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/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

//! Macros for `uniffi`.
//!
//! Currently this is just for easily generating integration tests, but maybe
//! we'll put some other code-annotation helper macros in here at some point.

use quote::{format_ident, quote};
use std::env;
use std::path::PathBuf;
use syn::{bracketed, punctuated::Punctuated, LitStr, Token};

/// A macro to build testcases for a component's generated bindings.
///
/// This macro provides some plumbing to write automated tests for the generated
/// foreign language bindings of a component. As a component author, you can write
/// script files in the target foreign language(s) that exercise you component API,
/// and then call this macro to produce a `cargo test` testcase from each one.
/// The generated code will execute your script file with appropriate configuration and
/// environment to let it load the component bindings, and will pass iff the script
/// exits successfully.
///
/// To use it, invoke the macro with the udl file as the first argument, then
/// one or more file paths relative to the crate root directory.
/// It will produce one `#[test]` function per file, in a manner designed to
/// play nicely with `cargo test` and its test filtering options.
#[proc_macro]
pub fn build_foreign_language_testcases(paths: proc_macro::TokenStream) -> proc_macro::TokenStream {
    let paths = syn::parse_macro_input!(paths as FilePaths);
    // We resolve each path relative to the crate root directory.
    let pkg_dir = env::var("CARGO_MANIFEST_DIR")
        .expect("Missing $CARGO_MANIFEST_DIR, cannot build tests for generated bindings");
    // For each file found, generate a matching testcase.
    let udl_file = &paths.udl_file;
    let test_functions = paths.test_scripts
        .iter()
        .map(|file_path| {
            let test_file_pathbuf: PathBuf = [&pkg_dir, &file_path].iter().collect();
            let test_file_path = test_file_pathbuf.to_string_lossy();
            let test_file_name = test_file_pathbuf
                .file_name()
                .expect("Test file has no name, cannot build tests for generated bindings")
                .to_string_lossy();
            let test_name = format_ident!(
                "uniffi_foreign_language_testcase_{}",
                test_file_name.replace(|c: char| !c.is_alphanumeric(), "_")
            );
            quote! {
                #[test]
                fn #test_name () -> uniffi::deps::anyhow::Result<()> {
                    uniffi::testing::run_foreign_language_testcase(#pkg_dir, #udl_file, #test_file_path)
                }
            }
        })
        .collect::<Vec<proc_macro2::TokenStream>>();
    let test_module = quote! {
        #(#test_functions)*
    };
    proc_macro::TokenStream::from(test_module)
}

/// Newtype to simplifying parsing a list of file paths from macro input.
#[derive(Debug)]
struct FilePaths {
    udl_file: String,
    test_scripts: Vec<String>,
}

impl syn::parse::Parse for FilePaths {
    fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
        let udl_file: LitStr = input.parse()?;
        let _comma: Token![,] = input.parse()?;
        let array_contents;
        bracketed!(array_contents in input);
        let test_scripts = Punctuated::<LitStr, Token![,]>::parse_terminated(&array_contents)?
            .iter()
            .map(|s| s.value())
            .collect();
        Ok(FilePaths {
            udl_file: udl_file.value(),
            test_scripts,
        })
    }
}