import { dt } from "@scandic-hotels/common/dt"

import type { Stay } from "@scandic-hotels/trpc/routers/user/output"

export interface StaysByYear {
  year: number
  stays: Stay[]
}

/**
 * Groups stays by year based on checkinDate.
 * @returns an array sorted by year in descending order (most recent first).
 */
export function groupStaysByYear(stays: Stay[]): StaysByYear[] {
  const groupedMap = new Map<number, Stay[]>()

  for (const stay of stays) {
    const year = dt(stay.attributes.checkinDate).year()

    if (!groupedMap.has(year)) {
      groupedMap.set(year, [])
    }
    groupedMap.get(year)!.push(stay)
  }

  return Array.from(groupedMap.entries())
    .sort(([yearA], [yearB]) => yearB - yearA)
    .map(([year, stays]) => ({ year, stays }))
}