package parsekit

// Tokenizer is the top-level struct that holds the configuration for
// a parser that is based solely on a TokenHandler function.
// The Tokenizer can be instantiated using the parsekit.NewTokenizer()
// method.
type Tokenizer struct {
	parser *Parser
	result *TokenHandlerResult
}

// TokenHandler is the function type that is involved in turning a low level
// stream of UTF8 runes into lexical tokens. Its purpose is to check if input
// data matches some kind of pattern and to report back the results.
//
// A TokenHandler function gets a TokenAPI as its input and returns a boolean to
// indicate whether or not it found a match on the input. The TokenAPI is used
// for retrieving input data to match against and for reporting back results.
type TokenHandler func(t *TokenAPI) bool

// NewTokenizer instantiates a new Tokenizer.
//
// This is a simple wrapper around a TokenHandler function. It can be used to
// match an input string against that TokenHandler function and retrieve the
// results in a straight forward way.
func NewTokenizer(tokenHandler TokenHandler) *Tokenizer {
	tokenizer := &Tokenizer{}
	tokenizer.parser = NewParser(func(p *ParseAPI) {
		if p.On(tokenHandler).Accept() {
			tokenizer.result = p.Result()
			p.Stop()
		} else {
			p.UnexpectedInput("")
		}
	})
	return tokenizer
}

// Execute feeds the input to the wrapped TokenHandler function.
// It returns the TokenHandler's TokenHandlerResult. When an error occurred
// during parsing, the error will be set, nil otherwise.
func (t *Tokenizer) Execute(input string) (*TokenHandlerResult, *Error) {
	err := t.parser.Execute(input)
	return t.result, err
}