package billing

import (
	"context"
	"crypto/hmac"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"log/slog"
	"net/http"
	"net/url"
	"strconv"
	"strings"
	"time"

	"github.com/descrybe/descrybe-v2/apps/api/internal/config"
	"github.com/google/uuid"
	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"
)

// StripeConfig holds Stripe settings (env bootstrap + optional platform_settings).
// Empty SecretKey enables mock mode for local/dev; checkout still fails closed
// unless ForceMock (STRIPE_MOCK / stripe.mock) is set. Live keys may live in
// admin platform settings; production only forbids STRIPE_MOCK=true at boot.
type StripeConfig struct {
	SecretKey     string
	WebhookSecret string
	WebOrigin     string
	PublicAPIURL  string
	// Price IDs keyed as "starter:monthly", "growth:yearly", …
	PriceIDs map[string]string
	// ForceMock runs mock even when SecretKey is set (local QA).
	ForceMock bool
	HTTP      *http.Client
}

func (c StripeConfig) MockMode() bool {
	if c.ForceMock {
		return true
	}
	return strings.TrimSpace(c.SecretKey) == ""
}

// AllowMockPurchase is true only when STRIPE_MOCK / ForceMock is explicit.
// An empty SecretKey alone must NOT grant paid plans (misconfigured staging).
func (c StripeConfig) AllowMockPurchase() bool {
	return c.ForceMock
}

func (c StripeConfig) client() *http.Client {
	if c.HTTP != nil {
		return c.HTTP
	}
	return &http.Client{Timeout: 30 * time.Second}
}

// StripeService creates Checkout / Portal sessions and applies webhook events.
type StripeService struct {
	Pool    *pgxpool.Pool
	Billing *Service
	Cfg     StripeConfig
	// ResolveCfg optionally merges admin platform_settings over Cfg per request.
	ResolveCfg func(ctx context.Context, base StripeConfig) (StripeConfig, error)
}

func (s *StripeService) effectiveCfg(ctx context.Context) (StripeConfig, error) {
	if s == nil {
		return StripeConfig{}, ErrStripeNotConfigured
	}
	if s.ResolveCfg == nil {
		return s.Cfg, nil
	}
	return s.ResolveCfg(ctx, s.Cfg)
}

type stripeCfgCtxKey struct{}

// bindCfg resolves platform settings into ctx so concurrent requests stay isolated.
func (s *StripeService) bindCfg(ctx context.Context) (context.Context, StripeConfig, error) {
	if ctx == nil {
		ctx = context.Background()
	}
	cfg, err := s.effectiveCfg(ctx)
	if err != nil {
		return ctx, s.Cfg, err
	}
	return context.WithValue(ctx, stripeCfgCtxKey{}, cfg), cfg, nil
}

func (s *StripeService) cfg(ctx context.Context) StripeConfig {
	if v, ok := ctx.Value(stripeCfgCtxKey{}).(StripeConfig); ok {
		return v
	}
	return s.Cfg
}

var (
	ErrStripeNotConfigured   = errors.New("stripe not configured")
	ErrStripePlanUnsupported = errors.New("plan is not available for self-serve checkout")
	ErrStripePriceMissing    = errors.New("stripe price id not configured for plan/term")
	ErrStripeBadSignature    = errors.New("invalid stripe signature")
)

// CheckoutRequest is the body for POST /api/billing/checkout.
// Set Pack for a one-time AI credit top-up, or Plan (+ Term) for a subscription.
type CheckoutRequest struct {
	Plan string `json:"plan"` // starter | plus | growth | business | scale
	Term string `json:"term"` // monthly | yearly
	Pack string `json:"pack"` // small | medium | large | xl (one-time credits)
}

// CheckoutResult is returned to the UI (redirect to URL).
type CheckoutResult struct {
	URL     string `json:"url"`
	Mock    bool   `json:"mock"`
	Applied bool   `json:"applied,omitempty"`
	Message string `json:"message,omitempty"`
}

// PortalResult is returned for Customer Portal.
type PortalResult struct {
	URL  string `json:"url"`
	Mock bool   `json:"mock"`
}

