feat: add wind conversion, Beaufort and compass tables

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

2 files changed, 91 insertions, 0 deletions

diff --git a/lib/weather.lua b/lib/weather.lua
index 0b4b1b7..6e2741a 100644
--- a/lib/weather.lua
+++ b/lib/weather.lua
@@ -63,4 +63,45 @@ function M.icon(id, now, sunrise, sunset)
   return M.ICON.unknown
 end
 
+-- OWM's metric units report wind in m/s. The card shows km/h.
+function M.kmh(ms)
+  if type(ms) ~= 'number' then return nil end
+  return ms * 3.6
+end
+
+-- Beaufort force from km/h. Upper bounds carried over from the polybar
+-- script; a value equal to a bound stays in the lower force.
+local BEAUFORT = { 1, 5, 11, 19, 28, 38, 49, 61, 74, 88, 102, 117 }
+
+function M.beaufort(kmh)
+  if type(kmh) ~= 'number' then return nil end
+  for force, bound in ipairs(BEAUFORT) do
+    if kmh <= bound then return force - 1 end
+  end
+  return 12
+end
+
+-- Eight compass points. The half-step offset is what makes north straddle
+-- zero: without it, 350 degrees would land in NW and 10 in NE, leaving north
+-- with only half its arc.
+local POINTS = { 'N', 'NE', 'E', 'SE', 'S', 'SW', 'W', 'NW' }
+
+function M.compass(deg)
+  if type(deg) ~= 'number' then return nil end
+  local i = math.floor(((deg % 360) + 22.5) / 45) % 8
+  return POINTS[i + 1]
+end
+
+-- Arrow glyphs, in the same order as POINTS but rotated half a turn: OWM
+-- reports the direction the wind comes FROM, and an arrow reads as the
+-- direction it goes TO.
+local ARROWS = { '\u{2193}', '\u{2199}', '\u{2190}', '\u{2196}',
+                 '\u{2191}', '\u{2197}', '\u{2192}', '\u{2198}' }
+
+function M.arrow(deg)
+  if type(deg) ~= 'number' then return '' end
+  local i = math.floor(((deg % 360) + 22.5) / 45) % 8
+  return ARROWS[i + 1]
+end
+
 return M
diff --git a/test/test_weather.lua b/test/test_weather.lua
index f61fa22..e18aa15 100644
--- a/test/test_weather.lua
+++ b/test/test_weather.lua
@@ -77,4 +77,54 @@ assert(weather.icon(800, DAY, nil, nil) == weather.ICON.clear_day,
 -- the plan's Step 5, and it is how a wrong-but-present codepoint was caught
 -- before this file existed.
 
+-- === Wind =================================================================
+-- OWM metric gives m/s; the card shows km/h. The conversion is where a wrong
+-- factor would look plausible but read 3.6x off.
+assert(weather.kmh(10) == 36, '10 m/s is 36 km/h')
+assert(weather.kmh(0) == 0, 'calm')
+assert(weather.kmh(nil) == nil, 'missing wind speed stays missing')
+
+-- Beaufort thresholds, in km/h, from the polybar script. Each assertion sits
+-- on a boundary and just past it, which is where an inclusive/exclusive
+-- mistake hides.
+assert(weather.beaufort(0) == 0, 'calm is force 0')
+assert(weather.beaufort(1) == 0, '1 km/h is still force 0')
+assert(weather.beaufort(2) == 1, 'just over 1 is force 1')
+assert(weather.beaufort(5) == 1, '5 is still force 1')
+assert(weather.beaufort(6) == 2, 'just over 5 is force 2')
+assert(weather.beaufort(11) == 2, '11 is still force 2')
+assert(weather.beaufort(12) == 3, 'just over 11 is force 3')
+assert(weather.beaufort(19) == 3, '19 is still force 3')
+assert(weather.beaufort(28) == 4, '28 is force 4')
+assert(weather.beaufort(38) == 5, '38 is force 5')
+assert(weather.beaufort(49) == 6, '49 is force 6')
+assert(weather.beaufort(61) == 7, '61 is force 7')
+assert(weather.beaufort(74) == 8, '74 is force 8')
+assert(weather.beaufort(88) == 9, '88 is force 9')
+assert(weather.beaufort(102) == 10, '102 is force 10')
+assert(weather.beaufort(117) == 11, '117 is force 11')
+assert(weather.beaufort(118) == 12, 'over 117 is hurricane force')
+
+-- Compass: eight points, each spanning 45 degrees, offset by half a step so
+-- north straddles 0 rather than starting at it. The wraparound is the case
+-- that a naive floor(deg/45) gets wrong.
+assert(weather.compass(0) == 'N', '0 is north')
+assert(weather.compass(360) == 'N', '360 wraps to north')
+assert(weather.compass(11) == 'N', 'just under the NE boundary')
+assert(weather.compass(349) == 'N', 'just over the NW boundary wraps to north')
+assert(weather.compass(45) == 'NE', '45 is northeast')
+assert(weather.compass(90) == 'E', '90 is east')
+assert(weather.compass(135) == 'SE', '135 is southeast')
+assert(weather.compass(180) == 'S', '180 is south')
+assert(weather.compass(225) == 'SW', '225 is southwest')
+assert(weather.compass(270) == 'W', '270 is west')
+assert(weather.compass(315) == 'NW', '315 is northwest')
+assert(weather.compass(nil) == nil, 'missing direction stays missing')
+
+-- The arrow points where the wind is going, and OWM reports where it comes
+-- from, so a north wind draws a downward arrow.
+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')
+
 print('test_weather: all assertions passed')