package chroma

// Coalesce is a Lexer interceptor that collapses runs of common types into a single token.

func Coalesce(lexer Lexer) Lexer { return &coalescer{lexer} }

type coalescer struct{ Lexer }

func (d *coalescer) Tokenise(options *TokeniseOptions, text string) (Iterator, error) {

	var prev Token

	it, err := d.Lexer.Tokenise(options, text)

	if err != nil {

		return nil, err

	}

	return func() Token {

		for token := it(); token != (EOF); token = it() {

			if len(token.Value) == 0 {

				continue

			}

			if prev == EOF {

				prev = token

			} else {

				if prev.Type == token.Type && len(prev.Value) < 8192 {

					prev.Value += token.Value

				} else {

					out := prev

					prev = token

					return out

				}

			}

		}

		out := prev

		prev = EOF

		return out

	}, nil

}