fix(index): throw error if file param is not rtf

package.json

@@ -76,6 +76,7 @@
     "typescript": "^4.1.3"
   },
   "dependencies": {
+    "file-type": "^16.5.0",
     "semver": "^7.3.4",
     "upath": "^2.0.1"
   }

src/index.js

@@ -1,3 +1,4 @@
+const fileType = require("file-type");
 const fs = require("fs");
 const path = require("upath");
 const semver = require("semver");
@@ -152,14 +153,28 @@ class UnRTF {
 		};
 
 		try {
-			// UnRTF still attempts to convert empty strings/files, so catch them here before
+			/**
+			 * UnRTF will attempt to convert empty strings/files, and non-RTF files
+			 * so catch them here
+			 */
 			if (
 				file === undefined ||
 				fs.existsSync(path.normalizeTrim(file)) === false
 			) {
 				throw new Error("File missing");
 			}
 
+			const results = await fileType.fromFile(path.normalizeTrim(file));
+			if (
+				results === undefined ||
+				results.mime === undefined ||
+				results.mime !== "application/rtf"
+			) {
+				throw new Error(
+					"File is not the correct media type, expected 'application/rtf'"
+				);
+			}
+
 			const { stderr } = await execFileAsync(
 				path.joinSafe(this.unrtfPath, "unrtf"),
 				["--version"]

src/index.test.js

@@ -132,6 +132,21 @@ describe("Convert Function", () => {
 		expect(isHtml(res)).toEqual(false);
 	});
 
+	test("Should return an Error object if file passed not RTF format", async () => {
+		const unRtf = new UnRTF(testBinaryPath);
+		const options = {
+			noPictures: true,
+		};
+		const testTxtFile = `${testDirectory}test.txt`;
+
+		expect.assertions(1);
+		await unRtf.convert(testTxtFile, options).catch((err) => {
+			expect(err.message).toEqual(
+				"File is not the correct media type, expected 'application/rtf'"
+			);
+		});
+	});
+
 	test("Should return an Error object if invalid value types provided for an option are passed to function", async () => {
 		const unRtf = new UnRTF(testBinaryPath);
 		const options = {

test_files/test.txt

@@ -0,0 +1 @@
+I am a test file!