Fix RFC 2047 encoded word length limit

Split long email subjects into multiple RFC 2047 encoded words to comply with the 75-character limit per RFC 2047 Section 2. Each encoded word now contains at most 45 bytes of UTF-8 content (producing max 60 chars of base64 + 12 chars overhead = 72 total). Multiple encoded words are separated by CRLF + space (folding whitespace).

Author: cursoragent

apps/sim/tools/gmail/utils.test.ts

@@ -0,0 +1,47 @@
+/**
+ * @vitest-environment node
+ */
+import{describe,expect,it}from'vitest'
+import{encodeRfc2047}from'./utils'
+
+describe('encodeRfc2047',()=>{
+it('returns ASCII text unchanged',()=>{
+constinput='Simple ASCII Subject'
+expect(encodeRfc2047(input)).toBe(input)
+})
+
+it('encodes short non-ASCII text in a single encoded word',()=>{
+constinput='Hello 世界'
+constresult=encodeRfc2047(input)
+expect(result).toMatch(/^=\?UTF-8\?B\?[A-Za-z0-9+/=]+\?=$/)
+expect(result.length).toBeLessThanOrEqual(75)
+})
+
+it('splits long non-ASCII text into multiple encoded words',()=>{
+constinput='今週のミーティングアジェンダについて検討します'
+constresult=encodeRfc2047(input)
+expect(result).toContain('\r\n ')
+constwords=result.split('\r\n ')
+expect(words.length).toBeGreaterThan(1)
+words.forEach((word)=>{
+expect(word.length).toBeLessThanOrEqual(75)
+expect(word).toMatch(/^=\?UTF-8\?B\?[A-Za-z0-9+/=]+\?=$/)
+})
+})
+
+it('handles very long subjects with emojis',()=>{
+constinput='🎉 '.repeat(30)
+constresult=encodeRfc2047(input)
+constwords=result.split('\r\n ')
+words.forEach((word)=>{
+expect(word.length).toBeLessThanOrEqual(75)
+expect(word).toMatch(/^=\?UTF-8\?B\?[A-Za-z0-9+/=]+\?=$/)
+})
+})
+
+it('handles edge case of exactly 47 bytes of UTF-8',()=>{
+constinput='a'.repeat(47)
+constresult=encodeRfc2047(input)
+expect(result).not.toContain('\r\n ')
+})
+})

apps/sim/tools/gmail/utils.ts

@@ -298,6 +298,8 @@ function generateBoundary(): string {
  * Encode a header value using RFC 2047 Base64 encoding if it contains non-ASCII characters.
  * Email headers per RFC 2822 must be ASCII-only. Non-ASCII characters (emojis, accented
  * characters, etc.) must be encoded as =?UTF-8?B?<base64>?= to avoid mojibake.
+ * Per RFC 2047, each encoded word must not exceed 75 characters. Long values are split
+ * into multiple encoded words separated by CRLF + space (folding whitespace).
  * @param value The header value to encode
  * @returns The encoded header value, or the original if it's already ASCII
  */
@@ -306,8 +308,20 @@ export function encodeRfc2047(value: string): string {
 if(/^[\x00-\x7F]*$/.test(value)){
 returnvalue
 }
-constencoded=Buffer.from(value,'utf-8').toString('base64')
-return`=?UTF-8?B?${encoded}?=`
+
+constutf8Bytes=Buffer.from(value,'utf-8')
+constencodedWords: string[]=[]
+constmaxBytesPerWord=45
+
+letoffset=0
+while(offset<utf8Bytes.length){
+constchunk=utf8Bytes.subarray(offset,offset+maxBytesPerWord)
+constencoded=chunk.toString('base64')
+encodedWords.push(`=?UTF-8?B?${encoded}?=`)
+offset+=maxBytesPerWord
+}
+
+returnencodedWords.join('\r\n ')
 }
 
 /**