8 files changed, 179 insertions, 34 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 842949d..062b9ba 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -11,4 +11,9 @@ name = "derive"
 version = "0.1.0"
 dependencies = [
  "crimtag",
+ "lookahead",
 ]
+
+[[package]]
+name = "lookahead"
+version = "0.1.0"
diff --git a/Cargo.toml b/Cargo.toml
index a20cdc3..dc6bbe8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [workspace]
-members = ["derive","crimtag"]
-default-members = ["derive","crimtag"]
+members = ["derive","crimtag", "lookahead"]
+default-members = ["lookahead", "derive","crimtag"]
 resolver = "3"
 
 [workspace.dependencies]
diff --git a/crimtag/src/context.rs b/crimtag/src/context.rs
index 6f8e04f..15448ee 100644
--- a/crimtag/src/context.rs
+++ b/crimtag/src/context.rs
@@ -107,24 +107,63 @@ pub enum MappedValue<'a> {
 impl<'a> fmt::Debug for MappedValue<'a> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
-            MappedValue::<'a>::Struct(_) => write!(f, "MappedValue"),
-            MappedValue::<'a>::List(_) => write!(f, "MappedList"),
-            MappedValue::<'a>::Str(v) => write!(f, "{:?}", v), 
-            MappedValue::<'a>::String(v) => write!(f, "{:?}", v),
-            MappedValue::<'a>::Int8(v) => write!(f, "{:?}", v),
-            MappedValue::<'a>::Int16(v) => write!(f, "{:?}", v),
-            MappedValue::<'a>::Int32(v) => write!(f, "{:?}", v),
-            MappedValue::<'a>::Int64(v) => write!(f, "{:?}", v),
-            MappedValue::<'a>::UInt8(v) => write!(f, "{:?}", v),
-            MappedValue::<'a>::UInt16(v) => write!(f, "{:?}", v),
-            MappedValue::<'a>::UInt32(v) => write!(f, "{:?}", v),
-            MappedValue::<'a>::UInt64(v) => write!(f, "{:?}", v),
-            MappedValue::<'a>::Float32(v) => write!(f, "{:?}", v),
-            MappedValue::<'a>::Float64(v) => write!(f, "{:?}", v),
-            MappedValue::<'a>::Bool(v) => write!(f, "{:?}", v),
+            MappedValue::<'a>::Struct(_)    => write!(f, "MappedValue"),
+            MappedValue::<'a>::List(_)      => write!(f, "MappedList"),
+            MappedValue::<'a>::Str(v)       => write!(f, "{:?}", v), 
+            MappedValue::<'a>::String(v)    => write!(f, "{:?}", v),
+            MappedValue::<'a>::Int8(v)      => write!(f, "{:?}", v),
+            MappedValue::<'a>::Int16(v)     => write!(f, "{:?}", v),
+            MappedValue::<'a>::Int32(v)     => write!(f, "{:?}", v),
+            MappedValue::<'a>::Int64(v)     => write!(f, "{:?}", v),
+            MappedValue::<'a>::UInt8(v)     => write!(f, "{:?}", v),
+            MappedValue::<'a>::UInt16(v)    => write!(f, "{:?}", v),
+            MappedValue::<'a>::UInt32(v)    => write!(f, "{:?}", v),
+            MappedValue::<'a>::UInt64(v)    => write!(f, "{:?}", v),
+            MappedValue::<'a>::Float32(v)   => write!(f, "{:?}", v),
+            MappedValue::<'a>::Float64(v)   => write!(f, "{:?}", v),
+            MappedValue::<'a>::Bool(v)      => write!(f, "{:?}", v),
         }
+    } 
+}
+
+macro_rules! basic_mapped_value_from {
+    ( $x:ident, $y:ident ) => {
+        impl<'a> From<&$x> for MappedValue<'a> {
+            fn from(val: &$x) -> MappedValue<'a> {
+                MappedValue::$y(*val)
+            }
+        }
+    };
+}
+
+basic_mapped_value_from!(i8, Int8);
+basic_mapped_value_from!(i16, Int16);
+basic_mapped_value_from!(i32, Int32);
+basic_mapped_value_from!(i64, Int64);
+basic_mapped_value_from!(u8, UInt8);
+basic_mapped_value_from!(u16, UInt16);
+basic_mapped_value_from!(u32, UInt32);
+basic_mapped_value_from!(u64, UInt64);
+basic_mapped_value_from!(f32, Float32);
+basic_mapped_value_from!(f64, Float64);
+basic_mapped_value_from!(bool, Bool);
+
+impl<'a> From<&'a String> for MappedValue<'a> {
+    fn from(val: &'a String ) -> MappedValue<'a> {
+        MappedValue::String(val)
+    }
+}
+
+impl<'a, T: MappedStructure<'a>> From<&'a Vec<T>> for MappedValue<'a> {
+    fn from(val: &'a Vec<T> ) -> MappedValue<'a> {
+        MappedValue::List(val)
+    }
+}
+
+impl<'a,T: MappedStructure<'a>> From<&'a T> for MappedValue<'a> {
+    fn from(val: &'a T ) -> MappedValue<'a> {
+        MappedValue::Struct(val)
     }
-    
 }
 