// StatusResult reports whether live Stripe or mock mode is active.
type StatusResult struct {
	Configured         bool   `json:"configured"`
	Mock               bool   `json:"mock"`
	HasCustomer        bool   `json:"has_customer"`
	HasSubscription    bool   `json:"has_subscription"`
	CustomerID         string `json:"customer_id,omitempty"`
	SubscriptionID     string `json:"subscription_id,omitempty"`
	SubscriptionStatus string `json:"subscription_status,omitempty"`
}

func normalizePlanTerm(plan, term string) (string, string, error) {
	plan = strings.ToLower(strings.TrimSpace(plan))
	term = strings.ToLower(strings.TrimSpace(term))
	if term == "" {
		term = "monthly"
	}
	switch plan {
	case "starter", "plus", "growth", "business", "scale":
	default:
		return "", "", ErrStripePlanUnsupported
	}
	if term != "monthly" && term != "yearly" {
		return "", "", fmt.Errorf("%w: term must be monthly or yearly", ErrStripePlanUnsupported)
	}
	return plan, term, nil
}

func priceKey(plan, term string) string {
	return plan + ":" + term
}

// Status returns Stripe linkage for the company.
func (s *StripeService) Status(ctx context.Context, companyID uuid.UUID) (StatusResult, error) {
	ctx, cfg, err := s.bindCfg(ctx)
	if err != nil {
		return StatusResult{}, err
	}
	out := StatusResult{
		Configured: !cfg.MockMode(),
		Mock:       cfg.MockMode(),
	}
	var customerID *string
	err = s.Pool.QueryRow(ctx, `
		SELECT stripe_customer_id FROM companies WHERE id = $1`, companyID).Scan(&customerID)
	if err != nil && !errors.Is(err, pgx.ErrNoRows) {
		return out, err
	}
	if customerID != nil && strings.TrimSpace(*customerID) != "" {
		out.HasCustomer = true
		out.CustomerID = strings.TrimSpace(*customerID)
	}
	var subID *string
	var planNotes *string
	_ = s.Pool.QueryRow(ctx, `
		SELECT stripe_subscription_id, notes FROM company_plans
		WHERE company_id = $1 AND is_active = true
		ORDER BY created_at DESC LIMIT 1`, companyID).Scan(&subID, &planNotes)
	if subID != nil && strings.TrimSpace(*subID) != "" {
		out.HasSubscription = true
		out.SubscriptionID = strings.TrimSpace(*subID)
	}
	out.SubscriptionStatus = ParseStripeStatusNote(planNotes)
	if out.SubscriptionStatus == "" && out.HasSubscription && !cfg.MockMode() {
		if status, statusErr := s.fetchSubscriptionStatus(ctx, out.SubscriptionID); statusErr == nil {
			out.SubscriptionStatus = status
			_ = s.setSubscriptionStatusNote(ctx, companyID, status)
		} else {
			slog.Warn("stripe_subscription_status_fetch_failed", "company_id", companyID, "subscription_id", out.SubscriptionID, "err", statusErr)
		}
	}
	return out, nil
}

// fetchSubscriptionStatus reads the live Stripe subscription status (best-effort).
func (s *StripeService) fetchSubscriptionStatus(ctx context.Context, subscriptionID string) (string, error) {
	subscriptionID = strings.TrimSpace(subscriptionID)
	if subscriptionID == "" {
		return "", errors.New("empty subscription id")
	}
	var sub struct {
		Status string `json:"status"`
	}
	endpoint := "https://api.stripe.com/v1/subscriptions/" + url.PathEscape(subscriptionID)
	if err := s.stripeGET(ctx, endpoint, &sub); err != nil {
		return "", err
	}
	return NormalizeSubscriptionStatus(sub.Status), nil
}

// NormalizeSubscriptionStatus lowercases and trims a Stripe subscription status.
func NormalizeSubscriptionStatus(status string) string {
	return strings.ToLower(strings.TrimSpace(status))
}

// IsPastDueSubscriptionStatus is true for past_due (grace — do not hard-lock day 1).
func IsPastDueSubscriptionStatus(status string) bool {
	return NormalizeSubscriptionStatus(status) == "past_due"
}

const stripeStatusNotePrefix = "stripe_status:"

// FormatStripeStatusNote stores subscription status in company_plans.notes (managed prefix only).
func FormatStripeStatusNote(status string) string {
	return stripeStatusNotePrefix + NormalizeSubscriptionStatus(status)
}

// ParseStripeStatusNote reads a managed stripe_status note; other notes are ignored.
func ParseStripeStatusNote(notes *string) string {
	if notes == nil {
		return ""
	}
	s := strings.TrimSpace(*notes)
	if !strings.HasPrefix(s, stripeStatusNotePrefix) {
		return ""
	}
	return NormalizeSubscriptionStatus(strings.TrimPrefix(s, stripeStatusNotePrefix))
}

// checkoutReturnURL builds the billing return page with plan/pack/term context.
// When withCheckoutSessionID is true, appends Stripe's unescaped {CHECKOUT_SESSION_ID} template.
func checkoutReturnURL(web, status, plan, term, pack string, withCheckoutSessionID bool) string {
	q := url.Values{}
	q.Set("checkout", status)
	if plan != "" {
		q.Set("plan", plan)
	}
	if term != "" {
		q.Set("term", term)
	}
	if pack != "" {
		q.Set("pack", pack)
	}
	out := strings.TrimRight(web, "/") + "/billing?" + q.Encode()
	if withCheckoutSessionID {
		out += "&session_id={CHECKOUT_SESSION_ID}"
	}
	return out
}

