package handlers

import (
	"encoding/json"
	"log"
	"time"

	stripego "github.com/stripe/stripe-go/v84"
	"github.com/stripe/stripe-go/v84/subscription"
)

const freeTierMonths = 3

// maybeScheduleFreeTierCancel fetches the subscription and, if it uses the free-tier
// price, sets cancel_at to 3 months from now so it auto-cancels at end of term.
func (a *App) maybeScheduleFreeTierCancel(subID string) {
	sub, err := a.stripe.GetSubscription(subID)
	if err != nil {
		log.Printf("webhook: could not fetch subscription %s: %v", subID, err)
		return
	}
	if sub.Items == nil || len(sub.Items.Data) == 0 {
		return
	}
	priceID := sub.Items.Data[0].Price.ID
	if !a.stripe.IsFreeTierPrice(priceID) {
		return
	}
	cancelAt := time.Now().AddDate(0, freeTierMonths, 0).Unix()
	if err := a.stripe.ScheduleSubscriptionCancelAt(subID, cancelAt); err != nil {
		log.Printf("webhook: failed to schedule free-tier cancel for sub %s: %v", subID, err)
		return
	}
	log.Printf("webhook: scheduled free-tier sub %s to cancel at %d (3 months)", subID, cancelAt)
}

type invoicePaidPayload struct {
	BillingReason stripego.InvoiceBillingReason `json:"billing_reason"`
	Subscription  interface{}                   `json:"subscription"`
	Lines         struct {
		Data []struct {
			Price struct {
				ID string `json:"id"`
			} `json:"price"`
		} `json:"data"`
	} `json:"lines"`
}

func (a *App) onInvoicePaid(event stripego.Event) {
	var raw invoicePaidPayload
	if err := json.Unmarshal(event.Data.Raw, &raw); err != nil {
		log.Printf("invoice unmarshal error: %v", err)
		return
	}
	if raw.BillingReason != stripego.InvoiceBillingReasonSubscriptionCycle {
		return
	}
	subID := ""
	switch v := raw.Subscription.(type) {
	case string:
		subID = v
	case map[string]interface{}:
		if id, ok := v["id"].(string); ok {
			subID = id
		}
	}
	if subID == "" || len(raw.Lines.Data) == 0 {
		return
	}
	priceID := raw.Lines.Data[0].Price.ID
	if priceID == "" || !a.stripe.IsYearTierPrice(priceID) {
		return
	}
	price100 := a.cfg.StripePriceIDMonth100
	if price100 == "" {
		log.Printf("webhook: STRIPE_PRICE_ID_MONTH_100 not set, cannot migrate sub %s", subID)
		return
	}
	sub, err := a.stripe.GetSubscription(subID)
	if err != nil || sub.Items == nil || len(sub.Items.Data) == 0 {
		log.Printf("webhook: could not get subscription %s for migration: %v", subID, err)
		return
	}
	subItemID := sub.Items.Data[0].ID
	params := &stripego.SubscriptionParams{
		Items: []*stripego.SubscriptionItemsParams{
			{ID: stripego.String(subItemID), Price: stripego.String(price100)},
		},
		ProrationBehavior: stripego.String("none"),
	}
	if _, err := subscription.Update(subID, params); err != nil {
		log.Printf("webhook: failed to migrate sub %s to $100/mo: %v", subID, err)
		return
	}
	log.Printf("webhook: migrated sub %s from $20/year to $100/month", subID)
}