61 lines
2.0 KiB
TypeScript
61 lines
2.0 KiB
TypeScript
import { clamp } from './types.ts'
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export const GAIN = 0.01
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export const DAILY_CAP = 0.05
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export const LOSS = 0.03
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export const IDLE_DAYS = 7
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export const HALF_LIFE_DAYS = 30
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const DAY = 86_400_000
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export type Stage = 0 | 1 | 2 | 3
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export const STAGE_NAMES = ['陌生', '熟悉', '親近', '特別'] as const
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// 升階門檻；降階門檻 = 升階 − 0.05（遲滯）
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const UP = [0.1, 0.3, 0.6]
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const HYST = 0.05
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export type Affinity = {
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value: number
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stage: Stage
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/** 今日已增加量與其日期 */
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gainDay: string
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gainToday: number
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lastSeen: number
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}
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export const initialAffinity = (now: number): Affinity => ({ value: 0, stage: 0, gainDay: dayKey(now), gainToday: 0, lastSeen: now })
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export const dayKey = (t: number) => new Date(t).toISOString().slice(0, 10)
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export function stageFor(value: number, prev: Stage): Stage {
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let s = prev
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while (s < 3 && value >= UP[s]!) s++
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while (s > 0 && value < UP[s - 1]! - HYST) s--
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return s as Stage
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}
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/** 讀取時計算：離開超過 7 天後以 30 天半衰期回到 0 */
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export function settle(a: Affinity, now: number): Affinity {
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const idleDays = (now - a.lastSeen) / DAY
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if (idleDays <= IDLE_DAYS) return a
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const f = Math.pow(0.5, (idleDays - IDLE_DAYS) / HALF_LIFE_DAYS)
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const value = a.value * f
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return { ...a, value, stage: stageFor(value, a.stage), lastSeen: now }
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}
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export function meaningful(a: Affinity, now: number): Affinity {
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const s = settle(a, now)
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const today = dayKey(now)
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const gainToday = s.gainDay === today ? s.gainToday : 0
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const gain = clamp(Math.min(GAIN, DAILY_CAP - gainToday), 0, GAIN)
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const value = clamp(s.value + gain, -1, 1)
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return { value, stage: stageFor(value, s.stage), gainDay: today, gainToday: gainToday + gain, lastSeen: now }
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}
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export function negative(a: Affinity, now: number): Affinity {
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const s = settle(a, now)
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const value = clamp(s.value - LOSS, -1, 1)
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const today = dayKey(now)
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return { ...s, value, stage: stageFor(value, s.stage), gainDay: today, gainToday: s.gainDay === today ? s.gainToday : 0, lastSeen: now }
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}
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