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//! [![crates.io version](https://img.shields.io/crates/v/safina-async-test-core.svg)](https://crates.io/crates/safina-async-test-core)
//! [![license: Apache 2.0](https://gitlab.com/leonhard-llc/safina-rs/-/raw/main/license-apache-2.0.svg)](http://www.apache.org/licenses/LICENSE-2.0)
//! [![unsafe forbidden](https://gitlab.com/leonhard-llc/safina-rs/-/raw/main/unsafe-forbidden-success.svg)](https://github.com/rust-secure-code/safety-dance/)
//! [![pipeline status](https://gitlab.com/leonhard-llc/safina-rs/badges/main/pipeline.svg)](https://gitlab.com/leonhard-llc/safina-rs/-/pipelines)
//!
//! Procedural macro for the [`safina-async-test`](https://crates.io/crates/safina-async-test)
//! package
//!
//! ## Changelog
//! - v0.1.1 - Fix paths.
//! - v0.1.0 - Initial version
//!
//! ## Happy Contributors 🙂
//! Fixing bugs and adding features is easy and fast.
//! Send us a pull request and we intend to:
//! - Always respond within 24 hours
//! - Provide clear & concrete feedback
//! - Immediately make a new release for your accepted change
//!
//! # Release Process
//! 1. Edit `Cargo.toml` and bump version number.
//! 1. Run `./release.sh`
#![forbid(unsafe_code)]

use proc_macro2::{Ident, TokenStream, TokenTree};
use quote::quote_spanned;

#[proc_macro_attribute]
pub fn async_test(
    attr: proc_macro::TokenStream,
    item: proc_macro::TokenStream,
) -> proc_macro::TokenStream {
    let mut result = proc_macro::TokenStream::from(impl_async_test(
        proc_macro2::TokenStream::from(attr),
        proc_macro2::TokenStream::from(item.clone()),
    ));
    result.extend(item);

    // let mut token_stream_string = String::new();
    // for tree in result {
    //     token_stream_string.push_str(format!("tree: {:?}\n", tree).as_str());
    // }
    // panic!("TokenStream:\n{}", token_stream_string);

    result
}

fn impl_async_test(attr: TokenStream, item: TokenStream) -> TokenStream {
    if let Some(tree) = attr.into_iter().next() {
        return quote_spanned!(tree.span()=>compile_error!("parameters not allowed"););
    }
    // Ident { ident: "async", span: #0 bytes(50..55) }
    // Ident { ident: "fn", span: #0 bytes(56..58) }
    // Ident { ident: "should_run_async_fn", span: #0 bytes(59..78) }
    // Group { delimiter: Parenthesis, stream: TokenStream [], span: ...
    // Group { delimiter: Brace, stream: TokenStream [Ident { ident: "println",...
    let mut trees = item.into_iter();
    let first = trees.next();
    if let (
        Some(TokenTree::Ident(ref ident_async)),
        Some(TokenTree::Ident(ref ident_fn)),
        Some(TokenTree::Ident(ref ident_name)),
    ) = (&first, trees.next(), trees.next())
    {
        if *ident_async == "async" && *ident_fn == "fn" {
            let async_name = ident_name.to_string() + "_";
            let ident_async_name = Ident::new(&async_name, ident_name.span());
            return quote_spanned!(ident_name.span()=>
                #[test]
                pub fn #ident_async_name () {
                    safina_async_test::start_timer_thread();
                    safina_async_test::Executor::new(2, 1).block_on( #ident_name ())
                }
            );
        }
    }
    if let Some(tree) = first {
        return quote_spanned!(tree.span()=>compile_error!("expected async fn"););
    }
    panic!("expected async fn");
}

// The version below has two drawbacks:
// 1. IDEs don't know that the stuff inside `async_test! { async fn test1() { ... } }` is a
//    function, so they don't provide formatting, auto-complete, or other useful editor functions.
//    This is a fatal flaw.
// 2. It puts the test in a module with the same name as the test function,
//    and a test function named `async_test`.
//    So for `async_test! { async fn test1() {...} }` below, it makes
//    `mod test1 { #[test] fn async_test() {...} }`.
//    This makes IDE test output more verbose.  Each test appears as its own category.
//
// macro_rules! async_test {
//     (async fn $name:ident () $body:block) => {
//         async fn $name() $body
//
//         mod $name {
//             #[test]
//             fn async_test () {
//                 safina_executor::block_on(super::$name())
//             }
//         }
//     }
// }
//
// async_test! {
// async fn test1() {
//     println!("test1");
// }
// }

// The version below requires the user to keep the two names in sync.
// Also, the error messages are not great.
//
// macro_rules! async_test {
//     ($name:ident) => {
//         mod $name {
//             #[test]
//             fn async_test () {
//                 safina_executor::block_on(super::$name())
//             }
//         }
//     }
// }
//
// async_test!(test1);
// async fn test1() {
//     println!("test1");
// }
//
// async_test!(test1); // error[E0428]: the name `test1` is defined multiple times
// async fn test2() {
//     println!("test2");
// }
//
// async_test!(test3); // error[E0423]: expected function, found module `super::test3`
// async fn test4() {
//     println!("test4");
// }