package ast

import "matheval/token"

// Node is the interface all AST nodes implement.
// The unexported marker method seals the interface — only types
// in this package can implement it.
type Node interface {
	node() // sealed marker
}

// NumberLit represents a numeric literal (e.g. 3.14).
type NumberLit struct {
	Value float64
}

func (*NumberLit) node() {}

// BinaryExpr represents a binary operation (e.g. 1 + 2).
type BinaryExpr struct {
	Op    token.Type // Plus, Minus, Star, Slash
	Left  Node
	Right Node
}

func (*BinaryExpr) node() {}

// Ident represents a variable reference (e.g. x, y).
type Ident struct {
	Name string
}

func (*Ident) node() {}

// FuncCall represents a function call (e.g. f(1, 2+3)).
type FuncCall struct {
	Name string
	Args []Node
}

func (*FuncCall) node() {}

// Statement is the interface for top-level REPL input.
// A line is either an expression to evaluate or a function definition.
// The unexported marker method seals the interface.
type Statement interface {
	stmt() // sealed marker
}

// ExprStmt wraps an expression as a top-level statement.
type ExprStmt struct {
	Expr Node
}

func (*ExprStmt) stmt() {}

// FuncDef represents a function definition (e.g. f(x, y) = x + y).
type FuncDef struct {
	Name   string
	Params []string
	Body   Node
}

func (*FuncDef) stmt() {}