1 files changed, 131 insertions, 0 deletions
diff --git a/azalea-registry/registry-macros/src/lib.rs b/azalea-registry/registry-macros/src/lib.rs
new file mode 100644
index 00000000..fef698f5
--- /dev/null
+++ b/azalea-registry/registry-macros/src/lib.rs
@@ -0,0 +1,131 @@
+use proc_macro::TokenStream;
+use quote::quote;
+use syn::{
+    self, braced,
+    parse::{Parse, ParseStream, Result},
+    parse_macro_input,
+    punctuated::Punctuated,
+    Ident, LitStr, Token,
+};
+
+struct RegistryItem {
+    name: Ident,
+    id: String,
+}
+
+struct Registry {
+    name: Ident,
+    items: Vec<RegistryItem>,
+}
+
+impl Parse for RegistryItem {
+    // Air => "minecraft:air"
+    fn parse(input: ParseStream) -> Result<Self> {
+        let name = input.parse()?;
+        input.parse::<Token![=>]>()?;
+        let id = input.parse::<LitStr>()?.value();
+        Ok(RegistryItem { name, id })
+    }
+}
+
+impl Parse for Registry {
+    fn parse(input: ParseStream) -> Result<Self> {
+        // Block, {
+        //     Air => "minecraft:air",
+        //     Stone => "minecraft:stone"
+        // }
+        let name = input.parse()?;
+        let _ = input.parse::<Token![,]>()?;
+        let content;
+        braced!(content in input);
+        let items: Punctuated<RegistryItem, Token![,]> =
+            content.parse_terminated(RegistryItem::parse)?;
+
+        Ok(Registry {
+            name,
+            items: items.into_iter().collect(),
+        })
+    }
+}
+
+#[proc_macro]
+pub fn registry(input: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(input as Registry);
+    let name = input.name;
+    let mut generated = quote! {};
+
+    // enum Block {
+    //     Air = 0,
+    //     Stone,
+    // }
+    let mut enum_items = quote! {};
+    for (i, item) in input.items.iter().enumerate() {
+        let name = &item.name;
+        let protocol_id = i as u32;
+        enum_items.extend(quote! {
+            #name = #protocol_id,
+        });
+    }
+    generated.extend(quote! {
+        #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+        #[repr(u32)]
+        pub enum #name {
+            #enum_items
+        }
+    });
+
+    let max_id = input.items.len() as u32;
+    generated.extend(quote! {
+        impl #name {
+            /// Transmutes a u32 to a #name.
+            ///
+            /// # Safety
+            /// The `id` should be at most #max_id.
+            #[inline]
+            pub unsafe fn from_u32_unchecked(id: u32) -> Self {
+                std::mem::transmute::<u32, #name>(id)
+            }
+
+            #[inline]
+            pub fn is_valid_id(id: u32) -> bool {
+                id <= #max_id
+            }
+        }
+    });
+
+    generated.extend(quote! {
+        impl TryFrom<u32> for #name {
+            type Error = ();
+
+            /// Safely converts a state id to a block state.
+            fn try_from(id: u32) -> Result<Self, Self::Error> {
+                if Self::is_valid_id(id) {
+                    Ok(unsafe { Self::from_u32_unchecked(id) })
+                } else {
+                    Err(())
+                }
+            }
+        }
+    });
+
+    // Display that uses registry ids
+    let mut display_items = quote! {};
+    for item in input.items.iter() {
+        let name = &item.name;
+        let id = &item.id;
+        display_items.extend(quote! {
+            Self::#name => write!(f, #id),
+        });
+    }
+    generated.extend(quote! {
+        impl std::fmt::Display for #name {
+            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+                match self {
+                    #display_items
+                }
+            }
+        }
+    });
+
+    generated.into()
+}