feat: show habit history in details

frontend/src/lib/mvp-utils.ts

@@ -80,6 +80,33 @@ export function isHabitComplete(kind: string | undefined, value: number | boolea
   return Boolean(value)
 }
 
+export type HabitHistoryLog = { day: string; value: number }
+
+export function habitHistoryWindow(toDay: string, size = 90) {
+  const [year, month, day] = toDay.split('-').map(Number)
+  const to = new Date(year, month - 1, day)
+  const from = new Date(to)
+  from.setDate(from.getDate() - (size - 1))
+  return { from: dateKey(from), to: dateKey(to) }
+}
+
+export function dayBefore(day: string) {
+  const [year, month, date] = day.split('-').map(Number)
+  const value = new Date(year, month - 1, date)
+  value.setDate(value.getDate() - 1)
+  return dateKey(value)
+}
+
+export function mergeHabitHistory(previous: HabitHistoryLog[], incoming: HabitHistoryLog[]) {
+  const merged = new Map(previous.map((item) => [item.day, item]))
+  for (const item of incoming) merged.set(item.day, { day: item.day, value: Number(item.value) })
+  return [...merged.values()].sort((a, b) => b.day.localeCompare(a.day))
+}
+
+export function formatHabitHistoryNumber(value: number) {
+  return Number.isInteger(value) ? String(value) : String(Number(value.toFixed(6)))
+}
+
 type HabitSchedule = {
   kind?: string
   cells?: Array<{ day: string; scheduled?: boolean; paused?: boolean; value?: number | boolean }>