feat: add tests, utils and refactor resizer class

src/app/constants.py

@@ -0,0 +1,2 @@
+ALLOWED_INPUT_FORMATS = ["png", "jpeg"]
+ALLOWED_CONTENT_TYPE = ["image/png", "image/jpeg"]

src/app/image_resizer.py

@@ -4,6 +4,8 @@
 
 
 class ImageResizer:
+    """Generate the resized image output."""
+
     def __init__(
         self,
         image: PngImageFile,
@@ -20,9 +22,15 @@ def __init__(
         self.output_image = None
 
     def get_original_image_size(self):
+        """Get the original input image
+
+        Returns:
+            tuple: (width, height).
+        """
         return self.image_width, self.image_height
 
     def resize(self):
+        """Resize image and store it internally"""
         self.output_image = self.image.resize(
             (
                 int(self.target_width),
@@ -31,11 +39,24 @@ def resize(self):
         )
 
     def get_output_image(self):
+        """Get the resized image.
+
+        Returns:
+            bytes: Resized image.
+        """
         if self.output_image is None:
-            self.output_image = self.resize()
+            self.resize()
         return self.output_image
 
     def get_output_buffer(self):
+        """Return a stremeable buffer for response purposes.
+
+        Returns:
+            io.Bytes(): Resized image buffer.
+        """
+        print(self.output_image)
+        if self.output_image is None:
+            self.resize()
         self.image_buffer = io.BytesIO()
         self.output_image.convert("RGB").save(
             self.image_buffer, self.output_format.upper()

src/app/main.py

@@ -1,12 +1,13 @@
 import io
 from typing import Annotated, Literal
 
-from fastapi import FastAPI, File, Form, Response, UploadFile, status
+from fastapi import FastAPI, File, Form, UploadFile, status
 from fastapi.responses import JSONResponse, StreamingResponse
 from mangum import Mangum
 from PIL import Image
 
 from src.app.image_resizer import ImageResizer
+from src.app.utils import validate_content_type
 
 app = FastAPI(
     title="Thumbnail Generator",
@@ -58,27 +59,15 @@ async def get_thumbnail(
         File: IOBytes of the resized image, default format is PNG.
     """
     # Validate input file type
-    if file.content_type not in ["image/png", "image/jpeg"]:
-        return Response(
-            status_code=status.HTTP_400_BAD_REQUEST,
-            content=f"Supported formats: [.png, .jpeg]; provided '{file.filename}'.",
-        )
+    validate_content_type(file.filename, file.content_type)
 
-    # Read image data
-    image_data = await file.read()
-
-    image = ImageResizer(
-        image=Image.open(io.BytesIO(image_data)),
+    # Get image resizer
+    image_buffer = ImageResizer(
+        image=Image.open(io.BytesIO(await file.read())),
         target_width=width,
         target_height=height,
         output_format=output_format,
-    )
-
-    # Perfrom resizing
-    image.resize()
-
-    # Get output buffer
-    image_buffer = image.get_output_buffer()
+    ).get_output_buffer()
 
     # Send image as response
     return StreamingResponse(image_buffer, media_type=f"image/{output_format.lower()}")

src/app/utils.py

@@ -0,0 +1,11 @@
+from src.app.constants import ALLOWED_CONTENT_TYPE, ALLOWED_INPUT_FORMATS
+from fastapi.exceptions import HTTPException
+from fastapi import status
+
+
+def validate_content_type(filename: str, content_type: str) -> bool:
+    if content_type not in ALLOWED_CONTENT_TYPE:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=f"Supported formats: {ALLOWED_INPUT_FORMATS}; provided '{filename}'.",
+        )

tests/image_resizer_test.py

@@ -14,7 +14,6 @@ def test_resize_image(self):
             target_height=128,
             output_format="png",
         )
-        image.resize()
 
         # Act
         result = image.get_output_image()

tests/validate_content_type_test.py

@@ -0,0 +1,26 @@
+from unittest import TestCase
+from src.app.utils import validate_content_type
+from fastapi.exceptions import HTTPException
+
+
+class TestValidateContentType(TestCase):
+    def test_validate_content_type_as_valid(self):
+        # Arrange
+        content_type = "image/png"
+
+        # Act
+        result = validate_content_type("fake.file", content_type)
+
+        # Assert
+        self.assertIsNone(result)
+
+    def test_validate_content_type_as_invalid(self):
+        # Arrange
+        content_type = "image/invalid"
+
+        # Act
+        with self.assertRaises(Exception) as context:
+            validate_content_type("fake.file", content_type)
+
+        # Assert
+        self.assertIsInstance(context.exception, HTTPException)