;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2017, 2019 Caleb Ristvedt <caleb.ristvedt@cune.org>
;;; Copyright © 2018, 2020, 2021 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2020 Jan (janneke) Nieuwenhuizen <janneke@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 store database)
  #:use-module (sqlite3)
  #:use-module (guix config)
  #:use-module (guix serialization)
  #:use-module (guix store deduplication)
  #:use-module (guix base16)
  #:use-module (guix progress)
  #:use-module (guix build syscalls)
  #:use-module ((guix build utils)
                #:select (mkdir-p executable-file?))
  #:use-module (guix build store-copy)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-11)
  #:use-module (srfi srfi-19)
  #:use-module (srfi srfi-26)
  #:use-module (rnrs io ports)
  #:use-module (ice-9 match)
  #:use-module (system foreign)
  #:export (sql-schema
            %default-database-file
            store-database-file
            call-with-database
            with-database
            path-id
            sqlite-register
            register-items
            %epoch
            reset-timestamps))

;;; Code for working with the store database directly.

(define sql-schema
  ;; Name of the file containing the SQL scheme or #f.
  (make-parameter #f))

(define* (store-database-directory #:key prefix state-directory)
  "Return the store database directory, taking PREFIX and STATE-DIRECTORY into
account when provided."
  ;; Priority for options: first what is given, then environment variables,
  ;; then defaults. %state-directory, %store-directory, and
  ;; %store-database-directory already handle the "environment variables /
  ;; defaults" question, so we only need to choose between what is given and
  ;; those.
  (cond (state-directory
         (string-append state-directory "/db"))
        (prefix
         (string-append prefix %localstatedir "/guix/db"))
        (else
         %store-database-directory)))

(define* (store-database-file #:key prefix state-directory)
  "Return the store database file name, taking PREFIX and STATE-DIRECTORY into
account when provided."
  (string-append (store-database-directory #:prefix prefix
                                           #:state-directory state-directory)
                 "/db.sqlite"))

(define (initialize-database db)
  "Initializing DB, an empty database, by creating all the tables and indexes
as specified by SQL-SCHEMA."
  (define schema
    (or (sql-schema)
        (search-path %load-path "guix/store/schema.sql")))

  (sqlite-exec db (call-with-input-file schema get-string-all)))

(define* (call-with-database file proc #:key (wal-mode? #t))
  "Pass PROC a database record corresponding to FILE.  If FILE doesn't exist,
create it and initialize it as a new database.  Unless WAL-MODE? is set to #f,
set journal_mode=WAL."
  (let ((new? (and (not (file-exists? file))
                   (begin
                     (mkdir-p (dirname file))
                     #t)))
        (db   (sqlite-open file)))
    ;; Using WAL breaks for the Hurd <https://bugs.gnu.org/42151>.
    (when wal-mode?
      ;; Turn DB in "write-ahead log" mode, which should avoid SQLITE_LOCKED
      ;; errors when we have several readers: <https://www.sqlite.org/wal.html>.
      (sqlite-exec db "PRAGMA journal_mode=WAL;"))

    ;; Install a busy handler such that, when the database is locked, sqlite
    ;; retries until 30 seconds have passed, at which point it gives up and
    ;; throws SQLITE_BUSY.
    (sqlite-exec db "PRAGMA busy_timeout = 30000;")

    (dynamic-wind noop
                  (lambda ()
                    (when new?
                      (initialize-database db))
                    (proc db))
                  (lambda ()
                    (sqlite-close db)))))

;; XXX: missing in guile-sqlite3@0.1.2
(define SQLITE_BUSY 5)

(define (call-with-SQLITE_BUSY-retrying thunk)
  "Call THUNK, retrying as long as it exits abnormally due to SQLITE_BUSY
errors."
  (catch 'sqlite-error
    thunk
    (lambda (key who code errmsg)
      (if (= code SQLITE_BUSY)
          (call-with-SQLITE_BUSY-retrying thunk)
          (throw key who code errmsg)))))

