finish trying to write the new perser

mono-fmt-macro/src/lib.rs

@@ -65,9 +65,9 @@ impl std::fmt::Debug for FmtPart {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
             Self::Literal(arg0) => f.debug_tuple("Literal").field(arg0).finish(),
-            Self::Debug(arg0) => f.debug_tuple("Debug").finish(),
-            Self::Display(arg0) => f.debug_tuple("Display").finish(),
-            Self::Advanced(arg0, arg1) => f.debug_tuple("Advanced").field(arg0).finish(),
+            Self::Debug(_) => f.debug_tuple("Debug").finish(),
+            Self::Display(_) => f.debug_tuple("Display").finish(),
+            Self::Advanced(arg0, _) => f.debug_tuple("Advanced").field(arg0).finish(),
         }
     }
 }
@@ -234,7 +234,9 @@ impl ToTokens for FmtPart {
 pub fn format_args(tokens: TokenStream) -> TokenStream {
     let input = parse_macro_input!(tokens as Input);
 
-    parser::FmtSpecParser::new(&mut input.format_str.chars().peekable()).parse();
+    if false {
+        parser::FmtSpecParser::new(&mut input.format_str.chars().peekable()).parse().unwrap();
+    }
 
     let formatter = Formatter {
         string: input.format_str.chars().peekable(),

mono-fmt-macro/src/parser.rs

@@ -1,9 +1,27 @@
 use std::{iter::Peekable, str::Chars};
 
-#[derive(Debug, PartialEq, Default)]
+#[derive(Debug, PartialEq)]
+pub enum Alignment {
+    Left,
+    Center,
+    Right,
+}
+
+impl Alignment {
+    fn from_char(char: char) -> Result<Self, ()> {
+        match char {
+            '<' => Ok(Self::Left),
+            '^' => Ok(Self::Center),
+            '>' => Ok(Self::Right),
+            _ => Err(()),
+        }
+    }
+}
+
+#[derive(Debug, PartialEq)]
 pub struct Align {
-    amount: usize,
-    char: Option<char>,
+    kind: Alignment,
+    fill: Option<char>,
 }
 
 #[derive(Debug, PartialEq, Default)]
@@ -24,6 +42,12 @@ pub enum FmtType {
     Other(String),
 }
 
+#[derive(Debug, PartialEq)]
+enum Precision {
+    Num(usize),
+    Asterisk,
+}
+
 #[derive(Debug, PartialEq, Default)]
 pub struct FmtSpec {
     arg: Argument,
@@ -32,12 +56,13 @@ pub struct FmtSpec {
     alternate: bool,
     zero: bool,
     width: Option<usize>,
-    precision: Option<usize>,
+    precision: Option<Precision>,
     kind: FmtType,
 }
 
 pub struct FmtSpecParser<'a> {
     chars: &'a mut Peekable<Chars<'a>>,
+    /// The last state of the parser.
     state: State,
     argument: FmtSpec,
 }
@@ -47,13 +72,12 @@ enum State {
     Initial,
     Argument,
     // : here
-    Fill,
     Align,
     Sign,
+    Alternate,
     Zero,
     Width,
     Precision,
-    Type,
     Done,
 }
 
@@ -89,21 +113,33 @@ impl<'a> FmtSpecParser<'a> {
         false
     }
 
-    fn eat_until(&mut self, char: char) -> Option<String> {
+    fn expect(&mut self, char: char) -> Result<(), ()> {
+        if !self.eat(char) {
+            return Err(());
+        }
+        Ok(())
+    }
+
+    fn eat_until(&mut self, should_stop: impl Fn(char) -> bool) -> Option<String> {
         let mut string = String::new();
         let mut has_char = false;
-        while self.peek() != Some(char) {
-            self.next();
-            string.push(char);
+        // let_chains would be neat here
+        while self.peek().is_some() && !should_stop(self.peek().unwrap()) {
+            let next = self.next().unwrap();
+            string.push(next);
             has_char = true;
         }
         has_char.then_some(string)
     }
 
+    fn eat_until_match(&mut self, char: char) -> Option<String> {
+        self.eat_until(|c| c == char)
+    }
+
     fn step(&mut self) -> Result<(), ()> {
         match self.state {
             State::Initial => {
-                let argument = if let Some(arg) = self.eat_until(':') {
+                let argument = if let Some(arg) = self.eat_until_match(':') {
                     if let Ok(num) = arg.parse() {
                         Argument::PositionalExplicit(num)
                     } else {
@@ -119,18 +155,94 @@ impl<'a> FmtSpecParser<'a> {
                 if !self.eat(':') {
                     return Err(());
                 }
-
-                Ok(())
             }
-            State::Argument => todo!(),
-            State::Fill => todo!(),
-            State::Align => todo!(),
-            State::Sign => todo!(),
-            State::Zero => todo!(),
-            State::Width => todo!(),
-            State::Precision => todo!(),
-            State::Type => todo!(),
+            State::Argument => match self.next().ok_or(())? {
+                c @ ('>' | '^' | '<') => {
+                    self.argument.align = Some(Align {
+                        kind: Alignment::from_char(c)?,
+                        fill: None,
+                    });
+                    self.state = State::Align;
+                }
+                other => {
+                    if let Some(c @ ('>' | '^' | '<')) = self.peek() {
+                        self.argument.align = Some(Align {
+                            kind: Alignment::from_char(c).unwrap(),
+                            fill: Some(other),
+                        });
+                    }
+
+                    self.state = State::Align;
+                }
+            },
+            State::Align => {
+                if let Some(c @ ('+' | '-')) = self.peek() {
+                    self.next();
+                    self.argument.sign = Some(c);
+                }
+                self.state = State::Sign;
+            }
+            State::Sign => {
+                if self.eat('#') {
+                    self.argument.alternate = true;
+                }
+                self.state = State::Alternate;
+            }
+            State::Alternate => {
+                if self.eat('0') {
+                    self.argument.zero = true;
+                }
+                self.state = State::Zero;
+            }
+            State::Zero => {
+                if let Some(width) = self.eat_until(|c| !c.is_ascii_digit()) {
+                    let width = width.parse().map_err(|_| ())?;
+                    self.argument.width = Some(width);
+                }
+                self.state = State::Width;
+            }
+            State::Width => {
+                if self.eat('.') {
+                    if let Some(precision) = self.eat_until(|c| c != '*' && !c.is_ascii_digit()) {
+                        let precision = if precision == "*" {
+                            Precision::Asterisk
+                        } else {
+                            Precision::Num(precision.parse().map_err(|_| ())?)
+                        };
+                        self.argument.precision = Some(precision);
+                    }
+                }
+                self.state = State::Precision;
+            }
+            State::Precision => match self.next() {
+                Some('?') => {
+                    self.argument.kind = FmtType::Debug;
+                    self.expect('}')?;
+                }
+                Some('x') => {
+                    self.expect('?')?;
+                    self.argument.kind = FmtType::LowerHex;
+                    self.expect('}')?;
+                }
+                Some('X') => {
+                    self.expect('?')?;
+                    self.argument.kind = FmtType::UpperHex;
+                    self.expect('}')?;
+                }
+                Some('}') | None => {}
+                Some(other) => {
+                    if let Some(kind) = self.eat_until(|c| c == '}') {
+                        self.argument.kind = FmtType::Other(format!("{other}{kind}"));
+                        self.expect('}')?;
+                    } else {
+                        self.argument.kind = FmtType::Default;
+                        self.expect('}')?;
+                    }
+                }
+            },
             State::Done => unreachable!(),
         }
+
+        Ok(())
     }
 }