Move export into task system

I'm very pleased with how this turned out. In my tests, the export
function took ~150ms, and opening the file explorer took ~22ms. This
completely offloads that work to keep the UI responsive.

src/Export.cake

@@ -1,10 +1,13 @@
 ;; This file is somewhat misnamed. It handles taking categorized entries and processing them into a
 ;; format which can be exported. It also helps in cases where pure entries are desired
 (import "FileHelper.cake" "FileSystem.cake"
-        "Dictionary.cake" "DynamicArray.cake"
+        "Dictionary.cake" "DynamicArray.cake" "TaskSystem.cake"
         "Utilities.cake"
         &comptime-only "CHelpers.cake")
 
+;; TODO Need infect
+(add-c-search-directory-module "Dependencies/enkiTS/src")
+
 (c-import "<cstdio>" "<cassert>")
 
 (forward-declare (struct directory-entry-userdata)
@@ -177,8 +180,8 @@
   (dynarray-free child-entries)
   (set child-entries null))
 
-(defun export-category-paths (entries (* directory-entry-userdata) ;; strdict
-                              categories (* category-spec)) ;; dictionary
+(def-task export-category-paths (entries (* directory-entry-userdata) ;; strdict
+                                 categories (* category-spec)) ;; dictionary
   (var num-entries (unsigned int) (strdict-length entries))
   (unless num-entries
     (return))
@@ -258,3 +261,42 @@
       (fclose (path category-file > file-handle))))
   (dynarray-free category-out-files)
   (dynarray-free sorted-entries))
+
+(var g-is-export-running bool false)
+
+(def-task on-export-complete (entries (* directory-entry-userdata) ;; strdict
+                              categories (* category-spec)) ;; dictionary
+  (dict-free entries)
+  (strdict-free categories)
+  (fprintf stderr "Finished export\n")
+  (set g-is-export-running false))
+
+;; Do this on a separate thread because it takes a while. A quick scan of SDL code seems to suggest
+;; this is fine. This isn't in on-export-complete because that's only on the main thread
+(def-task open-userdata-system-file-explorer (should-open bool)
+  (when should-open
+    (open-system-file-explorer g-userdata-output-dir)))
+
+(defun export-category-paths-start (entries (* directory-entry-userdata) ;; strdict
+                                    categories (* category-spec) ;; dictionary
+                                    open-file-explorer-on-complete bool)
+  ;; Only one can be running at a time. TODO: User feedback?
+  (when g-is-export-running
+    (fprintf stderr "Already running an export job\n")
+    (return))
+
+  ;; TODO: Use Introspection to more easily copy
+  (var copied-entries (* directory-entry-userdata) null) ;; strdict
+  (var copied-categories (* category-spec) null) ;; dictionary
+  (each-item-in-dict entries i entry (* directory-entry-userdata)
+    (strdict-set-struct copied-entries (deref entry)))
+  (each-item-in-dict categories i category (* category-spec)
+    (dict-set-struct copied-categories (deref category)))
+
+  (set g-is-export-running true)
+  (task-system-execute
+   (export-category-paths copied-entries copied-categories)
+   (parallel
+    (open-userdata-system-file-explorer open-file-explorer-on-complete)
+    (on-export-complete :pin-to-main-thread
+                        copied-entries copied-categories))))

src/FileHelper.cake

@@ -458,7 +458,7 @@
   (path-append-divider-if-necessary path)
   (dynstring-append path file-or-dir-name))
 
-(defun-local open-system-file-explorer (in-directory (* (const char)))
+(defun open-system-file-explorer (in-directory (* (const char)))
   (var url-current-directory ([] 1024 char) (array 0))
   (snprintf url-current-directory (sizeof url-current-directory) "file://%s"
             in-directory)
@@ -1026,9 +1026,7 @@
 
   (var-static open-explorer-on-export bool true)
   (when (imgui-call Button "Export all to text")
-    (export-category-paths g-userdata-dict g-categories-dict)
-    (when open-explorer-on-export
-      (open-system-file-explorer g-userdata-output-dir)))
+    (export-category-paths-start g-userdata-dict g-categories-dict open-explorer-on-export))
   (when (imgui-call IsItemHovered)
     (imgui-call BeginTooltip)
     (imgui-call Text "Export a list of all files and directories in each category.")