// ======================================================================
// \title Os/Posix/Task.cpp
// \brief implementation of Posix implementation of Os::Task
// ======================================================================
#include <pthread.h>
#include <unistd.h>
#include <cerrno>
#include <climits>
#include <cstring>

#include "Fw/Logger/Logger.hpp"
#include "Fw/Types/Assert.hpp"
#include "Fw/Types/StringUtils.hpp"
#include "Os/Posix/Task.hpp"
#include "Os/Posix/error.hpp"
#include "Os/Task.hpp"

namespace Os {
namespace Posix {
namespace Task {
std::atomic<bool> PosixTask::s_permissions_reported(false);
static const int SCHED_POLICY = SCHED_RR;

typedef void* (*pthread_func_ptr)(void*);

// Forward declaration
int set_task_name(pthread_t thread, char* name);

void* pthread_entry_wrapper(void* wrapper_pointer) {
    FW_ASSERT(wrapper_pointer != nullptr);
    // Both downcasts are safe because we know the types
    Os::Task::TaskRoutineWrapper& wrapper = *reinterpret_cast<Os::Task::TaskRoutineWrapper*>(wrapper_pointer);
#if defined(POSIX_THREADS_ENABLE_NAMES) && POSIX_THREADS_ENABLE_NAMES
    auto handle = reinterpret_cast<Os::Posix::Task::PosixTaskHandle*>(wrapper.m_task.getHandle());
    FW_ASSERT(handle != nullptr);
    // Task name is on a best effort basis
    (void)set_task_name(handle->m_task_descriptor, handle->m_name);
#endif
    wrapper.run(&wrapper);
    return nullptr;
}

int set_stack_size(pthread_attr_t& attributes, const Os::Task::Arguments& arguments) {
    int status = PosixTaskHandle::SUCCESS;
    FwSizeType stack = arguments.m_stackSize;
// Check for stack size multiple of page size or skip when the function
// is unavailable.
#ifdef _SC_PAGESIZE
    long page_size = sysconf(_SC_PAGESIZE);
#else
    long page_size = -1;  // Force skip and warning
#endif
    if (page_size <= 0) {
        Fw::Logger::log("[WARNING] %s could not determine page size %s. Skipping stack-size check.\n",
                        const_cast<CHAR*>(arguments.m_name.toChar()), strerror(errno));
    } else if ((stack % static_cast<FwSizeType>(page_size)) != 0) {
        // Round-down to nearest page size multiple
        FwSizeType rounded = (stack / static_cast<FwSizeType>(page_size)) * static_cast<FwSizeType>(page_size);
        Fw::Logger::log("[WARNING] %s stack size of %" PRI_FwSizeType
                        " is not multiple of page size %ld, rounding to %" PRI_FwSizeType "\n",
                        const_cast<CHAR*>(arguments.m_name.toChar()), stack, page_size, rounded);
        stack = rounded;
    }

    // Clamp invalid stack sizes
    if (stack <= static_cast<FwSizeType>(PTHREAD_STACK_MIN)) {
        Fw::Logger::log(
            "[WARNING] %s stack size of %" PRI_FwSizeType "  is too small, clamping to %" PRI_FwSizeType "\n",
            const_cast<CHAR*>(arguments.m_name.toChar()), stack, static_cast<FwSizeType>(PTHREAD_STACK_MIN));
        stack = static_cast<FwSizeType>(PTHREAD_STACK_MIN);
    }
    status = pthread_attr_setstacksize(&attributes, static_cast<size_t>(stack));
    return status;
}

int set_priority_params(pthread_attr_t& attributes, const Os::Task::Arguments& arguments) {
    const FwSizeType min_priority = static_cast<FwSizeType>(sched_get_priority_min(SCHED_POLICY));
    const FwSizeType max_priority = static_cast<FwSizeType>(sched_get_priority_max(SCHED_POLICY));
    int status = PosixTaskHandle::SUCCESS;
    FwSizeType priority = arguments.m_priority;
    // Clamp to minimum priority
    if (priority < min_priority) {
        Fw::Logger::log("[WARNING] %s low task priority of %" PRI_FwSizeType " clamped to %" PRI_FwSizeType "\n",
                        const_cast<CHAR*>(arguments.m_name.toChar()), priority, min_priority);
        priority = min_priority;
    }
    // Clamp to maximum priority
    else if (priority > max_priority) {
        Fw::Logger::log("[WARNING] %s high task priority of %" PRI_FwSizeType " clamped to %" PRI_FwSizeType "\n",
                        const_cast<CHAR*>(arguments.m_name.toChar()), priority, max_priority);
        priority = max_priority;
    }

