Initial commit

.gitignore

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+/target
+/Cargo.lock

Cargo.toml

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+[workspace]
+members = [
+	"seed_router",
+	"seed_router_derive",
+]

seed_router/Cargo.toml

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+[package]
+name = "seed_router"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+seed = "*"
+
+[dependencies.seed_router_derive]
+path = "../seed_router_derive"

seed_router/src/lib.rs

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+use seed::prelude::{Node, Orders, Url};
+
+pub use seed_router_derive::Router;
+
+pub trait Page {
+    type Msg: 'static;
+    fn new(orders: &mut impl Orders<Self::Msg>) -> Self;
+    fn update(&mut self, msg: Self::Msg, orders: &mut impl Orders<Self::Msg>);
+    fn view(&self) -> Node<Self::Msg>;
+}
+
+pub trait Router: Sized {
+    type Msg: 'static;
+    fn from_url(url: Url, orders: &mut impl Orders<Self::Msg>) -> Option<Self>;
+    fn update(&mut self, msg: Self::Msg, orders: &mut impl Orders<Self::Msg>);
+    fn view(&self) -> Node<Self::Msg>;
+}
+
+pub const fn assert_impl_page(_: &impl Page) {}

seed_router_derive/Cargo.toml

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+[package]
+name = "seed_router_derive"
+version = "0.1.0"
+authors = ["Joakim Hulthe <joakim@hulthe.net>"]
+edition = "2021"
+
+[lib]
+proc_macro = true
+
+[dependencies]
+proc-macro2 = "1"
+quote = "1"
+regex = "1"
+serde = "1"
+seed = "*"
+
+[dependencies.syn]
+version = "1"
+features = ["derive", "parsing", "extra-traits"]

seed_router_derive/src/lib.rs

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+use proc_macro2::{Span, TokenStream};
+use quote::{quote, quote_spanned};
+use syn::{
+    parse_macro_input, spanned::Spanned, Data, DeriveInput, Error, Ident, Lit, Meta, NestedMeta,
+};
+
+#[proc_macro_derive(Router, attributes(page))]
+pub fn derive_router(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    let input = parse_macro_input!(input as DeriveInput);
+    match inner_derive_router(input) {
+        Ok(tokens) => tokens.into(),
+        Err(e) => e.into_compile_error().into(),
+    }
+}
+
+fn inner_derive_router(input: DeriveInput) -> syn::Result<TokenStream> {
+    let ident = input.ident;
+    let data = match input.data {
+        Data::Enum(data) => data,
+        Data::Struct(_) => panic!("Struct not supported"),
+        Data::Union(_) => panic!("Union not supported"),
+    };
+
+    let mut pages = vec![];
+
+    // TODO
+    let msg_type = Ident::new("PageMsg", Span::call_site());
+
+    // parse enum
+    let page_attribute = Ident::new("page", Span::call_site());
+    for punct in data.variants.into_iter() {
+        assert!(
+            punct.discriminant.is_none(),
+            "Enum discriminant not supported"
+        );
+
+        let ident = punct.ident;
+        let fields = punct.fields;
+        let attributes = punct.attrs;
+        let page_attribute = attributes
+            .iter()
+            .map(|attribute| attribute.parse_meta().expect("expected a string literatl"))
+            .filter_map(|meta| match meta {
+                Meta::Path(_) | Meta::NameValue(_) => None,
+                Meta::List(meta_list) => Some(meta_list),
+            })
+            .find(|meta_list| meta_list.path.is_ident(&page_attribute))
+            .ok_or_else(|| Error::new(ident.span(), "Missing \"page\" attribute"))?;
+
+        let mut page_attribute_values = page_attribute.nested.iter();
+        let page_location = match page_attribute_values.next() {
+            Some(NestedMeta::Lit(Lit::Str(literal))) => literal.value(),
+            Some(NestedMeta::Lit(literal)) => {
+                return Err(Error::new(literal.span(), "Expected string literal"))
+            }
+            Some(NestedMeta::Meta(meta)) => {
+                return Err(Error::new(meta.span(), "Expected string literal"))
+            }
+            None => {
+                return Err(Error::new(
+                    page_attribute.span(),
+                    "Missing attribute value: location",
+                ))
+            }
+        };
+
+        let msg_type = match page_attribute_values.next() {
+            Some(NestedMeta::Meta(Meta::Path(path))) => path
+                .get_ident()
+                .cloned()
+                .ok_or_else(|| Error::new(path.span(), "Expected Identifier"))?,
+            Some(NestedMeta::Meta(meta)) => {
+                return Err(Error::new(meta.span(), "Expected identifier"))
+            }
+            Some(NestedMeta::Lit(literal)) => {
+                return Err(Error::new(literal.span(), "Expected identifier"))
+            }
+            None => {
+                return Err(Error::new(
+                    page_attribute.span(),
+                    "Missing attribute value: Message Type",
+                ))
+            }
+        };
+
+        pages.push((ident, page_location, msg_type));
+    }
+
+    // generate implementation
+    let from_url_match_arms: TokenStream = pages
+        .iter()
+        .map(|(variant, page_location, msg_variant)| {
+            quote_spanned! { variant.span() =>
+                [#page_location] => {
+                    let mut orders = orders.proxy(#msg_type::#msg_variant);
+                    Some(Self::#variant(::seed_router::Page::new(&mut orders)))
+                }
+            }
+        })
+        .collect();
+
+    let update_match_arms: TokenStream = pages
+        .iter()
+        .map(|(variant, _page_location, msg_variant)| {
+            quote_spanned! { variant.span() =>
+                Self::#variant(page) => {
+                    ::seed_router::assert_impl_page(page);
+                    if let #msg_type::#msg_variant(msg) = msg {
+                        let mut orders = orders.proxy(#msg_type::#msg_variant);
+                        page.update(msg, &mut orders);
+                    }
+                }
+            }
+        })
+        .collect();
+
+    let view_match_arms: TokenStream = pages
+        .iter()
+        .map(|(variant, _page_location, msg_variant)| {
+            quote_spanned! { variant.span() =>
+                Self::#variant(page) => page.view().map_msg(#msg_type::#msg_variant),
+            }
+        })
+        .collect();
+
+    let output = quote! {
+        impl ::seed_router::Router for #ident {
+            type Msg = #msg_type;
+
+            fn from_url(
+                mut url: ::seed::prelude::Url,
+                orders: &mut impl ::seed::prelude::Orders<Self::Msg>,
+            ) -> Option<Self> {
+                use ::seed_router::Page as _;
+                match url.remaining_path_parts().as_slice() {
+                    #from_url_match_arms
+                    _ => None,
+                }
+            }
+
+            fn update(&mut self, msg: Self::Msg, orders: &mut impl ::seed::prelude::Orders<Self::Msg>) {
+                use ::seed_router::Page as _;
+                match self {
+                    #update_match_arms
+                }
+            }
+
+            fn view(&self) -> ::seed::prelude::Node<Self::Msg> {
+                use ::seed_router::Page as _;
+                match self {
+                    #view_match_arms
+                }
+            }
+        }
+    };
+
+    Ok(output)
+}