package order

import "github.com/perfect-panel/server/internal/types"

// getDiscount returns the discount factor for the given quantity.
//
// Design: when a quantity has both a new_user_only=true entry and a new_user_only=false entry,
// the new_user_only=true entry is a "gating marker" (its discount value is irrelevant).
// The actual discounted price is always carried by the new_user_only=false entry.
// Whether the buyer is eligible to use this quantity is enforced by isNewUserOnlyForQuantity
// before calling this function. Here we simply return the best applicable discount.
//
// Priority: new_user_only=false entry beats new_user_only=true entry for the same quantity.
func getDiscount(discounts []types.SubscribeDiscount, inputMonths int64, isNewUser bool) float64 {
	var best float64 = 1
	foundFallback := false
	for _, d := range discounts {
		if d.Quantity != inputMonths || d.Discount <= 0 || d.Discount >= 100 {
			continue
		}
		factor := d.Discount / float64(100)
		if !d.NewUserOnly {
			// Prefer the non-new-user-only tier as the actual price tier.
			best = factor
			foundFallback = true
		} else if !foundFallback && isNewUser {
			// Fall back to new-user-only tier only when no general tier exists
			// and the buyer qualifies.
			best = factor
		}
	}
	return best
}

// isNewUserOnlyForQuantity checks whether the matched discount tier has new_user_only enabled.
// Returns true only when all matching tiers for the given quantity require new-user status
// (i.e. no fallback tier with new_user_only=false exists). When both a new-user-only tier
// and a general tier exist for the same quantity, non-new-users can still purchase via the
// general tier, so this returns false.
func isNewUserOnlyForQuantity(discounts []types.SubscribeDiscount, inputQuantity int64) bool {
	hasNewUserOnly := false
	hasFallback := false
	for _, d := range discounts {
		if d.Quantity != inputQuantity {
			continue
		}
		if d.NewUserOnly {
			hasNewUserOnly = true
		} else {
			hasFallback = true
		}
	}
	return hasNewUserOnly && !hasFallback
}