package ast

import (
	"bytes"
	"monkey/token"
)

type Node interface {
	TokenLiteral() string
	String() string
}

type Statement interface {
	Node
	statement_node()
}

type Expression interface {
	Node
	expression_node()
}

func (l_program *Program) String() string {
	var out bytes.Buffer
	for _, s := range l_program.Statements {
		out.WriteString(s.String())
	}
	return out.String()
}

type Program struct {
	Statements []Statement
}

type Identifier struct {
	Token token.Token // the token.IDENT token
	Value string
}

type LetStatement struct {
	Token token.Token // token.LET token
	Name  *Identifier
	Value Expression
}

type ReturnStatement struct {
	Token       token.Token // token.RETURN token
	ReturnValue Expression
}

type ExpressionStatement struct {
	Token      token.Token // the first token in the expression
	Expression Expression
}

// Let Statements
func (ls *LetStatement) statement_node() {}

func (ls *LetStatement) TokenLiteral() string {
	return ls.Token.Literal
}

func (ls *LetStatement) String() string {
	var out bytes.Buffer
	out.WriteString(ls.TokenLiteral() + " ")
	out.WriteString(ls.Name.String())
	out.WriteString(" = ")

	if ls.Value != nil {
		out.WriteString(ls.Value.String())
	}
	out.WriteString(";")
	return out.String()
}

// Identifier
func (i *Identifier) expression_node() {}

func (i *Identifier) TokenLiteral() string {
	return i.Token.Literal
}

func (i *Identifier) String() string {
	return i.Value
}

// Program
func (p *Program) TokenLiteral() string {
	if len(p.Statements) > 0 {
		return p.Statements[0].TokenLiteral()
	} else {
		return ""
	}
}

// Return Statements
func (rs *ReturnStatement) statement_node() {}

func (rs *ReturnStatement) TokenLiteral() string {
	return rs.Token.Literal
}

func (rs *ReturnStatement) String() string {
	var out bytes.Buffer
	out.WriteString(rs.TokenLiteral() + " ")
	if rs.ReturnValue != nil {
		out.WriteString(rs.ReturnValue.String())
	}
	out.WriteString(";")
	return out.String()
}

// Expression Statement
func (es *ExpressionStatement) statement_node() {}

func (es *ExpressionStatement) TokenLiteral() string {
	return es.Token.Literal
}

func (es *ExpressionStatement) String() string {
	if es.Expression != nil {
		return es.Expression.String()
	}
	return ""
}