#|
utils.scm -- parsing utilities

Copyright © 2026 Hernán Ibarra Mejia.

This file is part of `raw`.

`raw` is free software: you can redistribute it and/or modify it under the terms
of the GNU General Public License as published by the Free Software Foundation,
version 3 of the License.

`raw` is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with
`raw` If not, see <https://www.gnu.org/licenses/>.
|#

(import (chicken format))

(define (indent-char? char)
  (or (char=? char #\space)
      (char=? char #\tab)))

(define (char->string char) (make-string 1 char))

(define (program-error errmsg)
  (error (string-append "raw: " errmsg)))
(define (error-eof) (program-error "unexpected end of file"))
(define (error-unexpected-char char)
  (program-error (sprintf "unexpected char: ~A" char)))
(define (error-invalid-expression obj)
  (program-error (sprintf "invalid expression: ~A" obj)))
(define (error-string-expected obj)
  (program-error (sprintf "expected string, got: ~A" obj)))
(define (error-fatal) (program-error "fatal error"))

(define (consume-indent port)
  (let loop ((result '()))
    (if (indent-char? (peek-char port))
      (loop (cons (read-char port) result))
      (reverse result))))

(define (consume-char expected-char port)
  (let ((char (read-char port)))
    (cond ((eof-object? char) (error-eof))
          ((not (char=? char expected-char))
           (error-unexpected-char char)))))

(define (consume-char-list char-list port)
  (for-each (cut consume-char <> port) char-list))