otherwise
            ;; 'delete-file-recursively' might fail to delete all of
            ;; '.git'--see <https://issues.guix.gnu.org/54893>.
            (setenv "GUIX_LOCPATH"
                    #+(file-append glibc-locales "/lib/locale"))
            (setlocale LC_ALL "en_US.utf8")

            ;; The 'git submodule' commands expects Coreutils, sed, grep,
            ;; etc. to be in $PATH.  This also ensures that git extensions are
            ;; found.
            (set-path-environment-variable "PATH" '("bin") '#+inputs)

            (setvbuf (current-output-port) 'line)
            (setvbuf (current-error-port) 'line)

            (git-fetch-with-fallback (getenv "git url") (getenv "git commit")
                                     #$output
                                     #:lfs? lfs?
                                     #:recursive? recursive?
                                     #:git-command "git")))))

  (mlet %store-monad ((guile (package->derivation (or guile (default-guile))
                                                  system)))
    (gexp->derivation (or name "git-checkout") build

                      ;; Use environment variables and a fixed script name so
                      ;; there's only one script in store for all the
                      ;; downloads.
                      #:script-name "git-download"
                      #:env-vars
                      `(("git url" . ,(match (%download-fallback-test)
                                        ('content-addressed-mirrors
                                         "https://example.org/does-not-exist")
                                        (_
                                         (git-reference-url ref))))
                        ("git commit" . ,(git-reference-commit ref))
                        ("git recursive?" . ,(object->string
                                              (git-reference-recursive? ref)))
                        ("git lfs?" . ,(if git-lfs "#t" "#f")))
                      #:leaked-env-vars '("http_proxy" "https_proxy"
                                          "LC_ALL" "LC_MESSAGES" "LANG"
                                          "COLUMNS")

                      #:system system
                      #:local-build? #t ;don't offload repo cloning
                      #:hash-algo hash-algo
                      #:hash hash
                      #:recursive? #t
                      #:guile-for-build guile)))

(define* (git-fetch/in-band ref hash-algo hash
                             #:optional name
                             #:key (system (%current-system))
                             (guile (default-guile))
                             (git (git-package)))
  "Return a fixed-output derivation that performs a Git checkout of REF, using
GIT and GUILE (thus, said derivation depends on GIT and GUILE).

This method is deprecated in favor of the \"builtin:git-download\" builder.
It will be removed when versions of guix-daemon implementing
\"builtin:git-download\" will be sufficiently widespread."
  (git-fetch/in-band* ref hash-algo hash name
                      #:system system
                      #:guile guile
                      #:git git))

(define* (git-fetch/lfs ref hash-algo hash
                        #:optional name
                        #:key (system (%current-system))
                        (guile (default-guile))
                        (git (git-package))
                        (git-lfs (git-lfs-package)))
  "Like git-fetch/in-band, but with support for the Git Large File
Storage (LFS) extension."
  (git-fetch/in-band* ref hash-algo hash name
                      #:system system
                      #:guile guile
                      #:git git
                      #:git-lfs git-lfs))

(define* (git-fetch/built-in ref hash-algo hash
                             #:optional name
                             #:key (system (%current-system)))
  "Return a fixed-output derivation that performs a Git checkout of REF, using
the \"builtin:git-download\" derivation builder.

This is an \"out-of-band\" download in that the returned derivation does not
explicitly depend on Git, Guile, etc.  Instead, the daemon performs the
download by itself using its own dependencies."
  (raw-derivation (or name "git-checkout") "builtin:git-download" '()
                  #:system system
                  #:hash-algo hash-algo
                  #:hash hash
                  #:recursive? #t
                  #:env-vars
                  `(("url" . ,(object->string
                               (match (%download-fallback-test)
                                 ('content-addressed-mirrors
                                  "https://example.org/does-not-exist")
                                 (_
                                  (git-reference-url ref)))))
                    ("commit" . ,(git-reference-commit ref))
                    ("recursive?" . ,(object->string
                                      (git-reference-recursive? ref))))
                  #:leaked-env-vars '("http_proxy" "https_proxy"
                                      "LC_ALL" "LC_MESSAGES" "LANG"
                                      "COLUMNS")
                  #:local-build? #t))

(define built-in-builders*
  (store-lift built-in-builders))

