nomiscript/

ast.rs

use core::fmt;

use num_rational::Ratio;

pub type Fraction = Ratio<i64>;

/// Kind tag for one server-entity wasm struct. Each variant maps to a
/// concrete `$<kind>` GC struct registered in
/// `CompileContext::new_skeleton`, plus a set of typed field accessors
/// in the native registry. Adding an entity adds one variant here +
/// one row in the `nomi_entity!` macro invocation; the compiler and
/// host-side allocators pick up the rest by expansion.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub enum EntityKind {
    Account,
    Commodity,
    Transaction,
    Split,
    Tag,
    Price,
    SshKey,
    /// Error condition raised by `(error 'code "msg")` and caught by
    /// `(handler-case)`. Maps to the `$nomi_condition` struct registered
    /// for exception support; the clause variable `e` binds at this kind so
    /// `(error-code e)` / `(error-message e)` type-check.
    Condition,
}

impl EntityKind {
    /// Name of the wasm struct type the compiler registers in
    /// `CompileContext::new_skeleton` for this entity kind. Keep in
    /// lockstep with the `register_struct_type` calls there.
    #[must_use]
    pub fn type_name(self) -> &'static str {
        match self {
            Self::Account => "account",
            Self::Commodity => "commodity_entity",
            Self::Transaction => "transaction",
            Self::Split => "split",
            Self::Tag => "tag_entity",
            Self::Price => "price",
            Self::SshKey => "ssh_key",
            Self::Condition => "nomi_condition",
        }
    }
}

impl fmt::Display for EntityKind {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.type_name())
    }
}

/// Element type of a homogeneous `$pair` chain. Tracked at compile time so
/// CAR/CDR emit the right downcast and CONS refuses heterogeneous mixing
/// with a structured type error. Kept as a `Copy` enum so `WasmType` stays
/// `Copy` — and so adding a new element type stays a one-line variant
/// addition. Nesting (pairs-of-pairs) waits for a follow-up sub-slice
/// once flat lists are stable across the consumers.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub enum PairElement {
    I32,
    /// Truth-value cell: shares `I32`'s i31-boxed car representation (CAR/CDR
    /// emit the same i31 downcast), but distinct so a bool extracted from a
    /// list serializes as `Nil` / `Bool`, not `Number` — the list-element
    /// analogue of [`WasmType::Bool`] vs `I32`.
    Bool,
    Ratio,
    Commodity,
    StringRef,
    Entity(EntityKind),
    /// Heterogeneous escape hatch (ADR-0025). Cars stay as raw
    /// `anyref`; CAR returns `WasmType::AnyRef` and the script must
    /// downcast at the use site (or consume via type-test natives like
    /// `ok?` / `err-code`). CONS widens to this variant when the two
    /// arms disagree on element type, and host fns that produce
    /// fundamentally heterogeneous lists (e.g. =catch-each= result
    /// cells) construct directly into `PairRef(AnyRef)`.
    AnyRef,
}

impl fmt::Display for PairElement {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::I32 => write!(f, "i32"),
            Self::Bool => write!(f, "bool"),
            Self::Ratio => write!(f, "ratio"),
            Self::Commodity => write!(f, "commodity"),
            Self::StringRef => write!(f, "string"),
            Self::Entity(kind) => write!(f, "{kind}"),
            Self::AnyRef => write!(f, "any"),
        }
    }
}

impl PairElement {
    /// The matching `WasmType` for a pair's car when extracted.
    #[must_use]
    pub fn as_wasm_type(self) -> WasmType {
        match self {
            Self::I32 => WasmType::I32,
            Self::Bool => WasmType::Bool,
            Self::Ratio => WasmType::Ratio,
            Self::Commodity => WasmType::Commodity,
            Self::StringRef => WasmType::StringRef,
            Self::Entity(kind) => WasmType::EntityRef(kind),
            Self::AnyRef => WasmType::AnyRef,
        }
    }

    /// Inverse of `as_wasm_type`: returns `None` if the given type can't
    /// ride a `$pair`'s anyref car. `WasmType::AnyRef` round-trips to
    /// `PairElement::AnyRef`; nested pairs and closures still need their
    /// own follow-up lattice extension.
    #[must_use]
    pub fn from_wasm_type(ty: WasmType) -> Option<Self> {
        match ty {
            WasmType::I32 => Some(Self::I32),
            // `Bool` keeps its own slot — it shares `I32`'s i31-boxed car
            // representation (the CAR/CDR downcast is identical) but stays
            // distinct so a bool extracted from a list serializes as Nil/Bool,
            // not Number.
            WasmType::Bool => Some(Self::Bool),
            WasmType::Ratio => Some(Self::Ratio),
            WasmType::Commodity => Some(Self::Commodity),
            WasmType::StringRef => Some(Self::StringRef),
            WasmType::EntityRef(kind) => Some(Self::Entity(kind)),
            WasmType::AnyRef => Some(Self::AnyRef),
            WasmType::PairRef(_) | WasmType::Closure(_) => None,
        }
    }

