From eb83d1202a4bdb2dbe76106b188b730c501cb430 Mon Sep 17 00:00:00 2001
From: Jesse Brault <jbrault@mac.com>
Date: Tue, 23 Sep 2025 10:56:11 -0500
Subject: [PATCH] Make polymorphic enum loop build fn.

---
 ast-generator/src/build_fn/mod.rs             |   3 +-
 .../polymorphic_enum_loop_build_fn.rs         | 100 ++++++++++++++++++
 2 files changed, 102 insertions(+), 1 deletion(-)
 create mode 100644 ast-generator/src/build_fn/polymorphic_enum_loop_build_fn.rs

diff --git a/ast-generator/src/build_fn/mod.rs b/ast-generator/src/build_fn/mod.rs
index afbff1f..38f5dc9 100644
--- a/ast-generator/src/build_fn/mod.rs
+++ b/ast-generator/src/build_fn/mod.rs
@@ -1,8 +1,9 @@
 pub mod leaf_enum_build_fn;
 pub mod leaf_struct_build_fn;
-mod node_production_build_fn;
+pub mod node_production_build_fn;
 pub mod polymorphic_build_build_fn;
 pub mod polymorphic_enum_build_fn;
+pub mod polymorphic_enum_loop_build_fn;
 pub mod polymorphic_type_build_fn;
 pub mod production_build_fn;
 pub mod struct_build_fn;
diff --git a/ast-generator/src/build_fn/polymorphic_enum_loop_build_fn.rs b/ast-generator/src/build_fn/polymorphic_enum_loop_build_fn.rs
new file mode 100644
index 0000000..33c781f
--- /dev/null
+++ b/ast-generator/src/build_fn/polymorphic_enum_loop_build_fn.rs
@@ -0,0 +1,100 @@
+use crate::deserialize::util::{make_build_fn_name, make_build_pair};
+use crate::spec::polymorphic_enum_loop_spec::{
+    PolymorphicEnumLoopBuildSpec, PolymorphicEnumLoopRule,
+    PolymorphicEnumLoopRuleBuild, PolymorphicEnumLoopRuleBuildChild,
+    PolymorphicEnumLoopRuleChildOnEach, PolymorphicEnumLoopRulePassThrough,
+};
+use proc_macro2::TokenStream;
+use quote::{format_ident, quote};
+
+fn make_pass_through(pass_through: &PolymorphicEnumLoopRulePassThrough) -> TokenStream {
+    let rule_ident = format_ident!("{}", pass_through.name());
+    let inner_build_fn_ident = format_ident!("{}", pass_through.with());
+    quote! {
+        Rule::#rule_ident => {
+            result = Some(#inner_build_fn_ident(inner_pair))
+        }
+    }
+}
+
+fn make_on_each_child_build(child: &PolymorphicEnumLoopRuleChildOnEach) -> TokenStream {
+    let child_build_fn_ident = format_ident!("{}", make_build_fn_name(child.rule()));
+    quote! {
+        #child_build_fn_ident(inner_pair)
+    }
+}
+
+fn make_build(
+    spec: &PolymorphicEnumLoopBuildSpec,
+    build: &PolymorphicEnumLoopRuleBuild,
+) -> TokenStream {
+    let rule_ident = format_ident!("{}", build.name());
+    let variant_type_ident = format_ident!("{}", build.name());
+    let return_type_ident = format_ident!("{}", spec.kind());
+    let variant_ident = format_ident!("{}", build.variant());
+
+    let on_each_child = build
+        .children()
+        .find(|child| match child {
+            PolymorphicEnumLoopRuleBuildChild::OnEach(_) => true,
+            _ => false,
+        })
+        .map(|child| {
+            match child {
+                PolymorphicEnumLoopRuleBuildChild::OnEach(on_each) => on_each,
+                _ => unreachable!(),
+            }
+        })
+        .unwrap();
+    
+    let build_on_each_child = make_on_each_child_build(on_each_child);
+
+    let child_args = build
+        .children()
+        .map(|child| match child {
+            PolymorphicEnumLoopRuleBuildChild::UseCurrent(_) => {
+                quote! { result.unwrap() }
+            }
+            PolymorphicEnumLoopRuleBuildChild::OnEach(_) => quote! { on_each_child },
+        })
+        .collect::<Vec<_>>();
+
+    quote! {
+        Rule::#rule_ident => {
+            let on_each_child = #build_on_each_child;
+            let built = #variant_type_ident::new(#(#child_args),*);
+            result = Some(#return_type_ident::#variant_ident(built))
+        }
+    }
+}
+
+fn make_match_arm(spec: &PolymorphicEnumLoopBuildSpec, rule: &PolymorphicEnumLoopRule) -> TokenStream {
+    match rule {
+        PolymorphicEnumLoopRule::PassThrough(pass_through) => make_pass_through(pass_through),
+        PolymorphicEnumLoopRule::Build(build) => make_build(spec, build),
+    }
+}
+
+pub fn make_polymorphic_enum_loop_build_fn(spec: &PolymorphicEnumLoopBuildSpec) -> TokenStream {
+    let build_fn_ident = format_ident!("{}", make_build_fn_name(spec.name()));
+    let pair_ident = format_ident!("{}", make_build_pair(spec.name()));
+    let return_type_ident = format_ident!("{}", spec.kind());
+
+    let match_arms = spec
+        .rules()
+        .map(|rule| make_match_arm(spec, rule))
+        .collect::<Vec<_>>();
+
+    quote! {
+        fn #build_fn_ident(#pair_ident: Pair<Rule>) -> #return_type_ident {
+            let mut result: Option<#return_type_ident> = None;
+            for inner_pair in #pair_ident.into_inner() {
+                match inner_pair.as_rule() {
+                    #(#match_arms,)*,
+                    _ => unreachable!()
+                }
+            }
+            result.unwrap()
+        }
+    }
+}