use std::rc::Rc;
use crate::ast::*;

//TODO maybe these functions should take closures that return a KeepRecursing | StopHere type,
//or a tuple of (T, <that type>)

pub trait ASTVisitor: Sized {
  type BlockHandler: BlockVisitor = ();
  fn ast(&mut self, _ast: &AST) {}
  fn block(&mut self) -> Self::BlockHandler { Self::BlockHandler::new() }
  fn block_finished(&mut self, handler: Self::BlockHandler) {}
  fn statement(&mut self, _statement: &Statement) {}
  fn declaration(&mut self, _declaration: &Declaration) {}
  fn signature(&mut self, _signature: &Signature) {}
  fn type_declaration(&mut self, _name: &TypeSingletonName, _body: &TypeBody, _mutable: bool) {}
  fn type_alias(&mut self, _alias: &Rc<String>, _original: &Rc<String>) {}
  fn binding(&mut self, _name: &Rc<String>, _constant: bool, _type_anno: Option<&TypeIdentifier>, _expr: &Expression) {}
  fn implemention(&mut self, _type_name: &TypeIdentifier, _interface_name: Option<&TypeSingletonName>, _block: &Vec<Declaration>) {}
  fn interface(&mut self, _name: &Rc<String>, _signatures: &Vec<Signature>) {}
  fn expression(&mut self, _expression: &Expression) {}
  fn expression_kind(&mut self, _kind: &ExpressionKind) {}
  fn type_annotation(&mut self, _type_anno: Option<&TypeIdentifier>) {}
  fn named_struct(&mut self, _name: &QualifiedName, _fields: &Vec<(Rc<String>, Expression)>) {}
  fn call(&mut self, _f: &Expression, _arguments: &Vec<InvocationArgument>) {}
  fn index(&mut self, _indexee: &Expression, _indexers: &Vec<Expression>) {}
  fn if_expression(&mut self, _discrim: Option<&Expression>, _body: &IfExpressionBody) {}
  fn condition_arm(&mut self, _arm: &ConditionArm) {}
  fn while_expression(&mut self, _condition: Option<&Expression>, _body: &Block) {}
  fn for_expression(&mut self, _enumerators: &Vec<Enumerator>, _body: &ForBody) {}
  fn lambda(&mut self, _params: &Vec<FormalParam>, _type_anno: Option<&TypeIdentifier>, _body: &Block) {}
  fn invocation_argument(&mut self, _arg: &InvocationArgument) {}
  fn formal_param(&mut self, _param: &FormalParam) {}
  fn import(&mut self, _import: &ImportSpecifier) {}
  fn module(&mut self, _module: &ModuleSpecifier) {}
  fn qualified_name(&mut self, _name: &QualifiedName) {}
  fn nat_literal(&mut self, _n: u64) {}
  fn float_literal(&mut self, _f: f64) {}
  fn string_literal(&mut self, _s: &Rc<String>) {}
  fn bool_literal(&mut self, _b: bool) {}
  fn binexp(&mut self, _op: &BinOp, _lhs: &Expression, _rhs: &Expression) {}
  fn prefix_exp(&mut self, _op: &PrefixOp, _arg: &Expression) {}
  fn pattern(&mut self, _pat: &Pattern) {}
}

pub trait BlockVisitor {
  fn new() -> Self;
  fn pre_block(&mut self) {}
  fn post_block(&mut self) {}
}

impl BlockVisitor for () {
  fn new() -> () { () }
}