allow constructing your own date/tm values

4 files changed, 43 insertions, 13 deletions

diff --git a/date/init.janet b/date/init.janet
index aaf2272..215b019 100644
--- a/date/init.janet
+++ b/date/init.janet
@@ -1,15 +1,30 @@
 (import date/native)
 
-(defn time
-  `Return an opaque datetime representation of the current moment.`
-  []
-  (native/time))
+(def time
+  `Return an opaque date/time representation of the current moment.`
+  native/time)
 
 (defn time?
   `Check if x is a date/time object.`
   [x]
   (= :date/time (type x)))
 
+(defn- tm
+  [f &opt o]
+  (def out (native/tm o))
+  (f out)
+  out)
+
+(def utc
+  `Generate a date/tm object from a compatible dictionary. Implying UTC.
+  Non-specified fields will be initialized to their default values (usually zero).`
+  (partial tm native/timegm!))
+
+(def local
+  `Generate a date/tm object from a compatible dictionary. Implying localtime.
+  Non-specified fields will be initialized to their default values (usually zero).`
+  (partial tm native/mktime!))
+
 (defn tm?
   `Check if x is a date/tm object.`
   [x]
diff --git a/src/time.c b/src/time.c
index f9bda70..eee419e 100644
--- a/src/time.c
+++ b/src/time.c
@@ -22,10 +22,14 @@ static int jd_time_get(void *p, Janet key, Janet *out) {
 	return janet_getmethod(janet_unwrap_keyword(key), jd_time_methods, out);
 }
 
-// time_t is always a UTC-representation
+// time_t is an arithmetic type, which means some width of int or float
+// instead of trying to guess the type,
+// we give the number of seconds from the zero-value of time_t
+// on UNIX platforms, this is the number of seconds since UNIX epoch (1970)
+// ultimately, the user knows what platform they're on, making the output useful
 static void jd_time_tostring(void *p, JanetBuffer *buffer) {
-	// print ISO 8601
-	strftime_buffer("%F %T%z", gmtime(p), buffer);
+	double dt = difftime(*(time_t*)p, 0);
+	janet_formatb(buffer, "%f", dt);
 }
 
 static const JanetAbstractType jd_time_t = {
diff --git a/src/tm.c b/src/tm.c
index f04e9a9..a029627 100644
--- a/src/tm.c
+++ b/src/tm.c
@@ -215,15 +215,18 @@ struct tm *jd_opttm(Janet *argv, int32_t argc, int32_t n) {
 
 JANET_FN(jd_tm,
 		"(tm {:sec 0 ...})",
-		"Construct a date/tm object from a compatible dictionary.") {
-	janet_fixarity(argc, 1);
-	JanetDictView view = janet_getdictionary(argv, 0);
+		"Construct a date/tm object from a compatible dictionary.\n"
+		"Note that you *must* immediate pass this into timegm or mktime.") {
+	janet_arity(argc, 0, 1);
 
 	struct tm *out = jd_maketm();
+	// default values
 	memset(out, 0, sizeof(struct tm));
-#ifdef TM_GMTOFF
-	out->TM_GMTOFF = 0;
-#endif
+	out->tm_mday = 1; // range is 1-31
+
+	if (argc == 0 || janet_checktype(argv[0], JANET_NIL)) return janet_wrap_abstract(out);
+
+	JanetDictView view = janet_getdictionary(argv, 0);
 
 	for (int32_t i = 0; i < view.cap; i++) {
 		const JanetKV e = view.kvs[i];
diff --git a/test/02-api.janet b/test/02-api.janet
index eb0666f..2a9c0ec 100644
--- a/test/02-api.janet
+++ b/test/02-api.janet
@@ -19,3 +19,11 @@
 (assert (date/format now :default true))
 # format string
 (assert (date/format now :%c))
+
+# ensure tm + gmtime are spec-compliant
+(def u (date/utc   {:year 1970}))
+(def l (date/local {:year 1970}))
+(assert (= u
+           (:gmtime (:timegm u))))
+(assert (= l
+           (:localtime (:mktime l))))