Add deletions.

.vscode/launch.json

@@ -10,7 +10,7 @@
             "name": "Jasmine Tests with SQLite",
             "env": {
                 "MUDBASE_DB_CONFIG": "{\"client\": \"sqlite3\", \"connection\": \":memory:\"}",
-                "TEST_RANDOM_SEED": "0.61658"
+                "TEST_RANDOM_SEED": "0.77715"
             },
             "program": "${workspaceFolder}/server/node_modules/jasmine-ts/lib/index",
             "args": [

client/src/api/endpoints/data.ts

@@ -5,10 +5,14 @@
 // referencing between objects. They do not correspond to IDs in the actual
 // database.
 // Upon import, they might be replaced, and upon export, they might be randomly
+// generated.
 
 import { AlbumWithRefsWithId, ArtistWithRefsWithId, isAlbumWithRefs, isArtistWithRefs, isTagWithRefs, isTrackBaseWithRefs, isTrackWithRefs, TagWithRefsWithId, TrackWithRefsWithId } from "../types/resources";
 
-// generated.
+// The import/export DB format is just a set of lists of objects.
+// Each object has an ID and references others by ID.
+// Any object referenced by ID also has a reverse reference.
+// In other words, if A references B, B must also reference A.
 export interface DBDataFormat {
     tracks: TrackWithRefsWithId[],
     albums: AlbumWithRefsWithId[],

server/db/Album.ts

@@ -73,7 +73,7 @@ export async function getAlbum(id: number, userId: number, knex: Knex):
 
 // Returns the id of the created album.
 export async function createAlbum(userId: number, album: AlbumWithRefs, knex: Knex): Promise<number> {
-    return await knex.transaction(async (trx) => {        
+    return await knex.transaction(async (trx) => {
         // Start retrieving artists.
         const artistIdsPromise: Promise<number[]> =
             trx.select('id')
@@ -181,10 +181,10 @@ export async function modifyAlbum(userId: number, albumId: number, album: AlbumB
         // Start retrieving tracks if we are modifying those.
         const trackIdsPromise: Promise<number[] | undefined> =
             album.trackIds ?
-                trx.select('artistId')
-                    .from('tracks_albums')
+                trx.select('id')
+                    .from('tracks')
                     .whereIn('albumId', album.trackIds)
-                    .then((as: any) => as.map((a: any) => a['trackId']))
+                    .then((as: any) => as.map((a: any) => a['id']))
                 : (async () => undefined)();
 
         // Start retrieving tags if we are modifying those.
@@ -229,11 +229,11 @@ export async function modifyAlbum(userId: number, albumId: number, album: AlbumB
             .whereNotIn('tagId', album.tagIds || [])
             .delete() : undefined;
 
-        // Remove unlinked tracks.
-        const removeUnlinkedTracks = tracks ? trx('tracks_albums')
+        // Remove unlinked tracks by setting their references to null.
+        const removeUnlinkedTracks = tracks ? trx('tracks')
             .where({ 'albumId': albumId })
-            .whereNotIn('trackId', album.trackIds || [])
-            .delete() : undefined;
+            .whereNotIn('id', album.trackIds || [])
+            .update({ 'albumId': null }) : undefined;
 
         // Link new artists.
         const addArtists = artists ? trx('artists_albums')
@@ -356,11 +356,11 @@ export async function deleteAlbum(userId: number, albumId: number, knex: Knex):
                 .from('albums_tags')
                 .where({ 'albumId': albumId });
 
-        // Start deleting track associations with the album.
+        // Start deleting track associations with the album by setting their references to null.
         const deleteTracksPromise: Promise<any> =
-            trx.delete()
-                .from('tracks_albums')
-                .where({ 'albumId': albumId });
+            trx.update({ 'album': null })
+                .from('tracks')
+                .where({ 'album': albumId });
 
         // Start deleting the album.
         const deleteAlbumPromise: Promise<any> =

server/endpoints/Tag.ts

@@ -37,7 +37,7 @@ export const DeleteTag: EndpointHandler = async (req: any, res: any, knex: Knex)
 
     try {
 
-        deleteTag(userId, req.params.id, knex);
+        await deleteTag(userId, req.params.id, knex);
         res.status(200).send();
 