(define* (call-with-transaction db proc #:key restartable?)
  "Start a transaction with DB and run PROC.  If PROC exits abnormally, abort
the transaction, otherwise commit the transaction after it finishes.
RESTARTABLE? may be set to a non-#f value when it is safe to run PROC multiple
times.  This may reduce contention for the database somewhat."
  (define (exec sql)
    (with-statement db sql stmt
      (sqlite-fold cons '() stmt)))
  ;; We might use begin immediate here so that if we need to retry, we figure
  ;; that out immediately rather than because some SQLITE_BUSY exception gets
  ;; thrown partway through PROC - in which case the part already executed
  ;; (which may contain side-effects!) might have to be executed again for
  ;; every retry.
  (exec (if restartable? "begin;" "begin immediate;"))
  (catch #t
    (lambda ()
      (let-values ((result (proc)))
        (exec "commit;")
        (apply values result)))
    (lambda args
      ;; The roll back may or may not have occurred automatically when the
      ;; error was generated. If it has occurred, this does nothing but signal
      ;; an error. If it hasn't occurred, this needs to be done.
      (false-if-exception (exec "rollback;"))
      (apply throw args))))

(define* (call-with-savepoint db proc
                              #:optional (savepoint-name "SomeSavepoint"))
  "Call PROC after creating a savepoint named SAVEPOINT-NAME.  If PROC exits
abnormally, rollback to that savepoint.  In all cases, remove the savepoint
prior to returning."
  (define (exec sql)
    (with-statement db sql stmt
      (sqlite-fold cons '() stmt)))

  (dynamic-wind
    (lambda ()
      (exec (string-append "SAVEPOINT " savepoint-name ";")))
    (lambda ()
      (catch #t
        proc
        (lambda args
          (exec (string-append "ROLLBACK TO " savepoint-name ";"))
          (apply throw args))))
    (lambda ()
      (exec (string-append "RELEASE " savepoint-name ";")))))

(define* (call-with-retrying-transaction db proc #:key restartable?)
  (call-with-SQLITE_BUSY-retrying
   (lambda ()
     (call-with-transaction db proc #:restartable? restartable?))))

(define* (call-with-retrying-savepoint db proc
                                       #:optional (savepoint-name
                                                   "SomeSavepoint"))
  (call-with-SQLITE_BUSY-retrying
   (lambda ()
     (call-with-savepoint db proc savepoint-name))))

(define %default-database-file
  ;; Default location of the store database.
  (string-append %store-database-directory "/db.sqlite"))

(define-syntax with-database
  (syntax-rules ()
    "Open DB from FILE and close it when the dynamic extent of EXP... is left.
If FILE doesn't exist, create it and initialize it as a new database.  Pass
#:wal-mode? to call-with-database."
    ((_ file db #:wal-mode? wal-mode? exp ...)
     (call-with-database file (lambda (db) exp ...) #:wal-mode? wal-mode?))
    ((_ file db exp ...)
     (call-with-database file (lambda (db) exp ...)))))

(define (call-with-statement db sql proc)
  (let ((stmt (sqlite-prepare db sql #:cache? #t)))
    (dynamic-wind
      (const #t)
      (lambda ()
        (proc stmt))
      (lambda ()
        (sqlite-finalize stmt)))))

(define-syntax-rule (with-statement db sql stmt exp ...)
  "Run EXP... with STMT bound to a prepared statement corresponding to the sql
string SQL for DB."
  (call-with-statement db sql
                       (lambda (stmt) exp ...)))

(define (last-insert-row-id db)
  ;; XXX: (sqlite3) currently lacks bindings for 'sqlite3_last_insert_rowid'.
  ;; Work around that.
  (with-statement db "SELECT last_insert_rowid();" stmt
    (match (sqlite-fold cons '() stmt)
      ((#(id)) id)
      (_ #f))))

(define path-id-sql
  "SELECT id FROM ValidPaths WHERE path = :path")

(define* (path-id db path)
  "If PATH exists in the 'ValidPaths' table, return its numerical
identifier.  Otherwise, return #f."
  (with-statement db path-id-sql stmt
    (sqlite-bind-arguments stmt #:path path)
    (match (sqlite-fold cons '() stmt)
      ((#(id) . _) id)
      (_ #f))))

