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Created Jan 21, 2009
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;;; A date library that follows principle of least surprise
(import 'java.util.Calendar)
(import 'java.util.TimeZone)
(def #^{:doc "Conversion of Calendar weekdays to keywords"}
{Calendar/SUNDAY :sunday
Calendar/MONDAY :monday
Calendar/TUESDAY :tuesday
Calendar/WEDNESDAY :wednesday
Calendar/THURSDAY :thursday
Calendar/FRIDAY :friday
Calendar/SATURDAY :saturday})
(defn- make-calendar
"Given some date values, create a Java Calendar object with only
that data."
([] (doto (Calendar/getInstance)
(.setLenient true)))
([year month day]
(doto (make-calendar)
(.set year (dec month) day)))
([year month day hours minutes]
(doto (make-calendar)
(.set year (dec month) day hours minutes)))
([year month day hours minutes seconds]
(doto (make-calendar)
(.set year (dec month) day hours minutes seconds))))
(defn- time-zone-object
"Gets a Java TimeZone object from a string ID.
If no ID is given, use the default time zone for the current locale."
([] (TimeZone/getDefault))
([id] (TimeZone/getTimeZone id)))
(defn- time-zone-id
"Gets the string ID of a Java TimeZone object"
(.getID tz-obj))
(defn date-dispatcher
"Gets a type keyword for a Date object. Uses ::Calendar for Java
Calendar objects, and the symbol in the :type slot for Clojure dates."
(if (instance? Calendar x)
(:type x)))
(derive ::Date ::Instant)
(derive ::Time ::Instant)
(defmulti to-date date-dispatcher)
(defmethod to-date ::Calendar [cal]
(let [d {:year (.get cal Calendar/YEAR)
:month (inc (.get cal Calendar/MONTH))
:day (.get cal Calendar/DAY_OF_MONTH)
:zone (time-zone-id (.getTimeZone cal))}
h (.get cal Calendar/HOUR_OF_DAY)
m (.get cal Calendar/MINUTE)
s (.get cal Calendar/SECOND)]
(if (= 0 h m s)
(assoc d :type ::Date)
(assoc d
:type ::Time
:hour h
:minute m
:second s))))
(defmulti to-calendar date-dispatcher)
(defmethod to-calendar ::Date [date]
(doto (Calendar/getInstance)
(.set (:year date)
(dec (:month date))
(:day date))
(.setTimeZone (time-zone-object (:zone date)))))
(defmethod to-calendar ::Instant [date]
(doto (Calendar/getInstance)
(.set (:year date)
(dec (:month date))
(:day date)
(:hour date)
(:minute date)
(:second date))
(.setTimeZone (time-zone-object (:zone date)))))
(defn date
"Creates a Date or Time object with exactly the given information."
[& args]
(to-date (apply make-calendar args)))
(defn now
"Creates a Time object with the current date and time."
(to-date (Calendar/getInstance)))
(defn today
"Creates a Date object with the current date."
(assoc (dissoc (now) :hour :minute :second)
:type ::Date))
(defn day-of-week [date]
(weekday-map (.get (to-calendar date) Calendar/DAY_OF_WEEK)))
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