package server

import (
	"encoding/json"
	"errors"
	"net/http"
	"net/url"
	"strconv"

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

	"scrabble/backend/internal/payments"
)

// Ledger/order provider tags per rail.
const (
	providerRobokassa = "robokassa" // the direct (RUB) rail
	providerVK        = "vk"        // the VK Votes rail
)

// walletOrderRequest is the POST body of a chip-pack purchase: the pack to fund.
type walletOrderRequest struct {
	ProductID string `json:"product_id"`
}

// walletOrderResponse returns the created order id and the provider launch URL the client opens.
type walletOrderResponse struct {
	OrderID     string `json:"order_id"`
	RedirectURL string `json:"redirect_url"`
}

// handleWalletOrder opens a pending order to fund a chip pack and returns the Robokassa
// hosted-payment URL for the client to open. It is direct-rail only for now (VK/TG land later);
// it enforces the wallet gate and D36 (a direct purchase requires a confirmed email anchor). No
// chips are credited here — only later, by the verified Result callback.
func (s *Server) handleWalletOrder(c *gin.Context) {
	uid, ok := userID(c)
	if !ok {
		return
	}
	var req walletOrderRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		c.AbortWithStatusJSON(http.StatusBadRequest, errorResponse{Error: errorBody{Code: "invalid_request", Message: "invalid request body"}})
		return
	}
	productID, err := uuid.Parse(req.ProductID)
	if err != nil {
		c.AbortWithStatusJSON(http.StatusBadRequest, errorResponse{Error: errorBody{Code: "invalid_request", Message: "invalid product id"}})
		return
	}
	ctx := c.Request.Context()
	cxt, present, err := s.walletGate(ctx, uid)
	if err != nil {
		s.abortErr(c, err)
		return
	}
	switch cxt.Kind {
	case payments.SourceDirect:
		if s.robokassa.MerchantLogin == "" {
			c.AbortWithStatusJSON(http.StatusNotImplemented, errorResponse{Error: errorBody{Code: "rail_unavailable", Message: "this payment method is not available"}})
			return
		}
		// D36: a direct purchase requires a confirmed email anchor.
		hasEmail, err := s.accounts.HasConfirmedEmail(ctx, uid)
		if err != nil {
			s.abortErr(c, err)
			return
		}
		if !hasEmail {
			c.AbortWithStatusJSON(http.StatusForbidden, errorResponse{Error: errorBody{Code: "email_required", Message: "confirm your email before making a purchase"}})
			return
		}
		res, err := s.payments.CreateOrder(ctx, uid, cxt, present, productID, providerRobokassa)
		if err != nil {
			s.abortErr(c, err)
			return
		}
		c.JSON(http.StatusOK, walletOrderResponse{
			OrderID:     res.OrderID.String(),
			RedirectURL: s.robokassa.PaymentURL(res.OrderID, res.Amount.Major(), res.Title),
		})
	case payments.SourceVK:
		res, err := s.payments.CreateOrder(ctx, uid, cxt, present, productID, providerVK)
		if err != nil {
			s.abortErr(c, err)
			return
		}
		// The client passes the order id to VKWebAppShowOrderBox as the item; there is no redirect.
		c.JSON(http.StatusOK, walletOrderResponse{OrderID: res.OrderID.String()})
	default:
		c.AbortWithStatusJSON(http.StatusNotImplemented, errorResponse{Error: errorBody{Code: "rail_unavailable", Message: "this payment method is not available yet"}})
	}
}

// handleRobokassaResult is the verified Robokassa Result callback, reached only through the gateway
// (which forwards the provider's form parameters as a JSON object on the internal, gateway-only
// route). It verifies the Password2 signature, credits the matched order exactly once (idempotent,
// and honoured even if the order expired), records a succeeded event, and answers Robokassa's
// expected "OK<InvId>". A duplicate callback credits nothing but still answers OK.
func (s *Server) handleRobokassaResult(c *gin.Context) {
	var params map[string]string
	if err := c.ShouldBindJSON(&params); err != nil {
		c.String(http.StatusBadRequest, "bad request")
		return
	}
	v := url.Values{}
	for k, val := range params {
		v.Set(k, val)
	}
	orderID, outSum, ok := s.robokassa.VerifyResult(v)
	if !ok {
		s.log.Warn("robokassa result: bad signature")
		c.String(http.StatusBadRequest, "bad sign")
		return
	}
	paid, err := payments.ParseMoney(outSum, payments.CurrencyRUB)
	if err != nil {
		c.String(http.StatusBadRequest, "bad amount")
		return
	}
	ctx := c.Request.Context()
	outcome, err := s.payments.Fund(ctx, orderID, providerRobokassa, orderID.String(), paid)
	if err != nil {
		if errors.Is(err, payments.ErrOrderNotFound) || errors.Is(err, payments.ErrAmountMismatch) ||
			errors.Is(err, payments.ErrNotAPack) || errors.Is(err, payments.ErrProductNotFound) {
			s.log.Warn("robokassa result rejected", zap.String("order", orderID.String()), zap.Error(err))
			c.String(http.StatusBadRequest, "rejected")
			return
		}
		s.log.Error("robokassa fund failed", zap.String("order", orderID.String()), zap.Error(err))
		c.String(http.StatusInternalServerError, "error")
		return
	}
	if !outcome.AlreadyCredited {
		payload, _ := json.Marshal(map[string]any{"chips": outcome.Chips, "source": string(outcome.Source)})
		if err := s.payments.RecordPaymentEvent(ctx, outcome.AccountID, &orderID, "succeeded", payload); err != nil {
			s.log.Error("record payment event failed", zap.String("order", orderID.String()), zap.Error(err))
		}
	}
	// The gateway echoes response verbatim to Robokassa, which requires the body "OK<InvId>".
	c.JSON(http.StatusOK, gin.H{"response": "OK" + v.Get("InvId")})
}

