First commit

src/lib.rs

@@ -0,0 +1,97 @@
+extern crate proc_macro;
+use paste::paste;
+use proc_macro::TokenStream;
+use quote::quote;
+use syn::parse::{Parse, ParseStream, Result};
+use syn::punctuated::Punctuated;
+use syn::{Expr, Ident, Token, parse_macro_input};
+
+macro_rules! generate_headings {
+    ($($v:expr),*) => {
+        $(
+            paste! {
+                #[proc_macro]
+                pub fn [<heading$v>](item: TokenStream) -> TokenStream {
+                    heading(stringify!($v), item)
+                }
+            }
+        )*
+    };
+}
+
+generate_headings!(1, 2, 3, 4, 5, 6);
+
+struct Property {
+    name: Ident,
+    value: Expr,
+}
+
+impl Parse for Property {
+    fn parse(input: ParseStream) -> Result<Self> {
+        let name: Ident = input.parse()?;
+        input.parse::<Token![=]>()?;
+        let value: Expr = input.parse()?;
+        Ok(Property { name, value })
+    }
+}
+
+struct Argument {
+    value: Option<Ident>,
+}
+
+impl Parse for Argument {
+    fn parse(input: ParseStream) -> Result<Self> {
+        let value: Option<Ident> =
+            if input.peek(Ident) && input.peek2(Token![:]) && !input.peek3(Token![:]) {
+                let val = input.parse()?;
+                input.parse::<Token![:]>()?;
+                val
+            } else {
+                None
+            };
+        Ok(Argument { value })
+    }
+}
+
+struct BaseElement {
+    value: Expr,
+    params: Punctuated<Property, Token![,]>,
+}
+
+impl Parse for BaseElement {
+    fn parse(input: ParseStream) -> Result<Self> {
+        let value: Expr = input.parse()?;
+        let _ = input.parse::<Token![,]>();
+        let params: Punctuated<Property, Token![,]> = Punctuated::parse_terminated(input)?;
+        Ok(BaseElement { value, params })
+    }
+}
+
+fn heading(level: &str, item: TokenStream) -> TokenStream {
+    let BaseElement { value, params } = parse_macro_input!(item as BaseElement);
+
+    let expanded = match params.is_empty() {
+        false => {
+            let mut values = Vec::new();
+
+            let formated_names = params
+                .iter()
+                .map(|x| format!("{}=\"{{}}\"", x.name))
+                .collect::<Vec<String>>()
+                .join(" ");
+
+            let format_string = format!("<h{} {formated_names}>{{}}</h{}>", level, level);
+
+            for property in params {
+                values.push(property.value);
+            }
+
+            quote!(format!(#format_string, #(#values), *, #value))
+        }
+        true => {
+            let format_string = format!("<h{}>{{}}</h{}>", level, level);
+            quote!(format!(#format_string, #value))
+        }
+    };
+    TokenStream::from(expanded)
+}