parse semantic DLL version in Advisor Lua script

This allows to not show the advisor message if only the patch level is
higher than expected. For example:

- expected version: 1.2.0
- installed version: 1.2.3

This allows to release patches for the DLL without necessarily having to publish a new Lua script at the same time.
(Regardless, the Lua script should be updated with the following proper NAM release to ensure DLL versions without the patch are rejected, from then on.)

(Also increments the expected DLL version to 1.2.3.)

Author: memo33

lua/adv_nam_dll.lua

@@ -3,12 +3,32 @@
 -- This file defines advisor messages related to the NAM DLL.
 
 -- Note that this Lua file is not intended for distribution with the DLL itself, but for distribution with the NAM DBPF files to ensure compatibility between NAM and DLL.
-nam_dll_version_expected = "1.2.0"  -- needs to be updated whenever a new DLL version is released
+nam_dll_version_expected = "1.2.3"  -- needs to be updated whenever a new DLL version is released
 
--- (When this script is first executed, the `nam_dll_version` is still `nil`, but it gets defined before the trigger conditions are evaluated.)
+local _cached_result = nil
 function is_nam_dll_correct()
+    -- (When this script is first executed, the `nam_dll_version` is still `nil`, but it gets defined before the trigger conditions are evaluated.)
     local version = rawget(globals(), "nam_dll_version")
-    return version ~= nil and version == nam_dll_version_expected
+    if (version == nil) then
+        return false
+    elseif (_cached_result ~= nil) then
+        return _cached_result
+    else
+        if (version == nam_dll_version_expected) then
+            _cached_result = true
+        else
+            -- check semantic versions to allow a patch level higher than expected by this Lua script
+            local semver_pattern = "^(%d+%.%d+)%.(%d+)"
+            local i, _, v12, v3 = string.find(version, semver_pattern)
+            local j, _, e12, e3 = string.find(nam_dll_version_expected, semver_pattern)
+            if (i == nil or j == nil) then
+                _cached_result = false
+            else
+                _cached_result = (v12 == e12 and tonumber(v3) >= tonumber(e3))
+            end
+        end
+        return _cached_result
+    end
 end
 
 ------------ Advice record ----