add logic for metadata migration (#218)

* [#215] Handle metadata migration

Makes it possible to change "metadata keys" and the "app metadata key prefix" without losing data

* [#215] Fix checking and handling missing reader settings in metadata

With the new migration logic missing reader settings couldn't be detected anymore in case the metadata included outdated app metadata keys for the reader settings.

* [#215] Fix name of "IReaderSettings" property

src/util/metadata.ts

@@ -11,7 +11,21 @@ import client from './client';
 
 const APP_METADATA_KEY_PREFIX = 'webUI_';
 
-const getMetadataKey = (key: string) => `${APP_METADATA_KEY_PREFIX}${key}`;
+const migrations: IMetadataMigration[] = [
+    {
+        keys: [
+            { oldKey: 'loadNextonEnding', newKey: 'loadNextOnEnding' },
+        ],
+    },
+];
+
+const getMetadataKey = (key: string, appPrefix: string = APP_METADATA_KEY_PREFIX) => `${appPrefix}${key}`;
+
+const doesMetadataKeyExistIn = (
+    meta: IMetadata | undefined,
+    key: string,
+    appPrefix?: string,
+): boolean => Object.prototype.hasOwnProperty.call(meta ?? {}, getMetadataKey(key, appPrefix));
 
 const convertValueFromMetadata = <
     T extends AllowedMetadataValueTypes = AllowedMetadataValueTypes,
@@ -33,31 +47,121 @@ const convertValueFromMetadata = <
     return value as T;
 };
 
+const getAppMetadataFrom = (
+    meta: IMetadata,
+    appPrefix: string = APP_METADATA_KEY_PREFIX,
+): IMetadata => {
+    const appMetadata: IMetadata = {};
+
+    Object.entries(meta).forEach(([key, value]) => {
+        if (key.startsWith(appPrefix)) {
+            appMetadata[key] = value;
+        }
+    });
+
+    return appMetadata;
+};
+
+const applyAppKeyPrefixMigration = (meta: IMetadata, migration: IMetadataMigration): IMetadata => {
+    const migratedMetadata: IMetadata = { ...meta };
+
+    if (!migration.appKeyPrefix) {
+        return migratedMetadata;
+    }
+
+    const { oldPrefix, newPrefix } = migration.appKeyPrefix;
+
+    const oldAppMetadata = getAppMetadataFrom(meta, oldPrefix);
+    const newAppMetadata = getAppMetadataFrom(meta, newPrefix);
+
+    const missingMetadataKeys = Object.keys(oldAppMetadata)
+        .filter((key) => !Object.keys(newAppMetadata).includes(key));
+
+    const isMissingOldMetadata = missingMetadataKeys.length;
+    if (isMissingOldMetadata) {
+        missingMetadataKeys.forEach((oldKey) => {
+            const keyWithNewPrefix = oldKey.replace(oldPrefix, newPrefix);
+            migratedMetadata[keyWithNewPrefix] = oldAppMetadata[oldKey];
+        });
+    }
+
+    return migratedMetadata;
+};
+
+const applyMetadataKeyMigration = (meta: IMetadata, migration: IMetadataMigration): IMetadata => {
+    const migratedMetadata: IMetadata = { ...meta };
+
+    if (!migration.keys) {
+        return migratedMetadata;
+    }
+
+    const metadataKeyChanges = migration.keys;
+
+    metadataKeyChanges.forEach(({ oldKey, newKey }) => {
+        if (!doesMetadataKeyExistIn(meta, oldKey)) {
+            return;
+        }
+
+        if (doesMetadataKeyExistIn(meta, newKey)) {
+            return;
+        }
+
+        migratedMetadata[getMetadataKey(newKey)] = meta[getMetadataKey(oldKey)];
+    });
+
+    return migratedMetadata;
+};
+
+const applyMetadataMigrations = (meta?: IMetadata): IMetadata | undefined => {
+    if (!meta) {
+        return undefined;
+    }
+
+    const migrationToMetadata: [number, IMetadata][] = [[0, meta]];
+
+    migrations.forEach((migration, index) => {
+        const migrationId = index + 1;
+        const metadataToMigrate = migrationToMetadata[migrationId - 1][1];
+        const appKeyPrefixMigrated = applyAppKeyPrefixMigration(metadataToMigrate, migration);
+        const metadataKeysMigrated = applyMetadataKeyMigration(appKeyPrefixMigrated, migration);
+
+        migrationToMetadata.push([migrationId, metadataKeysMigrated]);
+    });
+
+    const appliedMigration = migrationToMetadata.length > 1;
+    if (!appliedMigration) {
+        return { ...meta };
+    }
+
+    return migrationToMetadata.pop()![1];
+};
+
 export const getMetadataValueFrom = <
     T extends AllowedMetadataValueTypes = AllowedMetadataValueTypes,
 >(
     { meta }: IMetadataHolder,
     key: AppMetadataKeys,
     defaultValue?: T,
+    applyMigrations: boolean = true,
 ): T | undefined => {
-    const metadataKey = getMetadataKey(key);
+    const metadata = applyMigrations ? applyMetadataMigrations(meta) : meta;
 
-    const isMissingKey = !Object.prototype.hasOwnProperty.call(meta ?? {}, metadataKey);
-    if (meta === undefined || isMissingKey) {
+    if (metadata === undefined || !doesMetadataKeyExistIn(metadata, key)) {
         return defaultValue;
     }
 
-    return convertValueFromMetadata(meta[metadataKey]);
+    return convertValueFromMetadata(metadata[getMetadataKey(key)]);
 };
 
 export const getMetadataFrom = (
     { meta }: IMetadataHolder,
     keysToDefaultValues: MetadataKeyValuePair[],
+    applyMigrations?: boolean,
 ): IMetadata<AllowedMetadataValueTypes> => {
     const appMetadata: IMetadata<AllowedMetadataValueTypes> = {};
 
     keysToDefaultValues.forEach(([key, defaultValue]) => {
-        appMetadata[key] = getMetadataValueFrom({ meta }, key, defaultValue);
+        appMetadata[key] = getMetadataValueFrom({ meta }, key, defaultValue, applyMigrations);
     });
 
     return appMetadata;