package billing

import (
	"context"
	"errors"
	"fmt"
	"net/http"
	"net/url"
	"strconv"
	"strings"
	"time"

	"github.com/google/uuid"
)

// SalesQuoteCheckoutInput drives Checkout for an admin-prepared custom deal.
type SalesQuoteCheckoutInput struct {
	QuoteID                uuid.UUID
	CompanyID              uuid.UUID
	PlanID                 int64
	PlanName               string
	Email                  string
	CompanyName            string
	Currency               string
	TotalAmountCents       int
	InstallmentCount       int
	InstallmentInterval    string // month | quarter | year
	InstallmentAmountCents int
}

// SalesQuoteCheckoutResult is returned to admin after preparing Checkout for a quote.
type SalesQuoteCheckoutResult struct {
	URL       string `json:"url"`
	Mock      bool   `json:"mock"`
	Applied   bool   `json:"applied,omitempty"`
	Message   string `json:"message,omitempty"`
	ProductID string `json:"product_id,omitempty"`
	PriceID   string `json:"price_id,omitempty"`
	SessionID string `json:"session_id,omitempty"`
}

// CreateSalesQuoteCheckout creates a Stripe Price + Checkout Session for a sales quote.
//
// ASSUMPTION (installments):
//   - installment_count == 1 → Checkout mode=payment (one-time Price).
//   - installment_count  > 1 → Checkout mode=subscription with a recurring Price equal to
//     installment_amount_cents; subscription_data.cancel_at ends billing after N intervals
//     (month / quarter=3 months / year). Stripe collects the first installment at Checkout;
//     later invoices are charged automatically on the subscription.
func (s *StripeService) CreateSalesQuoteCheckout(ctx context.Context, in SalesQuoteCheckoutInput) (SalesQuoteCheckoutResult, error) {
	if in.QuoteID == uuid.Nil || in.CompanyID == uuid.Nil || in.PlanID <= 0 {
		return SalesQuoteCheckoutResult{}, fmt.Errorf("%w: quote identifiers", ErrStripePlanUnsupported)
	}
	if in.InstallmentAmountCents <= 0 || in.TotalAmountCents <= 0 {
		return SalesQuoteCheckoutResult{}, fmt.Errorf("%w: amounts", ErrStripePlanUnsupported)
	}
	count := in.InstallmentCount
	if count <= 0 {
		count = 1
	}
	interval := strings.ToLower(strings.TrimSpace(in.InstallmentInterval))
	if interval == "" {
		interval = "month"
	}
	currency := strings.ToLower(strings.TrimSpace(in.Currency))
	if currency == "" {
		currency = "usd"
	}

	ctx, cfg, err := s.bindCfg(ctx)
	if err != nil {
		return SalesQuoteCheckoutResult{}, err
	}
	web := strings.TrimRight(cfg.WebOrigin, "/")
	if web == "" {
		web = "http://localhost:5174"
	}

	if cfg.AllowMockPurchase() {
		if err := s.applySalesQuotePurchase(ctx, in.CompanyID, in.PlanID, in.QuoteID, "cus_mock_"+in.CompanyID.String()[:8], "sub_mock_"+uuid.NewString()[:8], "price_mock_quote"); err != nil {
			return SalesQuoteCheckoutResult{}, err
		}
		return SalesQuoteCheckoutResult{
			URL:     web + "/billing?checkout=success&mock=1&sales_quote=" + url.QueryEscape(in.QuoteID.String()),
			Mock:    true,
			Applied: true,
			Message: "Mock mode: custom sales quote plan assigned without Stripe.",
		}, nil
	}
	if cfg.MockMode() {
		return SalesQuoteCheckoutResult{}, ErrStripeNotConfigured
	}

	productID, err := s.ensureSalesQuoteProduct(ctx, in)
	if err != nil {
		return SalesQuoteCheckoutResult{}, err
	}
	priceID, err := s.createSalesQuotePrice(ctx, productID, in, count == 1)
	if err != nil {
		return SalesQuoteCheckoutResult{}, err
	}

	customerID, err := s.ensureCustomer(ctx, in.CompanyID, in.Email, in.CompanyName)
	if err != nil {
		return SalesQuoteCheckoutResult{}, err
	}

