package handler

import (
	"strconv"
	"strings"

	"github.com/Wei-Shaw/sub2api/internal/pkg/pagination"
	"github.com/Wei-Shaw/sub2api/internal/pkg/response"
	middleware2 "github.com/Wei-Shaw/sub2api/internal/server/middleware"
	"github.com/Wei-Shaw/sub2api/internal/service"

	"github.com/gin-gonic/gin"
)

// PaymentHandler handles user-facing payment requests.
type PaymentHandler struct {
	channelService *service.ChannelService
	paymentService *service.PaymentService
	configService  *service.PaymentConfigService
}

// NewPaymentHandler creates a new PaymentHandler.
func NewPaymentHandler(paymentService *service.PaymentService, configService *service.PaymentConfigService, channelService *service.ChannelService) *PaymentHandler {
	return &PaymentHandler{
		channelService: channelService,
		paymentService: paymentService,
		configService:  configService,
	}
}

// GetPaymentConfig returns the payment system configuration.
// GET /api/v1/payment/config
func (h *PaymentHandler) GetPaymentConfig(c *gin.Context) {
	cfg, err := h.configService.GetPaymentConfig(c.Request.Context())
	if err != nil {
		response.ErrorFrom(c, err)
		return
	}
	response.Success(c, cfg)
}

// GetPlans returns subscription plans available for sale.
// GET /api/v1/payment/plans
func (h *PaymentHandler) GetPlans(c *gin.Context) {
	plans, err := h.configService.ListPlansForSale(c.Request.Context())
	if err != nil {
		response.ErrorFrom(c, err)
		return
	}
	// Enrich plans with group platform for frontend color coding
	type planWithPlatform struct {
		ID            int64    `json:"id"`
		GroupID       int64    `json:"group_id"`
		GroupPlatform string   `json:"group_platform"`
		Name          string   `json:"name"`
		Description   string   `json:"description"`
		Price         float64  `json:"price"`
		OriginalPrice *float64 `json:"original_price,omitempty"`
		ValidityDays  int      `json:"validity_days"`
		ValidityUnit  string   `json:"validity_unit"`
		Features      string   `json:"features"`
		ProductName   string   `json:"product_name"`
		ForSale       bool     `json:"for_sale"`
		SortOrder     int      `json:"sort_order"`
	}
	platformMap := h.configService.GetGroupPlatformMap(c.Request.Context(), plans)
	result := make([]planWithPlatform, 0, len(plans))
	for _, p := range plans {
		result = append(result, planWithPlatform{
			ID: int64(p.ID), GroupID: p.GroupID, GroupPlatform: platformMap[p.GroupID],
			Name: p.Name, Description: p.Description, Price: p.Price, OriginalPrice: p.OriginalPrice,
			ValidityDays: p.ValidityDays, ValidityUnit: p.ValidityUnit, Features: p.Features,
			ProductName: p.ProductName, ForSale: p.ForSale, SortOrder: p.SortOrder,
		})
	}
	response.Success(c, result)
}

// GetChannels returns enabled payment channels.
// GET /api/v1/payment/channels
func (h *PaymentHandler) GetChannels(c *gin.Context) {
	channels, _, err := h.channelService.List(c.Request.Context(), pagination.PaginationParams{Page: 1, PageSize: 1000}, "active", "")
	if err != nil {
		response.ErrorFrom(c, err)
		return
	}
	response.Success(c, channels)
}

// GetCheckoutInfo returns all data the payment page needs in a single call:
// payment methods with limits, subscription plans, and configuration.
// GET /api/v1/payment/checkout-info
func (h *PaymentHandler) GetCheckoutInfo(c *gin.Context) {
	ctx := c.Request.Context()

	// Fetch limits (methods + global range)
	limitsResp, err := h.configService.GetAvailableMethodLimits(ctx)
	if err != nil {
		response.ErrorFrom(c, err)
		return
	}

	// Fetch payment config
	cfg, err := h.configService.GetPaymentConfig(ctx)
	if err != nil {
		response.ErrorFrom(c, err)
		return
	}

	// Fetch plans with group info
	plans, _ := h.configService.ListPlansForSale(ctx)
	groupInfo := h.configService.GetGroupInfoMap(ctx, plans)
	planList := make([]checkoutPlan, 0, len(plans))
	for _, p := range plans {
		gi := groupInfo[p.GroupID]
		planList = append(planList, checkoutPlan{
			ID: int64(p.ID), GroupID: p.GroupID,
			GroupPlatform: gi.Platform, GroupName: gi.Name,
			RateMultiplier: gi.RateMultiplier, DailyLimitUSD: gi.DailyLimitUSD,
			WeeklyLimitUSD: gi.WeeklyLimitUSD, MonthlyLimitUSD: gi.MonthlyLimitUSD,
			ModelScopes: gi.ModelScopes,
			Name:        p.Name, Description: p.Description, Price: p.Price, OriginalPrice: p.OriginalPrice,
			ValidityDays: p.ValidityDays, ValidityUnit: p.ValidityUnit, Features: parseFeatures(p.Features),
			ProductName: p.ProductName,
		})
	}