     } catch (e) {

server/migrations/20200828124218_init_db.ts

@@ -204,7 +204,6 @@ export async function down(knex: Knex): Promise<void> {
     await knex.schema.dropTable('albums');
     await knex.schema.dropTable('tags');
     await knex.schema.dropTable('tracks_artists');
-    await knex.schema.dropTable('tracks_albums');
     await knex.schema.dropTable('tracks_tags');
     await knex.schema.dropTable('artists_tags');
     await knex.schema.dropTable('albums_tags');

server/test/integration/flows/ResourceFlow.ts

@@ -144,10 +144,20 @@ function transformActionIDs(action: DBAction, mappings: IDMappings, rng: any) {
             tag.parentId = tag.parentId ? doMap(tag.parentId, mappings.tags) : null;
             break;
         }
-        case DBActionType.DeleteTrack: {
-            r.payload = mappings.tracks[r.payload];
-            break;
-        }
+        case DBActionType.DeleteTrack:
+        case DBActionType.DeleteArtist:
+        case DBActionType.DeleteAlbum:
+        case DBActionType.DeleteTag:
+            {
+                let keys = {
+                    [DBActionType.DeleteTrack]: 'tracks',
+                    [DBActionType.DeleteArtist]: 'artists',
+                    [DBActionType.DeleteAlbum]: 'albums',
+                    [DBActionType.DeleteTag]: 'tags',
+                }
+                r.payload = (mappings as any)[keys[r.type]][r.payload];
+                break;
+            }
     }
     return r;
 }
@@ -208,11 +218,14 @@ describe('Randomized model-based DB back-end tests', () => {
             // be generated.
             let dist: RandomDBActionDistribution = {
                 type: new Map([
-                    [DBActionType.CreateTrack, 0.2],
-                    [DBActionType.CreateArtist, 0.2],
-                    [DBActionType.CreateAlbum, 0.2],
-                    [DBActionType.CreateTag, 0.2],
-                    [DBActionType.DeleteTrack, 0.2]
+                    [DBActionType.CreateTrack, 0.125],
+                    [DBActionType.CreateArtist, 0.125],
+                    [DBActionType.CreateAlbum, 0.125],
+                    [DBActionType.CreateTag, 0.125],
+                    [DBActionType.DeleteTrack, 0.125],
+                    [DBActionType.DeleteArtist, 0.125],
+                    [DBActionType.DeleteAlbum, 0.125],
+                    [DBActionType.DeleteTag, 0.125],
                 ]),
                 userId: new Map([[1, 1.0]]),
                 createTrackParams: {
@@ -259,8 +272,17 @@ describe('Randomized model-based DB back-end tests', () => {
 
                 },
                 deleteTrackParams: {
-                    validTrack: new Map([[false, 0.2], [true, 0.8]])
-                }
+                    validId: new Map([[false, 0.2], [true, 0.8]])
+                },
+                deleteArtistParams: {
+                    validId: new Map([[false, 0.2], [true, 0.8]])
+                },
+                deleteAlbumParams: {
+                    validId: new Map([[false, 0.2], [true, 0.8]])
+                },
+                deleteTagParams: {
+                    validId: new Map([[false, 0.2], [true, 0.8]])
+                },
             }
 
             // Loop to generate and execute a bunch of random actions.
@@ -284,14 +306,12 @@ describe('Randomized model-based DB back-end tests', () => {
 
                 // If this was an object creation action, we need to update the mappings.
                 if (refStatus === 200 && realStatus === 200) {
-                    if (refAction.type === DBActionType.CreateTrack) {
-                        idMappingsRefToReal.tracks[refResponse.id] = realResponse.id;
-                    } else if (refAction.type === DBActionType.CreateAlbum) {
-                        idMappingsRefToReal.albums[refResponse.id] = realResponse.id;
-                    } else if (refAction.type === DBActionType.CreateArtist) {
-                        idMappingsRefToReal.artists[refResponse.id] = realResponse.id;
-                    } else if (refAction.type === DBActionType.CreateTag) {
-                        idMappingsRefToReal.tags[refResponse.id] = realResponse.id;
+                    switch(refAction.type) {
+                        case DBActionType.CreateTrack: { idMappingsRefToReal.tracks[refResponse.id] = realResponse.id; break; }
+                        case DBActionType.CreateArtist: { idMappingsRefToReal.artists[refResponse.id] = realResponse.id; break; }
+                        case DBActionType.CreateAlbum: { idMappingsRefToReal.albums[refResponse.id] = realResponse.id; break; }
+                        case DBActionType.CreateTag: { idMappingsRefToReal.tags[refResponse.id] = realResponse.id; break; }
+                        default: { break; }
                     }
                 }
 
