package handlers

import (
	"errors"
	"net/http"
	"strconv"

	"veza-backend-api/internal/core/subscription"
	apperrors "veza-backend-api/internal/errors"

	"github.com/gin-gonic/gin"
	"github.com/google/uuid"
	"go.uber.org/zap"
)

// SubscriptionHandler handles subscription-related HTTP endpoints
type SubscriptionHandler struct {
	service *subscription.Service
	logger  *zap.Logger
}

// NewSubscriptionHandler creates a new SubscriptionHandler
func NewSubscriptionHandler(service *subscription.Service, logger *zap.Logger) *SubscriptionHandler {
	return &SubscriptionHandler{
		service: service,
		logger:  logger,
	}
}

// ListPlans returns all available subscription plans
func (h *SubscriptionHandler) ListPlans(c *gin.Context) {
	plans, err := h.service.ListPlans(c.Request.Context())
	if err != nil {
		RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to list plans", err))
		return
	}
	RespondSuccess(c, http.StatusOK, gin.H{"plans": plans})
}

// GetPlan returns a specific plan by ID
func (h *SubscriptionHandler) GetPlan(c *gin.Context) {
	planID, err := uuid.Parse(c.Param("id"))
	if err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid plan ID"))
		return
	}

	plan, err := h.service.GetPlan(c.Request.Context(), planID)
	if err != nil {
		if errors.Is(err, subscription.ErrPlanNotFound) {
			RespondWithAppError(c, apperrors.NewNotFoundError("Plan"))
			return
		}
		RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to get plan", err))
		return
	}
	RespondSuccess(c, http.StatusOK, plan)
}

// GetMySubscription returns the authenticated user's current subscription
func (h *SubscriptionHandler) GetMySubscription(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	sub, err := h.service.GetUserSubscription(c.Request.Context(), userID)
	if err != nil {
		if errors.Is(err, subscription.ErrNoActiveSubscription) {
			RespondSuccess(c, http.StatusOK, gin.H{"subscription": nil, "plan": "free"})
			return
		}
		// v1.0.6.2: a subscription row exists but has no payment linkage.
		// Surface a specific payload so honest-path users who landed here
		// via a broken flow (payment never completed) get a clear message
		// rather than "you're on free" (misleading) or a 500.
		if errors.Is(err, subscription.ErrSubscriptionNoPayment) {
			RespondSuccess(c, http.StatusOK, gin.H{
				"subscription":  nil,
				"plan":          "free",
				"needs_payment": true,
				"message":       "Your subscription is not linked to a payment. Please contact support to resolve.",
			})
			return
		}
		RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to get subscription", err))
		return
	}
	RespondSuccess(c, http.StatusOK, gin.H{"subscription": sub})
}

// Subscribe creates a new subscription for the authenticated user
func (h *SubscriptionHandler) Subscribe(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	var req subscription.SubscribeRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid request: plan_id and billing_cycle required"))
		return
	}

	resp, err := h.service.Subscribe(c.Request.Context(), userID, req)
	if err != nil {
		switch {
		case errors.Is(err, subscription.ErrPlanNotFound):
			RespondWithAppError(c, apperrors.NewNotFoundError("Plan"))
		case errors.Is(err, subscription.ErrAlreadySubscribed):
			RespondWithAppError(c, apperrors.NewValidationError("Already subscribed to this plan"))
		case errors.Is(err, subscription.ErrInvalidBillingCycle):
			RespondWithAppError(c, apperrors.NewValidationError("Invalid billing cycle: must be 'monthly' or 'yearly'"))
		case errors.Is(err, subscription.ErrPaymentProviderRequired):
			// v1.0.9 item G: paid plan attempted but no PaymentProvider
			// is wired (HYPERSWITCH_ENABLED=false in dev, or missing
			// credentials in staging). Surface the misconfig as 503 so
			// ops sees it instead of silently absorbing it as a free
			// active subscription.
			RespondWithAppError(c, apperrors.NewServiceUnavailableError("Payment provider not configured — paid plans temporarily unavailable"))
		default:
			RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to subscribe", err))
		}
		return
	}

	RespondSuccess(c, http.StatusCreated, resp)
}

// Complete recovers the PSP client_secret for a subscription stuck in
// pending_payment so the frontend can drive the payment UI to
// completion. v1.0.9 item G Phase 3 — closes the recovery loop.
//
// Path:    POST /api/v1/subscriptions/complete/:id
// Auth:    required, ownership enforced server-side (sub.user_id = caller).
// Returns: 200 {subscription, client_secret, payment_id} on success.
//
//	404 if the subscription doesn't belong to the caller.
//	409 if the subscription is not in pending_payment.
//	503 if HYPERSWITCH_ENABLED=false.
//
// The PSP CreateSubscriptionPayment call is idempotent on sub.ID, so
// this endpoint is safe to retry from the frontend on transient
// network failures — the same payment intent is returned each time.
func (h *SubscriptionHandler) Complete(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	idStr := c.Param("id")
	subID, err := uuid.Parse(idStr)
	if err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid subscription id"))
		return
	}

