(define-module (rss-filter)
  :export (handle-feed)
  :use-module (ice-9 curried-definitions)
  :use-module (rss-filter feed-handler)
  :use-module (web client)
  :use-module (web response)
  :use-module (sxml simple)
  :use-module (sxml xpath)
  :use-module (sxml namespace)
  :use-module ((calp util) :select (path-append))
  )

(define ((handle-feed output-directory quiet?) feed)
  (define response
    (begin
      (when (not quiet?)
       (format (current-error-port) "Fetching ~a~%" (feed-url feed)))
      ;; TODO follow redirects
      (http-get (feed-url feed)
                #:streaming? #t)))

  (unless (= 200 (response-code response))
    (format (current-error-port) "HTTP error ~a"
            (response-code response))
    (exit 1))

  (let* ((feed-content (move-to-namespace (parse-rss (response-body-port response))
                                          '((#f . rss))))
         (feed-title (car ((sxpath '(// rss:channel rss:title *text*)) feed-content)))
         (safe-title (string-map (lambda (c) (if (char-set-contains? char-set:letter+digit c)
                                            c #\_))
                                 feed-title)))


    (let ((output (filter-tree (feed-transformer feed)
                               feed-content))
          (filename (string-append
                     (path-append output-directory safe-title)
                     ".rss")))
      (with-output-to-file filename
        (lambda ()
          (sxml->xml
           ;; Removing the rss prefix should be fine, but at least NewNewsWire
           ;; (for iPad) expects all rss elements to be un-namespaced.
           (move-to-namespace output '((rss . #f)))))))))