@@ -300,7 +320,7 @@ describe('Randomized model-based DB back-end tests', () => {
                 expect(normalizeResponse(realResponse)).to.deep.equal(normalizeResponse(refResponse));
 
                 // Compare the database state after the action.
-                let newRefState = refDB;
+                let newRefState = _.cloneDeep(refDB);
                 let newRealState = {
                     [1]: (await helpers.getExport(req)).body,
                 };
@@ -318,11 +338,15 @@ describe('Randomized model-based DB back-end tests', () => {
             e.idMappingsRefToReal = idMappingsRefToReal;
             if (e.actual && e.expected) {
                 let basename = tmp.tmpNameSync();
+                e.actualDump = basename + "_actual";
+                e.expectedDump = basename + "_expected";
                 e.actionTraceDump = basename + "_actiontrace";
                 e.startingDBDump = basename + "_startingDB";
                 e.lastRefDBDump = basename + "_lastRefDB";
                 e.lastRealDBDump = basename + "_lastRealDB";
                 e.idMappingsRefToRealDump = basename + "_idMappings";
+                fs.writeFileSync(e.actualDump, stringify(e.actual, { space: '  ' }));
+                fs.writeFileSync(e.expectedDump, stringify(e.expected, { space: '  ' }));
                 fs.writeFileSync(e.actionTraceDump, stringify(e.actionTrace, { space: '  ' }));
                 fs.writeFileSync(e.startingDBDump, stringify(e.startingDB, { space: '  ' }));
                 fs.writeFileSync(e.lastRefDBDump, stringify(e.lastRefDB, { space: '  ' }));
@@ -331,6 +355,8 @@ describe('Randomized model-based DB back-end tests', () => {
 
                 console.log(
                     "A comparison error occurred. Wrote compared values to temporary files for debugging:\n"
+                    + `  Actual value: ${e.actualDump}\n`
+                    + `  Expected value: ${e.actualDump}\n`
                     + `  DB action trace: ${e.actionTraceDump}\n`
                     + `  Starting DB: ${e.startingDBDump}\n`
                     + `  Reference DB before last action: ${e.lastRefDBDump}\n`

server/test/integration/helpers.ts

@@ -128,6 +128,20 @@ export async function checkArtist(
         })
 }
 
+export async function deleteArtist(
+    req: any,
+    id = 1,
+    expectStatus: number | undefined = undefined,
+) {
+    return await req
+        .delete('/artist/' + id)
+        .send()
+        .then((res: any) => {
+            expectStatus && expect(res).to.have.status(expectStatus);
+            return res;
+        });
+}
+
 export async function createTag(
     req: any,
     props = { name: "Tag" },
@@ -174,6 +188,20 @@ export async function checkTag(
         })
 }
 
+export async function deleteTag(
+    req: any,
+    id = 1,
+    expectStatus: number | undefined = undefined,
+) {
+    return await req
+        .delete('/tag/' + id)
+        .send()
+        .then((res: any) => {
+            expectStatus && expect(res).to.have.status(expectStatus);
+            return res;
+        });
+}
+
 export async function createAlbum(
     req: any,
     props = { name: "Album" },
@@ -220,6 +248,20 @@ export async function checkAlbum(
         })
 }
 
+export async function deleteAlbum(
+    req: any,
+    id = 1,
+    expectStatus: number | undefined = undefined,
+) {
+    return await req
+        .delete('/album/' + id)
+        .send()
+        .then((res: any) => {
+            expectStatus && expect(res).to.have.status(expectStatus);
+            return res;
+        });
+}
+
 export async function createUser(
     req: any,
     email: string,

server/test/reference_model/DBReferenceModel.ts

@@ -1,9 +1,10 @@
-import { AlbumWithRefsWithId, ArtistWithRefsWithId, DBDataFormat, PostAlbumRequest, PostArtistRequest, PostTagRequest, PostTrackRequest, TrackWithDetails, TrackWithRefsWithId } from "../../../client/src/api/api";
+import { AlbumWithRefsWithId, ArtistWithRefsWithId, DBDataFormat, PostAlbumRequest, PostArtistRequest, PostTagRequest, PostTrackRequest, TagWithRefsWithId, TrackWithDetails, TrackWithRefsWithId } from "../../../client/src/api/api";
 import { makeNotFoundError } from "../../db/common";
 import filterInPlace from "../../lib/filterInPlace";
 
