package domain

import "time"

// XpForLevel returns the total XP required to reach level n.
func XpForLevel(n int) int64 {
	return int64(n) * int64(n+1) * XPCurveMultiplier
}

// LevelForXP returns the level for a given total XP amount.
func LevelForXP(xp int64) int {
	l := 1
	for XpForLevel(l) <= xp {
		l++
	}
	return l - 1
}

// XpForWorkSeconds calculates XP earned for a given amount of work.
func XpForWorkSeconds(sec int64) int64 {
	return sec
}

// StreakBonus returns bonus XP for maintaining a streak.
func StreakBonus(streak int) int64 {
	b := int64(streak) * XPCurveMultiplier
	if b > StreakBonusCap {
		b = StreakBonusCap
	}
	return b
}

// ComputeStreakFromDates computes current and longest streak from a sorted list of date strings.
func ComputeStreakFromDates(dates []string, today string) (current, longest int) {
	if len(dates) == 0 {
		return 0, 0
	}

	dateSet := make(map[string]struct{}, len(dates))
	for _, d := range dates {
		dateSet[d] = struct{}{}
	}

	if _, ok := dateSet[today]; ok {
		current = 1
		for i := 1; ; i++ {
			t, _ := time.Parse(DateLayout, today)
			prev := t.AddDate(0, 0, -i).Format(DateLayout)
			if _, ok := dateSet[prev]; ok {
				current++
			} else {
				break
			}
		}
	}

	longest = 0
	run := 1
	for i := 1; i < len(dates); i++ {
		prev, _ := time.Parse(DateLayout, dates[i-1])
		curr, _ := time.Parse(DateLayout, dates[i])
		if curr.Sub(prev).Hours() == 24 {
			run++
		} else {
			if run > longest {
				longest = run
			}
			run = 1
		}
	}
	if run > longest {
		longest = run
	}

	return current, longest
}