feat: add shared date and time formatting

src/core/DateTime.lua

@@ -0,0 +1,90 @@
+-- Shared local date/time presentation for engine UI and mods. Preferences
+-- live in options.lua, never checkpoint progress. "device" uses the process
+-- time locale when the platform supplies one and otherwise falls back to the
+-- deterministic DD-MM-YYYY / 24-hour convention.
+
+local DateTime = {}
+
+local DATE_FORMATS = {
+  dmy = "%d-%m-%Y",
+  mdy = "%m-%d-%Y",
+  ymd = "%Y-%m-%d",
+}
+local TIME_FORMATS = {
+  ["24h"] = "%H:%M",
+  ["12h"] = "%I:%M %p",
+}
+
+local function validTimestamp(value)
+  return type(value) == "number" and value == value and value >= 0
+    and value ~= math.huge and value ~= -math.huge
+end
+
+local function render(timestamp, pattern)
+  local ok, value = pcall(os.date, pattern, math.floor(timestamp))
+  if not ok or type(value) ~= "string" or value == "" then return nil end
+  return value
+end
+
+local function currentLocale()
+  if not os.setlocale then return nil end
+  local ok, value = pcall(os.setlocale, nil, "time")
+  if not ok or type(value) ~= "string" then return nil end
+  return value
+end
+
+local function deviceAvailable(localeName)
+  return type(localeName) == "string" and localeName ~= ""
+    and localeName ~= "C" and localeName ~= "POSIX"
+end
+
+function DateTime.formatWithLocale(timestamp, datePreference, timePreference, localeName)
+  if not validTimestamp(timestamp) then return { date = "----", time = "----" } end
+  local datePattern = DATE_FORMATS[datePreference]
+  local timePattern = TIME_FORMATS[timePreference]
+  if not datePattern then
+    datePattern = deviceAvailable(localeName) and "%x" or DATE_FORMATS.dmy
+  end
+  if not timePattern then
+    if deviceAvailable(localeName) then
+      local sample = render(timestamp, "%X") or ""
+      local marker = render(timestamp, "%p") or ""
+      timePattern = marker ~= "" and sample:find(marker, 1, true)
+        and TIME_FORMATS["12h"] or TIME_FORMATS["24h"]
+    else
+      timePattern = TIME_FORMATS["24h"]
+    end
+  end
+  return {
+    date = render(timestamp, datePattern) or "----",
+    time = render(timestamp, timePattern) or "----",
+  }
+end
+
+local function preferences(game)
+  local options = game and game.save and game.save.options
+  options = type(options) == "table" and options or {}
+  return options.dateFormat or "device", options.timeFormat or "device"
+end
+
+function DateTime.date(game, timestamp)
+  local datePreference, timePreference = preferences(game)
+  return DateTime.formatWithLocale(timestamp, datePreference, timePreference,
+    currentLocale()).date
+end
+
+function DateTime.time(game, timestamp)
+  local datePreference, timePreference = preferences(game)
+  return DateTime.formatWithLocale(timestamp, datePreference, timePreference,
+    currentLocale()).time
+end
+
+function DateTime.dateTime(game, timestamp)
+  local datePreference, timePreference = preferences(game)
+  local value = DateTime.formatWithLocale(timestamp, datePreference, timePreference,
+    currentLocale())
+  if value.date == "----" or value.time == "----" then return "----" end
+  return value.date .. " " .. value.time
+end
+
+return DateTime