New simple REST API

Author: wichtounet

include/api/retirement_api.hpp

@@ -0,0 +1,19 @@
+//=======================================================================
+// Copyright (c) 2013-2020 Baptiste Wicht.
+// Distributed under the terms of the MIT License.
+// (See accompanying file LICENSE or copy at
+//  http://opensource.org/licenses/MIT)
+//=======================================================================
+
+#pragma once
+
+namespace httplib {
+struct Request;
+struct Response;
+}; // namespace httplib
+
+namespace budget {
+
+void retirement_countdown_api(const httplib::Request& req, httplib::Response& res);
+
+} // end of namespace budget

src/api/retirement_api.cpp

@@ -0,0 +1,62 @@
+//=======================================================================
+// Copyright (c) 2013-2020 Baptiste Wicht.
+// Distributed under the terms of the MIT License.
+// (See accompanying file LICENSE or copy at
+//  http://opensource.org/licenses/MIT)
+//=======================================================================
+
+#include "api/server_api.hpp"
+#include "api/retirement_api.hpp"
+
+#include "assets.hpp"
+#include "liabilities.hpp"
+#include "accounts.hpp"
+#include "data.hpp"
+#include "data_cache.hpp"
+#include "retirement.hpp"
+
+#include "pages/web_config.hpp"
+
+using namespace budget;
+
+void budget::retirement_countdown_api(const httplib::Request& req, httplib::Response& res) {
+    if (auto fi_expenses = budget::get_fi_expenses()){
+        data_cache cache;
+
+        const auto nw           = get_fi_net_worth(cache);
+        const auto savings_rate = running_savings_rate(cache);
+        const auto income       = running_income(cache);
+
+        const auto currency     = get_default_currency();
+        const auto wrate        = to_number<double>(internal_config_value("withdrawal_rate"));
+        const auto roi          = to_number<double>(internal_config_value("expected_roi"));
+        const auto years        = double(100.0 / wrate);
+        const auto fi_goal         = years * fi_expenses;
+
+        date_type fi_base_months = 0;
+        {
+            auto current_nw = nw;
+            while (current_nw < fi_goal) {
+                current_nw *= 1.0 + (roi / 100.0) / 12;
+                current_nw += (savings_rate * income) / 12;
+
+                ++fi_base_months;
+            }
+        }
+
+        if (nw > fi_goal) {
+            api_success_content(req, res, "You are FI!");
+        } else {
+            // TODO Add days granularity 
+
+            const auto missing_years = unsigned(fi_base_months / 12);
+            const auto missing_months = unsigned(fi_base_months - (missing_years * 12));
+
+            auto result = std::format("{} years, {} months", missing_years, missing_months);
+
+            api_success_content(req, res, result);
+        }
+    } else {
+        api_success_content(req, res, "No expenses");
+    }
+}

src/api/server_api.cpp

@@ -5,8 +5,6 @@
 //  http://opensource.org/licenses/MIT)
 //=======================================================================
 
-#include <set>
-
 #include "api/server_api.hpp"
 #include "api/earnings_api.hpp"
 #include "api/expenses_api.hpp"
@@ -19,6 +17,7 @@
 #include "api/fortunes_api.hpp"
 #include "api/assets_api.hpp"
 #include "api/user_api.hpp"
+#include "api/retirement_api.hpp"
 
 #include "pages/server_pages.hpp"
 
@@ -195,6 +194,8 @@ void budget::load_api(httplib::Server& server) {
     server.Get("/api/assets/delete/", api_wrapper(&delete_assets_api));
     server.Get("/api/assets/list/", api_wrapper(&list_assets_api));
 
+    server.Get("/api/retirement/countdown/", api_wrapper(&retirement_countdown_api));
+
     server.Post("/api/asset_values/add/", api_wrapper(&add_asset_values_api));
     server.Post("/api/asset_values/edit/", api_wrapper(&edit_asset_values_api));
     server.Post("/api/asset_values/batch/", api_wrapper(&batch_asset_values_api));