pub(all) enum Ast {
  String(String)
  Regex(pattern~ : String, flags~ : String)
  Number(Double)
  Boolean(Bool)
  Null
  Placeholder
  Path(Array[Step])
  Binary(op~ : String, lhs~ : Ast, rhs~ : Ast)
  Unary(op~ : String, expr~ : Ast)
  Conditional(condition~ : Ast, consequent~ : Ast, alternate~ : Ast?)
  Construct(Array[Ast])
  Group(Array[(Ast, Ast)])
  Sort(expr~ : Ast, terms~ : Array[SortTerm])
  Lambda(params~ : Array[String], body~ : Ast, signature~ : String?)
  Var(String)
  Bind(name~ : String, value~ : Ast, body~ : Ast)
  Apply(func~ : Ast, args~ : Array[Ast])
  Chain(Array[Ast])
  Block(Array[Ast])
} derive(Eq, 
@moonbitlang/core/debug.Debug
Debug)

pub(all) struct SortTerm {
  expr : Ast
  descending : Bool
} derive(Eq, 
@moonbitlang/core/debug.Debug
Debug)

pub(all) struct Step {
  kind : StepKind
  stage : StepStage
} derive(Eq, 
@moonbitlang/core/debug.Debug
Debug)

pub(all) enum StepKind {
  Name(String)
  Wildcard
  Index(Int)
  Slice(Int?, Int?)
  Eval(Ast)
  Filter(Ast)
  Map(Ast)
  Arrayify
} derive(Eq, 
@moonbitlang/core/debug.Debug
Debug)

pub(all) enum StepStage {
  Single
  Recursive
} derive(Eq, 
@moonbitlang/core/debug.Debug
Debug)

fn arrayify_step() -> Step

fn eval_step(expr : Ast) -> Step

fn map_step(expr : Ast) -> Step

fn name_step(name : String, recursive? : Bool) -> Step

fn wildcard_step(recursive? : Bool) -> Step