entitymap: add json parsing support

Add a json parsing method that given an entity map in the format:
[
  {
     "id" : 1,
     "containerEntityId" : 2,
     "containerEntityInstance" : 3,
     "isList" : false,
     "isLinked" : false,
     "entities" : [
         {"id" : 1, "instance" : 2},
         {"id" : 1, "instance" : 3},
         {"id" : 1, "instance" : 4},
         {"id" : 1, "instance" : 5}
     ]
  }
]

is constructed into the entity map used by sensorhandler.  This is meant
as part of the transition from the entity map in YAML to JSON.

This is step 2.  Step 1 moved access to the object behind a method.
This adds JSON validation and parsing.  Step 3 will add a file path to
check and parse.  Step 4 will provide a call to parse that file if
present and use its data if non-empty.

Tested: The method added has not been tested beyond unit-test validation.
Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: Ic29f022d3812fa9e3af775d542ad055629fd5a01

1 files changed, 74 insertions, 0 deletions

diff --git a/entity_map_json.cpp b/entity_map_json.cpp
new file mode 100644
index 0000000..db45b05
--- /dev/null
+++ b/entity_map_json.cpp
@@ -0,0 +1,74 @@
+#include "entity_map_json.hpp"
+
+#include <exception>
+#include <ipmid/types.hpp>
+#include <nlohmann/json.hpp>
+#include <string>
+#include <utility>
+
+namespace ipmi
+{
+namespace sensor
+{
+
+EntityInfoMap buildJsonEntityMap(const nlohmann::json& data)
+{
+    EntityInfoMap builtMap;
+
+    if (data.type() != nlohmann::json::value_t::array)
+    {
+        return builtMap;
+    }
+
+    try
+    {
+        for (const auto& entry : data)
+        {
+            /* It's an array entry with the following fields: id,
+             * containerEntityId, containerEntityInstance, isList, isLinked,
+             * entities[4]
+             */
+            EntityInfo obj;
+            Id recordId = entry.at("id").get<Id>();
+            obj.containerEntityId =
+                entry.at("containerEntityId").get<uint8_t>();
+            obj.containerEntityInstance =
+                entry.at("containerEntityInstance").get<uint8_t>();
+            obj.isList = entry.at("isList").get<bool>();
+            obj.isLinked = entry.at("isLinked").get<bool>();
+
+            auto jsonEntities = entry.at("entities");
+
+            if (jsonEntities.type() != nlohmann::json::value_t::array)
+            {
+                throw std::runtime_error(
+                    "Invalid type for entities entry, must be array");
+            }
+            if (jsonEntities.size() != obj.containedEntities.size())
+            {
+                throw std::runtime_error(
+                    "Entities must be in pairs of " +
+                    std::to_string(obj.containedEntities.size()));
+            }
+
+            for (std::size_t i = 0; i < obj.containedEntities.size(); i++)
+            {
+                obj.containedEntities[i] = std::make_pair(
+                    jsonEntities[i].at("id").get<uint8_t>(),
+                    jsonEntities[i].at("instance").get<uint8_t>());
+            }
+
+            builtMap.insert({recordId, obj});
+        }
+    }
+    catch (const std::exception& e)
+    {
+        /* If any entry is invalid, the entire file cannot be trusted. */
+        builtMap.clear();
+    }
+
+    return builtMap;
+}
+
+} // namespace sensor
+} // namespace ipmi