refactor: error handling by extracting messages

lib/graph/file.graph.ts

@@ -10,7 +10,7 @@ import {
   uuidType,
 } from '../interfaces';
 import { StorageFile } from './storage.file';
-import { AsyncTaskQueue, uuid } from '../utils';
+import { AsyncTaskQueue, uuid, createError } from '../utils';
 
 class FileGraphIml implements FileGraphAbstract {
   constructor(
@@ -93,8 +93,9 @@ class FileGraphIml implements FileGraphAbstract {
       const index = ids.indexOf(vertex.id);
       if (index === -1) return;
       const nextVertexId = ids[index + 1];
-      if (nextVertexId && !vertex.links.includes(nextVertexId))
+      if (nextVertexId && !vertex.links.includes(nextVertexId)) {
         return { links: [...vertex.links, nextVertexId] };
+      }
     };
 
     const updateResult = await this.storageFile.updateLine(updater);
@@ -107,12 +108,14 @@ class FileGraphIml implements FileGraphAbstract {
   ): Promise<boolean> {
     return this.updateArc(targetVertexId, vertex => {
       if (vertex.id !== sourceVertexId) return;
-      if (!vertex.links.includes(targetVertexId))
-        return { links: [...vertex.links, targetVertexId] };
-
-      throw new Error(
-        `targetVertexId: ${targetVertexId} already exists in vertex ${sourceVertexId}`,
-      );
+      if (vertex.links.includes(targetVertexId)) {
+        throw createError(
+          'TARGET_VERTEX_ALREADY_EXISTS',
+          targetVertexId,
+          sourceVertexId,
+        );
+      }
+      return { links: [...vertex.links, targetVertexId] };
     });
   }
 
@@ -122,12 +125,14 @@ class FileGraphIml implements FileGraphAbstract {
   ): Promise<boolean> {
     return this.updateArc(targetVertexId, vertex => {
       if (vertex.id !== sourceVertexId) return;
-      if (vertex.links.includes(targetVertexId))
-        return { links: vertex.links.filter(v => v !== targetVertexId) };
-
-      throw new Error(
-        `targetVertexId: ${targetVertexId} don't exists in vertex ${sourceVertexId}`,
-      );
+      if (!vertex.links.includes(targetVertexId)) {
+        throw createError(
+          'TARGET_VERTEX_DOES_NOT_EXIST',
+          targetVertexId,
+          sourceVertexId,
+        );
+      }
+      return { links: vertex.links.filter(v => v !== targetVertexId) };
     });
   }
 
@@ -138,8 +143,9 @@ class FileGraphIml implements FileGraphAbstract {
     const targetVertexExists = await this.findOne(
       vertex => vertex.id === sourceVertexId,
     );
-    if (!targetVertexExists)
-      throw new Error(`Target vertex with ID "${targetVertexId}" not found`);
+    if (!targetVertexExists) {
+      throw createError('TARGET_VERTEX_NOT_FOUND', targetVertexId);
+    }
 
     return targetVertexExists.links.includes(targetVertexId);
   }
@@ -148,13 +154,11 @@ class FileGraphIml implements FileGraphAbstract {
     vertexId: uuidType,
     maxLevel: number,
   ): Promise<IVertexTree<T>[]> {
-    if (maxLevel < 0) throw new Error('Level must be a non-negative integer.');
+    if (maxLevel < 0) throw createError('NEGATIVE_LEVEL');
     const startingVertex = await this.findOne<T>(
       vertex => vertex.id === vertexId,
     );
-
-    if (!startingVertex)
-      throw new Error(`Vertex with id ${vertexId} not found.`);
+    if (!startingVertex) throw createError('VERTEX_NOT_FOUND', vertexId);
 
     const resultVertices: IVertexTree<T>[] = [];
     const queue = [{ vertex: startingVertex, currentLevel: 0 }];
@@ -187,8 +191,9 @@ class FileGraphIml implements FileGraphAbstract {
       const targetVertexExists = await this.findOne(
         vertex => vertex.id === targetVertexId,
       );
-      if (!targetVertexExists)
-        throw new Error(`Target vertex with ID "${targetVertexId}" not found`);
+      if (!targetVertexExists) {
+        throw createError('TARGET_VERTEX_NOT_FOUND', targetVertexId);
+      }
 
       const updateResult = await this.storageFile.updateLine(updater);
       return updateResult;

lib/utils/errors.ts

@@ -0,0 +1,25 @@
+import { uuidType } from '../interfaces';
+
+const ERRORS = {
+  VERTEX_NOT_FOUND: (id: uuidType) => `Vertex with id ${id} not found.`,
+  TARGET_VERTEX_NOT_FOUND: (id: uuidType) =>
+    `Target vertex with ID "${id}" not found.`,
+  TARGET_VERTEX_DOES_NOT_EXIST: (targetId: uuidType, sourceId: uuidType) =>
+    `targetVertexId: ${targetId} don't exist in vertex ${sourceId}`,
+  TARGET_VERTEX_ALREADY_EXISTS: (targetId: uuidType, sourceId: uuidType) =>
+    `targetVertexId: ${targetId} already exists in vertex ${sourceId}`,
+  NEGATIVE_LEVEL: 'Level must be a non-negative integer.',
+};
+
+const createError = (type: keyof typeof ERRORS, ...args: any[]) => {
+  const errorTemplate: string | ((...args: any[]) => string) = ERRORS[type];
+  if (!errorTemplate) throw new Error('Unknown error type');
+
+  return new Error(
+    typeof errorTemplate === 'function'
+      ? errorTemplate(...args)
+      : errorTemplate,
+  );
+};
+
+export { createError };

lib/utils/index.ts

@@ -1,3 +1,4 @@
 export * from './uuid';
 export * from './async-task-queue';
 export * from './merge-vertex';
+export * from './errors';

test/graph.test.ts

@@ -2,6 +2,7 @@ import assert from 'node:assert';
 import { before, describe, it } from 'node:test';
 import { FileGraph, IUuidArray, uuidType } from 'lib';
 import { writeFileSync } from 'node:fs';
+import { createError } from 'lib/utils';
 
 const pathGraph = 'data.txt';
 const graph = FileGraph(pathGraph);
@@ -163,10 +164,7 @@ describe('Links operations', () => {
       await graph.findUpToLevel('A' as uuidType, -1);
       assert.fail('Expected error not thrown');
     } catch (error) {
-      assert.strictEqual(
-        error.message,
-        'Level must be a non-negative integer.',
-      );
+      assert.strictEqual(error.message, createError('NEGATIVE_LEVEL').message);
     }
   });
 
@@ -177,7 +175,7 @@ describe('Links operations', () => {
     } catch (error) {
       assert.strictEqual(
         error.message,
-        'Vertex with id NonExistentVertex not found.',
+        createError('VERTEX_NOT_FOUND', 'NonExistentVertex').message,
       );
     }
   });