	resp, err := h.service.CompletePendingPayment(c.Request.Context(), userID, subID)
	if err != nil {
		switch {
		case errors.Is(err, subscription.ErrSubscriptionNotFound):
			RespondWithAppError(c, apperrors.NewNotFoundError("Subscription"))
		case errors.Is(err, subscription.ErrSubscriptionNotPending):
			// 409 — the subscription has already transitioned out of
			// pending_payment (webhook arrived, manual admin action,
			// upgrade). Caller should refresh /me to see current state.
			RespondWithAppError(c, apperrors.New(apperrors.ErrCodeConflict, "Subscription is not in pending_payment state"))
		case errors.Is(err, subscription.ErrPaymentProviderRequired):
			RespondWithAppError(c, apperrors.NewServiceUnavailableError("Payment provider not configured — payment recovery unavailable"))
		default:
			RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to recover payment", err))
		}
		return
	}

	RespondSuccess(c, http.StatusOK, resp)
}

// CancelSubscription cancels the user's subscription at end of period
func (h *SubscriptionHandler) CancelSubscription(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	sub, err := h.service.CancelSubscription(c.Request.Context(), userID)
	if err != nil {
		switch {
		case errors.Is(err, subscription.ErrNoActiveSubscription),
			errors.Is(err, subscription.ErrSubscriptionNoPayment):
			RespondWithAppError(c, apperrors.NewNotFoundError("Active subscription"))
		case errors.Is(err, subscription.ErrFreePlanNoBilling):
			RespondWithAppError(c, apperrors.NewValidationError("Free plan cannot be canceled"))
		default:
			RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to cancel subscription", err))
		}
		return
	}

	RespondSuccess(c, http.StatusOK, gin.H{
		"subscription": sub,
		"message":      "Subscription canceled. Access continues until " + sub.CurrentPeriodEnd.Format("2006-01-02"),
	})
}

// ReactivateSubscription removes the cancellation of a subscription
func (h *SubscriptionHandler) ReactivateSubscription(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	sub, err := h.service.ReactivateSubscription(c.Request.Context(), userID)
	if err != nil {
		if errors.Is(err, subscription.ErrNoActiveSubscription) || errors.Is(err, subscription.ErrSubscriptionNoPayment) {
			RespondWithAppError(c, apperrors.NewNotFoundError("Active subscription"))
			return
		}
		RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to reactivate subscription", err))
		return
	}

	RespondSuccess(c, http.StatusOK, gin.H{"subscription": sub})
}

// ChangeBillingCycle switches between monthly and yearly billing
func (h *SubscriptionHandler) ChangeBillingCycle(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	var req struct {
		BillingCycle subscription.BillingCycle `json:"billing_cycle" binding:"required"`
	}
	if err := c.ShouldBindJSON(&req); err != nil {
		RespondWithAppError(c, apperrors.NewValidationError("Invalid request: billing_cycle required"))
		return
	}

	sub, err := h.service.ChangeBillingCycle(c.Request.Context(), userID, req.BillingCycle)
	if err != nil {
		switch {
		case errors.Is(err, subscription.ErrNoActiveSubscription),
			errors.Is(err, subscription.ErrSubscriptionNoPayment):
			RespondWithAppError(c, apperrors.NewNotFoundError("Active subscription"))
		case errors.Is(err, subscription.ErrInvalidBillingCycle):
			RespondWithAppError(c, apperrors.NewValidationError("Invalid billing cycle: must be 'monthly' or 'yearly'"))
		default:
			RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to change billing cycle", err))
		}
		return
	}

	RespondSuccess(c, http.StatusOK, gin.H{"subscription": sub})
}

// GetInvoices returns the user's subscription invoices
func (h *SubscriptionHandler) GetInvoices(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	limit, _ := strconv.Atoi(c.DefaultQuery("limit", "20"))
	limit = clampLimit(limit) // SECURITY(MEDIUM-004)
	offset, _ := strconv.Atoi(c.DefaultQuery("offset", "0"))

	invoices, err := h.service.GetUserInvoices(c.Request.Context(), userID, limit, offset)
	if err != nil {
		RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to get invoices", err))
		return
	}

	RespondSuccess(c, http.StatusOK, gin.H{"invoices": invoices})
}

// GetSubscriptionHistory returns the user's subscription history
func (h *SubscriptionHandler) GetSubscriptionHistory(c *gin.Context) {
	userID, ok := GetUserIDUUID(c)
	if !ok {
		return
	}

	limit, _ := strconv.Atoi(c.DefaultQuery("limit", "20"))
	limit = clampLimit(limit) // SECURITY(MEDIUM-004)
	offset, _ := strconv.Atoi(c.DefaultQuery("offset", "0"))

	subs, err := h.service.GetUserSubscriptionHistory(c.Request.Context(), userID, limit, offset)
	if err != nil {
		RespondWithAppError(c, apperrors.NewInternalErrorWrap("Failed to get subscription history", err))
		return
	}

	RespondSuccess(c, http.StatusOK, gin.H{"subscriptions": subs})
}