func main() {

	// load the libray of pre-built functions for usage in sql queries
	builtins.LoadAllBuiltins()

	// Add a custom function to the VM to make available to SQL language
	// showing lexer/parser accepts it
	expr.FuncAdd("email_is_valid", EmailIsValid)

	// Datasources are easy to write and can be added
	datasource.Register("csv", &datasource.CsvDataSource{})

	// now from here down is standard go database/sql query handling
	db, err := sql.Open("qlbridge", "csv:///dev/stdin")
	if err != nil {
		panic(err.Error())
	}
	defer db.Close()

	rows, err := db.Query(sqlText)
	if err != nil {
		panic(err.Error())
	}
	defer rows.Close()
	cols, _ := rows.Columns()

	// this is just stupid hijinx for getting pointers for unknown len columns
	readCols := make([]interface{}, len(cols))
	writeCols := make([]string, len(cols))
	for i, _ := range writeCols {
		readCols[i] = &writeCols[i]
	}

	for rows.Next() {
		rows.Scan(readCols...)
		fmt.Println(strings.Join(writeCols, ", "))
	}
}

// Example of a custom Function, that we are adding into the Expression VM
//
//         select
//              user_id AS theuserid, email, item_count * 2, reg_date
//         FROM stdio
//         WHERE email_is_valid(email)
func EmailIsValid(ctx vm.EvalContext, email value.Value) (value.BoolValue, bool) {
	emailstr, ok := value.ToString(email.Rv())
	if !ok || emailstr == "" {
		return value.BoolValueFalse, true
	}
	if _, err := mail.ParseAddress(emailstr); err == nil {
		return value.BoolValueTrue, true
	}

	return value.BoolValueFalse, true
}

// Tokens Specific to our PUBSUB
var TokenSubscribeTo lex.TokenType = 1000

// Custom lexer for our maybe hash function
func LexMaybe(l *ql.Lexer) ql.StateFn {

	l.SkipWhiteSpaces()

	keyWord := strings.ToLower(l.PeekWord())

	switch keyWord {
	case "maybe":
		l.ConsumeWord("maybe")
		l.Emit(lex.TokenIdentity)
		return ql.LexExpressionOrIdentity
	}
	return ql.LexExpressionOrIdentity
}

func main() {

	// We are going to inject new tokens into qlbridge
	lex.TokenNameMap[TokenSubscribeTo] = &lex.TokenInfo{Description: "subscribeto"}

	// OverRide the Identity Characters in qlbridge to allow a dash in identity
	ql.IDENTITY_CHARS = "_./-"

	ql.LoadTokenInfo()
	ourDialect.Init()

	// We are going to create our own Dialect that uses a "SUBSCRIBETO" keyword
	pubsub = &ql.Statement{TokenSubscribeTo, []*ql.Clause{
		{Token: TokenSubscribeTo, Lexer: ql.LexColumns},
		{Token: lex.TokenFrom, Lexer: LexMaybe},
		{Token: lex.TokenWhere, Lexer: ql.LexColumns, Optional: true},
	}}
	ourDialect = &ql.Dialect{
		"Subscribe To", []*ql.Statement{pubsub},
	}

	l := ql.NewLexer(`
			SUBSCRIBETO
				count(x), Name
			FROM ourstream
			WHERE 
				k = REPLACE(LOWER(Name),'cde','xxx');
		`, ourDialect)

}