1 files changed, 181 insertions, 23 deletions

diff --git a/src/syntax/mod.rs b/src/syntax/mod.rs
index 1b55fb4e..21088b83 100644
--- a/src/syntax/mod.rs
+++ b/src/syntax/mod.rs
@@ -1,9 +1,10 @@
 //! Tokenization and parsing of source code.
 
 use std::fmt::{self, Display, Formatter};
+use unicode_xid::UnicodeXID;
 
 use crate::func::LayoutFunc;
-use crate::size::Size;
+use crate::size::{Size, ScaleSize};
 
 mod tokens;
 #[macro_use]
@@ -88,54 +89,133 @@ pub enum Node {
     Func(FuncCall),
 }
 
-/// A function invocation, consisting of header and a dynamically parsed body.
+/// An invocation of a function.
 #[derive(Debug)]
 pub struct FuncCall {
-    pub header: Spanned<FuncHeader>,
-    pub body: Spanned<Box<dyn LayoutFunc>>,
+    pub call: Box<dyn LayoutFunc>,
 }
 
 impl PartialEq for FuncCall {
     fn eq(&self, other: &FuncCall) -> bool {
-        (self.header == other.header) && (&self.body == &other.body)
+        &self.call == &other.call
     }
 }
 
-/// Contains header information of a function invocation.
-#[derive(Debug, Clone, PartialEq)]
-pub struct FuncHeader {
-    pub name: Spanned<String>,
-    pub args: FuncArgs,
-}
-
 /// The arguments passed to a function.
 #[derive(Debug, Clone, PartialEq)]
 pub struct FuncArgs {
-    pub positional: Vec<Spanned<Expression>>,
-    pub keyword: Vec<Spanned<(Spanned<String>, Spanned<Expression>)>>
+    pub pos: Vec<Spanned<PosArg>>,
+    pub key: Vec<Spanned<KeyArg>>,
 }
 
 impl FuncArgs {
     /// Create an empty collection of arguments.
-    fn new() -> FuncArgs {
+    pub fn new() -> FuncArgs {
         FuncArgs {
-            positional: vec![],
-            keyword: vec![],
+            pos: vec![],
+            key: vec![],
         }
     }
+
+    /// Add a positional argument.
+    pub fn add_pos(&mut self, arg: Spanned<PosArg>) {
+        self.pos.push(arg);
+    }
+
+    /// Add a keyword argument.
+    pub fn add_key(&mut self, arg: Spanned<KeyArg>) {
+        self.key.push(arg);
+    }
+
+    /// Force-extract the first positional argument.
+    pub fn get_pos<E: ExpressionKind>(&mut self) -> ParseResult<Spanned<E>> {
+        expect(self.get_pos_opt())
+    }
+
+    /// Extract the first positional argument.
+    pub fn get_pos_opt<E: ExpressionKind>(&mut self) -> ParseResult<Option<Spanned<E>>> {
+        Ok(if !self.pos.is_empty() {
+            let spanned = self.pos.remove(0);
+            let span = spanned.span;
+            Some(Spanned::new(E::from_expr(spanned)?, span))
+        } else {
+            None
+        })
+    }
+
+    /// Iterator over positional arguments.
+    pub fn pos(&mut self) -> std::vec::IntoIter<Spanned<PosArg>> {
+        let vec = std::mem::replace(&mut self.pos, vec![]);
+        vec.into_iter()
+    }
+
+    /// Force-extract a keyword argument.
+    pub fn get_key<E: ExpressionKind>(&mut self, name: &str) -> ParseResult<Spanned<E>> {
+        expect(self.get_key_opt(name))
+    }
+
+    /// Extract a keyword argument.
+    pub fn get_key_opt<E: ExpressionKind>(&mut self, name: &str) -> ParseResult<Option<Spanned<E>>> {
+        Ok(if let Some(index) = self.key.iter().position(|arg| arg.v.key.v.0 == name) {
+            let Spanned { v, span } = self.key.swap_remove(index);
+            Some(Spanned::new(E::from_expr(v.value)?, span))
+        } else {
+            None
+        })
+    }
+
+    /// Extract any keyword argument.
+    pub fn get_key_next(&mut self) -> Option<Spanned<KeyArg>> {
+        self.key.pop()
+    }
+
+    /// Iterator over all keyword arguments.
+    pub fn keys(&mut self) -> std::vec::IntoIter<Spanned<KeyArg>> {
+        let vec = std::mem::replace(&mut self.key, vec![]);
+        vec.into_iter()
+    }
+
+    /// Clear the argument lists.
+    pub fn clear(&mut self) {
+        self.pos.clear();
+        self.key.clear();
+    }
+
+    /// Whether both the positional and keyword argument lists are empty.
+    pub fn is_empty(&self) -> bool {
+        self.pos.is_empty() && self.key.is_empty()
+    }
 }
 