    /// Widen `self` against `other` to the most-specific common
    /// element. Identical types stay; everything else widens to
    /// `AnyRef` so heterogeneous CONS no longer errors. Symmetric.
    #[must_use]
    pub fn widen(self, other: Self) -> Self {
        if self == other { self } else { Self::AnyRef }
    }
}

/// Identifier for a closure signature interned in the compile
/// context's closure registry. Distinct closures sharing the same
/// `(arg-types) -> ret-type` signature share an id (and therefore a
/// `$closure_<id>` wasm GC type); their env-struct types vary
/// independently per scope. The id is allocated in registration order
/// — small, dense, `Copy` — so it can ride inside `WasmType` without
/// growing the enum.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct ClosureSigId(pub u32);

impl fmt::Display for ClosureSigId {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.0)
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub enum WasmType {
    I32,
    /// Boolean: a comparison / predicate / `and` / `or` result, or a runtime
    /// `#t` / `#f`. Wasm representation is identical to `I32` (0 = false,
    /// nonzero = true), so it composes with `if` / `br_if` and boxes via
    /// `ref.i31` exactly like `I32`. It is a DISTINCT compile-time type only
    /// so the debug serializer can surface it as `Nil` / `Bool` rather than
    /// `Number`: an `I32` is a raw count (tag-count, split-count, …) that
    /// serializes as a number, whereas a `Bool` is a truth value. Refused by
    /// arithmetic like every non-numeric type.
    Bool,
    Ratio,
    StringRef,
    /// Commodity-bearing numeric: rational amount + originating commodity
    /// uuid. Distinct from `Ratio` so the compiler can refuse mixing money
    /// and pure-rational arithmetic at compile time. Wasm representation:
    /// `(i64 numer, i64 denom, i64 commodity_hi, i64 commodity_lo)`.
    Commodity,
    /// Homogeneous list cell: `$pair` WasmGC struct with an `anyref` car
    /// and a nullable `$pair` cdr. The `PairElement` records the car's
    /// type at compile time so CAR/CDR can emit the correct downcast and
    /// CONS refuses heterogeneous mixing. Retires the i32-only `$cons` —
    /// every runtime list shape in the compiler routes through this type.
    PairRef(PairElement),
    /// Raw `anyref` car payload extracted from a `PairRef(AnyRef)` or
    /// produced by a host fn that returns a heterogeneous value
    /// (ADR-0025). Refused by arithmetic / numeric comparison / closure
    /// call / typed pair construction; the script must downcast via
    /// type-test natives (e.g. `ok?`, `err-code`) before consuming.
    AnyRef,
    /// Typed server-entity reference: a `(ref null $<kind>)` GC struct
    /// whose field layout matches the `nomi_entity!` declaration for the
    /// kind. Refused by arithmetic / list-CONS / numeric comparison; the
    /// only legal operations are the entity-specific accessor natives
    /// (`account-id`, `commodity-name`, etc.) registered alongside the
    /// struct type.
    EntityRef(EntityKind),
    /// First-class closure value: `(ref null $closure_<sig>)` carrying a
    /// typed funcref + nullable env ref. The `ClosureSigId` indexes the
    /// per-context registry that owns the wasm types and per-call-site
    /// env-struct layouts. Eligible for FUNCALL / APPLY via `call_ref`;
    /// refused by arithmetic / numeric comparison / pair construction.
    Closure(ClosureSigId),
}

impl fmt::Display for WasmType {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::I32 => write!(f, "i32"),
            Self::Bool => write!(f, "bool"),
            Self::Ratio => write!(f, "ratio"),
            Self::StringRef => write!(f, "string"),
            Self::Commodity => write!(f, "commodity"),
            Self::PairRef(elem) => write!(f, "pair<{elem}>"),
            Self::EntityRef(kind) => write!(f, "entity<{kind}>"),
            Self::Closure(sig) => write!(f, "closure<{sig}>"),
            Self::AnyRef => write!(f, "any"),
        }
    }
}

#[derive(Debug, Clone, PartialEq)]
pub struct LambdaParams {
    pub required: Vec<String>,
    pub optional: Vec<(String, Option<Expr>)>,
    pub rest: Option<String>,
    pub key: Vec<(String, Option<Expr>)>,
    pub aux: Vec<(String, Option<Expr>)>,
}

impl LambdaParams {
    pub fn simple(params: Vec<String>) -> Self {
        Self {
            required: params,
            optional: Vec::new(),
            rest: None,
            key: Vec::new(),
            aux: Vec::new(),
        }
    }
}

