feat: add signature encoding, auto-detect base on decode, and show notification

dash.js

@@ -5,13 +5,27 @@ import * as speck32_64ecb from './speck32_64ecb.js';
 const textarea = document.getElementById('textarea');
 const encoderDropdown = document.getElementById('encoder');
 const cipherDropdown = document.getElementById('cipher');
+const signBtn = document.getElementById('sign');
+const sigDetect = document.getElementById('sigDetect');
+
+const SIG = {
+    3: '\u{200D}\u{200B}\u{00AD}\u{180E}',
+    6: '\u{200D}\u{200B}\u{00AD}\u{2060}',
+    8: '\u{200D}\u{200B}\u{00AD}\u{FEFF}'
+};
+
 document.getElementById('encodeButton').addEventListener('click', ACT);
 document.getElementById('decodeButton').addEventListener('click', ACT);
-document.getElementById('sign').addEventListener('click', e =>
+signBtn.addEventListener('click', e =>
     e.target.classList.toggle('on')
 );
 
+let fadeTimer;
+
 function ACT(event) {
+    clearTimeout(fadeTimer);
+    sigDetect.className = '';
+
     if (textarea.value === '') {
         textarea.value = 'The text box is empty.';
         return;
@@ -19,14 +33,35 @@ function ACT(event) {
 
     const op = event.target.id === 'encodeButton' ? 'NO' : 'YES';
     const cipher = getCipherKey();
-    const base = encoderDropdown.value.split('-')[1];
+    let base = encoderDropdown.value.split('-')[1];
+    let text = textarea.value;
+
+    if (op === 'YES') {
+        const sigBase = Object.keys(SIG).find(b => text.includes(SIG[b]));
+        if (sigBase) {
+            if (sigBase !== base) {
+                sigDetect.textContent = `ZWUS-${sigBase} signature detected`;
+                sigDetect.className = 'show';
+                fadeTimer = setTimeout(() =>
+                    sigDetect.className = '', 2000
+                );
+            }
+            base = sigBase;
+            encoderDropdown.value = 'ZWUS-' + base;
+            text = text.replace(SIG[base], '');
+        }
+    }
+
     const needsKey = cipher !== 'PLAIN';
     const kStr = needsKey && prompt('enter password.');
 
     if (needsKey && !kStr) return;
 
     try {
-        textarea.value = DESCRY[op][cipher](textarea.value, base, kStr);
+        let val = DESCRY[op][cipher](text, base, kStr);
+        if (op === 'NO' && signBtn.classList.contains('on'))
+            val = SIG[base] + val;
+        textarea.value = val;
     } catch (e) {
         console.log(e);
     }