 pub struct StatefulContext<'a> {
diff --git a/derive/Cargo.toml b/derive/Cargo.toml
index 65f3a75..bb5ddf3 100644
--- a/derive/Cargo.toml
+++ b/derive/Cargo.toml
@@ -6,5 +6,9 @@ edition = "2024"
 [lib]
 proc-macro = true
 
+[dependencies]
+lookahead = {path="../lookahead"}
+
 [dev-dependencies]
 crimtag = { path = "../crimtag"}
+
diff --git a/derive/src/lib.rs b/derive/src/lib.rs
index f9c9180..bb299d0 100644
--- a/derive/src/lib.rs
+++ b/derive/src/lib.rs
@@ -1,9 +1,11 @@
 extern crate proc_macro;
 use proc_macro::{TokenStream,TokenTree,Ident,Delimiter};
 
+use lookahead::LookAhead;
+
 #[proc_macro_derive(CrimtagMappable)]
 pub fn derive_crimtag_mappable(s: TokenStream) -> TokenStream {
-    let mut i = s.into_iter();
+    let mut i = LookAhead::<2,_,_>::new(s.into_iter());
     while let Some(t) = i.next() {
         if let TokenTree::Ident(ident) = t &&
             ident.to_string() == "struct" {
@@ -18,7 +20,7 @@ pub fn derive_crimtag_mappable(s: TokenStream) -> TokenStream {
 
     // TODO: Expand this to include the generic parameters and the where? at
     // least the parameters.
-    println!("struct name: {:?}", name);
+    //println!("struct name: {:?}", name);
 
     let mut newfunc = format!(
 r#"impl<'a> crimtag::MappedStructure<'a> for {} {{
@@ -34,24 +36,20 @@ r#"impl<'a> crimtag::MappedStructure<'a> for {} {{
         if let TokenTree::Group(g) = &n &&
             g.delimiter() == Delimiter::Brace {
             // Operate on the struct members.
-            let mut gi = g.stream().into_iter();
-            let mut cur = 0usize;
-            let mut tok = [gi.next(), gi.next()];
+            let mut gi = LookAhead::<2,_,_>::new(g.stream().into_iter());
             loop {
-                if let Some(TokenTree::Punct(ch)) = &tok[(cur+1)%2] &&
+                if let Some(TokenTree::Punct(ch)) = gi.peek(1) &&
                     ch.as_char() == ':' &&
-                    let Some(TokenTree::Ident(id)) = &tok[cur] {
-                    println!("!!!!!!!!!! -> {}", id);
+                    let Some(TokenTree::Ident(id)) = gi.peek(0) {
+                    //println!("!!!!!!!!!! -> {}", id);
                     newfunc.push_str(&format!(
-r#"            "{}" => Some(self.{}.into()),
+r#"            "{}" => Some((&self.{}).into()),
 "#, id, id));
                 }
-                println!(" - {:?} {:?}", tok[cur], tok[(cur+1)%2] );
+                //println!(" -> {:?} ", gi.peek(0));
+                //println!("    {:?}", gi.peek(1) );
                 // Update next.
-                if let Some(ni) = gi.next() {
-                    tok[cur].replace( ni );
-                    cur = (cur+1)%2;
-                } else {
+                if gi.next().is_none() {
                     break;
                 }
             }
@@ -63,13 +61,13 @@ r#"            _ => None,
         }
     }
 }"#);
-
+/*
     println!();
     println!();
     println!("{}", newfunc);
     println!();
     println!();
-
+*/
     newfunc.parse().unwrap()
 }
 