 // The mock reference database is in the same format as
 // the JSON import/export format, for multiple users.
+
 export type ReferenceDatabase = Record<number, DBDataFormat>
 
 type ObjectsType = "tracks" | "artists" | "tags" | "albums";
@@ -42,23 +43,27 @@ function ensureLinked(fromObjects: number[], fromObjectsType: ObjectsType,
 }
 
 // Create a new object.
-export interface LinkField { field: string, otherObjectType: ObjectsType };
+// The general procedure for this is:
+// - check that any existing objects referenced in the new object actually exist
+// - generate a new ID and insert the object
+// - add reverse references into any existing object referenced by the new object.
+export interface ReferencingField { field: string, otherObjectType: ObjectsType };
 export function createObject(
     userId: number,
     object: any,
     objectType: ObjectsType,
-    singularLinkFields: LinkField[],
-    pluralLinkFields: LinkField[],
+    singularReverseRefs: ReferencingField[],
+    pluralReverseRefs: ReferencingField[],
     db: ReferenceDatabase
 ): { id: number } {
     // Existence checks
     if (!(userId in db)) { throw makeNotFoundError() }
-    singularLinkFields.forEach((f: LinkField) => {
+    singularReverseRefs.forEach((f: ReferencingField) => {
         if (!checkExists(db[userId][f.otherObjectType], object[f.field] ? [object[f.field]] : [])) {
             throw makeNotFoundError();
         }
     });
-    pluralLinkFields.forEach((f: LinkField) => {
+    pluralReverseRefs.forEach((f: ReferencingField) => {
         if (!checkExists(db[userId][f.otherObjectType], object[f.field] || [])) {
             throw makeNotFoundError();
         }
@@ -72,16 +77,51 @@ export function createObject(
     })
 
     // reverse links
-    singularLinkFields.forEach((f: LinkField) => {
+    singularReverseRefs.forEach((f: ReferencingField) => {
         ensureLinked(object[f.field] ? [object[f.field]] : [], f.otherObjectType, id, objectType, db[userId]);
     });
-    pluralLinkFields.forEach((f: LinkField) => {
+    pluralReverseRefs.forEach((f: ReferencingField) => {
         ensureLinked(object[f.field] || [], f.otherObjectType, id, objectType, db[userId]);
     });
 
     return { id: id };
 }
 
+// Delete an object.
+// The general procedure for this is:
+// - check that the to-be-deleted object exists
+// - remove any references that exist to the object in other objects
+// - delete the object
+export function deleteObject(
+    userId: number,
+    objectId: number,
+    objectType: ObjectsType,
+    singularRefsToThisObject: ReferencingField[],
+    pluralRefsToThisObject: ReferencingField[],
+    db: ReferenceDatabase
+): void {
+    // Existence checks
+    if (!(userId in db)) { throw makeNotFoundError() }
+
+    // Find the object to delete.
+    let idx = db[userId][objectType].findIndex((o: any) => 'id' in o && o.id === objectId);
+    if (idx < 0) {
+        // Not found
+        throw makeNotFoundError();
+    }
+
+    // Remove references to this object
+    pluralRefsToThisObject.forEach((f: ReferencingField) => {
+        db[userId][f.otherObjectType].forEach((other: any) => { filterInPlace(other[f.field], (oid: number) => oid !== objectId) })
+    });
+    singularRefsToThisObject.forEach((f: ReferencingField) => {
+        db[userId][f.otherObjectType].forEach((other: any) => { if (other[f.field] === objectId) { other[f.field] = null; } })
+    });
+
+    // Delete the object
+    db[userId][objectType].splice(idx, 1);
+}
+
 // Create a new track.
 export function createTrack(userId: number, track: PostTrackRequest, db: ReferenceDatabase): { id: number } {
     return createObject(
@@ -143,20 +183,69 @@ export function createTag(userId: number, tag: PostTagRequest, db: ReferenceData
 