	form := url.Values{}
	form.Set("success_url", web+"/billing?checkout=success&sales_quote="+url.QueryEscape(in.QuoteID.String()))
	form.Set("cancel_url", web+"/billing?checkout=cancel&sales_quote="+url.QueryEscape(in.QuoteID.String()))
	form.Set("client_reference_id", in.CompanyID.String())
	form.Set("metadata[company_id]", in.CompanyID.String())
	form.Set("metadata[kind]", "sales_quote")
	form.Set("metadata[quote_id]", in.QuoteID.String())
	form.Set("metadata[plan_id]", strconv.FormatInt(in.PlanID, 10))
	form.Set("metadata[plan]", strings.ToLower(strings.TrimSpace(in.PlanName)))
	form.Set("metadata[installment_count]", strconv.Itoa(count))
	form.Set("metadata[installment_interval]", interval)
	form.Set("line_items[0][price]", priceID)
	form.Set("line_items[0][quantity]", "1")
	form.Set("allow_promotion_codes", "true")
	if customerID != "" {
		form.Set("customer", customerID)
	} else if in.Email != "" {
		form.Set("customer_email", in.Email)
	}

	if count == 1 {
		form.Set("mode", "payment")
		form.Set("payment_intent_data[metadata][company_id]", in.CompanyID.String())
		form.Set("payment_intent_data[metadata][kind]", "sales_quote")
		form.Set("payment_intent_data[metadata][quote_id]", in.QuoteID.String())
		form.Set("payment_intent_data[metadata][plan_id]", strconv.FormatInt(in.PlanID, 10))
	} else {
		form.Set("mode", "subscription")
		form.Set("subscription_data[metadata][company_id]", in.CompanyID.String())
		form.Set("subscription_data[metadata][kind]", "sales_quote")
		form.Set("subscription_data[metadata][quote_id]", in.QuoteID.String())
		form.Set("subscription_data[metadata][plan_id]", strconv.FormatInt(in.PlanID, 10))
		form.Set("subscription_data[metadata][plan]", strings.ToLower(strings.TrimSpace(in.PlanName)))
		cancelAt, err := salesQuoteCancelAt(time.Now().UTC(), count, interval)
		if err != nil {
			return SalesQuoteCheckoutResult{}, err
		}
		form.Set("subscription_data[cancel_at]", strconv.FormatInt(cancelAt.Unix(), 10))
	}

	var sess struct {
		ID  string `json:"id"`
		URL string `json:"url"`
	}
	if err := s.stripeForm(ctx, http.MethodPost, "https://api.stripe.com/v1/checkout/sessions", form, &sess); err != nil {
		return SalesQuoteCheckoutResult{}, err
	}
	if sess.URL == "" {
		return SalesQuoteCheckoutResult{}, errors.New("stripe checkout session missing url")
	}
	return SalesQuoteCheckoutResult{
		URL:       sess.URL,
		Mock:      false,
		ProductID: productID,
		PriceID:   priceID,
		SessionID: sess.ID,
	}, nil
}

func (s *StripeService) ensureSalesQuoteProduct(ctx context.Context, in SalesQuoteCheckoutInput) (string, error) {
	metaKey := in.QuoteID.String()
	q := url.QueryEscape(fmt.Sprintf("active:'true' AND metadata['descrybe_sales_quote']:'%s'", metaKey))
	var search struct {
		Data []struct {
			ID string `json:"id"`
		} `json:"data"`
	}
	if err := s.stripeGET(ctx, "https://api.stripe.com/v1/products/search?query="+q+"&limit=1", &search); err != nil {
		return "", err
	}
	if len(search.Data) > 0 && strings.TrimSpace(search.Data[0].ID) != "" {
		return search.Data[0].ID, nil
	}

	form := url.Values{}
	name := strings.TrimSpace(in.PlanName)
	if name == "" {
		name = "Custom Descrybe plan"
	}
	form.Set("name", "Descrybe — "+name)
	form.Set("description", fmt.Sprintf("Sales quote %s (%d installments)", in.QuoteID.String(), in.InstallmentCount))
	form.Set("metadata[descrybe_sales_quote]", metaKey)
	form.Set("metadata[company_id]", in.CompanyID.String())
	form.Set("metadata[plan_id]", strconv.FormatInt(in.PlanID, 10))
	var product struct {
		ID string `json:"id"`
	}
	if err := s.stripeForm(ctx, http.MethodPost, "https://api.stripe.com/v1/products", form, &product); err != nil {
		return "", err
	}
	if strings.TrimSpace(product.ID) == "" {
		return "", fmt.Errorf("stripe product missing id")
	}
	return product.ID, nil
}