// CreateCheckoutSession starts Stripe Checkout for a plan subscription or credit pack.
func (s *StripeService) CreateCheckoutSession(ctx context.Context, companyID uuid.UUID, email, companyName string, req CheckoutRequest) (CheckoutResult, error) {
	if strings.TrimSpace(req.Pack) != "" {
		return s.CreateCreditPackCheckout(ctx, companyID, email, companyName, req.Pack)
	}
	ctx, cfg, err := s.bindCfg(ctx)
	if err != nil {
		return CheckoutResult{}, err
	}
	plan, term, err := normalizePlanTerm(req.Plan, req.Term)
	if err != nil {
		return CheckoutResult{}, err
	}
	web := strings.TrimRight(cfg.WebOrigin, "/")
	if web == "" {
		web = "http://localhost:5174"
	}

	if cfg.AllowMockPurchase() {
		if s.Billing == nil {
			return CheckoutResult{}, errors.New("billing service not configured")
		}
		if err := s.applyPlanPurchase(ctx, companyID, plan, "cus_mock_"+companyID.String()[:8], "sub_mock_"+uuid.NewString()[:8], "price_mock_"+plan+"_"+term); err != nil {
			return CheckoutResult{}, err
		}
		return CheckoutResult{
			URL:     checkoutReturnURL(web, "success", plan, term, "", false) + "&mock=1",
			Mock:    true,
			Applied: true,
			Message: "Mock mode: plan assigned and credits granted without Stripe.",
		}, nil
	}
	if cfg.MockMode() {
		return CheckoutResult{}, ErrStripeNotConfigured
	}

	priceID := strings.TrimSpace(cfg.PriceIDs[priceKey(plan, term)])
	if priceID == "" {
		return CheckoutResult{}, fmt.Errorf("%w: %s %s", ErrStripePriceMissing, plan, term)
	}

	customerID, err := s.ensureCustomer(ctx, companyID, email, companyName)
	if err != nil {
		return CheckoutResult{}, err
	}

	form := url.Values{}
	form.Set("mode", "subscription")
	form.Set("success_url", checkoutReturnURL(web, "success", plan, term, "", true))
	form.Set("cancel_url", checkoutReturnURL(web, "cancel", plan, term, "", false))
	form.Set("client_reference_id", companyID.String())
	form.Set("metadata[company_id]", companyID.String())
	form.Set("metadata[kind]", "plan")
	form.Set("metadata[plan]", plan)
	form.Set("metadata[term]", term)
	form.Set("subscription_data[metadata][company_id]", companyID.String())
	form.Set("subscription_data[metadata][plan]", plan)
	form.Set("subscription_data[metadata][term]", term)
	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 email != "" {
		form.Set("customer_email", email)
	}

	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 CheckoutResult{}, err
	}
	if sess.URL == "" {
		return CheckoutResult{}, errors.New("stripe checkout session missing url")
	}
	return CheckoutResult{URL: sess.URL, Mock: false}, nil
}

// CreateCreditPackCheckout starts a one-time Stripe Checkout (or mock-grants credits).
func (s *StripeService) CreateCreditPackCheckout(ctx context.Context, companyID uuid.UUID, email, companyName, packID string) (CheckoutResult, error) {
	pack, ok := CreditPackByID(packID)
	if !ok {
		return CheckoutResult{}, fmt.Errorf("%w: unknown credit pack", ErrStripePlanUnsupported)
	}
	ctx, cfg, err := s.bindCfg(ctx)
	if err != nil {
		return CheckoutResult{}, err
	}
	web := strings.TrimRight(cfg.WebOrigin, "/")
	if web == "" {
		web = "http://localhost:5174"
	}

	if cfg.AllowMockPurchase() {
		if s.Billing == nil {
			return CheckoutResult{}, errors.New("billing service not configured")
		}
		if err := s.Billing.AddCredits(ctx, companyID, pack.Credits); err != nil {
			return CheckoutResult{}, err
		}
		return CheckoutResult{
			URL: checkoutReturnURL(web, "success", "", "", pack.ID, false) +
				"&mock=1&credits=" + strconv.Itoa(pack.Credits),
			Mock:    true,
			Applied: true,
			Message: fmt.Sprintf("Mock mode: added %d AI credits without Stripe.", pack.Credits),
		}, nil
	}
	if cfg.MockMode() {
		return CheckoutResult{}, ErrStripeNotConfigured
	}

	priceID := strings.TrimSpace(cfg.PriceIDs[CreditPackPriceKey(pack.ID)])
	if priceID == "" {
		return CheckoutResult{}, fmt.Errorf("%w: credit pack %s", ErrStripePriceMissing, pack.ID)
	}

