package httpapi

import (
	"context"
	"encoding/json"
	"errors"
	"io"
	"mime"
	"net/http"
	"strconv"
	"strings"
	"unicode/utf8"

	"git.nianxx.cn/wangxuming/NianAIGC/backend/internal/payments"
)

type PaymentRefundService interface {
	AdminList(context.Context, string, int, int) (payments.AdminOrdersPage, error)
	CreateRefund(context.Context, string, string, string, string, int64) (payments.Refund, error)
	GetRefund(context.Context, string) (payments.Refund, error)
	ListRefunds(context.Context, string) ([]payments.Refund, error)
	RefundNotify(context.Context, *http.Request) error
}

func (h *paymentHandler) adminPayments(w http.ResponseWriter, r *http.Request) {
	parts := strings.Split(strings.TrimPrefix(r.URL.Path, "/api/payments/admin/"), "/")
	list := len(parts) == 1 && parts[0] == "orders"
	order := len(parts) == 3 && parts[0] == "orders" && parts[2] == "refunds" && len(parts[1]) <= 32 && paymentIdentifier.MatchString(parts[1])
	refund := len(parts) == 2 && parts[0] == "refunds" && len(parts[1]) <= 64 && paymentIdentifier.MatchString(parts[1])
	if !list && !order && !refund {
		http.NotFound(w, r)
		return
	}
	if r.Method != http.MethodGet && !(order && r.Method == http.MethodPost) {
		w.WriteHeader(http.StatusMethodNotAllowed)
		return
	}
	session, err := h.authorizer.Authorize(r, PlatformSuperAdmin)
	if err != nil {
		writePaymentError(w, err)
		return
	}
	service, ok := h.service.(PaymentRefundService)
	if !ok {
		writeRefundError(w, payments.ErrUnavailable)
		return
	}
	if list {
		limit, offset := 50, 0
		if raw := r.URL.Query().Get("limit"); raw != "" {
			limit, err = strconv.Atoi(raw)
			if err != nil || limit < 1 || limit > 100 {
				writeAPIError(w, 400, "分页参数无效。")
				return
			}
		}
		if raw := r.URL.Query().Get("offset"); raw != "" {
			offset, err = strconv.Atoi(raw)
			if err != nil || offset < 0 || offset > 10000000 {
				writeAPIError(w, 400, "分页参数无效。")
				return
			}
		}
		org := r.URL.Query().Get("organizationId")
		if len(org) > 128 {
			writeAPIError(w, 400, "组织参数无效。")
			return
		}
		page, err := service.AdminList(r.Context(), org, limit, offset)
		if err != nil {
			writeRefundError(w, err)
			return
		}
		if page.Orders == nil {
			page.Orders = []payments.AdminOrder{}
		}
		for i := range page.Orders {
			page.Orders[i].CodeURL = ""
		}
		writeJSON(w, 200, page)
		return
	}
	if refund {
		value, err := service.GetRefund(r.Context(), parts[1])
		if err != nil {
			writeRefundError(w, err)
			return
		}
		writeJSON(w, 200, map[string]any{"refund": value})
		return
	}
	if r.Method == http.MethodGet {
		values, err := service.ListRefunds(r.Context(), parts[1])
		if err != nil {
			writeRefundError(w, err)
			return
		}
		if values == nil {
			values = []payments.Refund{}
		}
		writeJSON(w, 200, map[string]any{"refunds": values})
		return
	}
	if !h.sameOrigin(r) {
		writeAPIError(w, 403, "请从本站发起退款。")
		return
	}
	mediaType, _, err := mime.ParseMediaType(r.Header.Get("Content-Type"))
	if err != nil || mediaType != "application/json" {
		writeAPIError(w, 415, "请使用 JSON 请求。")
		return
	}
	var body struct {
		AmountFen  int64  `json:"amountFen"`
		Reason     string `json:"reason"`
		RequestKey string `json:"requestKey"`
	}
	r.Body = http.MaxBytesReader(w, r.Body, 4096)
	decoder := json.NewDecoder(r.Body)
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(&body); err != nil {
		writeAPIError(w, 400, "退款参数无效，金额必须是整数分。")
		return
	}
	body.Reason = strings.TrimSpace(body.Reason)
	if err := decoder.Decode(&struct{}{}); err != io.EOF || body.AmountFen <= 0 || !paymentIdentifier.MatchString(body.RequestKey) || body.Reason == "" || len(body.Reason) > 80 || !utf8.ValidString(body.Reason) {
		writeAPIError(w, 400, "退款金额、请求标识或原因无效（原因最多 80 字节）。")
		return
	}
	value, err := service.CreateRefund(r.Context(), parts[1], session.User.ID, body.RequestKey, body.Reason, body.AmountFen)
	if err != nil {
		writeRefundError(w, err)
		return
	}
	writeJSON(w, 200, map[string]any{"refund": value})
}

func (h *paymentHandler) refundNotify(w http.ResponseWriter, r *http.Request) {
	if !allow(w, r, http.MethodPost) {
		return
	}
	service, ok := h.service.(PaymentRefundService)
	if !ok {
		writeJSON(w, 503, map[string]string{"code": "FAIL", "message": "退款服务未启用"})
		return
	}
	r.Body = http.MaxBytesReader(w, r.Body, 64<<10)
	if err := service.RefundNotify(r.Context(), r); err != nil {
		status := http.StatusInternalServerError
		if errors.Is(err, payments.ErrVerification) {
			status = http.StatusBadRequest
		}
		writeJSON(w, status, map[string]string{"code": "FAIL", "message": "退款通知处理失败"})
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

func writeRefundError(w http.ResponseWriter, err error) {
	status, message := 500, "退款服务暂时不可用，请稍后刷新记录。"
	switch {
	case errors.Is(err, payments.ErrNotFound):
		status, message = 404, "充值或退款记录不存在。"
	case errors.Is(err, payments.ErrConflict):
		status, message = 409, "订单状态、可退金额或退款请求已变化，请刷新记录后重试。"
	case errors.Is(err, payments.ErrInvalidAmount):
		status, message = 400, "退款金额超过可退金额或参数无效。"
	case errors.Is(err, payments.ErrUnavailable):
		status, message = 503, "微信退款尚未启用。"
	}
	writeAPIError(w, status, message)
}