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;;; The Inevitable Game
;;; Copyright © 2018 David Thompson <davet@gnu.org>
;;; Copyright © 2021 Ricardo Wurmus <rekado@elephly.net>
;;;
;;; This program 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.
;;;
;;; This program 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 this program. If not, see
;;; <http://www.gnu.org/licenses/>.
(define-module (engine assets)
#:use-module (ice-9 ftw)
#:use-module (ice-9 match)
#:use-module (engine inotify)
#:use-module (oop goops)
#:use-module (srfi srfi-1)
#:use-module (config)
#:export (<asset>
artifact
file-name
loader
args
watch-asset-directory
reload-modified-assets
asset-ref
define-asset))
(define-class <asset> ()
;; class slots for asset cache and live reloading
(inotify #:allocation #:class #:init-form #f)
;; file-name -> assets mapping
(asset-map #:allocation #:class #:init-form (make-hash-table))
;; args -> artifact mapping
(artifact-cache #:allocation #:class #:init-form (make-weak-value-hash-table))
(watches #:allocation #:class #:init-form '())
;; instance slots
(artifact #:accessor artifact #:init-form #f)
(file-name #:getter file-name #:init-keyword #:file-name)
(loader #:getter loader #:init-keyword #:loader)
(loader-args #:getter loader-args #:init-form '()
#:init-keyword #:loader-args)
(watch #:accessor watch #:init-form #f))
(define (absolute-file-name file-name)
(if (absolute-file-name? file-name)
file-name
(string-append %assets-root "/" file-name)))
(define-method (initialize (asset <asset>) args)
(next-method)
(slot-set! asset 'file-name (absolute-file-name (file-name asset)))
(let* ((asset-map (class-slot-ref <asset> 'asset-map))
;; Using a weak key hash table instead of a list to keep
;; track of all the assets that are associated with a file.
;; This way, their presence in the cache won't save them from
;; the GC.
(sub-table (or (hash-ref asset-map (file-name asset))
(let ((wt (make-weak-key-hash-table)))
(hash-set! asset-map (file-name asset) wt)
wt))))
(hash-set! sub-table asset asset)))
(define (asset-inotify)
(class-slot-ref <asset> 'inotify))
(define (asset-map)
(class-slot-ref <asset> 'asset-map))
(define (artifact-cache)
(class-slot-ref <asset> 'artifact-cache))
(define (asset-watches)
(class-slot-ref <asset> 'watches))
(define (directory-watched? dir)
(find (lambda (watch)
(string=? (inotify-watch-file-name watch) dir))
(asset-watches)))
(define (watch-recursively dir)
(let ((inotify (asset-inotify)))
(file-system-fold (const #t) ; enter?
(lambda (name stat result) result) ; leaf
(lambda (name stat result) ; down
(cons (inotify-add-watch! inotify name '(create close-write moved-to))
result))
(lambda (name stat result) result) ; up
(lambda (name stat result) result) ; skip
(lambda (name stat errno result) result) ; error
'()
dir)))
(define (watch-asset-directory dir)
;; Lazily activate inotify.
(unless (asset-inotify)
(class-slot-set! <asset> 'inotify (make-inotify)))
(unless (directory-watched? dir)
(class-slot-set! <asset> 'watches
(append (watch-recursively dir)
(asset-watches)))))
(define (reload-modified-assets)
(let ((inotify (asset-inotify)))
(when inotify
(while (inotify-pending-events? inotify)
(let* ((event (inotify-read-event inotify))
(type (inotify-event-type event))
(file-name (string-append (inotify-watch-file-name
(inotify-event-watch event))
"/"
(inotify-event-file-name event)))
(assets (hash-ref (asset-map) file-name)))
(cond
((and assets (or (eq? type 'close-write) (eq? type 'moved-to)))
;; Expire everything from cache, then reload.
(hash-for-each (lambda (key asset)
(expire-cached-artifact (cache-key asset)))
assets)
(hash-for-each (lambda (key asset)
(load! asset))
assets))
;; ooh, a new directory to watch!
((eq? type 'create)
(watch-recursively file-name))))))))
(define (cache-key asset)
(list (loader asset) (file-name asset) (loader-args asset)))
(define (cache-artifact key artifact)
(hash-set! (artifact-cache) key artifact))
(define (expire-cached-artifact key)
(hash-remove! (artifact-cache) key))
(define (fetch-cached-artifact key)
(hash-ref (artifact-cache) key))
(define (load-artifact cache-key loader file-name loader-args)
(or (fetch-cached-artifact cache-key)
(let ((artifact (apply loader file-name loader-args)))
(cache-artifact cache-key artifact)
artifact)))
(define (load! asset)
(let ((thing (load-artifact (cache-key asset)
(loader asset)
(file-name asset)
(loader-args asset))))
(set! (artifact asset) thing)
thing))
(define-method (asset-ref (asset <asset>))
(or (artifact asset) (load! asset)))
(define-method (asset-ref anything)
anything)
(define-syntax-rule (define-asset name
(loader file-name loader-args ...))
(define name
(make <asset>
#:file-name file-name
#:loader loader
#:loader-args (list loader-args ...))))
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