	customerID, err := s.ensureCustomer(ctx, companyID, email, companyName)
	if err != nil {
		return CheckoutResult{}, err
	}

	form := url.Values{}
	form.Set("mode", "payment")
	form.Set("success_url", checkoutReturnURL(web, "success", "", "", pack.ID, true))
	form.Set("cancel_url", checkoutReturnURL(web, "cancel", "", "", pack.ID, false))
	form.Set("client_reference_id", companyID.String())
	form.Set("metadata[company_id]", companyID.String())
	form.Set("metadata[kind]", "credit_pack")
	form.Set("metadata[pack]", pack.ID)
	form.Set("metadata[credits]", strconv.Itoa(pack.Credits))
	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 email != "" {
		form.Set("customer_email", email)
	}

	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 CheckoutResult{}, err
	}
	if sess.URL == "" {
		return CheckoutResult{}, errors.New("stripe checkout session missing url")
	}
	return CheckoutResult{URL: sess.URL, Mock: false}, nil
}

// CreatePortalSession opens the Stripe Customer Portal (or a mock billing deep-link).
func (s *StripeService) CreatePortalSession(ctx context.Context, companyID uuid.UUID) (PortalResult, error) {
	ctx, cfg, err := s.bindCfg(ctx)
	if err != nil {
		return PortalResult{}, err
	}
	web := strings.TrimRight(cfg.WebOrigin, "/")
	if web == "" {
		web = "http://localhost:5174"
	}
	if cfg.AllowMockPurchase() || cfg.MockMode() {
		// Portal deep-link only; does not mutate billing.
		return PortalResult{URL: web + "/billing?portal=mock", Mock: true}, nil
	}
	var customerID *string
	err = s.Pool.QueryRow(ctx, `
		SELECT stripe_customer_id FROM companies WHERE id = $1`, companyID).Scan(&customerID)
	if errors.Is(err, pgx.ErrNoRows) || customerID == nil || strings.TrimSpace(*customerID) == "" {
		return PortalResult{}, ErrStripeNoCustomer
	}
	if err != nil {
		return PortalResult{}, err
	}
	form := url.Values{}
	form.Set("customer", strings.TrimSpace(*customerID))
	form.Set("return_url", web+"/billing")
	var sess struct {
		URL string `json:"url"`
	}
	if err := s.stripeForm(ctx, http.MethodPost, "https://api.stripe.com/v1/billing_portal/sessions", form, &sess); err != nil {
		return PortalResult{}, err
	}
	if sess.URL == "" {
		return PortalResult{}, errors.New("stripe portal session missing url")
	}
	return PortalResult{URL: sess.URL, Mock: false}, nil
}

func (s *StripeService) ensureCustomer(ctx context.Context, companyID uuid.UUID, email, name string) (string, error) {
	var existing *string
	err := s.Pool.QueryRow(ctx, `
		SELECT stripe_customer_id FROM companies WHERE id = $1`, companyID).Scan(&existing)
	if err != nil && !errors.Is(err, pgx.ErrNoRows) {
		return "", err
	}
	if existing != nil && strings.TrimSpace(*existing) != "" {
		return strings.TrimSpace(*existing), nil
	}
	form := url.Values{}
	form.Set("metadata[company_id]", companyID.String())
	if email != "" {
		form.Set("email", email)
	}
	if name != "" {
		form.Set("name", name)
	}
	var cust struct {
		ID string `json:"id"`
	}
	if err := s.stripeForm(ctx, http.MethodPost, "https://api.stripe.com/v1/customers", form, &cust); err != nil {
		return "", err
	}
	if cust.ID == "" {
		return "", errors.New("stripe customer create returned empty id")
	}
	_, err = s.Pool.Exec(ctx, `
		UPDATE companies SET stripe_customer_id = $2, updated_at = now() WHERE id = $1`,
		companyID, cust.ID)
	return cust.ID, err
}

func (s *StripeService) stripeForm(ctx context.Context, method, endpoint string, form url.Values, dest any) error {
	cfg := s.cfg(ctx)
	req, err := http.NewRequestWithContext(ctx, method, endpoint, strings.NewReader(form.Encode()))
	if err != nil {
		return err
	}
	req.Header.Set("Authorization", "Bearer "+strings.TrimSpace(cfg.SecretKey))
	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
	return s.doStripeJSON(req, dest)
}

func (s *StripeService) stripeGET(ctx context.Context, endpoint string, dest any) error {
	cfg := s.cfg(ctx)
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
	if err != nil {
		return err
	}
	req.Header.Set("Authorization", "Bearer "+strings.TrimSpace(cfg.SecretKey))
	return s.doStripeJSON(req, dest)
}

func (s *StripeService) doStripeJSON(req *http.Request, dest any) error {
	resp, err := s.cfg(req.Context()).client().Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	body, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
	if err != nil {
		return err
	}
	if resp.StatusCode >= 300 {
		return fmt.Errorf("stripe api %s: %s", resp.Status, truncate(string(body), 400))
	}
	if dest == nil {
		return nil
	}
	return json.Unmarshal(body, dest)
}

func truncate(s string, n int) string {
	if len(s) <= n {
		return s
	}
	return s[:n] + "…"
}

