From 15dc6ec45285f8bc9af3702965e83532f1011b0c Mon Sep 17 00:00:00 2001
From: Leah Neukirchen <leah@vuxu.org>
Date: Sat, 19 Feb 2022 22:37:24 +0100
Subject: support ISO week notation in -d

---
 README |  8 ++++++--
 wcal.1 |  6 +++++-
 wcal.c | 19 ++++++++++++++++++-
 3 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/README b/README
index b19ab33..1bdfeeb 100644
--- a/README
+++ b/README
@@ -4,7 +4,7 @@ NAME
      wcal – ISO weekly calendar
 
 SYNOPSIS
-     wcal [-13yci] [-d YYYY[-MM[-DD]]]
+     wcal [-13yci] [-d YYYY[-MM[-DD]]] [-d YYYY-WWW[-D]]
 
 DESCRIPTION
      The wcal utility prints a week-oriented calendar.  Each week is prefixed
@@ -29,6 +29,10 @@ DESCRIPTION
              Show the calendar for a different date than today.  Implies -y in
              case only a year is passed.
 
+     -d YYYY-WWW[-D]
+             Show the calendar for a different date (ISO week notation) than
+             today.  Defaults to Monday if no week day is given.
+
 EXIT STATUS
      The wcal utility exits 0 on success, and >0 if an error occurs.
 
@@ -53,4 +57,4 @@ CAVEATS
      This program uses a proleptic Gregorian Calendar and may yield unexpected
      results before 1752.  The year 0000 starts on a Saturday.
 
-Void Linux                     January 30, 2021                     Void Linux
+Void Linux                     Feburary 19, 2022                    Void Linux
diff --git a/wcal.1 b/wcal.1
index 60142bd..6ad706d 100644
--- a/wcal.1
+++ b/wcal.1
@@ -1,4 +1,4 @@
-.Dd January 30, 2021
+.Dd Feburary 19, 2022
 .Dt WCAL 1
 .Os
 .Sh NAME
@@ -8,6 +8,7 @@
 .Nm
 .Op Fl 13yci
 .Op Fl d Ar YYYY Ns Op Ar -MM Ns Op Ar -DD
+.Op Fl d Ar YYYY Ns Ar - Ns Cm W Ns Ar WW Ns Op Ar -D
 .Sh DESCRIPTION
 The
 .Nm
@@ -35,6 +36,9 @@ Show the calendar for a different date than today.
 Implies
 .Fl y
 in case only a year is passed.
+.It Fl d Ar YYYY Ns Ar - Ns Cm W Ns Ar WW Ns Op Ar -D
+Show the calendar for a different date (ISO week notation) than today.
+Defaults to Monday if no week day is given.
 .El
 .Sh EXIT STATUS
 .Ex -std
diff --git a/wcal.c b/wcal.c
index 3293f42..b555be8 100644
--- a/wcal.c
+++ b/wcal.c
@@ -103,8 +103,25 @@ parse_isodate(char *optarg, int *y, int *m, int *d)
 			*m = atoi(optarg+5);
 
 			if (isdigit(optarg[8]) && isdigit(optarg[9]) &&
-			    (!optarg[10] || optarg[10] == '-'))
+			    !optarg[10])
 				*d = atoi(optarg+8);
+		} else if (optarg[5] == 'W' &&
+		    isdigit(optarg[6]) && isdigit(optarg[7]) &&
+		    (!optarg[8] || optarg[8] == '-')) {
+			int w = atoi(optarg+6);
+			int wd = 1;
+
+			if (isdigit(optarg[9]) && !optarg[10])
+				wd = atoi(optarg+9);
+
+			int _;
+			int corr;
+			long jan4 = ymd2jd(*y, 1, 4);
+			jd2ymdwi(jan4, &_, &_, &_, &corr, &_, &_);
+			corr += 3;
+
+			jd2ymdwi(jan4 - 4 + 7*w + wd - corr,
+			    y, m, d, &_, &_, &_);
 		}
 	}
 }
-- 
cgit 1.4.1