From bd39e5df99edc495e0baf5e28662c2f81d0f071d Mon Sep 17 00:00:00 2001
From: Simon Michael <simon@joyful.com>
Date: Wed, 3 Dec 2014 18:12:02 -0800
Subject: [PATCH] showDateSpan: handle boundary-crossing 1-day spans

Eg recognise that 2014/11/30-2014/12/1 can be abbreviated to
2014/11/30d, similarly 2014/12/31-2015/1/1. Doesn't handle feb 29th
correctly, so eg 2000/2/28-2000/3/1 is wrongly abbreviated to
2000/2/28d.
---
 hledger-lib/Hledger/Data/Dates.hs | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/hledger-lib/Hledger/Data/Dates.hs b/hledger-lib/Hledger/Data/Dates.hs
index 0ff8dd4c3..b1fbe759c 100644
--- a/hledger-lib/Hledger/Data/Dates.hs
+++ b/hledger-lib/Hledger/Data/Dates.hs
@@ -90,6 +90,7 @@ instance Show DateSpan where
 showDate :: Day -> String
 showDate = formatTime defaultTimeLocale "%0C%y/%m/%d"
 
+-- XXX review for more boundary crossing issues
 -- | Render a datespan as a display string, abbreviating into a
 -- compact form if possible.
 showDateSpan ds@(DateSpan (Just from) (Just to)) =
@@ -117,8 +118,26 @@ showDateSpan ds@(DateSpan (Just from) (Just to)) =
                                                 -> formatTime defaultTimeLocale "%0C%y/%m/%dw%V" from
     -- a day, YYYY/MM/DDd (d suffix is to distinguish from a regular date in register)
     ((fy,fm,fd), (ty,tm,td)) | fy==ty && fm==tm && fd+1==td -> formatTime defaultTimeLocale "%0C%y/%m/%dd" from
+    -- crossing a year boundary
+    ((fy,fm,fd), (ty,tm,td)) | fy+1==ty && fm==12 && tm==1 && fd==31 && td==1 -> formatTime defaultTimeLocale "%0C%y/%m/%dd" from
+    -- crossing a month boundary XXX wrongly shows LEAPYEAR/2/28-LEAPYEAR/3/1 as LEAPYEAR/2/28
+    ((fy,fm,fd), (ty,tm,td)) | fy==ty && fm+1==tm && fd `elem` fromMaybe [] (lookup fm lastdayofmonth) && td==1 -> formatTime defaultTimeLocale "%0C%y/%m/%dd" from
     -- otherwise, YYYY/MM/DD-YYYY/MM/DD
     _                                           -> showDateSpan' ds
+  where lastdayofmonth = [(1,[31])
+                         ,(2,[28,29])
+                         ,(3,[31])
+                         ,(4,[30])
+                         ,(5,[30])
+                         ,(6,[31])
+                         ,(7,[31])
+                         ,(8,[31])
+                         ,(9,[30])
+                         ,(10,[31])
+                         ,(11,[30])
+                         ,(12,[31])
+                         ]
+
 showDateSpan ds = showDateSpan' ds
 
 -- | Render a datespan as a display string.