(define update-sql
  "UPDATE ValidPaths SET hash = :hash, registrationTime = :time, deriver =
:deriver, narSize = :size WHERE id = :id")

(define insert-sql
  "INSERT INTO ValidPaths (path, hash, registrationTime, deriver, narSize)
VALUES (:path, :hash, :time, :deriver, :size)")

(define-inlinable (assert-integer proc in-range? key number)
  (unless (integer? number)
    (throw 'wrong-type-arg proc
           "Wrong type argument ~A: ~S" (list key number)
           (list number)))
  (unless (in-range? number)
    (throw 'out-of-range proc
           "Integer ~A out of range: ~S" (list key number)
           (list number))))

(define* (update-or-insert db #:key path deriver hash nar-size time)
  "The classic update-if-exists and insert-if-doesn't feature that sqlite
doesn't exactly have... they've got something close, but it involves deleting
and re-inserting instead of updating, which causes problems with foreign keys,
of course. Returns the row id of the row that was modified or inserted."

  ;; Make sure NAR-SIZE is valid.
  (assert-integer "update-or-insert" positive? #:nar-size nar-size)
  (assert-integer "update-or-insert" (cut >= <> 0) #:time time)

  ;; It's important that querying the path-id and the insert/update operation
  ;; take place in the same transaction, as otherwise some other
  ;; process/thread/fiber could register the same path between when we check
  ;; whether it's already registered and when we register it, resulting in
  ;; duplicate paths (which, due to a 'unique' constraint, would cause an
  ;; exception to be thrown). With the default journaling mode this will
  ;; prevent writes from occurring during that sensitive time, but with WAL
  ;; mode it will instead arrange to return SQLITE_BUSY when a write occurs
  ;; between the start of a read transaction and its upgrading to a write
  ;; transaction (see https://sqlite.org/rescode.html#busy_snapshot).
  ;; Experimentally, it seems this SQLITE_BUSY will ignore a busy_timeout and
  ;; immediately return (makes sense, since waiting won't change anything).

  ;; Note that when that kind of SQLITE_BUSY error is returned, it will keep
  ;; being returned every time we try to upgrade the same outermost
  ;; transaction to a write transaction.  So when retrying, we have to restart
  ;; the *outermost* write transaction.  We can't inherently tell whether
  ;; we're the outermost write transaction, so we leave the retry-handling to
  ;; the caller.
  (call-with-savepoint db
    (lambda ()
      (let ((id (path-id db path)))
        (if id
            (with-statement db update-sql stmt
              (sqlite-bind-arguments stmt #:id id
                                     #:deriver deriver
                                     #:hash hash #:size nar-size #:time time)
              (sqlite-fold cons '() stmt))
            (with-statement db insert-sql stmt
              (sqlite-bind-arguments stmt
                                     #:path path #:deriver deriver
                                     #:hash hash #:size nar-size #:time time)
              (sqlite-fold cons '() stmt)))
        (last-insert-row-id db)))))

(define add-reference-sql
  "INSERT OR REPLACE INTO Refs (referrer, reference) VALUES (:referrer, :reference);")

(define (add-references db referrer references)
  "REFERRER is the id of the referring store item, REFERENCES is a list
ids of items referred to."
  (with-statement db add-reference-sql stmt
    (for-each (lambda (reference)
                (sqlite-reset stmt)
                (sqlite-bind-arguments stmt #:referrer referrer
                                       #:reference reference)
                (sqlite-fold cons '() stmt))
              references)))

(define (timestamp)
  "Return a timestamp, either the current time of SOURCE_DATE_EPOCH."
  (match (getenv "SOURCE_DATE_EPOCH")
    (#f
     (current-time time-utc))
    ((= string->number seconds)
     (if seconds
         (make-time time-utc 0 seconds)
         (current-time time-utc)))))

(define* (sqlite-register db #:key path (references '())
                          deriver hash nar-size
                          (time (timestamp)))
  "Registers this stuff in DB.  PATH is the store item to register and
REFERENCES is the list of store items PATH refers to; DERIVER is the '.drv'
that produced PATH, HASH is the base16-encoded Nix sha256 hash of
PATH (prefixed with \"sha256:\"), and NAR-SIZE is the size in bytes PATH after
being converted to nar form.  TIME is the registration time to be recorded in
the database or #f, meaning \"right now\".

