restructured route registration and added preliminary comments for exporter

1 files changed, 133 insertions, 0 deletions

diff --git a/src/server/ApiManagers/ExportManager.ts b/src/server/ApiManagers/ExportManager.ts
new file mode 100644
index 000000000..261acbbe0
--- /dev/null
+++ b/src/server/ApiManagers/ExportManager.ts
@@ -0,0 +1,133 @@
+import ApiManager, { Registration } from "./ApiManager";
+import RouteManager, { Method } from "../RouteManager";
+import RouteSubscriber from "../RouteSubscriber";
+import { RouteStore } from "../RouteStore";
+import * as Archiver from 'archiver';
+import * as express from 'express';
+import { Database } from "../database";
+import * as path from "path";
+import { DashUploadUtils } from "../DashUploadUtils";
+
+export type Hierarchy = { [id: string]: string | Hierarchy };
+export type ZipMutator = (file: Archiver.Archiver) => void | Promise<void>;
+export interface DocumentElements {
+    data: string | any[];
+    title: string;
+}
+
+export default class ExportManager extends ApiManager {
+
+    protected initialize(register: Registration): void {
+
+        register({
+            method: Method.GET,
+            subscription: new RouteSubscriber(RouteStore.imageHierarchyExport).add('docId'),
+            onValidation: async ({ req, res }) => {
+                const id = req.params.docId;
+                const hierarchy: Hierarchy = {};
+                await buildHierarchyRecursive(id, hierarchy);
+                BuildAndDispatchZip(res, zip => writeHierarchyRecursive(zip, hierarchy));
+            }
+        });
+    }
+
+}
+
+/**
+ * This utility function factors out the process
+ * of creating a zip file and sending it back to the client
+ * by piping it into a response.
+ * 
+ * Learn more about piping and readable / writable streams here!
+ * https://www.freecodecamp.org/news/node-js-streams-everything-you-need-to-know-c9141306be93/ 
+ * 
+ * @param res the writable stream response object that will transfer the generated zip file
+ * @param mutator the callback function used to actually modify and insert information into the zip instance
+ */
+export async function BuildAndDispatchZip(res: express.Response, mutator: ZipMutator): Promise<void> {
+    const zip = Archiver('zip');
+    zip.pipe(res);
+    await mutator(zip);
+    zip.finalize();
+}
+
+/**
+ * This function starts with a single document id as a seed,
+ * typically that of a collection, and then descends the entire tree
+ * of image or collection documents that are reachable from that seed. 
+ * @param seedId the id of the root of the subtree we're trying to capture, interesting only if it's a collection
+ * @param hierarchy the data structure we're going to use to record the nesting of the collections and images as we descend
+ */
+
+/*
+Below is an example of the JSON hierarchy built from two images contained inside a collection titled 'a nested collection',
+following the general recursive structure shown immediately below
+{
+    "parent folder name":{
+        "first child's fild name":"first child's url"
+        ...
+        "nth child's fild name":"nth child's url"
+    }
+}
+{ 
+    "a nested collection (865c4734-c036-4d67-a588-c71bb43d1440)":{ 
+        "an image of a cat (ace99ffd-8ed8-4026-a5d5-a353fff57bdd).jpg":"https://upload.wikimedia.org/wikipedia/commons/thumb/3/3a/Cat03.jpg/1200px-Cat03.jpg",
+        "1*SGJw31T5Q9Zfsk24l2yirg.gif (9321cc9b-9b3e-4cb6-b99c-b7e667340f05).gif":"https://cdn-media-1.freecodecamp.org/images/1*SGJw31T5Q9Zfsk24l2yirg.gif"
+    }
+}
+*/
+
+async function buildHierarchyRecursive(seedId: string, hierarchy: Hierarchy): Promise<void> {
+    const { title, data } = await getData(seedId);
+    const label = `${title} (${seedId})`;
+    // is the document a collection?
+    if (Array.isArray(data)) {
+        // recurse over all documents in the collection.
+        const local: Hierarchy = {}; // create a child hierarchy for this level, which will get passed in as the parent of the recursive call
+        hierarchy[label] = local; // store it at the index in the parent, so we'll end up with a map of maps of maps
+        await Promise.all(data.map(proxy => buildHierarchyRecursive(proxy.fieldId, local)));
+    } else {
+        // now, data can only be a string, namely the url of the image
+        const filename = label + path.extname(data); // this is the file name under which the output image will be stored
+        hierarchy[filename] = data;
+    }
+}
+
+async function getData(seedId: string): Promise<DocumentElements> {
+    return new Promise<DocumentElements>((resolve, reject) => {
+        Database.Instance.getDocument(seedId, async (result: any) => {
+            const { data, proto, title } = result.fields;
+            if (data) {
+                if (data.url) {
+                    resolve({ data: data.url, title });
+                } else if (data.fields) {
+                    resolve({ data: data.fields, title });
+                } else {
+                    reject();
+                }
+            }
+            if (proto) {
+                getData(proto.fieldId).then(resolve, reject);
+            }
+        });
+    });
+}
+
+async function writeHierarchyRecursive(file: Archiver.Archiver, hierarchy: Hierarchy, prefix = "Dash Export"): Promise<void> {
+    for (const key of Object.keys(hierarchy)) {
+        const result = hierarchy[key];
+        if (typeof result === "string") {
+            let path: string;
+            let matches: RegExpExecArray | null;
+            if ((matches = /\:1050\/files\/(upload\_[\da-z]{32}.*)/g.exec(result)) !== null) {
+                path = `${__dirname}/public/files/${matches[1]}`;
+            } else {
+                const information = await DashUploadUtils.UploadImage(result);
+                path = information.mediaPaths[0];
+            }
+            file.file(path, { name: key, prefix });
+        } else {
+            await writeHierarchyRecursive(file, result, `${prefix}/${key}`);
+        }
+    }
+}
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