(core) move home server into core

Summary: This moves enough server material into core to run a home server.  The data engine is not yet incorporated (though in manual testing it works when ported).

Test Plan: existing tests pass

Reviewers: dsagal

Reviewed By: dsagal

Differential Revision: https://phab.getgrist.com/D2552

app/server/lib/places.ts

@@ -0,0 +1,46 @@
+/**
+ * Utilities related to the layout of the application and where parts are stored.
+ */
+
+import * as path from 'path';
+
+/**
+ * codeRoot is the directory containing ./app with all the JS code.
+ */
+export const codeRoot = path.dirname(path.dirname(path.dirname(__dirname)));
+
+/**
+ * Returns the appRoot, i.e. the directory containing ./sandbox, ./node_modules, ./ormconfig.js,
+ * etc.
+ */
+export function getAppRoot(): string {
+  if (codeRoot.endsWith('/_build/core')) { return path.dirname(path.dirname(codeRoot)); }
+  return codeRoot.endsWith('/_build') ? path.dirname(codeRoot) : codeRoot;
+}
+
+/**
+ * When packaged as an electron application, most files are stored in a .asar
+ * archive.  Most, but not all.  This method takes the "application root"
+ * which is that .asar file in packaged form, and returns a directory where
+ * remaining files are available on the regular filesystem.
+ */
+export function getUnpackedAppRoot(appRoot: string): string {
+  return path.resolve(path.dirname(appRoot), path.basename(appRoot, '.asar'));
+}
+
+/**
+ * Return the correct root for a given subdirectory.
+ */
+export function getAppRootFor(appRoot: string, subdirectory: string): string {
+  if (['sandbox', 'plugins', 'public-api'].includes(subdirectory)) {
+    return getUnpackedAppRoot(appRoot);
+  }
+  return appRoot;
+}
+
+/**
+ * Return the path to a given subdirectory, from the correct appRoot.
+ */
+export function getAppPathTo(appRoot: string, subdirectory: string): string {
+  return path.resolve(getAppRootFor(appRoot, subdirectory), subdirectory);
+}