From 69bf156eb0a8523f64a8f90a3a183d7901be86d6 Mon Sep 17 00:00:00 2001
From: Christopher Lam <christopher.lck@gmail.com>
Date: Sun, 8 Sep 2024 22:52:35 +0800
Subject: [PATCH] [gnc-datetime] add boost UK/US/ISO date parsers

Thus "30 Sep 2024" and "30 September 2024" are accepted.
But ICU's "30 Sept 2024" is rightfully rejected.
---
 libgnucash/engine/gnc-datetime.cpp | 13 +++++++++++--
 libgnucash/engine/gnc-datetime.hpp |  9 +++++++++
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/libgnucash/engine/gnc-datetime.cpp b/libgnucash/engine/gnc-datetime.cpp
index 308ec24e4ef..e5d6cc789d1 100644
--- a/libgnucash/engine/gnc-datetime.cpp
+++ b/libgnucash/engine/gnc-datetime.cpp
@@ -77,13 +77,16 @@ static constexpr auto ticks_per_second = INT64_C(1000000);
 static constexpr auto ticks_per_second = INT64_C(1000000000);
 #endif
 
-/* Vector of date formats understood by gnucash and corresponding regex
- * to parse each from an external source
+/* Vector of date formats understood by gnucash and corresponding
+ * boost string->date or regex to parse each from an external source
  * Note: while the format names are using a "-" as separator, the
  * regexes will accept any of "-/.' " and will also work for dates
  * without separators.
  */
 const std::vector<GncDateFormat> GncDate::c_formats ({
+    GncDateFormat { N_("UK date"), boost::gregorian::from_uk_string },
+    GncDateFormat { N_("US date"), boost::gregorian::from_us_string },
+    GncDateFormat { N_("ISO date"), boost::gregorian::from_string },
     GncDateFormat {
         N_("y-m-d"),
         "(?:"                                   // either y-m-d
@@ -617,6 +620,12 @@ GncDateImpl::GncDateImpl(const std::string str, const std::string fmt) :
     if (iter == GncDate::c_formats.cend())
         throw std::invalid_argument(N_("Unknown date format specifier passed as argument."));
 
+    if (iter->m_str_to_date)
+    {
+        m_greg = (*iter->m_str_to_date)(str);
+        return;
+    }
+
     boost::regex r(iter->m_re);
     boost::smatch what;
     if(!boost::regex_search(str, what, r))  // regex didn't find a match
diff --git a/libgnucash/engine/gnc-datetime.hpp b/libgnucash/engine/gnc-datetime.hpp
index 77a6039b10a..677fdd59a3a 100644
--- a/libgnucash/engine/gnc-datetime.hpp
+++ b/libgnucash/engine/gnc-datetime.hpp
@@ -29,6 +29,10 @@
 #include <memory>
 #include <string>
 #include <vector>
+#include <functional>
+#include <optional>
+
+#include <boost/date_time/gregorian/gregorian.hpp>
 
 typedef struct
 {
@@ -172,6 +176,8 @@ class GncDateTime
  * GncDate::c_formats class variable and work with those.
  */
 
+using StringToDate = std::function<boost::gregorian::date(const std::string&)>;
+
 class GncDateFormat
 {
 public:
@@ -182,6 +188,8 @@ class GncDateFormat
      */
     GncDateFormat (const char* fmt, const char* re) :
     m_fmt(fmt), m_re(re) {}
+    GncDateFormat (const char* fmt, StringToDate str_to_date) :
+        m_fmt(fmt), m_str_to_date(str_to_date) {}
     /** A string representing the format. */
     const std::string m_fmt;
 private:
@@ -189,6 +197,7 @@ class GncDateFormat
      * only be used internally by the gnc-datetime code.
      */
     const std::string m_re;
+    std::optional<StringToDate> m_str_to_date;
 
     friend class GncDateImpl;
 };