 // Delete a track.
 export function deleteTrack(userId: number, id: number, db: ReferenceDatabase): void {
-    // Existence checks
-    if (!(userId in db)) { throw makeNotFoundError() }
+    return deleteObject(
+        userId,
+        id,
+        'tracks',
+        [],
+        [
+            { field: 'trackIds', otherObjectType: 'albums' },
+            { field: 'trackIds', otherObjectType: 'artists' },
+        ],
+        db
+    );
+}
 
-    // Find the object to delete.
-    let idx = db[userId].tracks.findIndex((track: TrackWithRefsWithId) => track.id === id);
-    if (idx < 0) {
-        // Not found
+// Delete an artist.
+export function deleteArtist(userId: number, id: number, db: ReferenceDatabase): void {
+    return deleteObject(
+        userId,
+        id,
+        'artists',
+        [],
+        [
+            { field: 'artistIds', otherObjectType: 'tracks' },
+            { field: 'artistIds', otherObjectType: 'albums' },
+        ],
+        db
+    );
+}
+
+// Delete a track.
+export function deleteAlbum(userId: number, id: number, db: ReferenceDatabase): void {
+    return deleteObject(
+        userId,
+        id,
+        'albums',
+        [{ field: 'albumId', otherObjectType: 'tracks' }],
+        [{ field: 'albumIds', otherObjectType: 'artists' },],
+        db
+    );
+}
+
+// Delete a tag.
+export function deleteTag(userId: number, id: number, db: ReferenceDatabase): void {
+    // Tags are special in that deleting them also deletes their children. Implement that here
+    // with recursive calls.
+    if (!(userId in db)) { throw makeNotFoundError() }
+    let tag = db[userId].tags.find((o: any) => 'id' in o && o.id === id);
+    if (!tag) {
         throw makeNotFoundError();
     }
+    let children = db[userId].tags.filter((t: TagWithRefsWithId) => t.parentId === id);
+    children.forEach((child: TagWithRefsWithId) => { deleteTag(userId, child.id, db) })
 
-    // Remove references
-    db[userId].albums.forEach((x: AlbumWithRefsWithId) => { filterInPlace(x.trackIds, (tid: number) => tid !== id); })
-    db[userId].artists.forEach((x: ArtistWithRefsWithId) => { filterInPlace(x.trackIds, (tid: number) => tid !== id); })
-
-    // Delete the object
-    db[userId].tracks.splice(idx, 1);
+    // Do the actual deletion of this tag.
+    return deleteObject(
+        userId,
+        id,
+        'tags',
+        [],
+        [
+            { field: 'tagIds', otherObjectType: 'albums' },
+            { field: 'tagIds', otherObjectType: 'artists' },
+            { field: 'tagIds', otherObjectType: 'tracks' },
+        ],
+        db
+    );
 }

server/test/reference_model/randomGen.ts

@@ -1,6 +1,6 @@
 import { AlbumWithRefs, AlbumWithRefsWithId, ArtistWithRefs, ArtistWithRefsWithId, TagWithRefs, TagWithRefsWithId, TrackWithRefs, TrackWithRefsWithId } from "../../../client/src/api/api";
 import { userEndpoints } from "../../endpoints/User";
-import { createAlbum, createArtist, createTag, createTrack, deleteTrack, ReferenceDatabase } from "./DBReferenceModel";
+import { createAlbum, createArtist, createTag, createTrack, deleteAlbum, deleteArtist, deleteTag, deleteTrack, ReferenceDatabase } from "./DBReferenceModel";
 import * as helpers from '../integration/helpers';
 import { DBErrorKind, isDBError } from "../../endpoints/types";
 
@@ -10,6 +10,9 @@ export enum DBActionType {
     CreateTag = "CreateTag",
     CreateArtist = "CreateArtist",
     DeleteTrack = "DeleteTrack",
+    DeleteAlbum = "DeleteAlbum",
+    DeleteArtist = "DeleteArtist",
+    DeleteTag = "DeleteTag",
 }
 
 export interface DBAction {
@@ -27,7 +30,10 @@ export interface RandomDBActionDistribution {
     createAlbumParams: RandomCreateAlbumDistribution,
     createArtistParams: RandomCreateArtistDistribution,
     createTagParams: RandomCreateTagDistribution,
-    deleteTrackParams: RandomDeleteTrackDistribution,
+    deleteTrackParams: RandomDeleteObjectDistribution,
+    deleteArtistParams: RandomDeleteObjectDistribution,
+    deleteAlbumParams: RandomDeleteObjectDistribution,
+    deleteTagParams: RandomDeleteObjectDistribution,
 }
 
 export interface RandomCreateTrackDistribution {
@@ -76,8 +82,8 @@ export interface RandomCreateTagDistribution {
     linkParent: Distribution<boolean | 'nonexistent'>,
 }
 