    // Set attributes required for priority
    status = pthread_attr_setschedpolicy(&attributes, SCHED_POLICY);
    if (status == PosixTaskHandle::SUCCESS) {
        status = pthread_attr_setinheritsched(&attributes, PTHREAD_EXPLICIT_SCHED);
    }
    if (status == PosixTaskHandle::SUCCESS) {
        sched_param schedParam;
        memset(&schedParam, 0, sizeof(sched_param));
        schedParam.sched_priority = static_cast<int>(priority);
        status = pthread_attr_setschedparam(&attributes, &schedParam);
    }
    return status;
}

int set_cpu_affinity(pthread_attr_t& attributes, const Os::Task::Arguments& arguments) {
    int status = 0;
// pthread_attr_setaffinity_np is a non-POSIX function. Notably, it is not available on musl.
// Limit its use to builds that involve glibc, on Linux, with _GNU_SOURCE defined.
// That's the circumstance in which we expect this feature to work.
#if defined(TGT_OS_TYPE_LINUX) && defined(__GLIBC__) && defined(_GNU_SOURCE)
    const FwSizeType affinity = arguments.m_cpuAffinity;
    cpu_set_t cpu_set;
    CPU_ZERO(&cpu_set);
    CPU_SET(static_cast<int>(affinity), &cpu_set);

    // According to the man-page this function sets errno rather than returning an error status like other functions
    status = pthread_attr_setaffinity_np(&attributes, sizeof(cpu_set_t), &cpu_set);
    status = (status == PosixTaskHandle::SUCCESS) ? status : errno;
#else
    Fw::Logger::log("[WARNING] %s setting CPU affinity is only available with GNU pthreads\n",
                    const_cast<CHAR*>(arguments.m_name.toChar()));
#endif
    return status;
}

int set_task_name(pthread_t thread, char* name) {
    int status = 0;
// pthread_setname_np is a non-POSIX function.
// Limit its use to builds that involve glibc, on Linux, with _GNU_SOURCE defined.
// That's the circumstance in which we expect this feature to work.
#if defined(TGT_OS_TYPE_LINUX) && defined(__GLIBC__) && defined(_GNU_SOURCE) && defined(POSIX_THREADS_ENABLE_NAMES) && \
    POSIX_THREADS_ENABLE_NAMES
    // Force safe name usage
    name[Os::Posix::Task::PosixTaskHandle::PTHREAD_NAME_LENGTH - 1] = '\0';
    status = pthread_setname_np(thread, name);
#endif
    return status;
}

Os::Task::Status PosixTask::create(const Os::Task::Arguments& arguments,
                                   const PosixTask::PermissionExpectation permissions) {
    int pthread_status = PosixTaskHandle::SUCCESS;
    PosixTaskHandle& handle = this->m_handle;
    const bool expect_permission = (permissions == EXPECT_PERMISSION);
    // Initialize and clear pthread attributes
    pthread_attr_t attributes;
    memset(&attributes, 0, sizeof(attributes));
    pthread_status = pthread_attr_init(&attributes);
    if ((arguments.m_stackSize != Os::Task::TASK_DEFAULT) && (expect_permission) &&
        (pthread_status == PosixTaskHandle::SUCCESS)) {
        pthread_status = set_stack_size(attributes, arguments);
    }
    if ((arguments.m_priority != Os::Task::TASK_PRIORITY_DEFAULT) && (expect_permission) &&
        (pthread_status == PosixTaskHandle::SUCCESS)) {
        pthread_status = set_priority_params(attributes, arguments);
    }
    if ((arguments.m_cpuAffinity != Os::Task::TASK_DEFAULT) && (expect_permission) &&
        (pthread_status == PosixTaskHandle::SUCCESS)) {
        pthread_status = set_cpu_affinity(attributes, arguments);
    }
    if (pthread_status == PosixTaskHandle::SUCCESS) {
        pthread_status =
            pthread_create(&handle.m_task_descriptor, &attributes, pthread_entry_wrapper, arguments.m_routine_argument);
    }
    // Successful execution of all precious steps will result in a valid task handle
    if (pthread_status == PosixTaskHandle::SUCCESS) {
        handle.m_is_valid = true;
    }

