From 322da6ec57d133009424089563b6f2736ceeabcc Mon Sep 17 00:00:00 2001
From: Lee Kerley <154285602+ld-kerley@users.noreply.github.com>
Date: Wed, 18 Sep 2024 08:24:23 -0700
Subject: [PATCH] Add `parseStructValueString` function (#2019)

Adding a simple function that tokenize a c++ style list initializer string, which will be used to initialize struct values.
---
 source/MaterialXCore/Value.cpp               | 54 ++++++++++++++++++++
 source/MaterialXCore/Value.h                 |  5 ++
 source/MaterialXTest/MaterialXCore/Value.cpp |  9 ++++
 3 files changed, 68 insertions(+)

diff --git a/source/MaterialXCore/Value.cpp b/source/MaterialXCore/Value.cpp
index 3e8c1f4462..68da4b5b9d 100644
--- a/source/MaterialXCore/Value.cpp
+++ b/source/MaterialXCore/Value.cpp
@@ -193,6 +193,60 @@ template <class T> T fromValueString(const string& value)
     return data;
 }
 
+StringVec parseStructValueString(const string& value)
+{
+    static const char SEPARATOR = ';';
+    static const char OPEN_BRACE = '{';
+    static const char CLOSE_BRACE = '}';
+
+    if (value.empty())
+        return StringVec();
+
+    // Validate the string is correctly formatted - must be at least 2 characters long and start and end with braces
+    if (value.size() < 2 || (value[0] != OPEN_BRACE || value[value.size()-1] != CLOSE_BRACE))
+    {
+        return StringVec();
+    }
+
+    StringVec split;
+
+    // Strip off the surrounding braces
+    string substring = value.substr(1, value.size()-2);
+
+    // Sequentially examine each character to parse the list initializer.
+    string part = "";
+    int braceDepth = 0;
+    for (const char c : substring)
+    {
+        if (c == OPEN_BRACE)
+        {
+            // We've already trimmed the starting brace, so any additional braces indicate members that are themselves list initializers.
+            // We will just return this as a string of the list initializer.
+            braceDepth += 1;
+        }
+        if (braceDepth > 0 && c == CLOSE_BRACE)
+        {
+            braceDepth -= 1;
+        }
+
+        if (braceDepth == 0 && c == SEPARATOR)
+        {
+            // When we hit a separator we store the currently accumulated part, and clear to start collecting the next.
+            split.emplace_back(part);
+            part = "";
+        }
+        else
+        {
+            part += c;
+        }
+    }
+
+    if (!part.empty())
+        split.emplace_back(part);
+
+    return split;
+}
+
 //
 // TypedValue methods
 //
diff --git a/source/MaterialXCore/Value.h b/source/MaterialXCore/Value.h
index 1bd29b1d2b..764a0ccc01 100644
--- a/source/MaterialXCore/Value.h
+++ b/source/MaterialXCore/Value.h
@@ -216,6 +216,11 @@ template <class T> MX_CORE_API string toValueString(const T& data);
 /// @throws ExceptionTypeError if the conversion cannot be performed.
 template <class T> MX_CORE_API T fromValueString(const string& value);
 
+/// Tokenize the string representation of a struct value i.e, "{1;2;3}" into a
+/// vector of substrings.
+/// Note: "{1;2;{3;4;5}}" will be split in to ["1", "2", "{3;4;5}"]
+MX_CORE_API StringVec parseStructValueString(const string& value);
+
 /// Forward declaration of specific template instantiations.
 /// Base types
 MX_CORE_EXTERN_TEMPLATE(TypedValue<int>);
diff --git a/source/MaterialXTest/MaterialXCore/Value.cpp b/source/MaterialXTest/MaterialXCore/Value.cpp
index 40d6b120e7..31c333d211 100644
--- a/source/MaterialXTest/MaterialXCore/Value.cpp
+++ b/source/MaterialXTest/MaterialXCore/Value.cpp
@@ -78,6 +78,15 @@ TEST_CASE("Value strings", "[value]")
     REQUIRE_THROWS_AS(mx::fromValueString<float>("text"), mx::ExceptionTypeError);
     REQUIRE_THROWS_AS(mx::fromValueString<bool>("1"), mx::ExceptionTypeError);
     REQUIRE_THROWS_AS(mx::fromValueString<mx::Color3>("1"), mx::ExceptionTypeError);
+
+    // Parse value strings using structure syntax features.
+    REQUIRE(mx::parseStructValueString("{{1;2;3};4}") == (std::vector<std::string>{"{1;2;3}","4"}));
+    REQUIRE(mx::parseStructValueString("{1;2;3;4}") == (std::vector<std::string>{"1","2","3","4"}));
+    REQUIRE(mx::parseStructValueString("{1;{2;3};4}") == (std::vector<std::string>{"1","{2;3}","4"}));
+    REQUIRE(mx::parseStructValueString("{1;{2;3;4}}") == (std::vector<std::string>{"1","{2;3;4}"}));
+    REQUIRE(mx::parseStructValueString("{1;{2;{3;4}}}") == (std::vector<std::string>{"1","{2;{3;4}}"}));
+    REQUIRE(mx::parseStructValueString("{1;2;{3};4}") == (std::vector<std::string>{"1","2","{3}","4"}));
+    REQUIRE(mx::parseStructValueString("{1;2;{3};4}") == (std::vector<std::string>{"1","2","{3}","4"}));
 }
 
 TEST_CASE("Typed values", "[value]")