-export interface RandomDeleteTrackDistribution {
-    validTrack: Distribution<boolean>,
+export interface RandomDeleteObjectDistribution {
+    validId: Distribution<boolean>,
 }
 
 export function applyDistribution<T>(
@@ -132,32 +138,37 @@ export function applyReferenceDBAction(
 
     try {
         switch (action.type) {
-            case DBActionType.CreateTrack: {
-                response = createTrack(action.userId, action.payload, db);
-                status = 200;
-                break;
-            }
-            case DBActionType.CreateAlbum: {
-                response = createAlbum(action.userId, action.payload, db);
-                status = 200;
-                break;
-            }
-            case DBActionType.CreateArtist: {
-                response = createArtist(action.userId, action.payload, db);
-                status = 200;
-                break;
-            }
-            case DBActionType.CreateTag: {
-                response = createTag(action.userId, action.payload, db);
-                status = 200;
-                break;
-            }
-            case DBActionType.DeleteTrack: {
-                deleteTrack(action.userId, action.payload, db);
-                response = {};
-                status = 200;
-                break;
-            }
+            case DBActionType.CreateTrack:
+            case DBActionType.CreateAlbum:
+            case DBActionType.CreateArtist:
+            case DBActionType.CreateTag:
+                {
+                    let funcs = {
+                        [DBActionType.CreateTrack]: createTrack,
+                        [DBActionType.CreateAlbum]: createAlbum,
+                        [DBActionType.CreateArtist]: createArtist,
+                        [DBActionType.CreateTag]: createTag,
+                    }
+                    response = funcs[action.type](action.userId, action.payload, db);
+                    status = 200;
+                    break;
+                }
+            case DBActionType.DeleteTrack:
+            case DBActionType.DeleteAlbum:
+            case DBActionType.DeleteArtist:
+            case DBActionType.DeleteTag:
+                {
+                    let funcs = {
+                        [DBActionType.DeleteTrack]: deleteTrack,
+                        [DBActionType.DeleteAlbum]: deleteAlbum,
+                        [DBActionType.DeleteArtist]: deleteArtist,
+                        [DBActionType.DeleteTag]: deleteTag,
+                    }
+                    funcs[action.type](action.userId, action.payload, db);
+                    response = {};
+                    status = 200;
+                    break;
+                }
         }
     } catch (e) {
         if (isDBError(e)) {
@@ -184,36 +195,39 @@ export async function applyRealDBAction(
     let status: number = 0;
 
     switch (action.type) {
-        case DBActionType.CreateTrack: {
-            let res = await helpers.createTrack(req, action.payload);
-            status = res.status;
-            response = res.body;
-            break;
-        }
-        case DBActionType.CreateAlbum: {
-            let res = await helpers.createAlbum(req, action.payload);
-            status = res.status;
-            response = res.body;
-            break;
-        }
-        case DBActionType.CreateArtist: {
-            let res = await helpers.createArtist(req, action.payload);
-            status = res.status;
-            response = res.body;
-            break;
-        }
-        case DBActionType.CreateTag: {
-            let res = await helpers.createTag(req, action.payload);
-            status = res.status;
-            response = res.body;
-            break;
-        }
-        case DBActionType.DeleteTrack: {
-            let res = await helpers.deleteTrack(req, action.payload);
-            status = res.status;
-            response = res.body;
-            break;
-        }
+        case DBActionType.CreateTrack:
+        case DBActionType.CreateAlbum:
+        case DBActionType.CreateArtist:
+        case DBActionType.CreateTag:
+            {
+                let funcs = {
+                    [DBActionType.CreateTrack]: helpers.createTrack,
+                    [DBActionType.CreateAlbum]: helpers.createAlbum,
+                    [DBActionType.CreateArtist]: helpers.createArtist,
+                    [DBActionType.CreateTag]: helpers.createTag,
+                }
+                let res = await funcs[action.type](req, action.payload);
+                status = res.status;
+                response = res.body;
+                break;
+            }
+
+        case DBActionType.DeleteTrack:
+        case DBActionType.DeleteAlbum:
+        case DBActionType.DeleteArtist:
+        case DBActionType.DeleteTag:
+            {
+                let funcs = {
+                    [DBActionType.DeleteTrack]: helpers.deleteTrack,
+                    [DBActionType.DeleteAlbum]: helpers.deleteAlbum,
+                    [DBActionType.DeleteArtist]: helpers.deleteArtist,
+                    [DBActionType.DeleteTag]: helpers.deleteTag,
+                }
+                let res = await funcs[action.type](req, action.payload);
+                status = res.status;
+                response = res.body;
+                break;
+            }
     }
 
