feat: add structures for MTR arrival and station information handling

main/external/mtr/line_info.h

@@ -0,0 +1,45 @@
+#pragma once
+#include "cJSON.h"
+#include "esp_log.h"
+#include "external/mtr/station_info.h"
+#include "external/mtr/mtr.h"
+#include <string>
+
+static const char* LINE_INFO_TAG = "LineInfo";
+
+// Forward declaration
+class MTRNextTrainHandler;
+struct StationInfo;
+
+struct LineInfo {
+public:
+
+  // caller does not own the returned char pointers
+  const char* code() const {
+    return _code.c_str();
+  }
+  // caller does not own the returned char pointers
+  const char* color() const {
+    return _color.c_str();
+  }
+  size_t station_count() const {
+    return _stations.size();
+  }
+  // caller does not own the returned array or StationInfo pointers
+  const std::vector<StationInfo>* stations() const {
+    return &_stations;
+  }
+
+  friend class MTRNextTrainHandler;
+
+private:
+  // Caller transfers ownership of stations array and its contents to LineInfo
+  LineInfo(
+    cJSON* line_json
+  );
+
+  std::string _code;
+  std::string _color;
+  std::vector<StationInfo> _stations;
+};
+