(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/manifest.ts

@@ -0,0 +1,79 @@
+import {BarePlugin} from 'app/plugin/PluginManifest';
+import PluginManifestTI from 'app/plugin/PluginManifest-ti';
+import * as fse from 'fs-extra';
+import * as yaml from 'js-yaml';
+import * as path from 'path';
+import {createCheckers} from "ts-interface-checker";
+
+const manifestChecker = createCheckers(PluginManifestTI).BarePlugin;
+/**
+ * Validate the manifest and generate appropriate errors.
+ */
+// TODO: should validate that the resources referenced within the manifest are located within the
+// plugin folder
+// TODO: Need a comprehensive test that triggers every notices;
+function isValidManifest(manifest: any, notices: string[]): boolean {
+  if (!manifest) {
+    notices.push("missing manifest");
+    return false;
+  }
+  try {
+    manifestChecker.check(manifest);
+  } catch (e) {
+    notices.push(`Invalid manifest: ${e.message}`);
+    return false;
+  }
+  try {
+    manifestChecker.strictCheck(manifest);
+  } catch (e) {
+    notices.push(`WARNING: ${e.message}` );
+    /* but don't fail */
+  }
+  if (Object.keys(manifest.contributions).length === 0) {
+    notices.push("WARNING: no valid contributions");
+  }
+  return true;
+}
+
+/**
+ * A ManifestError is an error caused by a wrongly formatted manifest or missing manifest. The
+ * `notices` property holds a user-friendly description of the error(s).
+ */
+export class ManifestError extends Error {
+  constructor(public notices: string[], message: string = "") {
+    super(message);
+  }
+}
+
+/**
+ * Parse the manifest. Look first for a Yaml manifest and then if missing for a Json manifest.
+ */
+export async function readManifest(pluginPath: string): Promise<BarePlugin> {
+  const notices: string[] = [];
+  const manifest = await _readManifest(pluginPath);
+  if (isValidManifest(manifest, notices)) {
+    return manifest as BarePlugin;
+  }
+  throw new ManifestError(notices);
+}
+
+async function _readManifest(pluginPath: string): Promise<object> {
+  try {
+    return yaml.safeLoad(await readManifestFile("yml"));
+  } catch (e) {
+    if (e instanceof yaml.YAMLException) {
+      throw new Error('error parsing yaml manifest: ' + e.message);
+    }
+  }
+  try {
+    return JSON.parse(await readManifestFile("json"));
+  } catch (e) {
+    if (e instanceof SyntaxError) {
+      throw new Error('error parsing json manifest' + e.message);
+    }
+    throw new Error('cannot read manifest file: ' + e.message);
+  }
+  async function readManifestFile(fileExtension: string): Promise<string> {
+    return await fse.readFile(path.join(pluginPath, "manifest." + fileExtension), "utf8");
+  }
+}