From 8a5064813881cfc286f39942627c02ae4f9bfc53 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jon=20B=C3=B6rjesson?= <jon@spuun.se>
Date: Tue, 17 Dec 2024 08:01:37 +0100
Subject: [PATCH] Explain macro

---
 src/lavinmq/metadata.cr | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/src/lavinmq/metadata.cr b/src/lavinmq/metadata.cr
index fcaad276e9..171f3cbcc1 100644
--- a/src/lavinmq/metadata.cr
+++ b/src/lavinmq/metadata.cr
@@ -84,6 +84,31 @@ module LavinMQ
     end
 
     private def fetch(path : Symbol | String, &default : -> Value)
+      # The macto will generate a case statement that matches "paths" to values in
+      # the wrapped namedtuple structure.
+      # For NamedTupleMetaData.new({a: {b: 1, c: "foo"}}) the generated
+      # statement will look like:
+      #
+      # case path
+      # when "a", :"a"
+      #   if value = @data[:a]
+      #     return Value.new(value)
+      #   end
+      #   return Value.nil
+      # when "a.b", :"a.b"
+      #   if value = @data[:a][:b]
+      #     return Value.new(value)
+      #   end
+      #   return Value.nil
+      # when "a.b.c", :"a.b.c"
+      #   if value = @data[:a][:b][:c]
+      #     return Value.new(value)
+      #   end
+      #   return Value.nil
+      # else
+      #   yield
+      # end
+      #
       {% begin %}
         {%
           paths = [] of Array(String)