	response.Success(c, checkoutInfoResponse{
		Methods:              limitsResp.Methods,
		GlobalMin:            limitsResp.GlobalMin,
		GlobalMax:            limitsResp.GlobalMax,
		Plans:                planList,
		BalanceDisabled:      cfg.BalanceDisabled,
		HelpText:             cfg.HelpText,
		HelpImageURL:         cfg.HelpImageURL,
		StripePublishableKey: cfg.StripePublishableKey,
	})
}

type checkoutInfoResponse struct {
	Methods              map[string]service.MethodLimits `json:"methods"`
	GlobalMin            float64                         `json:"global_min"`
	GlobalMax            float64                         `json:"global_max"`
	Plans                []checkoutPlan                  `json:"plans"`
	BalanceDisabled      bool                            `json:"balance_disabled"`
	HelpText             string                          `json:"help_text"`
	HelpImageURL         string                          `json:"help_image_url"`
	StripePublishableKey string                          `json:"stripe_publishable_key"`
}

type checkoutPlan struct {
	ID              int64    `json:"id"`
	GroupID         int64    `json:"group_id"`
	GroupPlatform   string   `json:"group_platform"`
	GroupName       string   `json:"group_name"`
	RateMultiplier  float64  `json:"rate_multiplier"`
	DailyLimitUSD   *float64 `json:"daily_limit_usd"`
	WeeklyLimitUSD  *float64 `json:"weekly_limit_usd"`
	MonthlyLimitUSD *float64 `json:"monthly_limit_usd"`
	ModelScopes     []string `json:"supported_model_scopes"`
	Name            string   `json:"name"`
	Description     string   `json:"description"`
	Price           float64  `json:"price"`
	OriginalPrice   *float64 `json:"original_price,omitempty"`
	ValidityDays    int      `json:"validity_days"`
	ValidityUnit    string   `json:"validity_unit"`
	Features        []string `json:"features"`
	ProductName     string   `json:"product_name"`
}

// parseFeatures splits a newline-separated features string into a string slice.
func parseFeatures(raw string) []string {
	if raw == "" {
		return []string{}
	}
	var out []string
	for _, line := range strings.Split(raw, "\n") {
		if s := strings.TrimSpace(line); s != "" {
			out = append(out, s)
		}
	}
	if out == nil {
		return []string{}
	}
	return out
}

// GetLimits returns per-payment-type limits derived from enabled provider instances.
// GET /api/v1/payment/limits
func (h *PaymentHandler) GetLimits(c *gin.Context) {
	resp, err := h.configService.GetAvailableMethodLimits(c.Request.Context())
	if err != nil {
		response.ErrorFrom(c, err)
		return
	}
	response.Success(c, resp)
}

// CreateOrderRequest is the request body for creating a payment order.
type CreateOrderRequest struct {
	Amount      float64 `json:"amount"`
	PaymentType string  `json:"payment_type" binding:"required"`
	OrderType   string  `json:"order_type"`
	PlanID      int64   `json:"plan_id"`
}

// CreateOrder creates a new payment order.
// POST /api/v1/payment/orders
func (h *PaymentHandler) CreateOrder(c *gin.Context) {
	subject, ok := requireAuth(c)
	if !ok {
		return
	}

	var req CreateOrderRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		response.BadRequest(c, "Invalid request: "+err.Error())
		return
	}

	result, err := h.paymentService.CreateOrder(c.Request.Context(), service.CreateOrderRequest{
		UserID:      subject.UserID,
		Amount:      req.Amount,
		PaymentType: req.PaymentType,
		ClientIP:    c.ClientIP(),
		IsMobile:    isMobile(c),
		SrcHost:     c.Request.Host,
		SrcURL:      c.Request.Referer(),
		OrderType:   req.OrderType,
		PlanID:      req.PlanID,
	})
	if err != nil {
		response.ErrorFrom(c, err)
		return
	}
	response.Success(c, result)
}

// GetMyOrders returns the authenticated user's orders.
// GET /api/v1/payment/orders/my
func (h *PaymentHandler) GetMyOrders(c *gin.Context) {
	subject, ok := requireAuth(c)
	if !ok {
		return
	}

	page, pageSize := response.ParsePagination(c)
	orders, total, err := h.paymentService.GetUserOrders(c.Request.Context(), subject.UserID, service.OrderListParams{
		Page:        page,
		PageSize:    pageSize,
		Status:      c.Query("status"),
		OrderType:   c.Query("order_type"),
		PaymentType: c.Query("payment_type"),
	})
	if err != nil {
		response.ErrorFrom(c, err)
		return
	}
	response.Paginated(c, orders, int64(total), page, pageSize)
}

// GetOrder returns a single order for the authenticated user.
// GET /api/v1/payment/orders/:id
func (h *PaymentHandler) GetOrder(c *gin.Context) {
	subject, ok := requireAuth(c)
	if !ok {
		return
	}

	orderID, err := strconv.ParseInt(c.Param("id"), 10, 64)
	if err != nil {
		response.BadRequest(c, "Invalid order ID")
		return
	}

	order, err := h.paymentService.GetOrder(c.Request.Context(), orderID, subject.UserID)
	if err != nil {
		response.ErrorFrom(c, err)
		return
	}
	response.Success(c, order)
}

