263 lines
10 KiB
C#
263 lines
10 KiB
C#
using System;
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namespace AcDream.Core.World;
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/// <summary>
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/// Asheron's Call "Portal Year" calendar + time-of-day math — faithful
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/// port of retail's <c>DerethDateTime</c> (r12 §1.2 + ACE
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/// <c>DerethDateTime.cs</c>).
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///
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/// <para>
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/// The server transports an absolute tick count as a double (seconds
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/// since a seed chosen at boot). The client doesn't need to know which
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/// seed was chosen — it just needs the tick count to derive:
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/// <list type="bullet">
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/// <item><description>
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/// Day fraction in [0, 1): where we are in the 16-hour Derethian day.
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/// </description></item>
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/// <item><description>
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/// Hour name (Darktide, Dawnsong, Midsong, Warmtide, Evensong,
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/// Gloaming and their "-and-Half" mid-hour variants).
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/// </description></item>
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/// <item><description>
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/// Day / night flag for spawn rules + lighting.
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/// </description></item>
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/// <item><description>
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/// Season / year / month for calendar UI.
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/// </description></item>
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/// </list>
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/// </para>
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///
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/// <para>
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/// Constants are retail-exact; changing them breaks the calendar panel's
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/// "today is" display.
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/// </para>
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/// </summary>
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public static class DerethDateTime
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{
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public const int HoursInADay = 16;
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public const int DaysInAMonth = 30;
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public const int MonthsInAYear = 12;
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/// <summary>Ticks per Derethian day (matches retail GameTime.DayLength).</summary>
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public const double DayTicks = 7620.0;
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/// <summary>Ticks per Derethian hour (DayTicks / 16).</summary>
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public const double HourTicks = DayTicks / HoursInADay; // 476.25
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/// <summary>Ticks per Derethian month.</summary>
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public const double MonthTicks = DayTicks * DaysInAMonth; // 228,600
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/// <summary>Ticks per Derethian year.</summary>
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public const double YearTicks = MonthTicks * MonthsInAYear; // 2,743,200
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/// <summary>
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/// Above this tick count the retail client crashes on connect.
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/// ~1.07 billion seconds = PY 401 Thistledown 2 Morntide-and-Half.
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/// </summary>
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public const double MaxTicks = 1_073_741_828.0;
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/// <summary>
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/// Base/anchor year for the Portal Year calendar (retail
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/// <c>GameTime.ZeroYear</c> = 10). Tick 0 corresponds to PY 10,
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/// Morningthaw 1, Morntide-and-Half. Retail's <c>TimeOfDay+0x64</c>
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/// ("absolute year") includes this offset, and
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/// <c>SkyDesc::CalcPresentDayGroup @ 0x00500E10</c> feeds the absolute year
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/// into its LCG seed (older-build cross-reference <c>FUN_00501990</c>).
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/// </summary>
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public const int ZeroYear = 10;
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/// <summary>
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/// The 16 named hour slots (r12 §1.2). Each one is half a Derethian
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/// hour; the "-and-Half" variants are the second half.
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/// </summary>
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public enum HourName
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{
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Darktide = 0,
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DarktideAndHalf,
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Foredawn,
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ForedawnAndHalf,
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Dawnsong, // day starts here (hour 5)
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DawnsongAndHalf,
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Morntide,
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MorntideAndHalf,
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Midsong,
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MidsongAndHalf,
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Warmtide,
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WarmtideAndHalf, // day ends here (hour 12)
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Evensong,
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EvensongAndHalf,
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Gloaming,
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GloamingAndHalf,
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}
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/// <summary>
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/// Derethian months in chronological order. Year-0 begins at month 0
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/// (<see cref="Morningthaw"/>) and progresses through the 12-month
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/// cycle. Names + order match retail's calendar display
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/// (<c>GameTime::CalcDayBegin</c> + <c>GetDateTimeString</c> at
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/// <c>0x005a6530</c>) and ACE's <c>DerethDateTime.cs</c>. Verified
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/// against retail's <c>@timestamp</c> output in 2026-04-27 dual-
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/// client comparison: at day-of-year 83, retail shows
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/// "Seedsow 24" — that fixes month index 2 = Seedsow.
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/// </summary>
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public enum MonthName
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{
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Morningthaw = 0,
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Solclaim,
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Seedsow,
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Leafdawning,
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Verdantine,
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Thistledown,
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Harvestgain,
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Leafcull,
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Frostfell,
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Snowreap,
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Coldeve,
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Wintersebb,
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}
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/// <summary>
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/// Default anchor ticks when no Region has been loaded: +7/16 of a
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/// full day (3333.75) per ACE's DerethDateTime comment "tick 0 =
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/// Morntide-and-Half". This is a fallback — retail reads
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/// <c>GameTime.ZeroTimeOfYear</c> from the Region dat (verified
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/// <c>3600</c> in Dereth, 2026-04-23 live dump) and uses that as
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/// the additive offset. Production installs that value on its
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/// instance <see cref="DerethCalendar"/>; this constant remains the
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/// offline/static-helper default.
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/// </summary>
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public const double DayFractionOriginOffsetTicks = (7.0 / 16.0) * DayTicks; // 3333.75
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/// <summary>
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/// Compatibility origin used by the pure static helpers. Production
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/// worlds use an instance <see cref="DerethCalendar"/> carrying their
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/// Region DAT origin, so multiple sessions never share mutable calendar
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/// state.
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///
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/// <para>
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/// Live Dereth dat value: <c>3600</c>. Retail's
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/// <c>GameTime::CalcDayBegin</c> at <c>0x005a6400</c> (decomp line
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/// 434549) computes <c>arg2 + zero_time_of_year</c> as the basis for
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/// year/day-of-year extraction, then derives <c>time_of_day_begin</c>
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/// such that <c>(arg2 - time_of_day_begin) / day_length</c> in
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/// <c>CalcTimeOfDay</c> gives <c>(arg2 + zero_time_of_year) mod day_length / day_length</c>.