diff --git a/derive/tests/basic.rs b/derive/tests/basic.rs
index 18fc366..a636faa 100644
--- a/derive/tests/basic.rs
+++ b/derive/tests/basic.rs
@@ -2,10 +2,19 @@ use derive::*;
 use crimtag::*;
 
 #[derive(CrimtagMappable)]
+pub struct SubTest {
+    name: String,
+    byline: String,
+    amount: i64,
+}
+
+#[derive(CrimtagMappable)]
 pub struct Test {
     number: i32,
     something: f64,
     inner_thing: String,
+    sub: SubTest,
+    stuff: Vec<SubTest>,
 }
 
 
diff --git a/lookahead/Cargo.toml b/lookahead/Cargo.toml
new file mode 100644
index 0000000..d79f913
--- /dev/null
+++ b/lookahead/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "lookahead"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
diff --git a/lookahead/src/lib.rs b/lookahead/src/lib.rs
new file mode 100644
index 0000000..08bf20e
--- /dev/null
+++ b/lookahead/src/lib.rs
@@ -0,0 +1,84 @@
+pub struct LookAhead<const C: usize, T, U>
+where
+    U: Iterator<Item=T> + Sized
+{
+    iter: U,
+    data: [Option<T>;C],
+    cur: usize,
+    fill: usize,
+}
+
+impl<const C: usize, T, U> LookAhead<C,T,U>
+where
+    U: Iterator<Item=T> + Sized
+{
+    pub fn new(iter: U) -> Self {
+        Self {
+            iter,
+            data: [const {None};C],
+            cur: 0,
+            fill: 0,
+        }
+    }
+
+    pub fn peek(&mut self, offset: usize) -> Option<&T> {
+        assert!(offset<C);
+        self.fill_to( offset );
+        self.data[(self.cur+offset)%C].as_ref()
+    }
+
+    fn fill_to(&mut self, qty: usize) {
+        for i in self.fill..=qty {
+            if let Some(x) = self.iter.next() {
+                self.data[(self.cur+i)%C].replace( x );
+                self.fill += 1;
+            }
+        }
+    }
+}
+
+impl<const C: usize, T, U> std::iter::Iterator for LookAhead<C,T,U> 
+where
+    U: Iterator<Item=T> + Sized
+{
+    type Item=T;
+
+    fn next(&mut self) -> Option<T> {
+        if self.fill == 0 {
+            self.iter.next()
+        } else {
+            let old = self.cur;
+            self.cur = (self.cur+1)%C;
+            self.fill -= 1;
+            self.data[old].take()
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn basic() {
+        let data = [1, 2, 3, 4, 5, 6, 7, 8];
+        let mut i = LookAhead::<3,_,_>::new(data.iter());
+        assert_eq!(i.next(), Some(&1));
+        assert_eq!(i.peek(1), Some(&&3));
+        assert_eq!(i.peek(0), Some(&&2));
+        assert_eq!(i.next(), Some(&2));
+        assert_eq!(i.peek(0), Some(&&3));
+        assert_eq!(i.next(), Some(&3));
+        assert_eq!(i.next(), Some(&4));
+        assert_eq!(i.next(), Some(&5));
+        assert_eq!(i.peek(0), Some(&&6));
+        assert_eq!(i.peek(1), Some(&&7));
+        assert_eq!(i.peek(2), Some(&&8));
+        assert_eq!(i.next(), Some(&6));
+        assert_eq!(i.peek(2), None);
+        assert_eq!(i.next(), Some(&7));
+        assert_eq!(i.peek(2), None);
+        assert_eq!(i.next(), Some(&8));
+        assert_eq!(i.next(), None);
+    }
+}