(define-module (pastebin data))

(use-modules (srfi srfi-9)

             (srfi srfi-1)

             (ice-9 ftw)

             (ice-9 textual-ports))

(export <pb-data>

        <pb-entry>

        pb-entry-id

        pb-entry-text

        pb-data-open

        pb-data-close

        call-with-dir-as-pb-data

        pb-data-get-top

        pb-data-new-entry)

(define-record-type <pb-data>

  (make-pb-data dir)

  pb-data?

  (dir pb-data-dir set-pb-data-dir!))

(define-record-type <pb-entry>

  (make-pb-entry id text)

  pb-entry?

  (id pb-entry-id set-pb-entry-id!)

  (text pb-entry-text set-pb-entry-text!))

;; input: dir: string

;; output: <pb-data>

(define (pb-data-open dir)

  (make-pb-data dir))

(define (pb-data-close pb-data) #t)

(define (call-with-dir-as-pb-data dir p)

  (let ((pb-data (pb-data-open dir)))

    (let ((R (p pb-data)))

      (pb-data-close pb-data)

      R)))

(define (get-file-path pb-data filename)

  (string-append (pb-data-dir pb-data) "/" filename))

;; input: <pb-data>, integer

;; output: list of <pb-entry>

(define (pb-data-get-top pb-data n)

  (map

   (lambda (filename)

     (make-pb-entry

      filename

      (call-with-input-file (get-file-path pb-data filename)

        (lambda (port)

          (get-string-all port)))))

   (let ((file-ls (list-files pb-data)))

     (reverse (take-right file-ls (min n (length file-ls)))))))

;; input: <pb-data>, text

;; output: <pb-entry>

(define (pb-data-new-entry pb-data text)

  (let ((next-filename (get-next-filename pb-data)))

    (call-with-output-file (get-file-path pb-data next-filename)

      (lambda (port)

        (put-string port text)))

    (make-pb-entry next-filename text)))

(define (list-files pb-data)

  (scandir (pb-data-dir pb-data) (lambda (filename) (= (string-length filename) 5))))

(define (get-next-filename pb-data)

  (let ((entries (list-files pb-data)))

    (if (null? entries)

        "00000"

        (get-next-5digit (last entries)))))

(define (get-next-5digit str)

  (let A ((add #t)

          (char-int-ls (reverse (map char->integer (string->list str))))

          (result '()))

    (if (null? char-int-ls)

        (list->string (map integer->char result))

        (if add

            (let* ((hd (car char-int-ls)) (tl (cdr char-int-ls)))

              (if (= hd #x7A)

                  (A #t tl (cons #x30 result))

                  (A #f tl (cons (case hd

                                   ((#x39) #x41)

                                   ((#x5A) #x61)

                                   (else (1+ hd))) result))))

            (A #f '() (append (reverse char-int-ls) result))))))