#[derive(Debug, Clone, PartialEq)]
pub enum Expr {
    Nil,
    Bool(bool),
    Number(Fraction),
    String(String),
    Symbol(String),
    Keyword(String),
    Bytes(Vec<u8>),
    Cons(Box<Expr>, Box<Expr>),
    List(Vec<Expr>),
    Quote(Box<Expr>),
    Quasiquote(Box<Expr>),
    Unquote(Box<Expr>),
    UnquoteSplicing(Box<Expr>),
    Lambda(LambdaParams, Box<Expr>),
    RuntimeValue(crate::runtime::Value),
    WasmRuntime(WasmType),
    /// Value stored in WASM local variable (index, type)
    WasmLocal(u32, WasmType),
}

impl Expr {
    #[must_use]
    pub fn cons(car: Expr, cdr: Expr) -> Self {
        Expr::Cons(Box::new(car), Box::new(cdr))
    }

    /// Returns the `WasmType` if this expression is a runtime value (`WasmRuntime` or `WasmLocal`).
    #[must_use]
    pub fn wasm_type(&self) -> Option<WasmType> {
        match self {
            Self::WasmRuntime(ty) | Self::WasmLocal(_, ty) => Some(*ty),
            _ => None,
        }
    }

    /// True if this is a runtime value (`WasmRuntime` or `WasmLocal`).
    #[must_use]
    pub fn is_wasm_runtime(&self) -> bool {
        matches!(self, Self::WasmRuntime(_) | Self::WasmLocal(_, _))
    }
}

#[derive(Debug, Clone, PartialEq)]
pub struct Annotation {
    pub name: String,
    pub value: Expr,
}

impl Expr {
    #[must_use]
    pub fn is_atom(&self) -> bool {
        !matches!(self, Expr::List(_) | Expr::Cons(_, _))
    }

    #[must_use]
    pub fn as_symbol(&self) -> Option<&str> {
        match self {
            Expr::Symbol(s) => Some(s),
            _ => None,
        }
    }

    #[must_use]
    pub fn as_list(&self) -> Option<&[Expr]> {
        match self {
            Expr::List(l) => Some(l),
            _ => None,
        }
    }

    /// Splits a `Symbol` into `(namespace, name)`. A qualified symbol is
    /// stored canonically as `NS:NAME` (ADR-0029); an unqualified one has no
    /// `:` and yields `(None, name)`. Non-symbols yield `None`. The split is
    /// on the single canonical `:` — `NS::NAME` was already folded to `NS:NAME`
    /// by the reader, so at most one `:` is ever present here.
    #[must_use]
    pub fn symbol_parts(&self) -> Option<(Option<&str>, &str)> {
        let name = self.as_symbol()?;
        Some(match name.split_once(':') {
            Some((ns, base)) => (Some(ns), base),
            None => (None, name),
        })
    }
}

/// Builds the canonical symbol-table key for a (possibly namespaced) name.
/// `NS:NAME` when a namespace is present, bare `NAME` otherwise — the single
/// source of truth for how a qualified name maps to its flat table key.
#[must_use]
pub fn canonical_symbol(namespace: Option<&str>, name: &str) -> String {
    match namespace {
        Some(ns) => format!("{ns}:{name}"),
        None => name.to_string(),
    }
}

#[derive(Debug, Clone, Default)]
pub struct Program {
    pub exprs: Vec<Expr>,
    pub annotations: Vec<Annotation>,
}

impl Program {
    #[must_use]
    pub fn new(exprs: Vec<Expr>) -> Self {
        Self {
            exprs,
            annotations: Vec::new(),
        }
    }

    #[must_use]
    pub fn with_annotations(exprs: Vec<Expr>, annotations: Vec<Annotation>) -> Self {
        Self { exprs, annotations }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_expr_is_atom() {
        assert!(Expr::Nil.is_atom());
        assert!(Expr::Bool(true).is_atom());
        assert!(Expr::Number(Fraction::from_integer(42)).is_atom());
        assert!(Expr::String("hello".into()).is_atom());
        assert!(Expr::Symbol("foo".into()).is_atom());
        assert!(Expr::Keyword("bar".into()).is_atom());
        assert!(!Expr::List(vec![]).is_atom());
        assert!(!Expr::cons(Expr::Nil, Expr::Nil).is_atom());
        assert!(Expr::Lambda(LambdaParams::simple(vec![]), Box::new(Expr::Nil)).is_atom());
    }

    #[test]
    fn test_expr_as_symbol() {
        assert_eq!(Expr::Symbol("foo".into()).as_symbol(), Some("foo"));
        assert_eq!(Expr::Number(Fraction::from_integer(1)).as_symbol(), None);
    }

    #[test]
    fn test_expr_as_list() {
        let list = Expr::List(vec![Expr::Symbol("a".into())]);
        assert!(list.as_list().is_some());
        assert_eq!(list.as_list().unwrap().len(), 1);
        assert!(Expr::Symbol("a".into()).as_list().is_none());
    }
}