mod maud;

use concat_string::concat_string;
use proc_macro::TokenStream;
use proc_macro_error::proc_macro_error;
use quote::{quote, quote_spanned, ToTokens};
use syn::{parse_macro_input, parse_str, ItemFn};

#[proc_macro]
#[proc_macro_error]
pub fn html(input: TokenStream) -> TokenStream {
    maud::expand(input.into()).into()
}

#[proc_macro_attribute]
pub fn fn_builder(_attr: TokenStream, item: TokenStream) -> TokenStream {
    let fn_item = parse_macro_input!(item as ItemFn);
    let fn_name = fn_item.sig.ident.to_string();

    if !fn_name.starts_with("alter_") {
        let expanded = quote_spanned! {
            fn_item.sig.ident.span() =>
                compile_error!("expected a \"pub fn alter_...() -> &mut Self\" method");
        };
        return expanded.into();
    }

    let args: Vec<String> = fn_item
        .sig
        .inputs
        .iter()
        .skip(1)
        .map(|arg| arg.to_token_stream().to_string())
        .collect();

    let param: Vec<String> = args
        .iter()
        .map(|arg| arg.split_whitespace().next().unwrap().to_string())
        .collect();

    #[rustfmt::skip]
    let fn_with = parse_str::<ItemFn>(concat_string!("
        pub fn ", fn_name.replace("alter_", "with_"), "(mut self, ", args.join(", "), ") -> Self {
            self.", fn_name, "(", param.join(", "), ");
            self
        }
    ").as_str()).unwrap();

    let fn_alter = fn_item.into_token_stream();

    let expanded = quote! {
        #fn_with
        #fn_alter
    };
    expanded.into()
}

/// Marks async main function as the PageTop entry-point.
///
/// # Examples
/// ```
/// #[pagetop::main]
/// async fn main() {
///     async { println!("Hello world"); }.await
/// }
/// ```
#[proc_macro_attribute]
pub fn main(_: TokenStream, item: TokenStream) -> TokenStream {
    let mut output: TokenStream = (quote! {
        #[::pagetop::service::rt::main(system = "::pagetop::service::rt::System")]
    })
    .into();

    output.extend(item);
    output
}

/// Marks async test functions to use the PageTop entry-point.
///
/// # Examples
/// ```
/// #[pagetop::test]
/// async fn test() {
///     assert_eq!(async { "Hello world" }.await, "Hello world");
/// }
/// ```
#[proc_macro_attribute]
pub fn test(_: TokenStream, item: TokenStream) -> TokenStream {
    let mut output: TokenStream = (quote! {
        #[::pagetop::service::rt::test(system = "::pagetop::service::rt::System")]
    })
    .into();

    output.extend(item);
    output
}