;; The first three lines of this file were inserted by DrScheme. They record metadata
;; about the language level of this file in a form that our tools can easily process.
#reader(lib "htdp-beginner-reader.ss" "lang")((modname parse-google-maps-places) (read-case-sensitive #t) (teachpacks ()) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ())))
;; Parses out the places.
;; See: http://mapki.com/wiki/Google_Map_Parameters


;; A location is the latitude/longitude pair.
(define-struct loc (lat long))

;; A place is a name string, a location, and a radius number.
(define-struct place (name loc radius))

;; The world is the URL for
(define-struct world (url places out-of-sync?))


;; make-mymaps-url: string -> string
;; Given the unique Google Maps "My Maps" identifier, returns a url
;; to get at its RSS feed.
(define (make-mymaps-url msid)
  (string-append "http://maps.google.com/maps/ms?ie=UTF8&hl=en&vps=1&jsv=151e&msa=0&output=georss&msid="
                 msid))


;; The initial world is one for dyoo's My Saved Places.
(define initial-world 
  (make-world (make-mymaps-url "106933521686950086948.00046579f4b482756abc5")
              (list)
              true))



;; parse-places: xexpr -> (listof place)
(define (parse-places xexpr)
  (parse-items
   (find-children 'item 
                  (children (first (find-children 'channel (children xexpr)))))))


;; parse-items: (listof xexpr) -> (listof place)
(define (parse-items xexprs)
  (cond
    [(empty? xexprs)
     empty]
    [else
     (cons (parse-item (first xexprs))
           (parse-items (rest xexprs)))]))


;; parse-item: xexpr -> place
(define (parse-item xexpr)
  ;; FIXME: wrong!  I need to return a place!
  (make-place (get-text (first (find-children 'title (children xexpr))))              
              (parse-georss:point (first (find-children 'georss:point (children xexpr))))
              ;; fixme!  We need the radius!
              0))


;; parse-georss:point: xexpr -> loc
(define (parse-georss:point xexpr)
  (make-loc (first (split-whitespace (get-text xexpr)))
            (second (split-whitespace (get-text xexpr)))))



;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; children: xexpr -> (listof xexpr)
(define (children an-xexpr)
  (cond
    [(string? an-xexpr)
     (error 'children "Can't have children of a string xexpr")]
    [else
     (rest (rest an-xexpr))]))

;; attrs: xexpr -> (listof (list symbol string))
(define (attrs an-xexpr)
  (cond
    [(string? an-xexpr)
     (error 'attrs "Can't get attributes of a string xexpr")]
    [else
     (second an-xexpr)]))

;; get-text: xexpr -> string
(define (get-text an-xexpr)
  (cond
    [(string? an-xexpr)
     an-xexpr]
    [(pair? an-xexpr)
     (get-text* (children an-xexpr))]))

;; get-text*: (listof xexpr) -> string
(define (get-text* xexprs)
  (cond
    [(empty? xexprs)
     ""]
    [else
     (string-append (get-text (first xexprs))
                    (get-text* (rest xexprs)))]))

;; find-children: symbol (listof xexpr) -> (listof xexpr)
(define (find-children name children)
  (cond [(empty? children)
         empty]
        [else
         (cond [(string? (first children))
                (find-children name (rest children))]
               [(pair? (first children))
                (cond
                  [(symbol=? name (first (first children)))
                   (cons (first children)
                         (find-children name (rest children)))]
                  [else
                   (find-children name (rest children))])]
               [else
                (error 'find-children children)])]))



;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; 

;; place->string: place -> string
(define (place->string a-place)
  (string-append (place-name a-place) 
                 " "
                 (loc->string (place-loc a-place))
                 " "
                 (number->string (place-radius a-place))))

;; loc->string: loc -> string
(define (loc->string a-loc)
  (string-append "(" (loc-lat a-loc) ", " (loc-long a-loc) ")"))
                 
;; places->string: (listof place) -> string
(define (places->string places)
  (cond
    [(empty? places)
     ""]
    [else
     (string-append (place->string (first places))
                    ", "
                    (places->string (rest places)))]))
         
;; description: world -> string
(define (description a-world)
  (cond [(world-out-of-sync? a-world)
         "Out of sync"]
        [else
         (places->string (world-places a-world))]))


;; reparse: world -> world
;; Reparses the places.
(define (reparse a-world)
  (make-world (world-url a-world)
              (parse-places (xml->s-exp (get-url (world-url a-world))))
              false))

(define view 
  (col (message description)
       (button "Parse" reparse)))


(big-bang initial-world view)