wip: fix(dsl): maybe getting somewhere?

dsl/src/dsl.rs

@@ -1,6 +1,11 @@
 use crate::*;
+use std::error::Error;
 
-#[derive(Error, Debug, Copy, Clone, PartialEq)] pub enum DslError {
+/// Standard result type for DSL-specific operations.
+pub type DslResult<T> = Result<T, DslErr>;
+
+/// DSL-specific error codes.
+#[derive(Error, Debug, Copy, Clone, PartialEq)] pub enum DslErr {
     #[error("parse failed: not implemented")]
     Unimplemented,
     #[error("parse failed: empty")]
@@ -13,41 +18,23 @@ use crate::*;
     Code(u8),
 }
 
-/// Thing that may construct itself from `State` and [DslValue].
-pub trait FromDsl<State>: Sized {
-    fn try_provide (
-        state: &State,
-        value: DslValue<impl DslStr, impl DslExp>
-    ) -> Perhaps<Self>;
-    fn provide (
-        state: &State,
-        value: DslValue<impl DslStr, impl DslExp>,
-        error: impl Fn()->Box<dyn std::error::Error>
-    ) -> Usually<Self> {
-        match Self::try_provide(state, value)? {
-            Some(value) => Ok(value),
-            _ => Err(error())
-        }
-    }
-}
-
-pub type DslResult<T> = Result<T, DslError>;
-
-/// Marker trait for supported string types.
-pub trait DslStr: PartialEq + Clone + Default + Debug + AsRef<str> {}
-impl<T: PartialEq + Clone + Default + Debug + AsRef<str>> DslStr for T {}
-
-/// Marker trait for supported expression types.
-pub trait DslExp: PartialEq + Clone + Default + Debug {}
-impl<T: PartialEq + Clone + Default + Debug> DslExp for T {}
-
-/// A DSL value generic over string and expression types.
-/// See [CstValue] and [AstValue].
+/// Enumeration of possible DSL tokens.
+/// Generic over string and expression storage.
+///
+/// * [ ] FIXME: Value may be [Err] which may shadow [Result::Err]
+/// * [DslVal::Exp] wraps an expression depth and a [CstIter]
+///   with the remaining part of the expression.
+///   * expression depth other that 0 mean unclosed parenthesis.
+///   * closing and unopened parenthesis panics during reading.
+///   * [ ] TODO: signed depth might be interesting
+/// * [DslVal::Sym] and [DslVal::Key] are stringish literals
+///   with slightly different parsing rules.
+/// * [DslVal::Num] is an unsigned integer literal.
 #[derive(Clone, Debug, PartialEq, Default)]
-pub enum DslValue<Str: DslStr, Exp: DslExp> {
+pub enum DslVal<Str, Exp> {
     #[default]
     Nil,
-    Err(DslError),
+    Err(DslErr),
     Num(usize),
     Sym(Str),
     Key(Str),
@@ -55,38 +42,69 @@ pub enum DslValue<Str: DslStr, Exp: DslExp> {
     Exp(usize, Exp),
 }
 
