feat(trade): implement second-hand trading/flea market feature

Add complete trade functionality including:
- TradeItem, TradeImage, TradeFavorite models with auto-migration
- TradeRepository with CRUD and favorite operations
- TradeService with business logic for listing, creating, updating, status management
- TradeHandler with RESTful endpoints for trade operations
- DTOs and converters for request/response handling

Routes include: list, get by id, create, update, delete, status update, view recording, favorite/unfavorite.

internal/handler/trade_handler.go

@@ -0,0 +1,220 @@
+package handler
+
+import (
+	"strconv"
+
+	"github.com/gin-gonic/gin"
+
+	"with_you/internal/dto"
+	"with_you/internal/model"
+	"with_you/internal/pkg/response"
+	"with_you/internal/service"
+)
+
+type TradeHandler struct {
+	tradeService service.TradeService
+}
+
+func NewTradeHandler(tradeService service.TradeService) *TradeHandler {
+	return &TradeHandler{tradeService: tradeService}
+}
+
+func (h *TradeHandler) List(c *gin.Context) {
+	currentUserID := c.GetString("user_id")
+	if currentUserID == "" {
+		currentUserID = ""
+	}
+
+	var tradeType *model.TradeType
+	if v := c.Query("trade_type"); v != "" {
+		t := model.TradeType(v)
+		tradeType = &t
+	}
+
+	var category *model.TradeCategory
+	if v := c.Query("category"); v != "" {
+		cat := model.TradeCategory(v)
+		category = &cat
+	}
+
+	cursorStr := c.Query("cursor")
+	pageSize := 20
+	if v := c.Query("page_size"); v != "" {
+		if ps, err := strconv.Atoi(v); err == nil && ps > 0 && ps <= 100 {
+			pageSize = ps
+		}
+	}
+
+	keyword := c.Query("keyword")
+
+	var currentUserIDPtr *string
+	if currentUserID != "" {
+		currentUserIDPtr = &currentUserID
+	}
+
+	var resp *dto.TradeCursorPageResponse
+	var err error
+	if keyword != "" {
+		resp, err = h.tradeService.Search(c.Request.Context(), keyword, tradeType, category, cursorStr, pageSize, currentUserIDPtr)
+	} else {
+		resp, err = h.tradeService.List(c.Request.Context(), tradeType, category, cursorStr, pageSize, currentUserIDPtr)
+	}
+	if err != nil {
+		response.HandleError(c, err, "获取交易列表失败")
+		return
+	}
+	response.Success(c, resp)
+}
+
+func (h *TradeHandler) GetByID(c *gin.Context) {
+	id := c.Param("id")
+	currentUserID := c.GetString("user_id")
+
+	var currentUserIDPtr *string
+	if currentUserID != "" {
+		currentUserIDPtr = &currentUserID
+	}
+
+	resp, err := h.tradeService.GetByID(c.Request.Context(), id, currentUserIDPtr)
+	if err != nil {
+		response.HandleError(c, err, "获取交易详情失败")
+		return
+	}
+	response.Success(c, resp)
+}
+
+func (h *TradeHandler) Create(c *gin.Context) {
+	userID := c.GetString("user_id")
+	if userID == "" {
+		response.Unauthorized(c, "请先登录")
+		return
+	}
+
+	var req dto.CreateTradeItemRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		response.BadRequest(c, err.Error())
+		return
+	}
+
+	item, err := h.tradeService.Create(c.Request.Context(), userID, req)
+	if err != nil {
+		response.HandleError(c, err, "创建交易失败")
+		return
+	}
+
+	var currentUserIDPtr *string
+	if userID != "" {
+		currentUserIDPtr = &userID
+	}
+	detail, err := h.tradeService.GetByID(c.Request.Context(), item.ID, currentUserIDPtr)
+	if err != nil {
+		response.Success(c, item)
+		return
+	}
+	response.Success(c, detail)
+}
+
+func (h *TradeHandler) Update(c *gin.Context) {
+	userID := c.GetString("user_id")
+	if userID == "" {
+		response.Unauthorized(c, "请先登录")
+		return
+	}
+
+	id := c.Param("id")
+
+	var req dto.UpdateTradeItemRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		response.BadRequest(c, err.Error())
+		return
+	}
+
+	if err := h.tradeService.Update(c.Request.Context(), userID, id, req); err != nil {
+		response.HandleError(c, err, "更新交易失败")
+		return
+	}
+
+	var currentUserIDPtr *string
+	if userID != "" {
+		currentUserIDPtr = &userID
+	}
+	detail, err := h.tradeService.GetByID(c.Request.Context(), id, currentUserIDPtr)
+	if err != nil {
+		response.Success(c, nil)
+		return
+	}
+	response.Success(c, detail)
+}
+
+func (h *TradeHandler) Delete(c *gin.Context) {
+	userID := c.GetString("user_id")
+	if userID == "" {
+		response.Unauthorized(c, "请先登录")
+		return
+	}
+
+	id := c.Param("id")
+	if err := h.tradeService.Delete(c.Request.Context(), userID, id); err != nil {
+		response.HandleError(c, err, "删除交易失败")
+		return
+	}
+	response.Success(c, nil)
+}
+
+func (h *TradeHandler) UpdateStatus(c *gin.Context) {
+	userID := c.GetString("user_id")
+	if userID == "" {
+		response.Unauthorized(c, "请先登录")
+		return
+	}
+
+	id := c.Param("id")
+
+	var req dto.UpdateTradeItemStatusRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		response.BadRequest(c, err.Error())
+		return
+	}
+
+	if err := h.tradeService.UpdateStatus(c.Request.Context(), userID, id, model.TradeItemStatus(req.Status)); err != nil {
+		response.HandleError(c, err, "更新交易状态失败")
+		return
+	}
+	response.Success(c, nil)
+}
+
+func (h *TradeHandler) RecordView(c *gin.Context) {
+	id := c.Param("id")
+	_ = h.tradeService.RecordView(c.Request.Context(), id)
+	response.Success(c, nil)
+}
+
+func (h *TradeHandler) Favorite(c *gin.Context) {
+	userID := c.GetString("user_id")
+	if userID == "" {
+		response.Unauthorized(c, "请先登录")
+		return
+	}
+
+	id := c.Param("id")
+	if err := h.tradeService.Favorite(c.Request.Context(), userID, id); err != nil {
+		response.HandleError(c, err, "收藏失败")
+		return
+	}
+	response.Success(c, dto.TradeFavoriteResponse{Favorited: true})
+}
+
+func (h *TradeHandler) Unfavorite(c *gin.Context) {
+	userID := c.GetString("user_id")
+	if userID == "" {
+		response.Unauthorized(c, "请先登录")
+		return
+	}
+
+	id := c.Param("id")
+	if err := h.tradeService.Unfavorite(c.Request.Context(), userID, id); err != nil {
+		response.HandleError(c, err, "取消收藏失败")
+		return
+	}
+	response.Success(c, dto.TradeFavoriteResponse{Favorited: false})
+}