create VKClient with get_posts() method to get wall posts

.gitmodules

@@ -10,3 +10,6 @@
 [submodule "curl"]
 	path = curl
 	url = git@github.com:curl/curl.git
+[submodule "json"]
+	path = json
+	url = git@github.com:nlohmann/json.git

CMakeLists.txt

@@ -2,10 +2,11 @@ cmake_minimum_required(VERSION 3.5)
 project(mmcs-quotes-bridge LANGUAGES CXX)
 
 add_subdirectory(curl)
+add_subdirectory(json)
 add_subdirectory(libuv)
 add_subdirectory(spdlog)
 add_subdirectory(td)
 
-add_executable(${PROJECT_NAME} main.cpp http.cpp)
+add_executable(${PROJECT_NAME} main.cpp http.cpp vk.cpp)
 
-target_link_libraries(${PROJECT_NAME} PRIVATE CURL::libcurl uv spdlog::spdlog Td::TdStatic $<$<BOOL:${MINGW}>:ws2_32>)
+target_link_libraries(${PROJECT_NAME} PRIVATE CURL::libcurl nlohmann_json::nlohmann_json uv spdlog::spdlog Td::TdStatic $<$<BOOL:${MINGW}>:ws2_32>)

json

@@ -0,0 +1 @@
+Subproject commit fde9a86c5ad9c671662c0e9802b621f2de3cf60a

vk.cpp

@@ -0,0 +1,78 @@
+#include "vk.h"
+#include "curl/curl.h"
+#include "http.h"
+#include "spdlog/sinks/stdout_color_sinks.h"
+#include <memory>
+#include <nlohmann/json.hpp>
+
+using namespace vk;
+using namespace nlohmann;
+
+const char *API_BASE_URL = "https://api.vk.com/method/";
+const char *API_VERSION = "5.199";
+const char *LOGGER_TAG = "vk";
+
+VKClient::VKClient(uv_loop_t *eventLoop) : m_httpClient(eventLoop) {
+  m_logger = spdlog::get(LOGGER_TAG);
+  if (!m_logger) {
+    m_logger = spdlog::stdout_color_mt(LOGGER_TAG);
+    m_logger->set_level(spdlog::level::debug);
+  }
+};
+
+VKClient::VKClient(uv_loop_t *eventLoop, std::string serviceKey) : VKClient(eventLoop) {
+  set_service_api_key(serviceKey);
+}
+
+void VKClient::set_service_api_key(std::string key) {
+  m_serviceApiKey = {key};
+}
+
+void VKClient::get_posts(std::variant<long, std::string> wall, int offset, int count, std::function<void(std::optional<WallChunk>, int)> callback) {
+  if (!m_serviceApiKey) {
+    m_logger->error("get_posts called without authorization");
+    return;
+  }
+  std::string url(API_BASE_URL);
+  url += "wall.get?access_token=";
+  url += *m_serviceApiKey;
+  url += "&v=";
+  url += API_VERSION;
+  url += "&offset=";
+  url += std::to_string(offset);
+  url += "&count=";
+  url += std::to_string(count);
+  if (wall.index() == 0) {
+    url += "&owner_id=";
+    url += std::to_string(std::get<long>(wall));
+  } else {
+    url += "&domain=";
+    url += std::get<std::string>(wall);
+  }
+  m_logger->debug("using URL: {}", url);
+
+  m_httpClient.send_request("GET", url, {}, [this, callback](std::unique_ptr<http::HttpResponse> resp, CURLcode r){
+    if (r == 0) {
+      auto parsedResponse = json::parse(resp->body);
+
+      if (parsedResponse.contains("error")) {
+        auto err = parsedResponse["error"];
+        m_logger->error("get_posts error {} {}", (int)err["error_code"], (std::string)err["error_msg"]);
+        callback({}, -1);
+        return;
+      }
+
+      auto responsePayload = parsedResponse["response"];
+      int count = responsePayload["count"];
+      std::vector<Post> posts;
+      for (auto post : responsePayload["items"]) {
+        posts.emplace_back(post["id"], post["date"], post["edited"], post["from_id"], post["type"], post["text"]);
+      }
+
+      callback({{count, std::move(posts)}}, 0);
+    } else {
+      m_logger->error("get_posts network error");
+      callback({}, r);
+    }
+  });
+}

vk.h

@@ -0,0 +1,38 @@
+#pragma once
+#include "http.h"
+#include "spdlog/logger.h"
+#include "uv.h"
+#include <memory>
+#include <optional>
+#include <string>
+#include <variant>
+
+namespace vk {
+  using namespace http;
+
+  struct Post {
+    Post(long id, long date, long editDate, long fromId, std::string postType, std::string text);
+
+    long id, date, editDate, fromId;
+    std::string postType, text;
+  };
+
+  struct WallChunk {
+    int count;
+    std::vector<Post> posts;
+  };
+
+  class VKClient {
+  public:
+    VKClient(uv_loop_t *eventLoop);
+    VKClient(VKClient&) = delete;
+    VKClient(uv_loop_t *eventLoop, std::string serviceKey);
+    
+    void set_service_api_key(std::string key);
+    void get_posts(std::variant<long, std::string> wall, int offset, int count, std::function<void(std::optional<WallChunk>, int)> callback);
+  private:
+    HttpClient m_httpClient;
+    std::optional<std::string> m_serviceApiKey;
+    std::shared_ptr<spdlog::logger> m_logger;
+  };
+}