♻ Extract patch verification into separate file

src/ssn/getPatch.ts

@@ -1,10 +1,9 @@
 import downloadUrlContents from '../cdn/downloadUrlContents';
 import getUrlContents from '../cdn/getUrlContents';
 import { Product } from '../interfaces/ISettings';
-import { SsnDiffType } from '../interfaces/ISsnFileEntry';
-import extractFile from './extractFile';
 import getSolidpkg from './getSolidpkg';
 import readSsnFile from './reader/readSsnFile';
+import verifyPatch from './verify/verifyPatch';
 
 export default async function getPatch(product: Product, from: number, to: number) {
   const solidpkg = await getSolidpkg(product, from, to);
@@ -24,12 +23,7 @@ export default async function getPatch(product: Product, from: number, to: numbe
   console.debug(fileEntries);
 
   //Verify file entries
-  if (from === -1) {
-    fileEntries.filter((file) => file.diffType !== SsnDiffType.NewFile).forEach((file) => {
-      throw new Error(`Patches from -1 must be included in full, but this patch had a file "${file.name}" with diff type ${file.diffType}.`);
-    });
-  }
-  //TODO: last file must always be `${product}.version` with diff type. Other files depend on diffType.
+  verifyPatch(fileEntries, product, from);
 
   //Then we need to wait for other files before we can extract them
   await Promise.all(diskFiles);

src/ssn/verify/verifyPatch.ts

@@ -0,0 +1,28 @@
+import { Product } from '../../interfaces/ISettings';
+import { ISsnFileEntry } from '../../interfaces/ISsnFileEntry';
+import { SsnDiffType } from '../../interfaces/ISsnFileEntry';
+
+/** Receives a list of file entries from the .zip file and checks them for correctness */
+export default function verifyPatch(fileEntries: ISsnFileEntry[], product: Product, from: number): void {
+  //There must be at least a .version file
+  if (fileEntries.length === 0) {
+    throw new Error('Expected at least a version file in the ');
+  }
+
+  //Check that last file is the .version file with diffType 0.
+  const lastFile = fileEntries[fileEntries.length - 1];
+  const validLastFileName = `${product}.version`;
+  if (lastFile.name !== validLastFileName) {
+    throw new Error(`Last file must be called "${validLastFileName}" but it was "${lastFile.name}".`);
+  }
+  if (lastFile.diffType !== SsnDiffType.NewFile) {
+    throw new Error(`Last file (.version file) must have diffType 0 but it had diffType ${lastFile.diffType}.`);
+  }
+
+  //Patches from -1 must not have diff type NewFile
+  if (from === -1) {
+    fileEntries.filter((file) => file.diffType !== SsnDiffType.NewFile).forEach((file) => {
+      throw new Error(`Patches from -1 must be included in full, but this patch had a file "${file.name}" with diff type ${file.diffType}.`);
+    });
+  }
+}

src/ssn/verify/verifyPatchmanifest.ts

@@ -2,7 +2,7 @@ import * as xmlJs from 'xml-js';
 import { Product } from '../../interfaces/ISettings';
 
 /** Receives a JSON-converted version of the manifest.xml file, and verifies that all required elements and attributes are present, and nothing more */
-export default function verifyPatchmanifest(manifestFile: xmlJs.Element, product: Product): any {
+export default function verifyPatchmanifest(manifestFile: xmlJs.Element, product: Product): void {
   //<?xml version="1.0" encoding="utf-8"?>
   if (manifestFile.declaration === undefined || manifestFile.declaration.attributes === undefined || Object.keys(manifestFile.declaration.attributes).length !== 2 || manifestFile.declaration.attributes.version !== '1.0' || manifestFile.declaration.attributes.encoding !== 'utf-8') {
     throw new Error('Expected declaration with version 1.0 and utf-8 encoding.');

src/ssn/verify/verifySolidpkg.ts

@@ -1,7 +1,7 @@
 import ISolid from '../../interfaces/ISolidFile';
 
 /** Verifies metafile.solid for correctness. See specification at <http://www.bittorrent.org/beps/bep_0003.html>. */
-export default function verifySolidpkg(file: ISolid, { product, from, to }: {product: string, from: number, to: number}) {
+export default function verifySolidpkg(file: ISolid, { product, from, to }: {product: string, from: number, to: number}): void {
   if (typeof file['creation date'] !== 'number') {
     throw new Error(`Expected creation date to be a number but it was "${file['creation date']}".`);
   }