-/// One argument passed to a function.
+fn expect<E: ExpressionKind>(opt: ParseResult<Option<Spanned<E>>>) -> ParseResult<Spanned<E>> {
+    match opt {
+        Ok(Some(spanned)) => Ok(spanned),
+        Ok(None) => error!("expected {}", E::NAME),
+        Err(e) => Err(e),
+    }
+}
+
+/// A positional argument passed to a function.
+pub type PosArg = Expression;
+
+/// A keyword argument passed to a function.
 #[derive(Debug, Clone, PartialEq)]
-pub enum FuncArg {
-    Positional(Spanned<Expression>),
-    Keyword(Spanned<(Spanned<String>, Spanned<Expression>)>),
+pub struct KeyArg {
+    pub key: Spanned<Ident>,
+    pub value: Spanned<Expression>,
+}
+
+/// Either a positional or keyword argument.
+#[derive(Debug, Clone, PartialEq)]
+pub enum DynArg {
+    Pos(Spanned<PosArg>),
+    Key(Spanned<KeyArg>),
 }
 
 /// An argument or return value.
 #[derive(Clone, PartialEq)]
 pub enum Expression {
-    Ident(String),
+    Ident(Ident),
     Str(String),
     Num(f64),
     Size(Size),
@@ -146,7 +226,7 @@ impl Display for Expression {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         use Expression::*;
         match self {
-            Ident(s) => write!(f, "{}", s),
+            Ident(i) => write!(f, "{}", i),
             Str(s) => write!(f, "{:?}", s),
             Num(n) => write!(f, "{}", n),
             Size(s) => write!(f, "{}", s),
@@ -156,3 +236,81 @@ impl Display for Expression {
 }
 
 debug_display!(Expression);
+
+/// An identifier.
+#[derive(Clone, PartialEq)]
+pub struct Ident(pub String);
+
+impl Ident {
+    fn new(string: String) -> ParseResult<Ident> {
+        if is_identifier(&string) {
+            Ok(Ident(string))
+        } else {
+            error!("invalid identifier: `{}`", string);
+        }
+    }
+}
+
+impl Display for Ident {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        write!(f, "{}", self.0)
+    }
+}
+
+debug_display!(Ident);
+
+/// Whether this word is a valid unicode identifier.
+fn is_identifier(string: &str) -> bool {
+    let mut chars = string.chars();
+
+    match chars.next() {
+        Some('-') => (),
+        Some(c) if UnicodeXID::is_xid_start(c) => (),
+        _ => return false,
+    }
+
+    while let Some(c) = chars.next() {
+        match c {
+            '.' | '-' => (),
+            c if UnicodeXID::is_xid_continue(c) => (),
+            _ => return false,
+        }
+    }
+
+    true
+}
+
+/// Kinds of expressions.
+pub trait ExpressionKind: Sized {
+    const NAME: &'static str;
+
+    /// Create from expression.
+    fn from_expr(expr: Spanned<Expression>) -> ParseResult<Self>;
+}
+
+macro_rules! kind {
+    ($type:ty, $name:expr, $($patterns:tt)*) => {
+        impl ExpressionKind for $type {
+            const NAME: &'static str = $name;
+
+            fn from_expr(expr: Spanned<Expression>) -> ParseResult<Self> {
+                #[allow(unreachable_patterns)]
+                Ok(match expr.v {
+                    $($patterns)*,
+                    _ => error!("expected {}", Self::NAME),
+                })
+            }
+        }
+    };
+}
+
+kind!(Expression, "expression", e                         => e);
+kind!(Ident,      "identifier", Expression::Ident(ident)  => ident);
+kind!(String,     "string",     Expression::Str(string)   => string);
+kind!(f64,        "number",     Expression::Num(num)      => num);
+kind!(bool,       "boolean",    Expression::Bool(boolean) => boolean);
+kind!(Size,       "size",       Expression::Size(size)    => size);
+kind!(ScaleSize,  "number or size",
+    Expression::Size(size) => ScaleSize::Absolute(size),
+    Expression::Num(scale) => ScaleSize::Scaled(scale as f32)
+);