/*
 * Copyright (C) 2023 The Android Open Source Project
 *
 * Licensed 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.
 */

//! A FFI wrapper for APEX support library

mod apexinfo;

use apexinfo::{AApexInfo, AApexInfoError};
use std::ffi::c_char;

/// NOTE: Keep these constants in sync with apexsupport.h
const AAPEXINFO_OK: i32 = 0;
const AAPEXINFO_NO_APEX: i32 = 1;
const AAPEXINFO_ERROR_GET_EXECUTABLE_PATH: i32 = 2;
const AAPEXINFO_INALID_APEX: i32 = 3;

fn as_error_code(err: &AApexInfoError) -> i32 {
    match err {
        AApexInfoError::PathNotFromApex(_) => AAPEXINFO_NO_APEX,
        AApexInfoError::ExePathUnavailable(_) => AAPEXINFO_ERROR_GET_EXECUTABLE_PATH,
        AApexInfoError::InvalidApex(_) => AAPEXINFO_INALID_APEX,
    }
}

#[no_mangle]
/// Creates AApexInfo object when called by the executable from an APEX
///
/// # Safety
///
/// The provided pointer must be valid and have no aliases for the duration of the call.
pub unsafe extern "C" fn AApexInfo_create(out: *mut *mut AApexInfo) -> i32 {
    match AApexInfo::create() {
        Ok(info) => {
            let ptr = Box::into_raw(Box::new(info));
            // SAFETY: We have checked that `out` is not null, so the caller guarantees that it is
            // valid and unaliased.
            unsafe { *out = ptr };
            AAPEXINFO_OK
        }
        Err(err) => {
            // TODO(b/271488212): Use Rust logger.
            eprintln!("AApexInfo_create(): {err:?}");
            as_error_code(&err)
        }
    }
}

#[no_mangle]
/// Destroys AApexInfo object created by AApexInfo_create().
///
/// # Safety
///
/// The provided pointer must point to a valid object previously allocated by
/// `AApexInfo_create` (and not yet destroyed).
pub unsafe extern "C" fn AApexInfo_destroy(info: *mut AApexInfo) {
    // SAFETY: The pointer is not null, so the caller guarantees that it was previously returned by
    // AApexInfo_create. AApexInfo_create got the pointer from `Box::into_raw`, so converting it
    // back with `Box::from_raw` is valid.
    unsafe { drop(Box::from_raw(info)) };
}

#[no_mangle]
/// Returns a C-string for APEX name.
///
/// # Safety
///
/// The provided pointer must point to a valid object.
pub unsafe extern "C" fn AApexInfo_getName(info: *const AApexInfo) -> *const c_char {
    // SAFETY: The pointer is not null, so the caller guarantees that it is valid.
    unsafe { (*info).name.as_ptr() }
}

#[no_mangle]
/// Returns a version of the APEX.
///
/// # Safety
///
/// The provided pointer must point to a valid object.
pub unsafe extern "C" fn AApexInfo_getVersion(info: *const AApexInfo) -> i64 {
    // SAFETY: The pointer is not null, so the caller guarantees that it is valid.
    unsafe { (*info).version }
}