// HandleWebhook verifies Stripe-Signature when WebhookSecret is set; unsigned only if ForceMock.
func (s *StripeService) HandleWebhook(ctx context.Context, payload []byte, sigHeader string) error {
	ctx, cfg, err := s.bindCfg(ctx)
	if err != nil {
		return err
	}
	secret := strings.TrimSpace(cfg.WebhookSecret)
	// Always verify when a webhook secret is configured — even if STRIPE_MOCK=true.
	// Production never accepts unsigned events (ForceMock is also rejected at boot).
	if secret != "" {
		if err := verifyStripeSignature(payload, sigHeader, secret, 5*time.Minute); err != nil {
			return err
		}
	} else if !cfg.ForceMock || config.IsProductionEnv() {
		// Unsigned events only for explicit local mock (STRIPE_MOCK=true, no webhook secret).
		return ErrStripeNotConfigured
	}

	var event stripeEvent
	if err := json.Unmarshal(payload, &event); err != nil {
		return err
	}
	if event.ID == "" {
		return errors.New("stripe event missing id")
	}

	claimed, err := s.claimWebhookEvent(ctx, event.ID, event.Type, nil)
	if err != nil {
		return err
	}
	if !claimed {
		return nil // idempotent no-op
	}

	companyID, applyErr := s.dispatchEvent(ctx, event)
	if applyErr != nil {
		// Release claim so Stripe can retry after a transient apply failure.
		_, _ = s.Pool.Exec(ctx, `DELETE FROM stripe_webhook_events WHERE event_id = $1`, event.ID)
		return applyErr
	}
	if companyID != nil {
		_, _ = s.Pool.Exec(ctx, `
			UPDATE stripe_webhook_events SET company_id = $2 WHERE event_id = $1`, event.ID, *companyID)
	}
	return nil
}

func (s *StripeService) claimWebhookEvent(ctx context.Context, eventID, eventType string, companyID *uuid.UUID) (bool, error) {
	if s.Pool == nil {
		return false, errors.New("stripe store not configured")
	}
	ct, err := s.Pool.Exec(ctx, `
		INSERT INTO stripe_webhook_events (event_id, event_type, company_id)
		VALUES ($1, $2, $3)
		ON CONFLICT (event_id) DO NOTHING`, eventID, eventType, companyID)
	if err != nil {
		return false, err
	}
	return ct.RowsAffected() > 0, nil
}

type stripeEvent struct {
	ID   string          `json:"id"`
	Type string          `json:"type"`
	Data json.RawMessage `json:"data"`
}

type stripeEventData struct {
	Object json.RawMessage `json:"object"`
}

func (s *StripeService) dispatchEvent(ctx context.Context, event stripeEvent) (*uuid.UUID, error) {
	var data stripeEventData
	if len(event.Data) > 0 {
		_ = json.Unmarshal(event.Data, &data)
	}
	switch event.Type {
	case "checkout.session.completed":
		return s.onCheckoutCompleted(ctx, data.Object)
	case "customer.subscription.updated", "customer.subscription.created":
		return s.onSubscriptionUpsert(ctx, data.Object)
	case "customer.subscription.deleted":
		return s.onSubscriptionDeleted(ctx, data.Object)
	default:
		return nil, nil
	}
}

type checkoutSessionObj struct {
	ID                string            `json:"id"`
	Customer          string            `json:"customer"`
	Subscription      string            `json:"subscription"`
	ClientReferenceID string            `json:"client_reference_id"`
	Metadata          map[string]string `json:"metadata"`
}