Every store item in REFERENCES must already be registered."
  (let ((id (update-or-insert db #:path path
                              #:deriver deriver
                              #:hash hash
                              #:nar-size nar-size
                              #:time (time-second time))))
    ;; Call 'path-id' on each of REFERENCES.  This ensures we get a
    ;; "non-NULL constraint" failure if one of REFERENCES is unregistered.
    (add-references db id
                    (map (cut path-id db <>) references))))

\f
;;;
;;; High-level interface.
;;;

(define* (reset-timestamps file #:key preserve-permissions?)
  "Reset the modification time on FILE and on all the files it contains, if
it's a directory.  Canonicalize file permissions unless PRESERVE-PERMISSIONS?
is true."
  ;; Note: We're resetting to one second after the Epoch like 'guix-daemon'
  ;; has always done.
  (let loop ((file file)
             (type (stat:type (lstat file))))
    (case type
      ((directory)
       (unless preserve-permissions?
         (chmod file #o555))
       (utime file 1 1 0 0)
       (let ((parent file))
         (for-each (match-lambda
                     (("." . _) #f)
                     ((".." . _) #f)
                     ((file . properties)
                      (let ((file (string-append parent "/" file)))
                        (loop file
                              (match (assoc-ref properties 'type)
                                ((or 'unknown #f)
                                 (stat:type (lstat file)))
                                (type type))))))
                   (scandir* parent))))
      ((symlink)
       (utime file 1 1 0 0 AT_SYMLINK_NOFOLLOW))
      (else
       (unless preserve-permissions?
         (chmod file (if (executable-file? file) #o555 #o444)))
       (utime file 1 1 0 0)))))

(define %epoch
  ;; When it all began.
  (make-time time-utc 0 1))

(define* (register-items db items
                         #:key prefix
                         (registration-time (timestamp))
                         (log-port (current-error-port)))
  "Register all of ITEMS, a list of <store-info> records as returned by
'read-reference-graph', in DB.  ITEMS must be in topological order (with
leaves first.)  REGISTRATION-TIME must be the registration time to be recorded
in the database; #f means \"now\".  Write a progress report to LOG-PORT.  All
of ITEMS must be protected from GC and locked during execution of this,
typically by adding them as temp-roots."
  (define store-dir
    (if prefix
        (string-append prefix %storedir)
        %store-directory))

  (define (register db item)
    (define to-register
      (if prefix
          (string-append %storedir "/" (basename (store-info-item item)))
          ;; note: we assume here that if path is, for example,
          ;; /foo/bar/gnu/store/thing.txt and prefix isn't given, then an
          ;; environment variable has been used to change the store directory
          ;; to /foo/bar/gnu/store, since otherwise real-path would end up
          ;; being /gnu/store/thing.txt, which is probably not the right file
          ;; in this case.
          (store-info-item item)))

    (define real-file-name
      (string-append store-dir "/" (basename (store-info-item item))))


    ;; When TO-REGISTER is already registered, skip it.  This makes a
    ;; significant differences when 'register-closures' is called
    ;; consecutively for overlapping closures such as 'system' and 'bootcfg'.
    (unless (path-id db to-register)
      (let-values (((hash nar-size) (nar-sha256 real-file-name)))
        (call-with-retrying-transaction db
          (lambda ()
            (sqlite-register db #:path to-register
                             #:references (store-info-references item)
                             #:deriver (store-info-deriver item)
                             #:hash (string-append
                                     "sha256:"
                                     (bytevector->base16-string hash))
                             #:nar-size nar-size
                             #:time registration-time))))))

  (let* ((prefix   (format #f "registering ~a items" (length items)))
         (progress (progress-reporter/bar (length items)
                                          prefix log-port)))
    (call-with-progress-reporter progress
      (lambda (report)
        (for-each (lambda (item)
                    (register db item)
                    (report))
                  items)))))