From 5892ef60d865d174a0af03596d69adcc92023386 Mon Sep 17 00:00:00 2001
From: Kir_Antipov <kp.antipov@gmail.com>
Date: Sun, 8 Jan 2023 09:42:07 +0000
Subject: [PATCH] Implemented `FileNotFoundError`

---
 src/utils/errors/file-not-found-error.ts      | 48 +++++++++++++++++++
 .../errors.ts/file-not-found-error.spec.ts    | 42 ++++++++++++++++
 2 files changed, 90 insertions(+)
 create mode 100644 src/utils/errors/file-not-found-error.ts
 create mode 100644 tests/unit/utils/errors.ts/file-not-found-error.spec.ts

diff --git a/src/utils/errors/file-not-found-error.ts b/src/utils/errors/file-not-found-error.ts
new file mode 100644
index 0000000..8ec6a45
--- /dev/null
+++ b/src/utils/errors/file-not-found-error.ts
@@ -0,0 +1,48 @@
+import { PathLike, existsSync } from "node:fs";
+
+/**
+ * Represents an error that occurs when a specified file cannot be found.
+ */
+export class FileNotFoundError extends Error {
+    /**
+     * Default error message pattern.
+     */
+    private static readonly DEFAULT_FILE_NOT_FOUND_ERROR_MESSAGE_PATTERN = (fileName: string) => fileName ? `Could not find file '${fileName}'.` : "Could not find the specified file.";
+
+    /**
+     * The name of the file that could not be found.
+     */
+    private readonly _fileName?: string;
+
+    /**
+     * Constructs a new {@link FileNotFoundError} instance.
+     *
+     * @param fileName - The name of the file that could not be found.
+     * @param message - The error message to display.
+     * @param options - Optional settings for the error object.
+     */
+    constructor(fileName?: string, message?: string, options?: ErrorOptions) {
+        super(message ?? FileNotFoundError.DEFAULT_FILE_NOT_FOUND_ERROR_MESSAGE_PATTERN(fileName), options);
+
+        this.name = "FileNotFoundError";
+        this._fileName = fileName;
+    }
+
+    /**
+     * Gets the name of the file that could not be found.
+     */
+    get fileName(): string | undefined {
+        return this._fileName;
+    }
+
+    /**
+     * Throws a {@link FileNotFoundError} if the specified file does not exist.
+     *
+     * @param fileName - The name of the file to check for existence.
+     */
+    static throwIfNotFound(fileName: PathLike): void | never {
+        if (!existsSync(fileName)) {
+            throw new FileNotFoundError(String(fileName));
+        }
+    }
+}
diff --git a/tests/unit/utils/errors.ts/file-not-found-error.spec.ts b/tests/unit/utils/errors.ts/file-not-found-error.spec.ts
new file mode 100644
index 0000000..88623ad
--- /dev/null
+++ b/tests/unit/utils/errors.ts/file-not-found-error.spec.ts
@@ -0,0 +1,42 @@
+import { FileNotFoundError } from "@/utils/errors/file-not-found-error";
+import mockFs from "mock-fs";
+
+describe("FileNotFoundError", () => {
+    describe("constructor", () => {
+        test("initializes with default message if none provided", () => {
+            const error = new FileNotFoundError("test.txt");
+
+            expect(error).toBeInstanceOf(FileNotFoundError);
+            expect(error.name).toBe("FileNotFoundError");
+            expect(error.message).toBe("Could not find file 'test.txt'.");
+            expect(error.fileName).toBe("test.txt");
+        });
+
+        test("initializes with provided message", () => {
+            const error = new FileNotFoundError("test.txt", "Custom error message");
+
+            expect(error).toBeInstanceOf(FileNotFoundError);
+            expect(error.name).toBe("FileNotFoundError");
+            expect(error.message).toBe("Custom error message");
+            expect(error.fileName).toBe("test.txt");
+        });
+    });
+
+    describe("throwIfNotFound", () => {
+        beforeEach(() => {
+            mockFs({ "test": "test" });
+        });
+
+        afterEach(() => {
+            mockFs.restore();
+        });
+
+        test("throws error if file does not exist", () => {
+            expect(() => FileNotFoundError.throwIfNotFound("test.txt")).toThrow(FileNotFoundError);
+        });
+
+        test("does not throw error if file exists", () => {
+            expect(() => FileNotFoundError.throwIfNotFound("test")).not.toThrow();
+        });
+    });
+});