;; Copyright 2018-2022
;; Kaz Kylheku <kaz@kylheku.com>
;; Vancouver, Canada
;; All rights reserved.
;;
;; Redistribution and use in source and binary forms, with or without
;; modification, are permitted provided that the following conditions are met:
;;
;; 1. Redistributions of source code must retain the above copyright notice,
;;    this list of conditions and the following disclaimer.
;;
;; 2. Redistributions in binary form must reproduce the above copyright notice,
;;    this list of conditions and the following disclaimer in the documentation
;;    and/or other materials provided with the distribution.
;;
;; THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
;; AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
;; IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
;; ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
;; LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
;; CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
;; SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
;; INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
;; CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
;; ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
;; POSSIBILITY OF SUCH DAMAGE.

(eval-only
  (defsymacro copy-size 65536))

(defstruct copy-path-opts ()
  perms times owner symlinks (euid (geteuid)))

(defstruct copy-path-stack-node ()
  path stat new-p)

(defun make-copy-path-opts (opt-list)
  (if opt-list
    (let (opts)
      (each ((opt opt-list))
        (if (structp opt)
          (set opts opt)
          (progn
            (unless opts
              (set opts (new copy-path-opts)))
            (caseql opt
              (:perms (set opts.perms t))
              (:times (set opts.times t))
              (:owner (set opts.owner t))
              (:symlinks (set opts.symlinks t))
              (:all (set opts.perms t
                         opts.times t
                         opts.owner t
                         opts.symlinks t))
              (t (error "~s: unrecognized option ~s" 'copy-path opt))))))
      opts)
    (load-time (new copy-path-opts))))

(defun copy-file (from-path to-path : preserve-perms preserve-times)
  (with-resources ((buf (make-buf copy-size)
                        (buf-set-length buf 0) (buf-trim buf))
                   (ist (open-file from-path "b") (close-stream ist))
                   (ista (fstat ist))
                   (ost (if (path-dir-p ista)
                          (throwf 'path-permission `~s: ~a is a directory`
                                  'copy-file from-path)
                          (open-file to-path "wb"))
                        (close-stream ost)))
    (while (eql (len buf) copy-size)
      (fill-buf-adjust buf 0 ist)
      (put-buf buf 0 ost))
    (when preserve-perms
      (chmod ost ista.mode))
    (when preserve-times
      (flush-stream ost)
      (utimes ost
              ista.atime (or ista.atime-nsec 0)
              ista.mtime (or ista.mtime-nsec 0)))
    nil))

(defun copy-files (paths dest-dir : preserve-perms preserve-times)
  (each ((path paths))
    (while t
      (catch**
        (return (copy-file path (path-cat dest-dir (base-name path))
                           preserve-perms preserve-times))
        (skip `skip copying @path` (exc . args) (return))
        (retry `retry copying @path` (exc . args))))))

(defun cat-files (to-path . from-paths)
  (let ((buf (make-buf copy-size)))
    (with-stream (ost (open-file to-path "wb"))
      (each ((from-path from-paths))
        (with-stream (ist (open-file from-path "b"))
          (while (eql (len buf) copy-size)
            (fill-buf-adjust buf 0 ist)
            (put-buf buf 0 ost)))
        (buf-set-length buf copy-size)))
    (buf-set-length buf 0)
    (buf-trim buf)
    nil))

(defun do-tweak-obj (to-path st opts link-p)
  (when (and opts.perms (not link-p))
    (chmod to-path st.mode))
  (when opts.times
    (lutimes to-path
             st.atime (or st.atime-nsec 0)
             st.mtime (or st.mtime-nsec 0)))
  (when (and opts.owner
             (or (zerop opts.euid)
                 (and (path-mine-p st)
                      (path-my-group-p st))))
    (lchown to-path st.uid st.gid)))

(defun do-copy-obj (from-path to-path st opts)
  (let ((type (logand st.mode s-ifmt))
        (initial-perms (if opts.perms #o700 #o777))
        (tweak t))
    (caseql* type
      (s-ifreg
        (copy-file from-path to-path opts.perms opts.times))
      (s-ifsock
        (mknod to-path (logior type initial-perms)))
      (s-ififo
        (mkfifo to-path initial-perms))
      (s-iflnk
        (if opts.symlinks
          (symlink (readlink from-path) to-path)
          (progn
            (do-copy-obj from-path to-path (stat from-path) opts)
            (set tweak nil))))
      ((s-ifblk s-ifchr)
       (mknod to-path (logior type initial-perms) st.rdev))
      (s-ifdir
        (ensure-dir to-path)))
    (when tweak
      (do-tweak-obj to-path st opts (eq type s-iflnk)))))

(defun copy-path-rec (from-dir to-dir . opt-list)
  (let* ((opts (make-copy-path-opts opt-list))
         (dir-stack nil))
    (unwind-protect
      (ftw from-dir
           (lambda (path type stat . rest)
             (while t
               (catch**
                 (let* ((rel-path (rel-path from-dir path))
                        (tgt-path (path-cat to-dir rel-path)))
                   (caseql* type
                     ((ftw-dnr ftw-ns) (error "~s: unable to access ~s"
                                              'copy-path path))
                     (ftw-d (let ((new-p (ensure-dir tgt-path)))
                              (whilet ((top (car dir-stack))
                                       ((and top
                                             (not (starts-with tgt-path
                                                               top.path)))))
                                (do-tweak-obj top.path top.stat opts nil)
                                (pop dir-stack))
                              (push (new copy-path-stack-node
                                         path tgt-path
                                         stat stat
                                         new-p new-p)
                                    dir-stack)))
                     (t (iflet ((cur (car dir-stack)))
                          (unless cur.new-p
                            (remove-path tgt-path)))
                        (do-copy-obj path tgt-path stat opts)))
                   (return))
                 (skip `skip copying @path` (exc . args) (return))
                 (retry `retry copying @path` (exc . args)))))
           ftw-phys)
      (whilet ((top (pop dir-stack)))
        (do-tweak-obj top.path top.stat opts nil)))))

