From 7bcd1596b04a6a2c971569c5fdfdc96ba9e61c8c Mon Sep 17 00:00:00 2001
From: arkdro <arkdro@gmail.com>
Date: Thu, 21 Feb 2013 00:07:14 +0400
Subject: [PATCH 1/3] add api to check whether the dst is active

---
 src/ezic.erl | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/src/ezic.erl b/src/ezic.erl
index 18ce7f0..c6612f0 100644
--- a/src/ezic.erl
+++ b/src/ezic.erl
@@ -5,6 +5,8 @@
 	 localtime/1
 	 , utc_to_local/2
 	 , local_to_utc/2
+	 , has_dst_utc/2
+	 , has_dst_local/2
 	]).
 
 
@@ -30,7 +32,11 @@ local_to_utc(LocalDatetime, TzName) ->
     local_to_utc_handleFlatzone(LocalDatetime, ezic_db:flatzone(NormalDatetime, TzName)).
     
 
+has_dst_utc(Datetime, TzName) ->
+    has_dst(Datetime, TzName, u).
 
+has_dst_local(Datetime, TzName) ->
+    has_dst(Datetime, TzName, w).
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 % PRIVATE
@@ -55,3 +61,14 @@ local_to_utc_handleFlatzone(LocalDatetime, #flatzone{offset=Offset, dstoffset=DS
     	, Offset, {0,0,0})
       , DSTOffset, {0,0,0}).
 
+has_dst(Datetime, TzName, Flag) ->
+    NormalDatetime = ezic_date:normalize(Datetime, Flag),
+    case ezic_db:flatzone(NormalDatetime, TzName) of
+        #flatzone{dstoffset={0,0,0}} ->
+            false;
+        #flatzone{dstoffset={_,_,_}} ->
+            true;
+        _ ->
+            false
+    end.
+

From 511c7815dc7acafef31aa8aeef44d6580b95ed46 Mon Sep 17 00:00:00 2001
From: arkdro <arkdro@gmail.com>
Date: Sat, 2 Mar 2013 14:16:55 +0400
Subject: [PATCH 2/3] remove catch-all branch

---
 src/ezic.erl | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/src/ezic.erl b/src/ezic.erl
index c6612f0..4aec5b1 100644
--- a/src/ezic.erl
+++ b/src/ezic.erl
@@ -67,8 +67,6 @@ has_dst(Datetime, TzName, Flag) ->
         #flatzone{dstoffset={0,0,0}} ->
             false;
         #flatzone{dstoffset={_,_,_}} ->
-            true;
-        _ ->
-            false
+            true
     end.
 

From 9be6cde77b445e0c68ba5d9e9a497bd348b74d04 Mon Sep 17 00:00:00 2001
From: arkdro <arkdro@gmail.com>
Date: Sat, 2 Mar 2013 14:17:38 +0400
Subject: [PATCH 3/3] add tests for has_dst_{utc,local}

---
 test/ezic_tests.erl | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/test/ezic_tests.erl b/test/ezic_tests.erl
index 62b6a46..0e23bae 100644
--- a/test/ezic_tests.erl
+++ b/test/ezic_tests.erl
@@ -43,3 +43,30 @@ local_to_utc_funkyDST_test_() ->
      , ?_assertMatch({{1951,9,7},{17,0,0}}, ezic:local_to_utc({{1951,9,8},{2,0,0}}, "Asia/Tokyo")) %% DST off for the last time
      , ?_assertMatch({{1952,5,3},{17,0,0}}, ezic:local_to_utc({{1952,5,4},{2,0,0}}, "Asia/Tokyo")) %% ensure DST not in effect for 1952
     ].
+
+has_dst_local_test_() ->
+    [
+     ?_assertMatch(false, ezic:has_dst_local({{1998,3,1},{1,30,0}}, "Europe/Paris")),
+     ?_assertMatch(true, ezic:has_dst_local({{1998,9,30},{1,30,0}}, "Europe/Paris")),
+     ?_assertMatch(true, ezic:has_dst_local({{1998,8,30},{3,30,0}}, "America/Denver")),
+     ?_assertMatch(false, ezic:has_dst_local({{1998,10,30},{3,30,0}}, "America/Denver")),
+     %% weird date
+     ?_assertMatch(false, ezic:has_dst_local({{1998,2,31},{10,30,0}}, "Europe/Paris")),
+     %% invalid zone
+     ?_assertException(error, {case_clause, {error, no_zone}}, ezic:has_dst_local({{1998,10,20},{12,30,0}}, "non_existent")),
+     %% ambiguous zone
+     ?_assertException(error, {case_clause, {error, {ambiguous_zone, _}}}, ezic:has_dst_local({{1998,10,25},{1,30,0}}, "America/Denver"))
+    ].
+
+has_dst_utc_test_() ->
+    [
+     ?_assertMatch(false, ezic:has_dst_utc({{1998,3,28},{13,30,0}}, "Europe/Paris")),
+     ?_assertMatch(true, ezic:has_dst_utc({{1998,3,29},{1,30,0}}, "Europe/Paris")),
+     ?_assertMatch(true, ezic:has_dst_utc({{1998,10,25},{7,59,59}}, "America/Denver")),
+     ?_assertMatch(false, ezic:has_dst_utc({{1998,10,25},{8,0,0}}, "America/Denver")),
+     %% weird date
+     ?_assertMatch(false, ezic:has_dst_utc({{1998,2,31},{13,30,0}}, "Europe/Paris")),
+     %% invalid zone
+     ?_assertException(error, {case_clause, {error, no_zone}}, ezic:has_dst_utc({{1998,10,25},{1,30,0}}, "non_existent"))
+    ].
+