func (s *StripeService) onCheckoutCompleted(ctx context.Context, raw json.RawMessage) (*uuid.UUID, error) {
	var sess checkoutSessionObj
	if err := json.Unmarshal(raw, &sess); err != nil {
		return nil, err
	}
	companyID, err := parseCompanyID(sess.ClientReferenceID, sess.Metadata)
	if err != nil {
		return nil, err
	}
	kind := strings.ToLower(strings.TrimSpace(sess.Metadata["kind"]))
	if kind == "credit_pack" || strings.TrimSpace(sess.Metadata["pack"]) != "" {
		if err := s.applyCreditPackPurchase(ctx, companyID, sess.Metadata); err != nil {
			return &companyID, err
		}
		return &companyID, nil
	}
	if kind == "sales_quote" {
		planID, _ := strconv.ParseInt(strings.TrimSpace(sess.Metadata["plan_id"]), 10, 64)
		quoteID, _ := uuid.Parse(strings.TrimSpace(sess.Metadata["quote_id"]))
		priceID := ""
		if err := s.applySalesQuotePurchase(ctx, companyID, planID, quoteID, sess.Customer, sess.Subscription, priceID); err != nil {
			return &companyID, err
		}
		return &companyID, nil
	}
	plan := strings.ToLower(strings.TrimSpace(sess.Metadata["plan"]))
	term := strings.ToLower(strings.TrimSpace(sess.Metadata["term"]))
	if plan == "" {
		plan = "starter"
	}
	if term == "" {
		term = "monthly"
	}
	priceID := strings.TrimSpace(s.cfg(ctx).PriceIDs[priceKey(plan, term)])
	if err := s.applyPlanPurchase(ctx, companyID, plan, sess.Customer, sess.Subscription, priceID); err != nil {
		return &companyID, err
	}
	return &companyID, nil
}

// applyCreditPackPurchase grants one-time AI credits from Checkout metadata (mode=payment).
func (s *StripeService) applyCreditPackPurchase(ctx context.Context, companyID uuid.UUID, meta map[string]string) error {
	if s.Billing == nil {
		return errors.New("billing service not configured")
	}
	credits, err := creditsFromPackMetadata(meta)
	if err != nil {
		return err
	}
	return s.Billing.AddCredits(ctx, companyID, credits)
}

// creditsFromPackMetadata resolves one-time credit grants from Checkout metadata.
// Known catalog packs always win over metadata credits (anti-tamper), including
// garbage/non-numeric credits fields when pack id is valid.
func creditsFromPackMetadata(meta map[string]string) (int, error) {
	packID := ""
	if meta != nil {
		packID = strings.ToLower(strings.TrimSpace(meta["pack"]))
	}
	if pack, ok := CreditPackByID(packID); ok {
		return pack.Credits, nil
	}
	credits := 0
	if meta != nil {
		if raw := strings.TrimSpace(meta["credits"]); raw != "" {
			n, err := strconv.Atoi(raw)
			if err != nil || n <= 0 {
				return 0, fmt.Errorf("invalid credit pack credits metadata: %q", raw)
			}
			credits = n
		}
	}
	if credits <= 0 {
		return 0, fmt.Errorf("%w: credit pack %q", ErrStripePlanUnsupported, packID)
	}
	return credits, nil
}

type subscriptionObj struct {
	ID       string            `json:"id"`
	Customer string            `json:"customer"`
	Status   string            `json:"status"`
	Metadata map[string]string `json:"metadata"`
	Items    struct {
		Data []struct {
			Price struct {
				ID string `json:"id"`
			} `json:"price"`
		} `json:"data"`
	} `json:"items"`
}

func (s *StripeService) onSubscriptionUpsert(ctx context.Context, raw json.RawMessage) (*uuid.UUID, error) {
	var sub subscriptionObj
	if err := json.Unmarshal(raw, &sub); err != nil {
		return nil, err
	}
	companyID, err := s.resolveCompanyForSubscription(ctx, sub)
	if err != nil {
		return nil, err
	}
	status := strings.ToLower(sub.Status)
	kind := strings.ToLower(strings.TrimSpace(sub.Metadata["kind"]))
	if status == "canceled" || status == "unpaid" || status == "incomplete_expired" {
		// Sales-quote installments end via cancel_at after the paid term — keep the custom plan.
		if kind == "sales_quote" {
			_ = s.setSubscriptionStatusNote(ctx, companyID, status)
			return &companyID, nil
		}
		if err := s.downgradeToFree(ctx, companyID); err != nil {
			return &companyID, err
		}
		return &companyID, nil
	}
	if kind == "sales_quote" {
		planID, _ := strconv.ParseInt(strings.TrimSpace(sub.Metadata["plan_id"]), 10, 64)
		quoteID, _ := uuid.Parse(strings.TrimSpace(sub.Metadata["quote_id"]))
		priceID := ""
		if len(sub.Items.Data) > 0 {
			priceID = sub.Items.Data[0].Price.ID
		}
		if planID > 0 {
			if err := s.applySalesQuotePurchase(ctx, companyID, planID, quoteID, sub.Customer, sub.ID, priceID); err != nil {
				return &companyID, err
			}
		}
		_ = s.setSubscriptionStatusNote(ctx, companyID, status)
		return &companyID, nil
	}
	plan := strings.ToLower(strings.TrimSpace(sub.Metadata["plan"]))
	priceID := ""
	if len(sub.Items.Data) > 0 {
		priceID = sub.Items.Data[0].Price.ID
	}
	if plan == "" {
		plan = s.planFromPriceIDCtx(ctx, priceID)
	}
	if plan == "" {
		_ = s.setSubscriptionStatusNote(ctx, companyID, status)
		return &companyID, nil
	}
	if err := s.applyPlanPurchase(ctx, companyID, plan, sub.Customer, sub.ID, priceID); err != nil {
		return &companyID, err
	}
	_ = s.setSubscriptionStatusNote(ctx, companyID, status)
	return &companyID, nil
}

