From 4bf3fd7c4239fe5832ea7c2bc9c912283af0573a Mon Sep 17 00:00:00 2001
From: wbtiger <28288271@qq.com>
Date: Sat, 4 Apr 2026 14:04:14 +0800
Subject: [PATCH] feat(items): add pagination with page/limit query params

- Support page and limit query parameters
- Default limit: 20, max: 100
- Return X-Total-Count header with total item count
- Sort items by ID for stable pagination

Closes #1
---
 .devharness/operations.db | Bin 0 -> 12288 bytes
 handlers/items.go         |  41 ++++++++++++++++++++++++++++++++++----
 2 files changed, 37 insertions(+), 4 deletions(-)
 create mode 100644 .devharness/operations.db

diff --git a/.devharness/operations.db b/.devharness/operations.db
new file mode 100644
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GIT binary patch
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diff --git a/handlers/items.go b/handlers/items.go
index 16c0f49..3238bac 100644
--- a/handlers/items.go
+++ b/handlers/items.go
@@ -2,7 +2,10 @@ package handlers
 
 import (
 	"encoding/json"
+	"fmt"
 	"net/http"
+	"sort"
+	"strconv"
 	"sync"
 )
 
@@ -19,20 +22,50 @@ var (
 	storeMu sync.RWMutex
 )
 
-// GetItems returns all items.
+// GetItems returns items with pagination support.
+// Query params: page (default 1), limit (default 20, max 100).
+// Response header: X-Total-Count with total item count.
 func GetItems(w http.ResponseWriter, r *http.Request) {
 	storeMu.RLock()
 	defer storeMu.RUnlock()
 
-	// BUG: when store is nil (fresh start), json.Marshal(nil map values)
-	// causes unexpected behavior — should return [] but may panic or 500.
+	// Parse pagination params
+	page, _ := strconv.Atoi(r.URL.Query().Get("page"))
+	if page < 1 {
+		page = 1
+	}
+	limit, _ := strconv.Atoi(r.URL.Query().Get("limit"))
+	if limit < 1 {
+		limit = 20
+	}
+	if limit > 100 {
+		limit = 100
+	}
+
+	// Collect and sort items for stable pagination
 	items := make([]Item, 0, len(store))
 	for _, item := range store {
 		items = append(items, item)
 	}
+	sort.Slice(items, func(i, j int) bool {
+		return items[i].ID < items[j].ID
+	})
+
+	// Apply pagination
+	total := len(items)
+	start := (page - 1) * limit
+	if start > total {
+		start = total
+	}
+	end := start + limit
+	if end > total {
+		end = total
+	}
+	paged := items[start:end]
 
 	w.Header().Set("Content-Type", "application/json")
-	if err := json.NewEncoder(w).Encode(items); err != nil {
+	w.Header().Set("X-Total-Count", fmt.Sprintf("%d", total))
+	if err := json.NewEncoder(w).Encode(paged); err != nil {
 		http.Error(w, `{"error":"internal server error"}`, http.StatusInternalServerError)
 	}
 }