;;
;; util-parser.scm
;;
;; Common parts of the parsers.
;;
;; ISC License
;;
;; Copyright 2023 Brmlab, z.s.
;; Dominik Pantůček <dominik.pantucek@trustica.cz>
;;
;; Permission to use, copy, modify, and/or distribute this software
;; for any purpose with or without fee is hereby granted, provided
;; that the above copyright notice and this permission notice appear
;; in all copies.
;; 
;; THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
;; WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
;; WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE
;; AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR
;; CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
;; OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
;; NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
;; CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
;;

(declare (unit util-parser))

(module
 util-parser
 (
  parser-preprocess-line
  parser-parse-line
  parser-tests!
  )
 
 (import scheme
	 (chicken base)
	 (chicken irregex)
	 testing)

 ;; Pass 0: Removes any comments and removes any leading and trailing
 ;; whitespace.
 (define (parser-preprocess-line line)
   (irregex-replace (irregex "[ \\t]*$" 'u)
		    (irregex-replace (irregex "^[ \\t]*" 'u)
				     (irregex-replace (irregex "#.*$" 'u) line "")
				     "")
		    ""))

 ;; Pass 1: Expects line with comments and surrounding whitespace
 ;; removed, returns either #f if nothing was parsed, symbol if only
 ;; one token was there and pair of symbol and string if both key and
 ;; the value were present.
 (define (parser-parse-line line)
   (if (= (string-length line) 0)
       #f
       (let ((dm (irregex-search (irregex "[ \\t]" 'u) line)))
	 (if dm
	     (let* ((sep-idx (irregex-match-start-index dm))
		    (key-str (substring line 0 sep-idx))
		    (key (string->symbol key-str))
		    (sep+val (substring line sep-idx))
		    (val (irregex-replace (irregex "^[ \\t]*" 'u) sep+val "")))
	       (cons key val))
	     (string->symbol line)))))

 ;; Self-tests
 (define (parser-tests!)
   (run-tests
    parser
    (test-equal? parser-preprocess-line
		 (parser-preprocess-line "# all comment")
		 "")
    (test-equal? parser-preprocess-line
		 (parser-preprocess-line "   # all comment after spaces")
		 "")
    (test-equal? parser-preprocess-line
		 (parser-preprocess-line " test  # spaces and comment after spaces")
		 "test")
    (test-equal? parser-preprocess-line
		 (parser-preprocess-line "key value  # spaces and comment after spaces")
		 "key value")
    (test-false parser-parse-line
		(parser-parse-line ""))
    (test-eq? parser-parse-line
	      (parser-parse-line "key")
	      'key)
    (test-equal? parser-parse-line
		 (parser-parse-line "key value")
		 '(key . "value"))
    (test-equal? parser-parse-line
		 (parser-parse-line "key     value")
		 '(key . "value"))
    (test-equal? parser-parse-line
		 (parser-parse-line "key     value and some")
		 '(key . "value and some"))
    (test-equal? parser-parse-line
		 (parser-parse-line "key     value     lot of spaces")
		 '(key . "value     lot of spaces"))
    ))

 )