feat: add sun position along the daylight arc

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

1 files changed, 26 insertions, 0 deletions

diff --git a/test/test_weather.lua b/test/test_weather.lua
index e18aa15..1d35748 100644
--- a/test/test_weather.lua
+++ b/test/test_weather.lua
@@ -127,4 +127,30 @@ assert(weather.arrow(0) == '\u{2193}', 'a north wind blows southward')
 assert(weather.arrow(180) == '\u{2191}', 'a south wind blows northward')
 assert(weather.arrow(nil) == '', 'no direction draws nothing')
 
+-- === Sun position =========================================================
+-- t is the fraction of daylight elapsed, and the widget uses it to place the
+-- dot along the arc. Sunrise 1000, sunset 2000, so midday is 1500.
+assert(weather.sun_t(1000, 1000, 2000) == 0, 'at sunrise t is 0')
+assert(weather.sun_t(1500, 1000, 2000) == 0.5, 'at midday t is half')
+assert(weather.sun_t(2000, 1000, 2000) == 1, 'at sunset t is 1')
+
+-- OWM reports today's sunrise and sunset, so between midnight and sunrise the
+-- numerator is negative. The clamp is the whole handling; without it the dot
+-- would be drawn off the left end of the arc.
+assert(weather.sun_t(500, 1000, 2000) == 0, 'before dawn clamps to 0')
+assert(weather.sun_t(9999, 1000, 2000) == 1, 'after dusk clamps to 1')
+
+-- Degenerate input must not divide by zero.
+assert(weather.sun_t(1500, 2000, 2000) == 0, 'zero-length day gives 0, not nan')
+assert(weather.sun_t(nil, 1000, 2000) == nil, 'missing now gives nil')
+assert(weather.sun_t(1500, nil, 2000) == nil, 'missing sunrise gives nil')
+
+-- is_day drives both the icon face and the dot's colour: a dot parked at the
+-- end of the arc must not read as a sun that is still up.
+assert(weather.is_day(1500, 1000, 2000) == true, 'midday is day')
+assert(weather.is_day(1000, 1000, 2000) == true, 'sunrise counts as day')
+assert(weather.is_day(2000, 1000, 2000) == true, 'sunset counts as day')
+assert(weather.is_day(500, 1000, 2000) == false, 'before dawn is night')
+assert(weather.is_day(2500, 1000, 2000) == false, 'after dusk is night')
+
 print('test_weather: all assertions passed')