// CancelOrder cancels a pending order for the authenticated user.
// POST /api/v1/payment/orders/:id/cancel
func (h *PaymentHandler) CancelOrder(c *gin.Context) {
	subject, ok := requireAuth(c)
	if !ok {
		return
	}

	orderID, err := strconv.ParseInt(c.Param("id"), 10, 64)
	if err != nil {
		response.BadRequest(c, "Invalid order ID")
		return
	}

	msg, err := h.paymentService.CancelOrder(c.Request.Context(), orderID, subject.UserID)
	if err != nil {
		response.ErrorFrom(c, err)
		return
	}
	response.Success(c, gin.H{"message": msg})
}

// RefundRequestBody is the request body for requesting a refund.
type RefundRequestBody struct {
	Reason string `json:"reason"`
}

// RequestRefund submits a refund request for a completed order.
// POST /api/v1/payment/orders/:id/refund-request
func (h *PaymentHandler) RequestRefund(c *gin.Context) {
	subject, ok := requireAuth(c)
	if !ok {
		return
	}

	orderID, err := strconv.ParseInt(c.Param("id"), 10, 64)
	if err != nil {
		response.BadRequest(c, "Invalid order ID")
		return
	}

	var req RefundRequestBody
	if err := c.ShouldBindJSON(&req); err != nil {
		response.BadRequest(c, "Invalid request: "+err.Error())
		return
	}

	if err := h.paymentService.RequestRefund(c.Request.Context(), orderID, subject.UserID, req.Reason); err != nil {
		response.ErrorFrom(c, err)
		return
	}
	response.Success(c, gin.H{"message": "refund requested"})
}

// GetRefundEligibleProviders returns provider instance IDs that allow user refund.
func (h *PaymentHandler) GetRefundEligibleProviders(c *gin.Context) {
	ids, err := h.configService.GetUserRefundEligibleInstanceIDs(c.Request.Context())
	if err != nil {
		response.ErrorFrom(c, err)
		return
	}
	response.Success(c, gin.H{"provider_instance_ids": ids})
}

// VerifyOrderRequest is the request body for verifying a payment order.
type VerifyOrderRequest struct {
	OutTradeNo string `json:"out_trade_no" binding:"required"`
}

// VerifyOrder actively queries the upstream payment provider to check
// if payment was made, and processes it if so.
// POST /api/v1/payment/orders/verify
func (h *PaymentHandler) VerifyOrder(c *gin.Context) {
	subject, ok := requireAuth(c)
	if !ok {
		return
	}

	var req VerifyOrderRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		response.BadRequest(c, "Invalid request: "+err.Error())
		return
	}

	order, err := h.paymentService.VerifyOrderByOutTradeNo(c.Request.Context(), req.OutTradeNo, subject.UserID)
	if err != nil {
		response.ErrorFrom(c, err)
		return
	}
	response.Success(c, order)
}

// PublicOrderResult is the limited order info returned by the public verify endpoint.
// No user details are exposed — only payment status information.
type PublicOrderResult struct {
	ID          int64   `json:"id"`
	OutTradeNo  string  `json:"out_trade_no"`
	Amount      float64 `json:"amount"`
	PayAmount   float64 `json:"pay_amount"`
	PaymentType string  `json:"payment_type"`
	Status      string  `json:"status"`
}

// VerifyOrderPublic verifies payment status without requiring authentication.
// Returns limited order info (no user details) to prevent information leakage.
// POST /api/v1/payment/public/orders/verify
func (h *PaymentHandler) VerifyOrderPublic(c *gin.Context) {
	var req VerifyOrderRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		response.BadRequest(c, "Invalid request: "+err.Error())
		return
	}
	order, err := h.paymentService.VerifyOrderPublic(c.Request.Context(), req.OutTradeNo)
	if err != nil {
		response.ErrorFrom(c, err)
		return
	}
	response.Success(c, PublicOrderResult{
		ID:          order.ID,
		OutTradeNo:  order.OutTradeNo,
		Amount:      order.Amount,
		PayAmount:   order.PayAmount,
		PaymentType: order.PaymentType,
		Status:      order.Status,
	})
}

// requireAuth extracts the authenticated subject from the context.
// Returns the subject and true on success; on failure it writes an Unauthorized response and returns false.
func requireAuth(c *gin.Context) (middleware2.AuthSubject, bool) {
	subject, ok := middleware2.GetAuthSubjectFromContext(c)
	if !ok {
		response.Unauthorized(c, "User not authenticated")
		return middleware2.AuthSubject{}, false
	}
	return subject, true
}

// isMobile detects mobile user agents.
func isMobile(c *gin.Context) bool {
	ua := strings.ToLower(c.GetHeader("User-Agent"))
	for _, kw := range []string{"mobile", "android", "iphone", "ipad", "ipod"} {
		if strings.Contains(ua, kw) {
			return true
		}
	}
	return false
}
