/**
 * Copyright (c) 2022, 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.
 */

#include "ThreadPriorityController.h"

#include "UidProcStatsCollector.h"

namespace android {
namespace automotive {
namespace watchdog {

namespace {

using ::aidl::android::automotive::watchdog::internal::ThreadPolicyWithPriority;
using ::android::base::Error;
using ::android::base::Result;

constexpr int PRIORITY_MIN = 1;
constexpr int PRIORITY_MAX = 99;

}  // namespace

Result<void> ThreadPriorityController::checkPidTidUid(pid_t pid, pid_t tid, uid_t uid) {
    auto tidStatus = mSystemCallsInterface->readPidStatusFileForPid(tid);
    if (!tidStatus.ok()) {
        return Error(EX_ILLEGAL_STATE) << "Invalid thread ID: " << tid;
    }
    uid_t uidForThread = std::get<0>(*tidStatus);
    pid_t tgid = std::get<1>(*tidStatus);
    if (pid != tgid) {
        return Error(EX_ILLEGAL_STATE) << "Invalid process ID: " << pid;
    }
    if (uid != uidForThread) {
        return Error(EX_ILLEGAL_STATE) << "Invalid user ID: " << uid;
    }
    return {};
}

Result<void> ThreadPriorityController::setThreadPriority(int pid, int tid, int uid, int policy,
                                                         int priority) {
    pid_t tpid = static_cast<pid_t>(tid);
    pid_t ppid = static_cast<pid_t>(pid);
    uid_t uuid = static_cast<uid_t>(uid);
    if (auto result = checkPidTidUid(ppid, tpid, uuid); !result.ok()) {
        return result;
    }

    if (policy != SCHED_FIFO && policy != SCHED_RR && policy != SCHED_OTHER) {
        return Error(EX_ILLEGAL_ARGUMENT)
                << "Invalid policy: " << policy << ". Supported policies are SCHED_OTHER("
                << SCHED_OTHER << ") , SCHED_FIFO(" << SCHED_FIFO << ") and SCHED_RR(" << SCHED_RR
                << ")";
    }

    if (policy == SCHED_OTHER) {
        priority = 0;
    } else if (priority < PRIORITY_MIN || priority > PRIORITY_MAX) {
        return Error(EX_ILLEGAL_ARGUMENT)
                << "Invalid priority: " << priority << ". For policy: (" << policy
                << "), priority must be within " << PRIORITY_MIN << " and " << PRIORITY_MAX;
    }

    sched_param param{.sched_priority = priority};
    errno = 0;
    if (mSystemCallsInterface->setScheduler(tpid, policy, &param) != 0) {
        return Error(EX_SERVICE_SPECIFIC) << "sched_setscheduler failed, errno: " << errno;
    }
    return {};
}

Result<void> ThreadPriorityController::getThreadPriority(int pid, int tid, int uid,
                                                         ThreadPolicyWithPriority* result) {
    pid_t tpid = static_cast<pid_t>(tid);
    pid_t ppid = static_cast<pid_t>(pid);
    uid_t uuid = static_cast<uid_t>(uid);
    if (auto result = checkPidTidUid(ppid, tpid, uuid); !result.ok()) {
        return result;
    }

    errno = 0;
    int policy = mSystemCallsInterface->getScheduler(tpid);
    if (policy < 0) {
        return Error(EX_SERVICE_SPECIFIC) << "sched_getscheduler failed, errno: " << errno;
    }

    sched_param param = {};
    errno = 0;
    int callResult = mSystemCallsInterface->getParam(tpid, &param);
    if (callResult != 0) {
        return Error(EX_SERVICE_SPECIFIC) << "sched_getparam failed, errno: " << errno;
    }

    result->policy = policy;
    result->priority = param.sched_priority;
    return {};
}

int ThreadPriorityController::SystemCalls::setScheduler(pid_t tid, int policy,
                                                        const sched_param* param) {
    return sched_setscheduler(tid, policy, param);
}

int ThreadPriorityController::SystemCalls::getScheduler(pid_t tid) {
    return sched_getscheduler(tid);
}

int ThreadPriorityController::SystemCalls::getParam(pid_t tid, sched_param* param) {
    return sched_getparam(tid, param);
}

Result<std::tuple<uid_t, pid_t>> ThreadPriorityController::SystemCalls::readPidStatusFileForPid(
        pid_t pid) {
    return UidProcStatsCollector::readPidStatusFileForPid(pid);
}

}  // namespace watchdog
}  // namespace automotive
}  // namespace android