#lang scheme/base

(require (for-syntax scheme/base)
         (except-in srfi/1 any)

; path path -> boolean
; Returns #t if path2 is a subpath of path1.
(define (path-contains? path1 path2)
  (let ([elems1 (explode-path (simplify-path path1))]
        [elems2 (explode-path (simplify-path path2))])
    (and (>= (length elems2) (length elems1))
         (equal? elems1 (take elems2 (length elems1))))))

; folders-spec -> void
; Makes a tree of directories from a nested list specification:
;     folders-spec = (list folder-spec ...)
;     folder-spec  = string folders-spec
; For example:
;     '("top1"
;        ("folder1"
;         ("subfolder1a" "subfolder1b")
;         "folder2"
;         ("subfolder2a" "subfolder2b"))
;       "top2"
;        ("folder1"
;         ("subfolder1a" "subfolder1b")
;         "folder2"
;         ("subfolder2a" "subfolder2b")))
(define (make-directory-tree tree)
  (define (tree-fold seed tree)
    (define (list->path head rest)
      (apply build-path (reverse (cons head rest))))
    (match tree
      [(? string? here)
       (make-directory* (list->path here seed))]
      [(list) (void)]
      [`(,(? string? head) (,children ...) . ,rest)
       (make-directory* (list->path head seed))
       (tree-fold (cons head seed) children)
       (tree-fold seed rest)]
      [`(,(? string? here) . ,rest)
       (make-directory* (list->path here seed))
       (tree-fold seed rest)]))
  (tree-fold null tree))

; path string -> path
; The path version of make-non-conflicting-filename, explained
; below:
(define (make-non-conflicting-path path filename)
  (build-path path (make-non-conflicting-filename path filename)))

; path string -> string
; Searches the specified path for any files whose name might conflict
; with the suggested filename. If conflicting files are found, a
; non-conflicting variant of filename is returned.
; If no conflicting files are found, the filename is returned untouched.
; Non-conflicting names are generated in a nice, friendly, Windows-esque
; kind of way, where a digit is appended to the end of the stem of the
; file. There are a few subtleties to this: examples follow:
;   my-file.txt becomes:
;     my-file1.txt if my-file.txt exists
;     my-file2.txt if my-file.txt and my-file1.txt exist
;   test-file becomes:
;     test-file1 if test-file exists
;   my-file5.txt becomes:
;     my-file6.txt if my-file5.txt exists
;   my-file1.blah.txt becomes:
;     my-file1.blah1.txt if my-file1.blah.txt exists
(define (make-non-conflicting-filename path filename)
  ; string -> (values string integer)
  ; Strips trailing digits off a string and returns them as a number.
  ; For example:
  ;     "abc123" => (values "abc" 123)
  ;     "abc" =? (values "abc" 1)
  (define (stem->stem-and-index stem)
    (let loop ([stem stem] [index-string ""])
      (if (char-numeric? (string-ref stem (sub1 (string-length stem))))
          (loop (string-drop-right stem 1) 
                (string-append index-string (string-take-right stem 1)))
          (values stem
                  (if (= (string-length index-string) 0)
                      (string->number index-string))))))
  (if (file-exists? (build-path path filename))
      ; Split the filename into a stem and an extension
      (let* ([pos (string-index-right filename #\.)]
             [stem (if pos (string-take filename pos) filename)]
             [extension (if pos (string-drop filename pos) "")])
        ; Find a non-conflicting filename and return it
        (let-values ([(stem index) 
                      (stem->stem-and-index stem)])
          (let loop ([index index])
            (let ([filename 
                    (number->string index) 
              (if (file-exists? (build-path path filename))
                  (loop (add1 index))

; (U path string) -> string
(define (read-file->string path)
  (let ([in  (open-input-file path)]
        [out (open-output-string)])
    (let loop ()
      (let ([buf (read-string 1024 in)])
        (unless (eof-object? buf)
          (display buf out)
    (close-input-port in)
    (get-output-string out)))

; (U string path) (listof (U string path)) -> void
(define (concatenate-files des srcs)
  (with-output-to-file des
    (cut copy-port (apply input-port-append
                          (map open-input-file srcs))

;  (U path string)
;  [#:order (U 'pre 'post)]
;  [#:filter (path -> boolean)]
;  [#:follow-links? boolean]
; ->
;  (listof path)
(define (directory-tree
         #:order         [order         'pre]
         #:filter        [predicate     (lambda (path) #t)]
         #:follow-links? [follow-links? #t])
  ; path
  (define root
    (if (string? root-path+string)
        (string->path root-path+string)
  ; (listof path)
  ; Accumulated in reverse order.
  (define tree
    (letrec ([process (lambda (curr)
                        (cond [(directory-exists? curr)
                               (if (link-exists? curr)
                                   (if follow-links?
                                       (recurse curr)
                                       (list curr))
                                   (recurse curr))]
                              [(file-exists? curr)
                               (list curr)]
                              [else null]))]
             [recurse (lambda (curr)
                        (let*-values ([(children) 
                                       (map (cut build-path curr <>)
                                            (directory-list curr))]
                                      [(directory-children file-children)
                                       (partition directory-exists? children)])
                          (case order
                             `(,@(append-map process directory-children)
                               ,@(append-map process file-children)
                               ,@(append-map process file-children)
                               ,@(append-map process directory-children))])))])
      (process root)))
  ; (listof path)
  (filter predicate tree))

; (_ path kw-arg ...)
(define-sequence-syntax in-directory
  (lambda (stx)
    (raise-syntax-error #f "can only be used as a sequence" stx))
  (lambda (stx)
    (syntax-case stx ()
      [[ids (_ args ...)]
       #'[ids (in-list (directory-tree args ...))]])))

; path -> string
(define (file-pretty-size path)
  (prettify-file-size (file-size path)))

; natural -> string
(define (prettify-file-size size [unit 1])
  ; number -> string
  (define unit->string
      [1 "bytes"]
      [2 "KB"]
      [3 "MB"]
      [4 "GB"]
      [5 "TB"]))
  (cond [(and (>= size 1000) (< unit 5))
         (prettify-file-size (/ size 1024) (add1 unit))]
        [(> size 10)
         (let ([size (floor size)])
           (format "~a ~a" size (unit->string unit)))]
        [(and (= size 1) (= unit 1)) "1 byte"]
        [else (let ([whole    (floor size)]
                    [fraction (floor (remainder (floor (* size 10)) 10))])
                (if (zero? fraction)
                    (format "~a ~a" whole (unit->string unit))
                    (format "~a.~a ~a" whole fraction (unit->string unit))))]))

; Provide statements -----------------------------

(provide in-directory)

 [path-contains?                (-> path? path? boolean?)]
 [make-directory-tree           (-> any/c void?)] ; Can't work out how to contract the argument to this.
 [make-non-conflicting-filename (-> (or/c path? string?) string? string?)]
 [make-non-conflicting-path     (-> (or/c path? string?) string? path?)]
 [read-file->string             (-> (or/c path? string?) string?)]
 [concatenate-files             (-> (or/c path? string?) (listof (or/c path? string?)) void?)]
 [directory-tree                (->* ((or/c path? string?))
                                     (#:order (symbols 'pre 'post)
                                              #:filter (-> path? boolean?)
                                              #:follow-links? boolean?)
                                     (listof path?))]
 [file-pretty-size              (-> path? string?)]
 [prettify-file-size            (-> natural-number/c string?)])