#!/usr/bin/guile
!#

; depends on guile and sph-lib
(use-modules (srfi srfi-1) (sph) (sph cli) (sph list) (sph io))

(define cli
  (cli-create #:options
    (q
      ( (union #:names #\u) (intersection #:names #\i) (difference #:names #\d)
        (complement #:names #\c) ((file-path ...))))
    #:description
    "applies set operations to the lines of files. each file representing one set. writes the resulting lines to standard output"))

(define (file-lines-set-operations operation file-paths)
  (let
    (operation-f
      (case operation
        ((union) union)
        ((intersection) intersection)
        ((difference) difference)
        ((complement) complement)
        (else #f)))
    (if operation-f
      (apply call-with-input-files
        (l files
          (fold (l (file result) (operation-f result (port->lines file)))
            (port->lines (first files)) (tail files)))
        file-paths)
      null)))

(define (file-lines-set-operations-cli options)
  (let
    ( (operation
        (first-or-false
          (intersection (map first options) (q (union difference intersection complement)))))
      (file-paths (assq-ref options (q file-path))))
    (if (and operation file-paths)
      (each display-line (file-lines-set-operations operation file-paths)) (cli (list "--help")))))

(file-lines-set-operations-cli (cli))