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/// Net: the formula is ADD, not subtract — confirmed via the explicit
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/// add at line 434549. (A 2026-04-26 attempt to flip the sign over-
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/// corrected and broke DG selection; reverted in the same commit.)
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/// </para>
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/// </summary>
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public const double OriginOffsetTicks = DayFractionOriginOffsetTicks;
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/// <summary>
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/// Day fraction [0, 1): 0 = Darktide (midnight), 0.5 =
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/// Midsong-and-Half (noon-ish), 1.0 wraps to 0. Anchored by
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/// <see cref="OriginOffsetTicks"/> (dat's ZeroTimeOfYear).
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/// </summary>
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public static double DayFraction(double ticks)
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{
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if (ticks < 0) ticks = 0;
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double shifted = ticks + OriginOffsetTicks;
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double rem = shifted - Math.Floor(shifted / DayTicks) * DayTicks;
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return rem / DayTicks;
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}
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/// <summary>
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/// Hour name for the given tick count. Picked from
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/// <see cref="HourName"/> based on which named half-hour slot the
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/// current time falls in.
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/// </summary>
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public static HourName CurrentHour(double ticks)
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{
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double f = DayFraction(ticks);
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int slot = (int)Math.Floor(f * HoursInADay);
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if (slot < 0) slot = 0;
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if (slot > 15) slot = 15;
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return (HourName)slot;
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}
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/// <summary>
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/// True when the current time is "day" (Dawnsong through
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/// Warmtide-and-Half, hours 5–12 inclusive on the 16-hour scale).
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/// </summary>
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public static bool IsDaytime(double ticks)
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{
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int h = (int)CurrentHour(ticks);
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return h >= (int)HourName.Dawnsong && h <= (int)HourName.WarmtideAndHalf;
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}
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/// <summary>
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/// Derethian calendar breakdown: (year, month, day, hour).
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/// <see cref="Year"/> is the absolute Portal Year (= relative-year +
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/// <see cref="ZeroYear"/>) so the value matches retail's
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/// <c>@timestamp</c> output ("Date: <Month> <Day>,
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/// <Year> P.Y."). Day is 1-based within the month (1..30).
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/// </summary>
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public readonly record struct Calendar(int Year, MonthName Month, int Day, HourName Hour);
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public static Calendar ToCalendar(double ticks)
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{
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if (ticks < 0) ticks = 0;
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double shifted = ticks + OriginOffsetTicks;
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int relativeYear = (int)(shifted / YearTicks);
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double tYear = shifted - relativeYear * YearTicks;
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int monthIdx = (int)(tYear / MonthTicks);
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if (monthIdx > 11) monthIdx = 11;
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double tMonth = tYear - monthIdx * MonthTicks;
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int day = (int)(tMonth / DayTicks) + 1;
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if (day > DaysInAMonth) day = DaysInAMonth;
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// Absolute Portal Year for display: retail's @timestamp shows
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// PY-with-base (10 P.Y. == year 0 of the calendar epoch), so add
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// ZeroYear here. Matches AbsoluteYear() and the retail decomp at
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// FUN_005a7510:5300.
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return new Calendar(relativeYear + ZeroYear, (MonthName)monthIdx, day, CurrentHour(ticks));
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}
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/// <summary>
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/// Year offset from tick-0 (number of Derethian years elapsed since
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/// the PY <see cref="ZeroYear"/> anchor). Shifted by
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/// <see cref="OriginOffsetTicks"/> (dat's ZeroTimeOfYear) to match
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/// retail's TimeOfDay::OnTick extraction. Use for time-delta math.
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/// For calendar display and for the retail DayGroup LCG seed, use
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/// <see cref="AbsoluteYear"/> which adds the <c>ZeroYear</c> base.
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/// </summary>
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public static int Year(double ticks)
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{
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if (ticks < 0) ticks = 0;
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double shifted = ticks + OriginOffsetTicks;
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return (int)(shifted / YearTicks);
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}
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/// <summary>
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/// Absolute Portal Year (<see cref="ZeroYear"/> + relative year).
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/// Matches retail's <c>TimeOfDay + 0x64</c> field
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/// (<c>FUN_005a7510:5300</c>:
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/// <c>floor((worldTime+base)/secsPerYear) + baseYear</c>). This is
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/// the value the retail DayGroup picker
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/// (<c>SkyDesc::CalcPresentDayGroup @ 0x00500E10</c>) feeds
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/// into its LCG seed, so acdream must match for identical weather
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/// picks vs retail.
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/// </summary>
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public static int AbsoluteYear(double ticks) => Year(ticks) + ZeroYear;
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/// <summary>
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/// Day index within the current Derethian year in [0, 359] (360 days
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/// per year = 12 months × 30). Shifted by <see cref="OriginOffsetTicks"/>
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/// (dat's ZeroTimeOfYear) to match retail's <c>TimeOfDay + 0x68</c>
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/// field (<c>FUN_005a7510:5304</c>:
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/// <c>floor(withinYearSec / secsPerDay)</c>). Consumed by
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/// <c>SkyDesc::CalcPresentDayGroup</c> as part of the per-day seed.
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/// </summary>
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public static int DayOfYear(double ticks)
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{
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if (ticks < 0) ticks = 0;
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double shifted = ticks + OriginOffsetTicks;
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int year = (int)(shifted / YearTicks);
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double tYear = shifted - year * YearTicks;
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int d = (int)(tYear / DayTicks);
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if (d < 0) d = 0;
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if (d > 359) d = 359;
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return d;
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}
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}
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