Enhance capabilities based on the sample service

notes_server.cc

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+#include <iostream>
+#include <string>
+#include <unordered_map>
+#include <vector>
+#include <mutex>
+#include <atomic>
+#include "httplib.h"
+
+// 笔记结构体
+struct Note {
+    int id;
+    std::string title;
+    std::string content;
+};
+
+// 内存存储
+std::unordered_map<int, Note> notes_store;
+std::atomic<int> next_id{1};
+std::mutex store_mutex;
+
+// JSON 序列化单个笔记
+std::string note_to_json(const Note& note) {
+    return "{\"id\":" + std::to_string(note.id) + 
+           ",\"title\":\"" + note.title + 
+           "\",\"content\":\"" + note.content + "\"}";
+}
+
+// JSON 序列化笔记列表
+std::string notes_to_json(const std::vector<Note>& notes) {
+    std::string result = "[";
+    for (size_t i = 0; i < notes.size(); ++i) {
+        if (i > 0) result += ",";
+        result += note_to_json(notes[i]);
+    }
+    result += "]";
+    return result;
+}
+
+// 简单的 JSON 解析函数，提取字符串值
+std::string extract_json_string(const std::string& json, const std::string& key) {
+    std::string key_pattern = "\"" + key + "\":";
+    size_t pos = json.find(key_pattern);
+    if (pos == std::string::npos) return "";
+
+    pos += key_pattern.length();
+    // 跳过空白字符
+    while (pos < json.length() && (json[pos] == ' ' || json[pos] == '\t' || json[pos] == '\n' || json[pos] == '\r')) {
+        pos++;
+    }
+
+    if (pos >= json.length() || json[pos] != '"') return "";
+    pos++; // 跳过开头的引号
+
+    size_t end_pos = pos;
+    while (end_pos < json.length() && json[end_pos] != '"') {
+        // 处理转义字符
+        if (json[end_pos] == '\\' && end_pos + 1 < json.length()) {
+            end_pos += 2;
+        } else {
+            end_pos++;
+        }
+    }
+
+    if (end_pos >= json.length()) return "";
+    return json.substr(pos, end_pos - pos);
+}
+
+int main() {
+    using namespace httplib;
+
+    Server svr;
+
+    // 设置 CORS 头，方便前端调用
+    svr.set_default_headers({
+        {"Access-Control-Allow-Origin", "*"},
+        {"Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS"},
+        {"Access-Control-Allow-Headers", "Content-Type"}
+    });
+
+    // 处理 OPTIONS 请求
+    svr.Options("/notes", [](const Request& req, Response& res) {
+        res.status = 200;
+    });
+
+    svr.Options(R"(/notes/(\d+))", [](const Request& req, Response& res) {
+        res.status = 200;
+    });
+
+    // POST /notes - 新增笔记
+    svr.Post("/notes", [](const Request& req, Response& res) {
+        std::lock_guard<std::mutex> lock(store_mutex);
+
+        // 检查 Content-Type
+        if (!req.has_header("Content-Type") || 
+            req.get_header_value("Content-Type").find("application/json") == std::string::npos) {
+            res.status = 415; // Unsupported Media Type
+            res.set_content("{\"error\":\"Content-Type must be application/json\"}", "application/json");
+            return;
+        }
+
+        // 解析 JSON
+        std::string title = extract_json_string(req.body, "title");
+        std::string content = extract_json_string(req.body, "content");
+
+        // 检查参数是否缺失
+        if (title.empty() || content.empty()) {
+            res.status = 400; // Bad Request
+            res.set_content("{\"error\":\"Missing required fields: title and content are required\"}", "application/json");
+            return;
+        }
+
+        // 创建新笔记
+        int id = next_id++;
+        Note new_note{id, title, content};
+        notes_store[id] = new_note;
+
+        // 返回创建的笔记
+        res.status = 201; // Created
+        res.set_content(note_to_json(new_note), "application/json");
+    });
+
+    // GET /notes - 获取全部笔记
+    svr.Get("/notes", [](const Request& req, Response& res) {
+        std::lock_guard<std::mutex> lock(store_mutex);
+
+        std::vector<Note> notes;
+        for (const auto& pair : notes_store) {
+            notes.push_back(pair.second);
+        }
+
+        res.status = 200;
+        res.set_content(notes_to_json(notes), "application/json");
+    });
+
+    // PUT /notes/{id} - 修改笔记
+    svr.Put(R"(/notes/(\d+))", [](const Request& req, Response& res) {
+        std::lock_guard<std::mutex> lock(store_mutex);
+
+        int id = std::stoi(req.matches[1]);
+
+        // 检查笔记是否存在
+        if (notes_store.find(id) == notes_store.end()) {
+            res.status = 404; // Not Found
+            res.set_content("{\"error\":\"Note not found\"}", "application/json");
+            return;
+        }
+
+        // 检查 Content-Type
+        if (!req.has_header("Content-Type") || 
+            req.get_header_value("Content-Type").find("application/json") == std::string::npos) {
+            res.status = 415; // Unsupported Media Type
+            res.set_content("{\"error\":\"Content-Type must be application/json\"}", "application/json");
+            return;
+        }
+
+        // 解析 JSON
+        std::string title = extract_json_string(req.body, "title");
+        std::string content = extract_json_string(req.body, "content");
+
+        // 检查参数是否缺失
+        if (title.empty() || content.empty()) {
+            res.status = 400; // Bad Request
+            res.set_content("{\"error\":\"Missing required fields: title and content are required\"}", "application/json");
+            return;
+        }
+
+        // 更新笔记
+        notes_store[id].title = title;
+        notes_store[id].content = content;
+
+        // 返回更新后的笔记
+        res.status = 200;
+        res.set_content(note_to_json(notes_store[id]), "application/json");
+    });
+
+    // DELETE /notes/{id} - 删除笔记
+    svr.Delete(R"(/notes/(\d+))", [](const Request& req, Response& res) {
+        std::lock_guard<std::mutex> lock(store_mutex);
+
+        int id = std::stoi(req.matches[1]);
+
+        // 检查笔记是否存在
+        if (notes_store.find(id) == notes_store.end()) {
+            res.status = 404; // Not Found
+            res.set_content("{\"error\":\"Note not found\"}", "application/json");
+            return;
+        }
+
+        // 删除笔记
+        notes_store.erase(id);
+
+        res.status = 204; // No Content
+    });
+
+    // 启动服务器
+    std::cout << "笔记服务已启动，监听端口 8080" << std::endl;
+    std::cout << "API 接口：" << std::endl;
+    std::cout << "  POST   /notes     - 新增笔记" << std::endl;
+    std::cout << "  GET    /notes     - 获取全部笔记" << std::endl;
+    std::cout << "  PUT    /notes/{id} - 修改笔记" << std::endl;
+    std::cout << "  DELETE /notes/{id} - 删除笔记" << std::endl;
+    std::cout << "按 Ctrl+C 停止服务" << std::endl;
+
+    svr.listen("0.0.0.0", 8080);
+
+    return 0;
+}