#if defined(POSIX_THREADS_ENABLE_NAMES) && POSIX_THREADS_ENABLE_NAMES
    Fw::StringUtils::string_copy(handle.m_name, arguments.m_name.toChar(), sizeof(handle.m_name));
#endif

    (void)pthread_attr_destroy(&attributes);
    return Posix::posix_status_to_task_status(pthread_status);
}

void PosixTask::onStart() {}

Os::Task::Status PosixTask::start(const Arguments& arguments) {
    FW_ASSERT(arguments.m_routine != nullptr);

    // Try to create thread with assuming permissions
    Os::Task::Status status = this->create(arguments, PermissionExpectation::EXPECT_PERMISSION);
    // Failure due to permission automatically retried
    if (status == Os::Task::Status::ERROR_PERMISSION) {
        if (not PosixTask::s_permissions_reported) {
            Fw::Logger::log("\n");
            Fw::Logger::log("[NOTE] Task Permissions:\n");
            Fw::Logger::log("[NOTE]\n");
            Fw::Logger::log(
                "[NOTE] You have insufficient permissions to create a task with priority and/or cpu affinity.\n");
            Fw::Logger::log("[NOTE] A task without priority and affinity will be created.\n");
            Fw::Logger::log("[NOTE]\n");
            Fw::Logger::log("[NOTE] There are three possible resolutions:\n");
            Fw::Logger::log("[NOTE] 1. Use tasks without priority and affinity using parameterless start()\n");
            Fw::Logger::log("[NOTE] 2. Run this executable as a user with task priority permission\n");
            Fw::Logger::log("[NOTE] 3. Grant capability with \"setcap 'cap_sys_nice=eip'\" or equivalent\n");
            Fw::Logger::log("\n");
            PosixTask::s_permissions_reported = true;
        }
        // Fallback with no permission
        status = this->create(arguments, PermissionExpectation::EXPECT_NO_PERMISSION);
    } else if (status != Os::Task::Status::OP_OK) {
        Fw::Logger::log("[ERROR] Failed to create task with status: %d", static_cast<int>(status));
    }
    return status;
}

Os::Task::Status PosixTask::join() {
    Os::Task::Status status = Os::Task::Status::JOIN_ERROR;
    if (not this->m_handle.m_is_valid) {
        status = Os::Task::Status::INVALID_HANDLE;
    } else {
        int stat = ::pthread_join(this->m_handle.m_task_descriptor, nullptr);
        status = (stat == PosixTaskHandle::SUCCESS) ? Os::Task::Status::OP_OK : Os::Task::Status::JOIN_ERROR;
    }
    return status;
}

TaskHandle* PosixTask::getHandle() {
    return &this->m_handle;
}

// Note: not implemented for Posix threads. Must be manually done using a mutex or other blocking construct as there
// is no top-level pthreads support for suspend and resume.
void PosixTask::suspend(Os::Task::SuspensionType suspensionType) {
    FW_ASSERT(0);
}

void PosixTask::resume() {
    FW_ASSERT(0);
}

Os::Task::Status PosixTask::_delay(Fw::TimeInterval interval) {
    Os::Task::Status task_status = Os::Task::OP_OK;
    timespec sleep_interval;
    sleep_interval.tv_sec = interval.getSeconds();
    sleep_interval.tv_nsec = interval.getUSeconds() * 1000;

    timespec remaining_interval;
    remaining_interval.tv_sec = 0;
    remaining_interval.tv_nsec = 0;

    while (true) {
        int status = nanosleep(&sleep_interval, &remaining_interval);
        // Success, return ok
        if (0 == status) {
            break;
        }
        // Interrupted, reset sleep and iterate
        else if (EINTR == errno) {
            sleep_interval = remaining_interval;
            continue;
        }
        // Anything else is an error
        else {
            task_status = Os::Task::Status::DELAY_ERROR;
            break;
        }
    }
    return task_status;
}

}  // end namespace Task
}  // end namespace Posix
}  // end namespace Os