== Zhuo Hong Wei's Blog ==
Any and everything

Who Are in Space Now

This weekend, I learnt how to fetch and parse JSON using the drakma HTTP client and cl-json libraries. And some simple error handling as well.


(ql:quickload :testlib)

(use-package :testlib)

(run (context "who is in space?"
        (context "people-p"
            (context "when key is people" 
                (test "it should return true" (people-p (cons :people '()))))
            (context "when key is not people" 
                (test "it should return false" (not (people-p (cons :foo '()))))))
        (context "get-name"
            (context "when name is present" 
                (test "it should return name" (string= (get-name `(,(cons :name "foo"))) "foo")))
            (context "when name is not present" 
                (test "it should return nil" (eq nil (get-name `(,(cons :craft "bar")))))))
        (context "get-craft"
            (context "when craft is present" 
                (test "it should return craft" (string= (get-craft `(,(cons :craft "foo"))) "foo")))
            (context "when craft is not present" 
                (test "it should return nil" (eq nil (get-craft `(,(cons :name "bar")))))))
        (context "format-astronaut"
            (test "it should format correctly"
                (string= (format-astronaut `(,(cons :name "foo") ,(cons :craft "iss")) nil) (format nil "~&foo (iss)~%"))))
        (context "get-people"
            (test "it should return people list from property pair"
                    (equal (get-people (cons :people '(1 2 3))) '(1 2 3))))))


(ql:quickload :drakma)
(ql:quickload :cl-json)

(defun people-p (pair)
    (and (consp pair) (eq (car pair) :people)))

(defun get-people (pair)
    (if (consp pair) (cdr pair)))

(defun format-astronaut (astronaut &optional (output-stream t))
    (format output-stream "~&~A (~A)~%" (get-name astronaut) (get-craft astronaut)))

(defmacro get-property-value (object property-name)
    `(if (listp ,object)
       (cdr (find-if #'(lambda (p) (and (consp p) (eq (car p) ,property-name))) ,object))))

(defun get-name (astronaut)
    (get-property-value astronaut :name))

(defun get-craft (astronaut)
    (get-property-value astronaut :craft))

(catch 'trap-errors 
    (handler-bind (
        (error #'(lambda (condition) 
                    (format *error-output* "~&~A~%" condition)
                    (throw 'trap-errors nil))))
            (data http-response-code) 
            (drakma:http-request "http://api.open-notify.org/astros.json")
                (if (= 200 http-response-code) 
                    (let* ((str (flexi-streams:octets-to-string data))
                           (json (json:decode-json-from-string str)))
                             (mapcar #'format-astronaut (get-people (find-if #'people-p json)))

Notice that the part about networking code has not been covered by the tests. To effectively unit test, I would need to extend testlib with mocking facilities so that I can mock the HTTP call.

So, who are the astronauts currently in space as of this writing?

Mike Hopkins (ISS)
Victor Glover (ISS)
Shannon Walker (ISS)
Soichi Noguchi (ISS)
Mark Vande Hei (ISS)
Oleg Novitskiy (ISS)
Pyotr Dubrov (ISS)
Thomas Pesquet (ISS)
Megan McArthur (ISS)
Shane Kimbrough (ISS)
Akihiko Hoshide (ISS)