(define* (git-fetch ref hash-algo hash
                    #:optional name
                    #:key (system (%current-system))
                    guile git)
  "Return a fixed-output derivation that fetches REF, a <git-reference>
object.  The output is expected to have recursive hash HASH of type
HASH-ALGO (a symbol).  Use NAME as the file name, or a generic name if #f."
  (mlet %store-monad ((builtins (built-in-builders*)))
    (if (member "git-download" builtins)
        (git-fetch/built-in ref hash-algo hash name
                            #:system system)
        (git-fetch/in-band ref hash-algo hash name
                           #:system system
                           #:guile guile
                           #:git git))))

(define (git-version version revision commit)
  "Return the version string for packages using git-download."
  ;; git-version is almost exclusively executed while modules are being loaded.
  ;; This makes any errors hide their backtrace. Avoid the mysterious error
  ;; "Value out of range 0 to N: 7" when the commit ID is too short, which
  ;; can happen, for example, when the user swapped the revision and commit
  ;; arguments by mistake.
  (when (< (string-length commit) 7)
    (raise
      (condition
        (&message (message "git-version: commit ID unexpectedly short")))))
  (string-append version "-" revision "." (string-take commit 7)))

(define (git-file-name name version)
  "Return the file-name for packages using git-download."
  (string-append name "-" version "-checkout"))


;;;
;;; 'git-predicate'.
;;;

(define* (git-file-list directory #:optional prefix #:key (recursive? #t))
  "Return the list of files checked in in the Git repository at DIRECTORY.
The result is similar to that of the 'git ls-files' command, except that it
also includes directories, not just regular files.

When RECURSIVE? is true, also list files in submodules, similar to the 'git
ls-files --recurse-submodules' command.  This is enabled by default.

The returned file names are relative to DIRECTORY, which is not necessarily
the root of the checkout.  If a PREFIX is provided, it is prepended to each
file name."
  (let* (;; 'repository-working-directory' always returns a trailing "/",
         ;; so add one here to ease the comparisons below.
         (directory  (string-append (canonicalize-path directory) "/"))
         (dot-git    (repository-discover directory))
         (repository (repository-open dot-git))
         (workdir    (repository-working-directory repository))
         (head       (repository-head repository))
         (oid        (reference-target head))
         (commit     (commit-lookup repository oid))
         (tree       (commit-tree commit))
         (files      (tree-list tree))
         (submodules (if recursive?
                         (map (lambda (name)
                                (submodule-path
                                 (submodule-lookup repository name)))
                              (repository-submodules repository))
                         '()))
         (relative      (and (not (string=? workdir directory))
                             (string-drop directory (string-length workdir))))
         (included?     (lambda (path)
                          (or (not relative)
                              (string-prefix? relative path))))
         (make-relative (lambda (path)
                          (if relative
                              (string-drop path (string-length relative))
                              path)))
         (add-prefix    (lambda (path)
                          (if prefix
                              (string-append prefix "/" path)
                              path)))
         (rectify       (compose add-prefix make-relative)))
    (repository-close! repository)
    (append
     (if (or relative prefix)
         (filter-map (lambda (file)
                       (and (included? file)
                            (rectify file)))
                     files)
         files)
     (append-map (lambda (submodule)
                   (if (included? submodule)
                       (git-file-list
                        (string-append workdir submodule)
                        (rectify submodule))
                       '()))
                 submodules))))

(define* (git-predicate directory #:key (recursive? #t))
  "Return a predicate that returns true if a file is part of the Git checkout
living at DIRECTORY.  If DIRECTORY does not lie within a Git checkout, and
upon Git errors, return #f instead of a predicate.

When RECURSIVE? is true, the predicate also returns true if a file is part of
any Git submodule under DIRECTORY.  This is enabled by default.

The returned predicate takes two arguments FILE and STAT where FILE is an
absolute file name and STAT is the result of 'lstat'."
  (libgit2-init!)
  (catch 'git-error
    (lambda ()
      (let* ((files  (git-file-list directory #:recursive? recursive?))
             (inodes (fold (lambda (file result)
                             (let* ((file (string-append directory "/" file))
                                    (stat (false-if-exception (lstat file))))
                               ;; Ignore FILE if it has been deleted.
                               (if stat
                                   (vhash-consv (stat:ino stat) (stat:dev stat)
                                                result)
                                   result)))
                           vlist-null
                           files)))
        (lambda (file stat)
          ;; Comparing file names is always tricky business so we rely on inode
          ;; numbers instead.
          (match (vhash-assv (stat:ino stat) inodes)
            ((_ . dev) (= dev (stat:dev stat)))
            (#f        #f)))))
    (const #f)))

;;; git-download.scm ends here