-impl<Str: DslStr, Exp: DslExp> DslValue<Str, Exp> {
+pub trait Dsl {
+    type Str: PartialEq + Clone + Default + Debug + AsRef<str>;
+    type Exp: PartialEq + Clone + Default + Debug + Dsl;
+    fn nth (&self, index: usize) -> Option<DslVal<Self::Str, Self::Exp>>;
+    fn val (&self) -> DslVal<Self::Str, Self::Exp> {
+        self.nth(0).unwrap_or(DslVal::Nil)
+    }
+    // exp-only nth here?
+}
+
+impl<
+    Str: PartialEq + Clone + Default + Debug + AsRef<str>,
+    Exp: PartialEq + Clone + Default + Debug + Dsl,
+> Dsl for DslVal<Str, Exp> {
+    type Str = Str;
+    type Exp = Exp;
+    fn val (&self) -> DslVal<Str, Exp> {
+        self.clone()
+    }
+    fn nth (&self, index: usize) -> Option<DslVal<Str, Exp>> {
+        todo!()
+    }
+}
+
+/// May construct self from state and DSL.
+pub trait DslFrom<State>: Sized {
+    fn try_dsl_from (state: &State, value: &impl Dsl) -> Perhaps<Self>;
+    fn dsl_from (
+        state: &State, value: &impl Dsl, error: impl Fn()->Box<dyn Error>
+    ) -> Usually<Self> {
+        match Self::try_dsl_from(state, value)? {
+            Some(value) => Ok(value),
+            _ => Err(error())
+        }
+    }
+}
+
+/// May construct another from self and DSL.
+pub trait DslInto<Item> {
+    fn try_dsl_into (&self, dsl: &impl Dsl) -> Perhaps<Item>;
+    fn dsl_into (
+        &self, value: &impl Dsl, error: impl Fn()->Box<dyn Error>
+    ) -> Usually<Item> {
+        match Self::try_dsl_into(self, value)? {
+            Some(value) => Ok(value),
+            _ => Err(error())
+        }
+    }
+}
+
+impl<Str, Exp> DslVal<Str, Exp> {
     pub fn is_nil (&self) -> bool {
         matches!(self, Self::Nil)
     }
-    pub fn as_err (&self) -> Option<&DslError> {
+    pub fn as_err (&self) -> Option<&DslErr> {
         if let Self::Err(e) = self { Some(e) } else { None }
     }
     pub fn as_num (&self) -> Option<usize> {
         if let Self::Num(n) = self { Some(*n) } else { None }
     }
-    pub fn as_sym (&self) -> Option<&str> {
-        if let Self::Sym(s) = self { Some(s.as_ref()) } else { None }
-    }
-    pub fn as_key (&self) -> Option<&str> {
-        if let Self::Key(k) = self { Some(k.as_ref()) } else { None }
-    }
-    pub fn as_str (&self) -> Option<&str> {
-        if let Self::Str(s) = self { Some(s.as_ref()) } else { None }
-    }
     pub fn as_exp (&self) -> Option<&Exp> {
         if let Self::Exp(_, x) = self { Some(x) } else { None }
     }
-    pub fn exp_match <T, F> (&self, namespace: &str, cb: F) -> Perhaps<T>
-    where F: Fn(&str, &Exp)-> Perhaps<T> {
-        if let Some(Self::Key(key)) = self.exp_head()
-        && key.as_ref().starts_with(namespace)
-        && let Some(tail) = self.exp_tail() {
-            cb(key.as_ref().split_at(namespace.len()).1, tail)
-        } else {
-            Ok(None)
-        }
-    }
     pub fn exp_depth (&self) -> Option<usize> {
         todo!()
     }
@@ -107,4 +125,54 @@ impl<Str: DslStr, Exp: DslExp> DslValue<Str, Exp> {
     }
 }
 
-impl<Str: DslStr + Copy, Exp: DslExp + Copy> Copy for DslValue<Str, Exp> {}
+impl<Str: Copy, Exp: Copy> Copy for DslVal<Str, Exp> {}
+
+impl<Str: AsRef<str>, Exp> DslVal<Str, Exp> {
+    pub fn as_sym (&self) -> Option<&str> {
+        if let Self::Sym(s) = self { Some(s.as_ref()) } else { None }
+    }
+    pub fn as_key (&self) -> Option<&str> {
+        if let Self::Key(k) = self { Some(k.as_ref()) } else { None }
+    }
+    pub fn as_str (&self) -> Option<&str> {
+        if let Self::Str(s) = self { Some(s.as_ref()) } else { None }
+    }
+    pub fn exp_match <T, F> (&self, namespace: &str, cb: F) -> Perhaps<T>
+    where F: Fn(&str, &Exp)-> Perhaps<T> {
+        if let Some(Self::Key(key)) = self.exp_head()
+        && key.as_ref().starts_with(namespace)
+        && let Some(tail) = self.exp_tail() {
+            cb(key.as_ref().split_at(namespace.len()).1, tail)
+        } else {
+            Ok(None)
+        }
+    }
+}
+
+macro_rules! from_str {
+    ($Struct:ty |$source:ident| $expr:expr) => {
+        impl<'s> From<&'s str> for $Struct {
+            fn from ($source: &'s str) -> Self {
+                $expr 
+            }
+        }
+    }
+}
+
+from_str!(Ast|source|Self::from(CstIter::from(source)));
+from_str!(Cst<'s>|source|Self(CstIter(CstConstIter(source))));
+from_str!(CstIter<'s>|source|Self(CstConstIter(source)));
+from_str!(CstConstIter<'s>|source|Self::new(source));
+
+pub fn dsl_val <A: Into<X>, B: Into<Y>, X, Y> (val: DslVal<A, B>) -> DslVal<X, Y> {
+    use DslVal::*;
+    match val {
+        Nil => Nil,
+        Err(e) => Err(e),
+        Num(u) => Num(u),
+        Sym(s) => Sym(s.into()),
+        Key(s) => Key(s.into()),
+        Str(s) => Str(s.into()),
+        Exp(d, x) => Exp(d, x.into()),
+    }
+}