; tee [-a] [file...]: the input passed on to the output and kept in each
; file (-a: after what the file has), a piece at a time. A file that cannot
; be opened or written is said and left; the rest go on, and $? is 1.

(def usage "usage: tee [-a] [file...]")
(def say (fn (name why) (do (err-write "tee: " name ": " why "\n") 1)))

(def main (fn ()
  (letv (opts files bad) (getopt ARGS "a")
    (if (not (= bad "")) (do (err-write usage "\n") (exit-status 2))
      (let ((mode (if (> (length opts) 0) "a" "w")))
        ; (open worst): open, the (name handle) still taking the input
        (letv (open worst)
              (fold (fn (st name)
                      (letv (open worst) st
                        (let ((h (file-open name mode)))
                          (if (= (type-of h) "string") (tuple open (say name h))
                            (tuple (list-append open (tuple name h)) worst)))))
                    (tuple (list) 0) files)
          (letv (open worst)
                (iterate (fn (st)
                           (letv (open worst) st
                             (let ((b (in-read 65536)))
                               (if (is-nil b) (list)
                                 (do (out-write b)
                                     (fold (fn (acc f)
                                             (letv (left w) acc
                                               (letv (name h) f
                                                 (let ((r (file-write h b)))
                                                   (if (= (type-of r) "string")
                                                     (do (file-close h) (tuple left (say name r)))
                                                     (tuple (list-append left f) w))))))
                                           (tuple (list) worst) open))))))
                         (tuple open worst))
            (exit-status
              (fold (fn (w f) (letv (name h) f (let ((r (file-close h))) (if (= (type-of r) "string") (say name r) w))))
                    worst open)))))))))

(main)