func (s *StripeService) onSubscriptionDeleted(ctx context.Context, raw json.RawMessage) (*uuid.UUID, error) {
	var sub subscriptionObj
	if err := json.Unmarshal(raw, &sub); err != nil {
		return nil, err
	}
	companyID, err := s.resolveCompanyForSubscription(ctx, sub)
	if err != nil {
		return nil, err
	}
	// Installment schedule complete: retain assigned custom plan (paid term).
	if strings.EqualFold(strings.TrimSpace(sub.Metadata["kind"]), "sales_quote") {
		_ = s.setSubscriptionStatusNote(ctx, companyID, "canceled")
		return &companyID, nil
	}
	if err := s.downgradeToFree(ctx, companyID); err != nil {
		return &companyID, err
	}
	return &companyID, nil
}

func (s *StripeService) resolveCompanyForSubscription(ctx context.Context, sub subscriptionObj) (uuid.UUID, error) {
	if id, err := parseCompanyID("", sub.Metadata); err == nil {
		return id, nil
	}
	if sub.Customer != "" {
		var id uuid.UUID
		err := s.Pool.QueryRow(ctx, `
			SELECT id FROM companies WHERE stripe_customer_id = $1`, sub.Customer).Scan(&id)
		if err == nil {
			return id, nil
		}
	}
	if sub.ID != "" {
		var id uuid.UUID
		err := s.Pool.QueryRow(ctx, `
			SELECT company_id FROM company_plans
			WHERE stripe_subscription_id = $1
			ORDER BY created_at DESC LIMIT 1`, sub.ID).Scan(&id)
		if err == nil {
			return id, nil
		}
	}
	return uuid.Nil, errors.New("could not resolve company for stripe subscription")
}

func parseCompanyID(clientRef string, meta map[string]string) (uuid.UUID, error) {
	if clientRef != "" {
		if id, err := uuid.Parse(clientRef); err == nil {
			return id, nil
		}
	}
	if meta != nil {
		if v := strings.TrimSpace(meta["company_id"]); v != "" {
			return uuid.Parse(v)
		}
	}
	return uuid.Nil, errors.New("company_id missing from stripe session")
}

func planNameFromPriceKey(key string) string {
	key = strings.ToLower(strings.TrimSpace(key))
	if key == "" || strings.HasPrefix(key, "pack:") {
		return ""
	}
	parts := strings.SplitN(key, ":", 2)
	if len(parts) == 0 {
		return ""
	}
	switch parts[0] {
	case "starter", "plus", "growth", "business", "scale":
		return parts[0]
	default:
		return ""
	}
}

func (s *StripeService) planFromPriceID(priceID string) string {
	priceID = strings.TrimSpace(priceID)
	if priceID == "" {
		return ""
	}
	for key, id := range s.Cfg.PriceIDs {
		if id == priceID {
			return planNameFromPriceKey(key)
		}
	}
	return ""
}

// planFromPriceIDCtx prefers request-bound PriceIDs from platform settings.
func (s *StripeService) planFromPriceIDCtx(ctx context.Context, priceID string) string {
	priceID = strings.TrimSpace(priceID)
	if priceID == "" {
		return ""
	}
	for key, id := range s.cfg(ctx).PriceIDs {
		if id == priceID {
			return planNameFromPriceKey(key)
		}
	}
	return s.planFromPriceID(priceID)
}

func (s *StripeService) applyPlanPurchase(ctx context.Context, companyID uuid.UUID, planName, customerID, subscriptionID, priceID string) error {
	if s.Billing == nil || s.Pool == nil {
		return errors.New("billing service not configured")
	}
	planName = strings.ToLower(strings.TrimSpace(planName))
	if !IsPublicProductPlan(planName) || IsFreePlanName(planName) || strings.EqualFold(planName, "enterprise") {
		return ErrStripePlanUnsupported
	}
	_ = s.Billing.EnsureDefaultPlans(ctx)
	var planID int64
	err := s.Pool.QueryRow(ctx, `
		SELECT id FROM plans WHERE lower(name) = lower($1) ORDER BY id LIMIT 1`, planName).Scan(&planID)
	if errors.Is(err, pgx.ErrNoRows) {
		return errors.New("plan not found: " + planName)
	}
	if err != nil {
		return err
	}
	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")
	return nil
}