// vkErrorResponse builds VK's error envelope for a payment callback.
func vkErrorResponse(code int, msg string, critical bool) gin.H {
	return gin.H{"error": gin.H{"error_code": code, "error_msg": msg, "critical": critical}}
}

// handleVKCallback is the VK Mini Apps payment callback, reached only through the gateway (which
// verifies the VK signature and forwards the provider's parameters as a JSON object on the internal
// route). It answers VK's two phases: get_item returns the ordered pack's title and vote price; a
// chargeable order_status_change credits the matched order exactly once (idempotent on VK's order
// id) and records a succeeded event. Both phases use VK's response envelope; the _test variants are
// the sandbox notifications and are handled identically.
func (s *Server) handleVKCallback(c *gin.Context) {
	var params map[string]string
	if err := c.ShouldBindJSON(&params); err != nil {
		c.JSON(http.StatusOK, vkErrorResponse(1, "bad request", true))
		return
	}
	ctx := c.Request.Context()
	switch params["notification_type"] {
	case "get_item", "get_item_test":
		orderID, err := uuid.Parse(params["item"])
		if err != nil {
			c.JSON(http.StatusOK, vkErrorResponse(20, "item not available", true))
			return
		}
		title, amount, err := s.payments.OrderItem(ctx, orderID)
		if err != nil {
			s.log.Warn("vk get_item lookup failed", zap.String("order", orderID.String()), zap.Error(err))
			c.JSON(http.StatusOK, vkErrorResponse(20, "item not available", true))
			return
		}
		c.JSON(http.StatusOK, gin.H{"response": gin.H{
			"item_id": orderID.String(),
			"title":   title,
			"price":   amount.Minor(),
		}})
	case "order_status_change", "order_status_change_test":
		if params["status"] != "chargeable" {
			c.JSON(http.StatusOK, vkErrorResponse(100, "unsupported status", false))
			return
		}
		orderID, err := uuid.Parse(params["item"])
		if err != nil {
			c.JSON(http.StatusOK, vkErrorResponse(20, "item not available", true))
			return
		}
		price, err := strconv.ParseInt(params["item_price"], 10, 64)
		if err != nil {
			c.JSON(http.StatusOK, vkErrorResponse(100, "bad price", false))
			return
		}
		paid, err := payments.MoneyFromMinor(price, payments.CurrencyVote)
		if err != nil {
			c.JSON(http.StatusOK, vkErrorResponse(100, "bad price", false))
			return
		}
		vkOrderID := params["order_id"]
		outcome, err := s.payments.Fund(ctx, orderID, providerVK, vkOrderID, paid)
		if err != nil {
			if errors.Is(err, payments.ErrOrderNotFound) || errors.Is(err, payments.ErrAmountMismatch) ||
				errors.Is(err, payments.ErrNotAPack) || errors.Is(err, payments.ErrProductNotFound) {
				s.log.Warn("vk order rejected", zap.String("order", orderID.String()), zap.Error(err))
				c.JSON(http.StatusOK, vkErrorResponse(100, "cannot process the order", false))
				return
			}
			s.log.Error("vk fund failed", zap.String("order", orderID.String()), zap.Error(err))
			c.JSON(http.StatusOK, vkErrorResponse(100, "internal error", false))
			return
		}
		if !outcome.AlreadyCredited {
			payload, _ := json.Marshal(map[string]any{"chips": outcome.Chips, "source": string(outcome.Source)})
			if err := s.payments.RecordPaymentEvent(ctx, outcome.AccountID, &orderID, "succeeded", payload); err != nil {
				s.log.Error("record vk payment event failed", zap.String("order", orderID.String()), zap.Error(err))
			}
		}
		// Echo VK's own order id; app_order_id is optional and our order id is a uuid, so omit it.
		appOrderID, _ := strconv.ParseInt(vkOrderID, 10, 64)
		c.JSON(http.StatusOK, gin.H{"response": gin.H{"order_id": appOrderID}})
	default:
		c.JSON(http.StatusOK, vkErrorResponse(100, "unknown notification", false))
	}
}