make building handlers from json more generic

Problem: version-handler, a new feature that will be added to this
repository will also parse json files from the same directory ipmi-flash
does. Currently buildjson is a mix of some code that can be reused and
other code that is pretty specific to firmware updates; this makes it
hard to reuse the code.

Solution: factor out the generic parts and place it in bmc and then
leave the specific parts in firmware-handler. Also code changes have
been made to buildjson: wrap functions in a templated class that leaves
feature specific parsing as a pure virtual method.

Tested:
Ran the unit tests, which do test the parsing functionality.

Signed-off-by: Jason Ling <jasonling@google.com>
Change-Id: I021dc829a82d1719b4cb862cdfb224eca629a44d
diff --git a/bmc/firmware-handler/firmware_handlers_builder.cpp b/bmc/firmware-handler/firmware_handlers_builder.cpp
new file mode 100644
index 0000000..d5f029c
--- /dev/null
+++ b/bmc/firmware-handler/firmware_handlers_builder.cpp
@@ -0,0 +1,152 @@
+/*
+ * Copyright 2019 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include "firmware_handlers_builder.hpp"
+
+#include "file_handler.hpp"
+#include "fs.hpp"
+#include "skip_action.hpp"
+
+#include <nlohmann/json.hpp>
+
+#include <algorithm>
+#include <cstdio>
+#include <exception>
+#include <fstream>
+#include <regex>
+#include <string>
+#include <vector>
+
+namespace ipmi_flash
+{
+std::vector<HandlerConfig<ActionPack>>
+    FirmwareHandlersBuilder::buildHandlerFromJson(const nlohmann::json& data)
+{
+    std::vector<HandlerConfig<ActionPack>> handlers;
+
+    for (const auto& item : data)
+    {
+        try
+        {
+            HandlerConfig<ActionPack> output;
+
+            /* at() throws an exception when the key is not present. */
+            item.at("blob").get_to(output.blobId);
+
+            /* name must be: /flash/... */
+            if (!std::regex_match(output.blobId, std::regex("^\\/flash\\/.+")))
+            {
+                throw std::runtime_error("Invalid blob name: '" +
+                                         output.blobId +
+                                         "' must start with /flash/");
+            }
+
+            /* handler is required. */
+            const auto& h = item.at("handler");
+            const std::string handlerType = h.at("type");
+            if (handlerType == "file")
+            {
+                const auto& path = h.at("path");
+                output.handler = std::make_unique<FileHandler>(path);
+            }
+            else
+            {
+                throw std::runtime_error("Invalid handler type: " +
+                                         handlerType);
+            }
+
+            /* actions are required (presently). */
+            const auto& a = item.at("actions");
+            std::unique_ptr<ActionPack> pack = std::make_unique<ActionPack>();
+
+            /* to make an action optional, assign type "skip" */
+            const auto& prep = a.at("preparation");
+            const std::string prepareType = prep.at("type");
+            if (prepareType == "systemd")
+            {
+                pack->preparation = std::move(buildSystemd(prep));
+            }
+            else if (prepareType == "skip")
+            {
+                pack->preparation = SkipAction::CreateSkipAction();
+            }
+            else
+            {
+                throw std::runtime_error("Invalid preparation type: " +
+                                         prepareType);
+            }
+
+            const auto& verify = a.at("verification");
+            const std::string verifyType = verify.at("type");
+            if (verifyType == "fileSystemdVerify")
+            {
+                pack->verification = std::move(buildFileSystemd(verify));
+            }
+            else if (verifyType == "systemd")
+            {
+                pack->verification = std::move(buildSystemd(verify));
+            }
+            else if (verifyType == "skip")
+            {
+                pack->verification = SkipAction::CreateSkipAction();
+            }
+            else
+            {
+                throw std::runtime_error("Invalid verification type:" +
+                                         verifyType);
+            }
+
+            const auto& update = a.at("update");
+            const std::string updateType = update.at("type");
+            if (updateType == "reboot")
+            {
+                pack->update = SystemdNoFile::CreateSystemdNoFile(
+                    sdbusplus::bus::new_default(), "reboot.target",
+                    "replace-irreversibly");
+            }
+            else if (updateType == "fileSystemdUpdate")
+            {
+                pack->update = std::move(buildFileSystemd(update));
+            }
+            else if (updateType == "systemd")
+            {
+                pack->update = std::move(buildSystemd(update));
+            }
+            else if (updateType == "skip")
+            {
+                pack->update = SkipAction::CreateSkipAction();
+            }
+            else
+            {
+                throw std::runtime_error("Invalid update type: " + updateType);
+            }
+
+            output.actions = std::move(pack);
+            handlers.push_back(std::move(output));
+        }
+        catch (const std::exception& e)
+        {
+            /* TODO: Once phosphor-logging supports unit-test injection, fix
+             * this to log.
+             */
+            std::fprintf(stderr,
+                         "Excepted building HandlerConfig from json: %s\n",
+                         e.what());
+        }
+    }
+
+    return handlers;
+}
+} // namespace ipmi_flash