package handler

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"mime"
	"net/http"
	"strings"

	"github.com/gin-gonic/gin"

	"laic-backend/common"
	"laic-backend/logger"
	"laic-backend/model"
	"laic-backend/service"
	"laic-backend/vo"
)

const maxAGPayCallbackBodyBytes = 64 * 1024

func CreateWechatPayment(c *gin.Context) {
	var req vo.PaymentCreateReq
	if err := c.ShouldBindJSON(&req); err != nil {
		common.FailWithBindError(c, common.ErrParam, err)
		return
	}
	data, e := service.DefaultPaymentService.CreateWechatPayment(common.GetUserId(c), &req)
	if e != nil {
		common.FailWithBusiError(c, e)
		return
	}
	common.OKWithData(c, data)
}

func GetPaymentTransaction(c *gin.Context) {
	id, e := parseID(c)
	if e != nil {
		common.FailWithBusiError(c, e)
		return
	}
	data, e := service.DefaultPaymentService.GetTransaction(common.GetUserId(c), id)
	if e != nil {
		common.FailWithBusiError(c, e)
		return
	}
	common.OKWithData(c, data)
}

func AGPayCallback(c *gin.Context) {
	c.Request.Body = http.MaxBytesReader(c.Writer, c.Request.Body, maxAGPayCallbackBodyBytes)
	body, err := c.GetRawData()
	if err != nil {
		logger.WARN("拒绝 AGPay 支付回调", "stage", "read_body", "error", err)
		c.Status(http.StatusBadRequest)
		return
	}
	callback, err := parseAGPayCallback(c.GetHeader("Content-Type"), body)
	if err != nil {
		logger.WARN("拒绝 AGPay 支付回调", "stage", "parse", "contentType", c.GetHeader("Content-Type"), "bodyBytes", len(body), "error", err)
		c.Status(http.StatusBadRequest)
		return
	}
	if err := service.DefaultPaymentService.ConfirmAGPayCallback(callback.TradeNo, body); err != nil {
		logger.WARN("拒绝 AGPay 支付回调", "stage", "confirm", "tradeNo", callback.TradeNo, "code", err.Code, "error", err)
		if err == common.ErrInternal {
			c.Status(http.StatusInternalServerError)
			return
		}
		c.Status(http.StatusBadRequest)
		return
	}
	c.JSON(http.StatusOK, gin.H{"code": "SUCCESS"})
}

func parseAGPayCallback(contentType string, body []byte) (model.AGPayCallback, error) {
	var callback model.AGPayCallback
	mediaType, _, err := mime.ParseMediaType(contentType)
	if err != nil || (mediaType != "application/json" && !strings.HasSuffix(mediaType, "+json")) {
		return callback, fmt.Errorf("unsupported content type %q", contentType)
	}
	decoder := json.NewDecoder(bytes.NewReader(body))
	// Gateways commonly add payment amount, provider transaction ID, and
	// signature fields. Only the merchant trade number is needed here; reject
	// malformed payloads, but do not reject otherwise valid gateway metadata.
	if err := decoder.Decode(&callback); err != nil {
		return callback, err
	}
	if err := decoder.Decode(&struct{}{}); err != io.EOF {
		if err == nil {
			return callback, fmt.Errorf("multiple JSON values")
		}
		return callback, err
	}
	callback.TradeNo = strings.TrimSpace(callback.TradeNo)
	if callback.TradeNo == "" || len(callback.TradeNo) > 128 {
		return callback, fmt.Errorf("invalid tradeNo")
	}
	return callback, nil
}