Strip base64 and attachment content

modules/ExpressionSearchFilter.jsm

@@ -125,12 +125,78 @@ function getPlainText(msgHdr) {
   let stream = folder.getMsgInputStream(msgHdr, reusable);
   let data = NetUtil.readInputStreamToString(stream, msgHdr.messageSize);
   if (!reusable.value) stream.close();
+
   let parser = Cc["@mozilla.org/parserutils;1"].getService(Ci.nsIParserUtils);
-  return parser.convertToPlainText(data,
-    Ci.nsIDocumentEncoder.OutputLFLineBreak |
-    Ci.nsIDocumentEncoder.OutputNoScriptContent |
-    Ci.nsIDocumentEncoder.OutputNoFramesContent |
-    Ci.nsIDocumentEncoder.OutputBodyOnly, 0);
+
+  try {
+    let root = MimeParser.parseSync(data, {strformat: "unicode"});
+    let parts = [];
+
+    function pushPlaceholder(type, info, bytes) {
+      bytes = bytes || 0;
+      let prettyType = type.split("/")[1] || type;
+      parts.push(`[${info}: ${prettyType}, ${bytes} bytes]`);
+    }
+
+    function byteSizeFromBase64(str) {
+      let clean = str.replace(/[^A-Za-z0-9+/=]/g, "");
+      return Math.floor(clean.length * 3 / 4);
+    }
+
+    function replaceInlineBase64(text) {
+      return text.replace(/[A-Za-z0-9+/]{100,}={0,2}/g,
+        m => `[base64: ${byteSizeFromBase64(m)} bytes]`);
+    }
+
+    function walk(node) {
+      if (node.parts && node.parts.length) {
+        for (let child of node.parts) {
+          walk(child);
+        }
+        return;
+      }
+
+      let ct = (node.contentType || "text/plain").toLowerCase();
+      let cd = (node.headers?.["content-disposition"]?.[0] || "").toLowerCase();
+      let enc = (node.headers?.["content-transfer-encoding"]?.[0] || "").toLowerCase();
+      let bodyText = String(node.body || "");
+
+      if (cd.includes("attachment")) {
+        pushPlaceholder(ct, "binary attachment", byteSizeFromBase64(bodyText));
+      } else if (ct.startsWith("text/plain")) {
+        if (enc === "base64") {
+          parts.push(`[base64: ${byteSizeFromBase64(bodyText)} bytes]`);
+        } else {
+          parts.push(replaceInlineBase64(bodyText));
+        }
+      } else if (ct.startsWith("text/html")) {
+        if (enc === "base64") {
+          parts.push(`[base64: ${byteSizeFromBase64(bodyText)} bytes]`);
+        } else {
+          let txt = parser.convertToPlainText(bodyText,
+            Ci.nsIDocumentEncoder.OutputLFLineBreak |
+            Ci.nsIDocumentEncoder.OutputNoScriptContent |
+            Ci.nsIDocumentEncoder.OutputNoFramesContent |
+            Ci.nsIDocumentEncoder.OutputBodyOnly, 0);
+          parts.push(replaceInlineBase64(txt));
+        }
+      } else {
+        // Other single part types treated as attachments
+        pushPlaceholder(ct, "binary attachment", byteSizeFromBase64(bodyText));
+      }
+    }
+
+    walk(root);
+    return parts.join("\n");
+  } catch (e) {
+    // Fallback: convert entire raw message to text
+    aiLog(`Failed to parse MIME, falling back to raw conversion`, {level: 'warn'}, e);
+    return parser.convertToPlainText(data,
+      Ci.nsIDocumentEncoder.OutputLFLineBreak |
+      Ci.nsIDocumentEncoder.OutputNoScriptContent |
+      Ci.nsIDocumentEncoder.OutputNoFramesContent |
+      Ci.nsIDocumentEncoder.OutputBodyOnly, 0);
+  }
 }
 
 let gEndpoint = "http://127.0.0.1:5000/v1/classify";