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// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

#![recursion_limit = "128"]

extern crate proc_macro;

use proc_macro::TokenStream;
use quote::{quote, ToTokens};
use syn::parse_macro_input;
use syn::spanned::Spanned;

/// Attribute to declare the init function of a plugin
/// ``` no_run
/// #[plugin_init]
/// fn plugin_init() -> Result<()> {}
/// ```
#[proc_macro_attribute]
pub fn plugin_init(_args: TokenStream, input: TokenStream) -> TokenStream {
    let f = parse_macro_input!(input as syn::ItemFn);
    let f_vis = &f.vis;
    let f_block = &f.block;
    let f_sig = &f.sig;
    let f_inputs = &f_sig.inputs;

    // check the function signature
    let valid_signature = f_sig.constness.is_none()
        && match f_vis {
            syn::Visibility::Inherited => true,
            _ => false,
        }
        && f_sig.abi.is_none()
        && f_inputs.len() == 0
        && f_sig.generics.where_clause.is_none()
        && f_sig.variadic.is_none()
        && check_return_type(&f);

    if !valid_signature {
        return syn::parse::Error::new(
            f.span(),
            "`#[plugin_init]` function must have signature `fn() -> optee_teec::Result<()>`",
        )
        .to_compile_error()
        .into();
    }

    quote!(
        pub fn _plugin_init() -> optee_teec::raw::TEEC_Result {
            fn inner() -> optee_teec::Result<()> {
                #f_block
            }
            match inner() {
                Ok(()) => optee_teec::raw::TEEC_SUCCESS,
                Err(err) => err.raw_code(),
            }
        }
    )
    .into()
}

// check if return_type of the function is `optee_teec::Result<()>`
fn check_return_type(item_fn: &syn::ItemFn) -> bool {
    if let syn::ReturnType::Type(_, return_type) = item_fn.sig.output.to_owned() {
        if let syn::Type::Path(path) = return_type.as_ref() {
            let expected_type = quote! { optee_teec::Result<()> };
            let actual_type = path.path.to_token_stream();
            if expected_type.to_string() == actual_type.to_string() {
                return true;
            }
        }
    }
    return false;
}

/// Attribute to declare the invoke function of a plugin
/// ``` no_run
/// #[plugin_invoke]
/// fn plugin_invoke(params: &mut PluginParameters) {}
/// ```
#[proc_macro_attribute]
pub fn plugin_invoke(_args: TokenStream, input: TokenStream) -> TokenStream {
    let f = parse_macro_input!(input as syn::ItemFn);
    let f_vis = &f.vis;
    let f_block = &f.block;
    let f_sig = &f.sig;
    let f_inputs = &f_sig.inputs;

    // check the function signature
    let valid_signature = f_sig.constness.is_none()
        && match f_vis {
            syn::Visibility::Inherited => true,
            _ => false,
        }
        && f_sig.abi.is_none()
        && f_inputs.len() == 1
        && f_sig.generics.where_clause.is_none()
        && f_sig.variadic.is_none()
        && check_return_type(&f);

    if !valid_signature {
        return syn::parse::Error::new(
            f.span(),
            concat!(
                "`#[plugin_invoke]` function must have signature",
                " `fn(params: &mut PluginParameters) -> optee_teec::Result<()>`"
            ),
        )
        .to_compile_error()
        .into();
    }

    let params = f_inputs
        .first()
        .expect("we have already verified its len")
        .into_token_stream();

    quote!(
        pub fn _plugin_invoke(
            cmd: u32,
            sub_cmd: u32,
            data: *mut core::ffi::c_char,
            in_len: u32,
            out_len: *mut u32
        ) -> optee_teec::raw::TEEC_Result {
            fn inner(#params) -> optee_teec::Result<()> {
                #f_block
            }
            let mut inbuf = unsafe { std::slice::from_raw_parts_mut(data, in_len as usize) };
            let mut params = optee_teec::PluginParameters::new(cmd, sub_cmd, inbuf);
            if let Err(err) = inner(&mut params) {
                return err.raw_code();
            };
            let outslice = params.get_out_slice();
            unsafe {
                *out_len = outslice.len() as u32;
                std::ptr::copy(outslice.as_ptr(), data, outslice.len());
            };
            return optee_teec::raw::TEEC_SUCCESS;
        }
    )
    .into()
}