package scheduler

import (
	"fmt"
	"time"

	"veola/internal/models"
	"veola/templates"
)

// PickBadge returns the highest-priority deal-quality badge that applies to
// an item, or an empty BadgeData if none match. Order:
//  1. All-time low
//  2. X% below 30-day avg (only when at least 10% below)
//  3. X% below target
func PickBadge(it models.Item, history []models.PricePoint, now time.Time) templates.BadgeData {
	if it.BestPrice == nil {
		return templates.BadgeData{}
	}
	best := *it.BestPrice

	// 1. All-time low
	if isAllTimeLow(best, history) {
		return templates.BadgeData{Label: "All-time low", Class: "v-badge-low"}
	}

	// 2. X% below 30-day average
	if avg, ok := windowedMean(history, now, 30*24*time.Hour); ok && best > 0 && avg > 0 {
		pct := (avg - best) / avg * 100
		if pct >= 10 {
			return templates.BadgeData{
				Label: fmt.Sprintf("%d%% below 30-day avg", int(pct+0.5)),
				Class: "v-badge-avg",
			}
		}
	}

	// 3. X% below target
	if it.TargetPrice != nil && *it.TargetPrice > 0 && best < *it.TargetPrice {
		pct := (*it.TargetPrice - best) / *it.TargetPrice * 100
		return templates.BadgeData{
			Label: fmt.Sprintf("%d%% below target", int(pct+0.5)),
			Class: "v-badge-target",
		}
	}

	return templates.BadgeData{}
}

func isAllTimeLow(best float64, history []models.PricePoint) bool {
	if len(history) == 0 {
		return false
	}
	for _, p := range history {
		if p.Price > 0 && p.Price < best {
			return false
		}
	}
	return true
}

func windowedMean(history []models.PricePoint, now time.Time, window time.Duration) (float64, bool) {
	cutoff := now.Add(-window)
	sum, n := 0.0, 0
	for _, p := range history {
		if p.PolledAt.Before(cutoff) {
			continue
		}
		sum += p.Price
		n++
	}
	if n == 0 {
		return 0, false
	}
	return sum / float64(n), true
}