(defun remove-path-rec (path)
  (ftw path
       (lambda (path type stat . rest)
         (while t
           (catch**
             (return
               (caseql* type
                 ((ftw-dnr ftw-ns) (error "~s: unable to access ~s"
                                          'remove-rec path))
                 (ftw-dp (rmdir path))
                 (t (remove-path path))))
             (skip `skip removing @path` (exc . args) (return))
             (retry `retry copying @path` (exc . args)))))
       (logior ftw-phys ftw-depth)))

(defun chmod-rec (path perm)
  (ftw path
       (lambda (path type stat . rest)
         (while t
           (catch**
             (return
               (caseql* type
                 ((ftw-dnr ftw-ns) (error "~s: unable to access ~s"
                                          'remove-rec path))
                 (ftw-sl)
                 (t (chmod path perm))))
             (skip `skip chmod @path` (exc . args) (return))
             (retry `retry chmod @path` (exc . args)))))
       (logior ftw-phys)))

(defun chown-rec (path uid gid)
  (ftw path
       (lambda (path type stat . rest)
         (while t
           (catch**
             (return
               (caseql* type
                 ((ftw-dnr ftw-ns) (error "~s: unable to access ~s"
                                          'remove-rec path))
                 (t (lchown path uid gid))))
             (skip `skip chown @path` (exc . args) (return))
             (retry `retry chown @path` (exc . args)))))
       (logior ftw-phys)))

(defun touch (path : ref-path)
  (with-stream (s (or (ignerr (open-file path "mn")) (open-file path "n")))
    (if ref-path
      (let ((rst (stat ref-path)))
        (utimes s 0 nil rst.mtime rst.mtime-nsec))
      (utimes s 0 nil 0 t))))

(defun path-simplify (comp)
  (let ((abs (equal (car comp) ""))
        out)
    (each ((c comp))
      (casequal c
        (".." (if (and (or out abs) (nequal (car out) ".."))
                (pop out)
                (push c out)))
        (("." ""))
        (t (push c out))))
    (nreverse out)))

(eval-only
  (defmacro if-windows (then : else)
    (if (eql 2 (sizeof wchar))
      then
      else))

  (defmacro if-native-windows (then else)
    (if-windows
      ^(if (find #\\ path-sep-chars) ,then ,else)
      else)))

(defun path-split (str)
  (let ((spl0 (sspl path-sep-chars str)))
    (if-native-windows
      (iflet ((head (car spl0))
              (p (pos #\: head)))
        (list* [head 0..(succ p)]
               [head (succ p)..:]
               (cdr spl0))
        spl0)
      spl0)))

(defun path-volume (comp)
  (let ((head (car comp)))
    (if-native-windows
      (let ((next (cadr comp))
            (more (cddr comp)))
        (cond
          ((and (equal head "") (equal next "") more)
           (let ((vol (car more)))
	     (cond
	       ((nequal "" vol)
		(set (car comp) "")
		(set (cdr comp) (cdr more))
		vol)
	       (t :abs))))
          ((and (m^ #/[A-Za-z0-9]+:/ head) head)
           (set (car comp) next)
           (set (cdr comp) more)
           (if (and (equal "" next) more)
             ^(:abs . ,head)
             ^(:rel . ,head)))))
      (if (equal head "") :abs))))

(defun rel-path (from to)
  (let* ((fspl (path-split from))
         (tspl (path-split to))
         (fvol (path-volume fspl))
         (tvol (path-volume tspl)))
    (when (nequal fvol tvol)
      (if (and (meq :abs fvol tvol) (meq nil fvol tvol))
        (error "~s: mixture of absolute and relative paths ~s ~s given"
               'rel-path from to))
      (if (meq :abs fvol tvol)
        (error "~s: mixture of absolute and volume paths ~s ~s given"
               'rel-path from to))
      (if-windows
        (progn
          (when (and (consp fvol) (consp tvol))
            (if (neq (car fvol) (car tvol))
              (error "~s: mixture of volume absolute and relative paths \
                     \ ~s ~s given"
                     'rel-path from to)))
        (when (neq (null fvol) (null tvol))
          (error "~s: mixture of volume and non-volume paths ~s ~s given"
                 'rel-path from to))
        (error "~s: paths on different volumes ~s ~s given"
               'rel-path from to))))
    (let* ((fcomp (path-simplify fspl))
           (tcomp (path-simplify tspl))
           (ncommon (mismatch fcomp tcomp)))
      (cond
        ((null ncommon) ".")
        ((find ".." (nthcdr ncommon fcomp))
         (error "~s: from path uses .. to escape common prefix: ~s ~s"
                'rel-path from to))
        (t (let ((nup (- (len fcomp) ncommon))
                 (down [tcomp ncommon..:]))
             (cat-str (append (repeat '("..") nup) down)
                      [path-sep-chars 0])))))))

(defun path-equal (left right)
  (if (and (stringp left) (equal left right))
    t
    (let* ((lspl (path-split left))
           (rspl (path-split right))
           (lvol (path-volume lspl))
           (rvol (path-volume rspl)))
      (if (nequal lvol rvol)
        nil
        (equal (path-simplify lspl)
               (path-simplify rspl))))))