-- Endor AST schema. Source syntax belongs to lexer.peg and grammar.peg.
-- Wire contract: endor-ast-json/1, kind/data tagged sums and UTF-8 byte spans.
-- Builtins: string (owned text), span (UTF-8 byte range), schema_id (wire ID).
-- * is a sequence; ? is optional. Recursion is boxed by the Rust generator.
module Endor {
    AstDocument = (schema_id schema, AstRoot root)
    AstRoot = Module(Program body)
            | Expression(Expr body)
            | Interactive(InteractiveInput body)

    Name = (string text, span span)
    Program = (Decl* declarations, span span)
    Decl = (DeclKind kind, span span)
    DeclKind = Function(Function definition)
             | Class(Class definition)
    Class = (Name name, Name? base, Parameter* fields, Function* methods, span span)
    Function = (Name name, Parameter* parameters, Name return_type, Block body, span span)
    Parameter = (Name name, Name type_name, span span)
    Block = (Stmt* statements, span span)
    Stmt = (StmtKind kind, span span)
    StmtKind = Binding(Binding binding)
             | Assignment(Assignment assignment)
             | MemberAssignment(MemberAssignment assignment)
             | If(IfStatement statement)
             | While(WhileStatement statement)
             | Return(ReturnStatement statement)
             | Expression(Expr expression)
             | Declaration(Decl declaration)
    Binding = (Name name, Expr value, span span)
    Assignment = (Name name, Expr value, span span)
    MemberAssignment = (Expr object, Name name, Expr value, span span)
    IfStatement = (Expr condition, Block body, Block? otherwise, span span)
    WhileStatement = (Expr condition, Block body, span span)
    ReturnStatement = (Expr? value, span span)
    InteractiveInput = (Stmt* statements, span span)

    Expr = (ExprKind kind, span span)
    ExprKind = Name(string text)
             | Number(string spelling)
             | String(string value)
             | Symbol(Name name)
             | Await(Expr operand)
             | Unary(UnaryOp operation, Expr operand)
             | Binary(BinaryOp operation, Expr left, Expr right)
             | Member(Expr object, Name name)
             | Call(Expr callee, Expr* arguments)
    UnaryOp = Negate
    BinaryOp = Add | Subtract | Multiply | Divide | Equal | NotEqual | Less | LessEqual | Greater | GreaterEqual
}