Implement editor.uploadFile syscall (#570)

* Implement editor.attachFile syscall

* Refactor attachFile to uploadFile

returns a promise with an UploadFile now

* Fix style

* Reject promise with errors

* Another code style fix

---------

Co-authored-by: prcrst <p-github@prcr.st>

web/syscalls/editor.ts

@@ -12,6 +12,7 @@ import {
 } from "../deps.ts";
 import { SysCallMapping } from "../../plugos/system.ts";
 import type { FilterOption } from "../types.ts";
+import { UploadFile } from "../../plug-api/types.ts";
 
 export function editorSyscalls(editor: Client): SysCallMapping {
   const syscalls: SysCallMapping = {
@@ -61,6 +62,46 @@ export function editorSyscalls(editor: Client): SysCallMapping {
       link.download = filename;
       link.click();
     },
+    "editor.uploadFile": (
+      _ctx,
+      accept?: string,
+      capture?: string
+    ): Promise<UploadFile> => {
+      return new Promise<UploadFile>((resolve, reject) => {
+        const input = document.createElement("input");
+        input.type = "file";
+        if (accept) {
+          input.accept = accept;
+        }
+        if (capture) {
+          input.capture = capture;
+        }
+
+        input.onchange = () => {
+          const file = input.files?.item(0);
+          if (!file) {
+            reject(new Error("No file found"));
+          } else {
+            var reader = new FileReader();
+            reader.readAsArrayBuffer(file);
+            reader.onloadend = async (evt) => {
+              if (evt.target?.readyState == FileReader.DONE) {
+                const arrayBuffer = evt.target.result;
+                resolve({
+                  name: file.name,
+                  content: new Uint8Array(await file.arrayBuffer())
+                });
+              }
+            };
+            reader.onabort = (e) => { reject(e) };
+            reader.onerror = (e) => { reject(e) };
+          }
+        }
+        input.onabort = (e) => { reject(e) };
+
+        input.click();
+      });
+    },
     "editor.flashNotification": (
       _ctx,
       message: string,