Fixed incorrect cursor position if prompt contains ANSI sequences

- And added delete key handling

main.c

@@ -161,6 +161,47 @@ size_t utf8_display_width(const char *buf, size_t len)
   return width;
 }
 
+size_t visible_width(const char *s)
+{
+  size_t i = 0;
+  size_t width = 0;
+
+  while (s[i]) {
+
+    // ANSI escape sequence
+    if (s[i] == '\x1b' && s[i+1] == '[') {
+      i += 2;
+
+      while (s[i] && !((s[i] >= '@' && s[i] <= '~')))
+        i++;
+
+      if (s[i]) i++;
+      continue;
+    }
+
+    unsigned char c = s[i];
+
+    if ((c & 0x80) == 0) {
+      i += 1;
+      width += 1;
+    }
+    else if ((c & 0xE0) == 0xC0) {
+      i += 2;
+      width += 1;
+    }
+    else if ((c & 0xF0) == 0xE0) {
+      i += 3;
+      width += 1;
+    }
+    else {
+      i += 4;
+      width += 1;
+    }
+  }
+
+  return width;
+}
+
 char* __readline_interactive(char* prompt)
 {
   enable_raw_mode();
@@ -179,7 +220,7 @@ char* __readline_interactive(char* prompt)
     write(STDOUT_FILENO, buf, len);
 
     swrite(STDOUT_FILENO, "\x1b[K");
-    size_t prompt_width = utf8_display_width(prompt, strlen(prompt));
+    size_t prompt_width = visible_width(prompt);
     size_t cell_cursor = utf8_display_width(buf, cursor);
     char seq[64];
     snprintf(seq, sizeof(seq), "\r\x1b[%zuC", prompt_width + cell_cursor);
@@ -193,7 +234,7 @@ char* __readline_interactive(char* prompt)
     if (clen <= 0) continue;
 
     if (utf8[0] == '\x1b') {
-      char seq[2];
+      char seq[3];
       if (read(STDIN_FILENO, &seq[0], 1) != 1) continue;
       if (read(STDIN_FILENO, &seq[1], 1) != 1) continue;
       
@@ -208,6 +249,22 @@ char* __readline_interactive(char* prompt)
 	  case 'D': // Arrow left
 	    cursor = prev_char_start(buffer, cursor);
 	    break;
+	  case '3':
+	    if (read(STDIN_FILENO, &seq[2], 1) != 1) continue;
+	    switch (seq[2])
+	    {
+	      case '~': // Delete
+		if (cursor < len) {
+
+		  size_t next = next_char_start(buffer, len, cursor);
+		  size_t diff = next - cursor;
+
+		  memmove(buffer + cursor, buffer + next, len - next);
+		  len -= diff;
+		}
+		break;
+	    }
+	    break;
 	}
       }
     } else if (utf8[0] == '\r') { // enter