func (s *StripeService) createSalesQuotePrice(ctx context.Context, productID string, in SalesQuoteCheckoutInput, oneTime bool) (string, error) {
	form := url.Values{}
	form.Set("product", productID)
	form.Set("currency", strings.ToLower(strings.TrimSpace(in.Currency)))
	if form.Get("currency") == "" {
		form.Set("currency", "usd")
	}
	form.Set("unit_amount", strconv.Itoa(in.InstallmentAmountCents))
	form.Set("metadata[descrybe_sales_quote]", in.QuoteID.String())
	form.Set("metadata[plan_id]", strconv.FormatInt(in.PlanID, 10))
	if oneTime {
		// default type one_time
	} else {
		stripeInterval, intervalCount, err := stripeRecurringFromInstallment(in.InstallmentInterval)
		if err != nil {
			return "", err
		}
		form.Set("recurring[interval]", stripeInterval)
		if intervalCount > 1 {
			form.Set("recurring[interval_count]", strconv.Itoa(intervalCount))
		}
	}
	var price struct {
		ID string `json:"id"`
	}
	if err := s.stripeForm(ctx, http.MethodPost, "https://api.stripe.com/v1/prices", form, &price); err != nil {
		return "", err
	}
	if strings.TrimSpace(price.ID) == "" {
		return "", fmt.Errorf("stripe price missing id")
	}
	return price.ID, nil
}

func stripeRecurringFromInstallment(interval string) (stripeInterval string, intervalCount int, err error) {
	switch strings.ToLower(strings.TrimSpace(interval)) {
	case "month", "":
		return "month", 1, nil
	case "quarter":
		return "month", 3, nil
	case "year":
		return "year", 1, nil
	default:
		return "", 0, fmt.Errorf("%w: installment interval %q", ErrStripePlanUnsupported, interval)
	}
}

func salesQuoteCancelAt(now time.Time, count int, interval string) (time.Time, error) {
	if count < 1 {
		return time.Time{}, fmt.Errorf("%w: installment count", ErrStripePlanUnsupported)
	}
	switch strings.ToLower(strings.TrimSpace(interval)) {
	case "month", "":
		return now.AddDate(0, count, 0), nil
	case "quarter":
		return now.AddDate(0, count*3, 0), nil
	case "year":
		return now.AddDate(count, 0, 0), nil
	default:
		return time.Time{}, fmt.Errorf("%w: installment interval %q", ErrStripePlanUnsupported, interval)
	}
}

func (s *StripeService) applySalesQuotePurchase(ctx context.Context, companyID uuid.UUID, planID int64, quoteID uuid.UUID, customerID, subscriptionID, priceID string) error {
	if s.Billing == nil {
		return errors.New("billing service not configured")
	}
	if planID <= 0 {
		return fmt.Errorf("%w: plan_id", ErrStripePlanUnsupported)
	}
	if err := s.Billing.AssignPlan(ctx, companyID, planID, false, 0); err != nil {
		return err
	}
	if customerID != "" {
		_, _ = s.Pool.Exec(ctx, `
			UPDATE companies SET stripe_customer_id = $2, updated_at = now() WHERE id = $1`,
			companyID, customerID)
	}
	_, _ = s.Pool.Exec(ctx, `
		UPDATE company_plans
		SET stripe_subscription_id = NULLIF($2, ''), stripe_price_id = NULLIF($3, ''), updated_at = now()
		WHERE company_id = $1 AND is_active = true`,
		companyID, subscriptionID, priceID)
	_ = s.setSubscriptionStatusNote(ctx, companyID, "active")

	if quoteID != uuid.Nil {
		_, err := s.Pool.Exec(ctx, `
			UPDATE sales_quotes
			SET status = 'paid', paid_at = COALESCE(paid_at, now()), updated_at = now()
			WHERE id = $1 AND status <> 'canceled'`, quoteID)
		if err != nil {
			return err
		}
		_, _ = s.Pool.Exec(ctx, `
			UPDATE sales_leads
			SET status = 'won', updated_at = now()
			WHERE id = (SELECT lead_id FROM sales_quotes WHERE id = $1)
			  AND status <> 'closed'`, quoteID)
	}
	return nil
}