From b6f27f6350a9eb3b7db0bbbe9856ff5ee83a1496 Mon Sep 17 00:00:00 2001
From: mrjvs <jellevs@gmail.com>
Date: Sun, 24 Oct 2021 23:10:47 +0200
Subject: [PATCH] versioned store implementation

---
 src/App.js                 |   8 ++
 src/lib/storage/base.js    | 146 +++++++++++++++++++++++++++++++++++++
 src/lib/storage/watched.js |  14 ++++
 3 files changed, 168 insertions(+)
 create mode 100644 src/lib/storage/base.js
 create mode 100644 src/lib/storage/watched.js

diff --git a/src/App.js b/src/App.js
index 8e248937..91ca1a56 100644
--- a/src/App.js
+++ b/src/App.js
@@ -2,6 +2,7 @@ import { SearchView } from './views/Search';
 import { MovieView } from './views/Movie';
 import { useMovie, MovieProvider } from './hooks/useMovie';
 import './index.css';
+import {store} from './lib/storage/watched.js'
 
 function Router() {
   const { streamData } = useMovie();
@@ -11,6 +12,13 @@ function Router() {
 function App() {
   return (
     <MovieProvider>
+      <div>
+        <p>Testing</p>
+        <button onClick={() => {
+          const data = store.get();
+          data.save();
+        }}>Click me</button>
+      </div>
       <Router />
     </MovieProvider>
   );
diff --git a/src/lib/storage/base.js b/src/lib/storage/base.js
new file mode 100644
index 00000000..4781ad67
--- /dev/null
+++ b/src/lib/storage/base.js
@@ -0,0 +1,146 @@
+function buildStoreObject(data) {
+    return {
+        versions: data.versions,
+        currentVersion: data.maxVersion,
+        id: data.storageString,
+        update(obj) {
+            if (!obj)
+                throw new Error("object to update is not an object");
+
+            // repeat until object fully updated
+            while (obj["--version"] !== this.currentVersion) {
+                // get version
+                let version = obj["--version"] || 0;
+                if (version === undefined || version.constructor !== Number)
+                    version = -42; // invalid on purpose so it will reset
+                else {
+                    version = (version+1).toString()
+                }
+
+                // check if version exists
+                if (!this.versions[version]) {
+                    console.error(`Version not found for storage item in store ${this.id}, resetting`);
+                    obj = null;
+                    break;
+                }
+
+                // update object
+                obj = this.versions[version].update(obj);
+                console.log(obj);
+            }
+
+            // if resulting obj is null, use latest version as init object
+            if (obj === null) {
+                console.error(`Storage item for store ${this.id} has been reset due to faulty updates`);
+                return this.versions[this.currentVersion.toString()].init();
+            }
+
+            // updates succesful, return
+            return obj;
+        },
+        get() {
+            // get from storage api
+            const store = this;
+            let data = localStorage.getItem(this.id);
+
+            // parse json if item exists
+            if (data) {
+                try {
+                    data = JSON.parse(data);
+                    if (!data.constructor) {
+                        console.error(`Storage item for store ${this.id} has not constructor`)
+                        throw new Error("storage item has no constructor")
+                    }
+                    if (data.constructor !== Object) {
+                        console.error(`Storage item for store ${this.id} is not an object`)
+                        throw new Error("storage item is not an object")
+                    }
+                } catch (_) {
+                    // if errored, set to null so it generates new one, see below
+                    console.error(`Failed to parse storage item for store ${this.id}`)
+                    data = null;
+                }
+            }
+
+            // if item doesnt exist, generate from version init
+            if (!data) {
+                data = this.versions[this.currentVersion.toString()].init();
+            }
+
+            // update the data if needed
+            data = this.update(data);
+
+            // add a save object to return value
+            data.save = function save() {
+                localStorage.setItem(store.id, JSON.stringify(data));
+            }
+
+            // return data
+            return data;
+        }
+    }
+}
+
+/*
+ * Builds a versioned store
+ *
+ * manages versioning of localstorage items
+*/
+export function versionedStoreBuilder() {
+    return {
+        _data: {
+            versionList: [],
+            maxVersion: 0,
+            versions: {},
+            storageString: null,
+        },
+        setKey(str) {
+            this._data.storageString = str;
+            return this;
+        },
+        addVersion(num, updateFunc, initFunc) {
+            // update max version list
+            if (num > this._data.maxVersion)
+                this._data.maxVersion = num;
+            // add to version list
+            this._data.versionList.push(num);
+
+            // register version
+            this._data.versions[num.toString()] = {
+                version: num, // version number
+                update: (data) => { // update function, and increment version
+                    updateFunc(data);
+                    data["--version"] = num;
+                    return data;
+                },
+                init: () => { // return an initial object
+                    const data = initFunc();
+                    data["--version"] = num;
+                    return data;
+                }
+            }
+            return this;
+        },
+        build() {
+            // check if version list doesnt skip versions
+            const versionListSorted = this._data.versionList.sort((a,b)=>a-b);
+            versionListSorted.forEach((v, i, arr) => {
+                if (i === 0)
+                    return;
+                if (v !== arr[i-1]+1)
+                    throw new Error("Version list of store is not incremental");
+            })
+
+            // version zero must exist
+            if (versionListSorted[0] !== 0)
+                throw new Error("Version 0 doesn't exist in version list of store");
+
+            // check storage string
+            if (!this._data.storageString)
+                throw new Error("storage key not set in store");
+
+            // build versioned store
+            return buildStoreObject(this._data);
+        }
+    }
+}
diff --git a/src/lib/storage/watched.js b/src/lib/storage/watched.js
new file mode 100644
index 00000000..51869788
--- /dev/null
+++ b/src/lib/storage/watched.js
@@ -0,0 +1,14 @@
+import { versionedStoreBuilder } from './base.js';
+
+export const store = versionedStoreBuilder()
+    .setKey('test-store')
+    .addVersion(0, (d) => {
+        d.v0 = "v0";
+    }, () => ({ v0: "v0" }))
+    .addVersion(1, (d) => {
+        d.v1 = "v1";
+    }, () => ({ v1: "v1" }))
+    .addVersion(2, (d) => {
+        d.v2 = "v2";
+    }, () => ({ v2: "v2" }))
+    .build()