diff --git a/Justfile b/Justfile
new file mode 100644
index 0000000..5de3e0b
--- /dev/null
+++ b/Justfile
@@ -0,0 +1,2 @@
+fmt:
+    cargo +nightly fmt --all
diff --git a/imap/src/proto/macros.rs b/imap/src/proto/macros.rs
index 308beaf..2d76e85 100644
--- a/imap/src/proto/macros.rs
+++ b/imap/src/proto/macros.rs
@@ -1,3 +1,4 @@
+#[macro_export]
 macro_rules! rule {
     ($vis:vis $name:ident : $ret:ty => $expr:expr) => {
         $vis fn $name(i: &[u8]) -> nom::IResult<&[u8], $ret> {
@@ -5,3 +6,20 @@ macro_rules! rule {
         }
     };
 }
+
+#[macro_export]
+macro_rules! pred {
+    ($($expr:tt)*) => { |c: u8| _pred!(expr { $($expr)* })(c) };
+}
+
+macro_rules! _pred {
+    (expr {}) => {};
+    (expr { $name:ident }) => { |b| $name(b) };
+    (expr { ! $($expr:tt)* }) => { |b| !_pred!(expr { $($expr)* })(b) };
+    (expr { ($($L:tt)*) && ($($R:tt)*) }) => {
+        |b| { _pred!(expr { $($L)* })(b) && _pred!(expr { $($R)* })(b) }
+    };
+    (expr { ($($L:tt)*) || ($($R:tt)*) }) => {
+        |b| { _pred!(expr { $($L)* })(b) || _pred!(expr { $($R)* })(b) }
+    };
+}
diff --git a/imap/src/proto/rfc2234.rs b/imap/src/proto/rfc2234.rs
index 4ab3de1..ce30f56 100644
--- a/imap/src/proto/rfc2234.rs
+++ b/imap/src/proto/rfc2234.rs
@@ -8,17 +8,20 @@ rule!(pub ALPHA : u8 => satisfy(|c| (c >= b'a' && c <= b'z') || (c >= b'A' && c
 
 rule!(pub BIT : u8 => satisfy(|c| c == b'0' || c == b'1'));
 
-rule!(pub CHAR : u8 => satisfy(|c| c != b'\0'));
+pub fn is_char(c: u8) -> bool { c != b'\0' }
+rule!(pub CHAR : u8 => satisfy(is_char));
 
 rule!(pub CR : u8 => byte(b'\x0d'));
 
 rule!(pub CRLF : (u8, u8) => pair(CR, LF));
 
-rule!(pub CTL : u8 => satisfy(|c| c <= b'\x1f' || c == b'\x7f'));
+pub fn is_ctl(c: u8) -> bool { c <= b'\x1f' || c == b'\x7f' }
+rule!(pub CTL : u8 => satisfy(is_ctl));
 
 rule!(pub DIGIT : u8 => satisfy(|c| c >= b'\x30' && c <= b'\x39'));
 
-rule!(pub DQUOTE : u8 => byte(b'\x22'));
+pub fn is_dquote(c: u8) -> bool { c == b'\x22' }
+rule!(pub DQUOTE : u8 => satisfy(is_dquote));
 
 rule!(pub HEXDIG : u8 => alt((DIGIT, satisfy(|c| c >= b'A' && c <= b'F'))));
 
@@ -30,7 +33,8 @@ rule!(pub LWSP : () => skip(many0(alt((skip(WSP), skip(pair(CRLF, WSP)))))));
 
 rule!(pub OCTET : char => anychar);
 
-rule!(pub SP : u8 => byte(b'\x20'));
+pub fn is_sp(c: u8) -> bool { c == b'\x20' }
+rule!(pub SP : u8 => satisfy(is_sp));
 
 rule!(pub VCHAR : u8 => satisfy(|c| c >= b'\x21' && c <= b'\x7e'));
 
diff --git a/imap/src/proto/rfc3501.rs b/imap/src/proto/rfc3501.rs
index 8191e4e..5c7767c 100644
--- a/imap/src/proto/rfc3501.rs
+++ b/imap/src/proto/rfc3501.rs
@@ -10,8 +10,8 @@ use nom::{
     IResult,
 };
 
-use super::rfc2234::{CRLF, DIGIT, DQUOTE};
-use super::parsers::byte;
+use super::parsers::satisfy;
+use super::rfc2234::{is_char, is_ctl, is_dquote, is_sp, CRLF, DIGIT, DQUOTE};
 
 rule!(pub astring : Vec<u8> => alt((many1(ASTRING_CHAR), string)));
 
@@ -19,9 +19,26 @@ rule!(pub ASTRING_CHAR : u8 => alt((ATOM_CHAR, resp_specials)));
 
 rule!(pub atom : Vec<u8> => many1(ATOM_CHAR));
 
-pub fn ATOM_CHAR(i: &[u8]) -> IResult<&[u8], u8> {
-    todo!()
+// TODO: somehow incorporate CHAR in here?
+// technically ATOM_CHAR is defined as <any CHAR except atom-specials>
+// but "except"-style rules don't really make sense except for character sets
+// and some other niche cases so probably doesn't warrant a separate combinator
+rule!(pub ATOM_CHAR : u8 => satisfy(pred!((is_char) && (!is_atom_specials))));
+
+pub fn is_atom_specials(c: u8) -> bool {
+    c == b'('
+        || c == b')'
+        || c == b'{'
+        || is_sp(c)
+        || is_ctl(c)
+        || is_list_wildcards(c)
+        || is_quoted_specials(c)
+        || is_resp_specials(c)
 }
+rule!(pub atom_specials : u8 => satisfy(is_atom_specials));
+
+pub fn is_list_wildcards(c: u8) -> bool { c == b'%' || c == b'*' }
+rule!(pub list_wildcards : u8 => satisfy(is_list_wildcards));
 
 /// literal = "{" number "}" CRLF *CHAR8
 ///         ; Number represents the number of CHAR8s
@@ -52,14 +69,14 @@ pub fn number(i: &[u8]) -> IResult<&[u8], u32> {
 
 rule!(pub quoted : Vec<u8> => delimited(DQUOTE, many0(QUOTED_CHAR), DQUOTE));
 
-pub fn QUOTED_CHAR(i: &[u8]) -> IResult<&[u8], u8> {
-    todo!()
-}
+pub fn QUOTED_CHAR(i: &[u8]) -> IResult<&[u8], u8> { todo!() }
 
-rule!(pub resp_specials : u8 => byte(b']'));
+pub fn is_quoted_specials(c: u8) -> bool { is_dquote(c) || c == b'\\' }
+rule!(pub quoted_specials : u8 => satisfy(is_quoted_specials));
+
+pub fn is_resp_specials(c: u8) -> bool { c == b']' }
+rule!(pub resp_specials : u8 => satisfy(is_resp_specials));
 
 rule!(pub string : Vec<u8> => alt((quoted, literal)));
 
-pub fn TEXT_CHAR(i: &[u8]) -> IResult<&[u8], u8> {
-    todo!()
-}
+pub fn TEXT_CHAR(i: &[u8]) -> IResult<&[u8], u8> { todo!() }
diff --git a/rustfmt.toml b/rustfmt.toml
new file mode 100644
index 0000000..397187f
--- /dev/null
+++ b/rustfmt.toml
@@ -0,0 +1,3 @@
+fn_single_line = true
+max_width = 100
+wrap_comments = true
\ No newline at end of file