From 45b0df3e0b6bd658f8f30d7d713b409665573f69 Mon Sep 17 00:00:00 2001
From: Dan Paulat <dpaulat@gmail.com>
Date: Mon, 29 May 2023 00:47:47 -0500
Subject: [PATCH] Fix text product start time when first P-VTEC uses
 000000T0000Z

---
 scwx-qt/source/scwx/qt/model/alert_model.cpp  |  3 +-
 .../scwx/awips/text_product_message.hpp       |  9 +-
 .../scwx/awips/text_product_message.cpp       | 83 +++++++++++++++++++
 3 files changed, 90 insertions(+), 5 deletions(-)

diff --git a/scwx-qt/source/scwx/qt/model/alert_model.cpp b/scwx-qt/source/scwx/qt/model/alert_model.cpp
index 8ea4ccc1..793d67b4 100644
--- a/scwx-qt/source/scwx/qt/model/alert_model.cpp
+++ b/scwx-qt/source/scwx/qt/model/alert_model.cpp
@@ -421,8 +421,7 @@ AlertModelImpl::GetStartTime(const types::TextEventKey& key)
    if (messageList.size() > 0)
    {
       auto& firstMessage = messageList.front();
-      auto  firstSegment = firstMessage->segment(0);
-      return firstSegment->header_->vtecString_[0].pVtec_.event_begin();
+      return firstMessage->segment_event_begin(0);
    }
    else
    {
diff --git a/wxdata/include/scwx/awips/text_product_message.hpp b/wxdata/include/scwx/awips/text_product_message.hpp
index ec90f82d..80ba4a16 100644
--- a/wxdata/include/scwx/awips/text_product_message.hpp
+++ b/wxdata/include/scwx/awips/text_product_message.hpp
@@ -91,11 +91,14 @@ public:
    std::shared_ptr<WmoHeader>                  wmo_header() const;
    std::vector<std::string>                    mnd_header() const;
    std::vector<std::string>                    overview_block() const;
-   size_t                                      segment_count() const;
+   std::size_t                                 segment_count() const;
    std::vector<std::shared_ptr<const Segment>> segments() const;
-   std::shared_ptr<const Segment>              segment(size_t s) const;
+   std::shared_ptr<const Segment>              segment(std::size_t s) const;
 
-   size_t data_size() const;
+   std::chrono::system_clock::time_point
+   segment_event_begin(std::size_t s) const;
+
+   std::size_t data_size() const;
 
    bool Parse(std::istream& is) override;
 
diff --git a/wxdata/source/scwx/awips/text_product_message.cpp b/wxdata/source/scwx/awips/text_product_message.cpp
index a27e593d..262ec01a 100644
--- a/wxdata/source/scwx/awips/text_product_message.cpp
+++ b/wxdata/source/scwx/awips/text_product_message.cpp
@@ -1,5 +1,6 @@
 #include <scwx/awips/text_product_message.hpp>
 #include <scwx/common/characters.hpp>
+#include <scwx/util/logger.hpp>
 #include <scwx/util/streams.hpp>
 
 #include <istream>
@@ -15,6 +16,7 @@ namespace awips
 {
 
 static const std::string logPrefix_ = "scwx::awips::text_product_message";
+static const auto        logger_    = scwx::util::Logger::Create(logPrefix_);
 
 // Issuance date/time takes one of the following forms:
 // * <hhmm>_xM_<tz>_day_mon_<dd>_year
@@ -101,6 +103,87 @@ std::shared_ptr<const Segment> TextProductMessage::segment(size_t s) const
    return p->segments_[s];
 }
 
+std::chrono::system_clock::time_point
+TextProductMessage::segment_event_begin(std::size_t s) const
+{
+   std::chrono::system_clock::time_point eventBegin {};
+
+   auto& header = segment(s)->header_;
+   if (header.has_value() && !header->vtecString_.empty())
+   {
+      // Determine event begin from P-VTEC string
+      eventBegin = header->vtecString_[0].pVtec_.event_begin();
+
+      // If event begin is 000000T0000Z
+      if (eventBegin == std::chrono::system_clock::time_point {})
+      {
+         using namespace std::chrono;
+
+         // Determine event end from P-VTEC string
+         system_clock::time_point eventEnd =
+            header->vtecString_[0].pVtec_.event_end();
+
+         auto           endDays = floor<days>(eventEnd);
+         year_month_day endDate {endDays};
+
+         // Determine WMO date/time
+         std::string wmoDateTime = wmo_header()->date_time();
+
+         bool          wmoDateTimeValid = false;
+         unsigned long dayOfMonth       = 0;
+         unsigned long beginHour        = 0;
+         unsigned long beginMinute      = 0;
+
+         try
+         {
+            // WMO date time is in the format DDHHMM
+            dayOfMonth       = std::stoul(wmoDateTime.substr(0, 2));
+            beginHour        = std::stoul(wmoDateTime.substr(2, 2));
+            beginMinute      = std::stoul(wmoDateTime.substr(4, 2));
+            wmoDateTimeValid = true;
+         }
+         catch (const std::exception&)
+         {
+            logger_->warn("Malformed WMO date/time: {}", wmoDateTime);
+         }
+
+         if (wmoDateTimeValid)
+         {
+            // Combine end date year and month with WMO date time
+            eventBegin =
+               sys_days {endDate.year() / endDate.month() / day {dayOfMonth}} +
+               hours {beginHour} + minutes {beginMinute};
+
+            // If the begin date is after the end date, assume the start time
+            // was the previous month
+            if (eventBegin > eventEnd)
+            {
+               // If the current end month is January
+               if (endDate.month() == January)
+               {
+                  // The begin month must be December of last year
+                  eventBegin = sys_days {year {(endDate.year() - 1y).count()} /
+                                         December / day {dayOfMonth}} +
+                               hours {beginHour} + minutes {beginMinute};
+               }
+               else
+               {
+                  // Back up one month
+                  eventBegin =
+                     sys_days {endDate.year() /
+                               month {static_cast<unsigned int>(
+                                  (endDate.month() - month {1}).count())} /
+                               day {dayOfMonth}} +
+                     hours {beginHour} + minutes {beginMinute};
+               }
+            }
+         }
+      }
+   }
+
+   return eventBegin;
+}
+
 size_t TextProductMessage::data_size() const
 {
    return 0;