zenno/race/gate: new calculator

zenno/src/lib/race.ts

@@ -93,6 +93,20 @@ export function distance(raceLen: number): Distance {
 	return Distance.Long;
 }
 
+/**
+ * Get the distances at which each phase of a race ends.
+ * @param raceLen Length of the race in meters
+ * @returns Ends of each phase in meters
+ */
+export function phases(raceLen: number) {
+	const sixth = raceLen / 6;
+	return {
+		[Phase.EarlyRace]: sixth,
+		[Phase.MidRace]: 4 * sixth,
+		[Phase.LateRace]: raceLen,
+	}
+}
+
 /**
  * Race surfaces.
  */
@@ -372,7 +386,13 @@ export function fullSpurtHP(raceLen: number, spurtSpeed: number, hpRate: number)
 	return spurtTime * hpRate;
 }
 
-function baseSpeed(raceLen: number): number {
+/**
+ * Calculate the base speed for a race.
+ * Note that this is not the base target speed for a horse.
+ * @param raceLen Race length in meters
+ * @returns Base speed for the race
+ */
+export function baseSpeed(raceLen: number): number {
 	return 20 - (raceLen - 2000) / 1000;
 }
 
@@ -748,13 +768,22 @@ export function duelAccelMod(gutsStat: number): number {
  * Calculate the speed modifier for running uphill.
  * Contrary to the race mechanics document, this is expressed as a negative number.
  * @param powerStat Final power stat
- * @param slopePer Slope percentage, generally one of 0.5, 1.0, 1.5, or 2.0
+ * @param slopePer Slope percentage, one of 1.0, 1.5, or 2.0
  * @returns Speed modifier for running uphill, a negative value
  */
 export function uphillMod(powerStat: number, slopePer: number): number {
 	return (slopePer * -200) / powerStat;
 }
 
+/**
+ * Calculate the speed modifier while running in downhill accel mode.
+ * @param slopePer Slope percentage, one of -1.0, -1.5, or -2.0
+ * @returns Speed modifier for downhill accel mode
+ */
+export function downhillAccelMod(slopePer: number): number {
+	return 0.3 - slopePer/10;
+}
+
 /**
  * Calculate the forward speed boost given when moving lanewise while a skill
  * that grants a lane change speed boost is active.