func (s *StripeService) setSubscriptionStatusNote(ctx context.Context, companyID uuid.UUID, status string) error {
	status = NormalizeSubscriptionStatus(status)
	if status == "" {
		return nil
	}
	note := FormatStripeStatusNote(status)
	_, err := s.Pool.Exec(ctx, `
		UPDATE company_plans
		SET notes = $2, updated_at = now()
		WHERE company_id = $1 AND is_active = true
			AND (notes IS NULL OR btrim(notes) = '' OR notes LIKE 'stripe_status:%')`,
		companyID, note)
	return err
}

func (s *StripeService) clearSubscriptionStatusNote(ctx context.Context, companyID uuid.UUID) error {
	_, err := s.Pool.Exec(ctx, `
		UPDATE company_plans
		SET notes = NULL, updated_at = now()
		WHERE company_id = $1 AND is_active = true
			AND notes LIKE 'stripe_status:%'`, companyID)
	return err
}

func (s *StripeService) downgradeToFree(ctx context.Context, companyID uuid.UUID) error {
	if s.Billing == nil || s.Pool == nil {
		return errors.New("billing service not configured")
	}
	_ = s.Billing.EnsureDefaultPlans(ctx)
	var planID int64
	err := s.Pool.QueryRow(ctx, `
		SELECT id FROM plans WHERE lower(name) = 'free' ORDER BY id LIMIT 1`).Scan(&planID)
	if err != nil {
		return err
	}
	if err := s.Billing.AssignPlan(ctx, companyID, planID, false, 0); err != nil {
		return err
	}
	_, _ = s.Pool.Exec(ctx, `
		UPDATE company_plans
		SET stripe_subscription_id = NULL, stripe_price_id = NULL, updated_at = now()
		WHERE company_id = $1 AND is_active = true`, companyID)
	_ = s.clearSubscriptionStatusNote(ctx, companyID)
	return nil
}

// verifyStripeSignature implements Stripe's signed payload check (t=,v1=).
func verifyStripeSignature(payload []byte, header, secret string, tolerance time.Duration) error {
	header = strings.TrimSpace(header)
	if header == "" {
		return ErrStripeBadSignature
	}
	var timestamp int64
	var signatures []string
	for _, part := range strings.Split(header, ",") {
		kv := strings.SplitN(strings.TrimSpace(part), "=", 2)
		if len(kv) != 2 {
			continue
		}
		switch kv[0] {
		case "t":
			ts, err := strconv.ParseInt(kv[1], 10, 64)
			if err != nil {
				return ErrStripeBadSignature
			}
			timestamp = ts
		case "v1":
			signatures = append(signatures, kv[1])
		}
	}
	if timestamp == 0 || len(signatures) == 0 {
		return ErrStripeBadSignature
	}
	if tolerance > 0 {
		age := time.Since(time.Unix(timestamp, 0))
		if age > tolerance || age < -tolerance {
			return fmt.Errorf("%w: timestamp outside tolerance", ErrStripeBadSignature)
		}
	}
	mac := hmac.New(sha256.New, []byte(secret))
	_, _ = fmt.Fprintf(mac, "%d.", timestamp)
	_, _ = mac.Write(payload)
	expected := hex.EncodeToString(mac.Sum(nil))
	for _, sig := range signatures {
		if hmac.Equal([]byte(expected), []byte(sig)) {
			return nil
		}
	}
	return ErrStripeBadSignature
}

// LoadStripePriceIDs reads STRIPE_PRICE_* env into the price map.
func LoadStripePriceIDs(getenv func(string) string) map[string]string {
	out := map[string]string{}
	pairs := []struct {
		key string
		env string
	}{
		{"starter:monthly", "STRIPE_PRICE_STARTER_MONTHLY"},
		{"starter:yearly", "STRIPE_PRICE_STARTER_YEARLY"},
		{"plus:monthly", "STRIPE_PRICE_PLUS_MONTHLY"},
		{"plus:yearly", "STRIPE_PRICE_PLUS_YEARLY"},
		{"growth:monthly", "STRIPE_PRICE_GROWTH_MONTHLY"},
		{"growth:yearly", "STRIPE_PRICE_GROWTH_YEARLY"},
		{"business:monthly", "STRIPE_PRICE_BUSINESS_MONTHLY"},
		{"business:yearly", "STRIPE_PRICE_BUSINESS_YEARLY"},
		{"scale:monthly", "STRIPE_PRICE_SCALE_MONTHLY"},
		{"scale:yearly", "STRIPE_PRICE_SCALE_YEARLY"},
	}
	for _, p := range pairs {
		if v := strings.TrimSpace(getenv(p.env)); v != "" {
			out[p.key] = v
		}
	}
	for _, pack := range DefaultCreditPacks() {
		if v := strings.TrimSpace(getenv(CreditPackEnvVar(pack.ID))); v != "" {
			out[CreditPackPriceKey(pack.ID)] = v
		}
	}
	return out
}