fix: avoid regexp when checking long base64 data uris

packages/app/src/lib/utils/getTypeAndExtension.test.ts

@@ -29,3 +29,29 @@ test('getTypeAndExtension', () => {
     outputType: ClapOutputType.VIDEO,
   })
 })
+
+/**
+ * Related to the `Maximum call stack size exceeded` issue
+ * when using RegExp, now with string/array manipulation is
+ * much faster and the `stack` error solved; I wasn't able to easily
+ * replicate the stack size error in vitest env, seems happening only
+ * in Next env; so only a "performance" test is done.
+ *
+ * Issue: https://github.com/jbilcke-hf/clapper/issues/72
+ */
+test('getTypeAndExtension should be fast for long uris', () => {
+  const startTime = Date.now()
+  const longBase64String = 'a'.repeat(500_000_000)
+  const dataUri = `data:image/png;base64,${longBase64String}`
+  const result = getTypeAndExtension(dataUri)
+  expect(result).toStrictEqual({
+    assetFileFormat: 'image/png',
+    category: 'image',
+    extension: 'png',
+    outputType: ClapOutputType.IMAGE,
+  })
+  const endTime = Date.now()
+  const duration = endTime - startTime
+  // Original regexp approach was running around ~350ms; new one is around ~70ms
+  expect(duration).toBeLessThan(200)
+})

packages/app/src/lib/utils/getTypeAndExtension.ts

@@ -1,7 +1,7 @@
 import { ClapOutputType } from '@aitube/clap'
 
 /**
- * break a base64 string into sub-components
+ * break a base64 data uri string into sub-components
  */
 export function getTypeAndExtension(base64: string = ''): {
   // category eg. video, audio, text
@@ -15,17 +15,15 @@ export function getTypeAndExtension(base64: string = ''): {
 
   outputType: ClapOutputType
 } {
-  // Regular expression to extract the MIME type and the base64 data
-  const matches = base64.match(/^data:([A-Za-z-+0-9/]+);base64,(.+)$/)
-
-  if (!matches || matches.length !== 3) {
-    throw new Error('Invalid base64 string')
+  if (!base64.startsWith('data:') || !base64.includes('base64,')) {
+    throw new Error('Invalid base64 data uri provided.')
   }
 
-  const assetFileFormat = matches[1] || ''
+  const base64Index = base64.indexOf('base64,')
+  const mimeType = base64.slice(5, base64Index - 1)
 
   // this should be enough for most media formats (jpeg, png, webp, mp4)
-  const [category, extension] = assetFileFormat.split('/')
+  const [category, extension] = mimeType.split('/')
 
   let outputType = ClapOutputType.TEXT
 
@@ -39,7 +37,7 @@ export function getTypeAndExtension(base64: string = ''): {
 
   return {
     category,
-    assetFileFormat,
+    assetFileFormat: mimeType,
     extension,
     outputType,
   }