fix(PPT-764): Prefer AVIF over WebP in format auto-selection

source/constructs/lib/v8/functions/dit-header-normalization.js

@@ -1,7 +1,7 @@
 // Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 // SPDX-License-Identifier: Apache-2.0
 
-const FORMAT_PRIORITY = ['webp', 'avif', 'jpeg', 'png', 'heif', 'tiff', 'raw', 'gif'];
+const FORMAT_PRIORITY = ['avif', 'webp', 'jpeg', 'png', 'heif', 'tiff', 'raw', 'gif'];
 
 const FORMAT_MAPPING = {
   'image/webp': 'webp',

source/constructs/lib/v8/test/snapshot/__snapshots__/image-processing-stack.test.ts.snap

@@ -878,7 +878,7 @@ exports[`ImageProcessingStack Snapshot Test 1`] = `
         "FunctionCode": "// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 // SPDX-License-Identifier: Apache-2.0
 
-const FORMAT_PRIORITY = ['webp', 'avif', 'jpeg', 'png', 'heif', 'tiff', 'raw', 'gif'];
+const FORMAT_PRIORITY = ['avif', 'webp', 'jpeg', 'png', 'heif', 'tiff', 'raw', 'gif'];
 
 const FORMAT_MAPPING = {
   'image/webp': 'webp',

source/constructs/lib/v8/test/unit/dit-function.test.ts

@@ -164,7 +164,7 @@ describe("DIT CloudFront Function", () => {
   describe("Accept header normalization", () => {
     test("should select highest priority format from Accept header", async () => {
       const testCases = [
-        { input: "image/avif,image/webp,image/png", expected: "image/webp" },
+        { input: "image/avif,image/webp,image/png", expected: "image/avif" },
         { input: "image/png,image/jpeg", expected: "image/jpeg" },
         { input: "image/avif,image/heif", expected: "image/avif" },
         { input: "image/gif", expected: "image/gif" },

source/container/src/services/transformation-resolver/auto-optimization/auto-optimizer.test.ts

@@ -46,7 +46,7 @@ describe('applyAutoOptimizations', () => {
       });
     });
 
-    it('should prioritize formats by priority order (webp, avif, jpeg, png)', () => {
+    it('should prioritize formats by priority order (avif, webp, jpeg, png)', () => {
       mockPolicy.outputs = [{ type: 'format', value: 'auto' }];
       mockRequest.headers = { 'dit-accept': 'image/jpeg,image/avif,image/avif,*/*' };
 
@@ -56,6 +56,17 @@ describe('applyAutoOptimizations', () => {
       expect(result[0].value).toBe('avif');
     });
 
+    it('should prefer avif over webp when both are accepted', () => {
+      mockPolicy.outputs = [{ type: 'format', value: 'auto' }];
+      mockRequest.headers = { 'dit-accept': 'image/avif,image/webp' };
+      const imageRequest = { sourceImageContentType: 'image/jpeg' } as ImageProcessingRequest;
+
+      const result = applyAutoOptimizations(baseTransformations, mockRequest as Request, mockPolicy, imageRequest);
+
+      expect(result).toHaveLength(1);
+      expect(result[0]).toEqual({ type: 'format', value: 'avif', source: 'auto' });
+    });
+
     it('should apply static format when policy format is not auto', () => {
       mockPolicy.outputs = [{ type: 'format', value: 'jpeg' }];
       mockRequest.headers = { 'dit-accept': 'image/webp,*/*' };

source/container/src/services/transformation-resolver/auto-optimization/auto-optimizer.ts

@@ -5,7 +5,7 @@ import { Request } from 'express';
 import { Transformation, TransformationPolicy } from '../../../types/transformation';
 import { ImageProcessingRequest } from '../../../types/image-processing-request';
 
-const FORMAT_PRIORITY = ['webp', 'avif', 'jpeg', 'png', 'heif', 'tiff', 'raw', 'gif'];
+const FORMAT_PRIORITY = ['avif', 'webp', 'jpeg', 'png', 'heif', 'tiff', 'raw', 'gif'];
 // TODO, DISCUSS WITH TEAM FOR OPTIMAL FORMAT PRIORITIY LIST
 const ANIMATION_CAPABLE_FORMATS = new Set(['webp', 'avif', 'gif']);
 const FORMAT_MAPPING: Record<string, string> = {