     return { response: response, status: status };
@@ -234,60 +248,55 @@ export function randomDBAction(
     );
 
     switch (type) {
-        case DBActionType.CreateTrack: {
-            return {
-                type: type,
-                payload: createRandomTrack(
-                    db,
-                    userId,
-                    distribution.createTrackParams,
-                    randomNumGen
-                ),
-                userId: userId,
-            };
-        }
-        case DBActionType.CreateArtist: {
-            return {
-                type: type,
-                payload: createRandomArtist(
-                    db,
-                    userId,
-                    distribution.createArtistParams,
-                    randomNumGen
-                ),
-                userId: userId,
-            };
-        }
-        case DBActionType.CreateAlbum: {
-            return {
-                type: type,
-                payload: createRandomAlbum(
-                    db,
-                    userId,
-                    distribution.createAlbumParams,
-                    randomNumGen
-                ),
-                userId: userId,
-            };
-        }
-        case DBActionType.CreateTag: {
-            return {
-                type: type,
-                payload: createRandomTag(
-                    db,
-                    userId,
-                    distribution.createTagParams,
-                    randomNumGen
-                ),
-                userId: userId,
-            };
-        }
-        case DBActionType.DeleteTrack: {
+        case DBActionType.CreateTrack:
+        case DBActionType.CreateArtist:
+        case DBActionType.CreateAlbum:
+        case DBActionType.CreateTag:
+            {
+                let funcs = {
+                    [DBActionType.CreateTrack]: createRandomTrack,
+                    [DBActionType.CreateArtist]: createRandomArtist,
+                    [DBActionType.CreateAlbum]: createRandomAlbum,
+                    [DBActionType.CreateTag]: createRandomTag,
+                }
+                let params = {
+                    [DBActionType.CreateTrack]: distribution.createTrackParams,
+                    [DBActionType.CreateArtist]: distribution.createArtistParams,
+                    [DBActionType.CreateAlbum]: distribution.createAlbumParams,
+                    [DBActionType.CreateTag]: distribution.createTagParams,
+                }
+                return {
+                    type: type,
+                    payload: funcs[type](
+                        db,
+                        userId,
+                        params[type] as any,
+                        randomNumGen
+                    ),
+                    userId: userId,
+                };
+            }
+        case DBActionType.DeleteTrack:
+        case DBActionType.DeleteArtist:
+        case DBActionType.DeleteAlbum:
+        case DBActionType.DeleteTag: {
+            let params = {
+                [DBActionType.DeleteTrack]: distribution.deleteTrackParams,
+                [DBActionType.DeleteArtist]: distribution.deleteArtistParams,
+                [DBActionType.DeleteAlbum]: distribution.deleteAlbumParams,
+                [DBActionType.DeleteTag]: distribution.deleteTagParams,
+            }
+            let objectArrays = {
+                [DBActionType.DeleteTrack]: db[userId].tracks,
+                [DBActionType.DeleteArtist]: db[userId].artists,
+                [DBActionType.DeleteAlbum]: db[userId].albums,
+                [DBActionType.DeleteTag]: db[userId].tags,
+            }
             return {
                 type: type,
-                payload: applyDistribution(distribution.deleteTrackParams.validTrack, randomNumGen) ?
-                    Math.floor(randomNumGen() * db[userId].tracks.length) + 1 :
-                    Math.floor(randomNumGen() * db[userId].tracks.length) + 1 + db[userId].tracks.length,
+                payload: applyDistribution(params[type].validId, randomNumGen) ?
+                    Math.floor(randomNumGen() * objectArrays[type].length) + 1 :
+                    Math.floor(randomNumGen() * objectArrays[type].length) + 1 + objectArrays[type].length,
                 userId: userId,
             }
         }