/**
 * Native CPU kernel_intern.h and sched.h implementation
 *
 * in-process preemptive context switching utilizes POSIX ucontexts.
 * (ucontext provides for architecture independent stack handling)
 *
 * Copyright (C) 2013 Ludwig Ortmann
 *
 * This file is subject to the terms and conditions of the GNU Lesser General
 * Public License. See the file LICENSE in the top level directory for more
 * details.
 *
 * @ingroup native_cpu
 * @{
 * @file
 * @author  Ludwig Ortmann <ludwig.ortmann@fu-berlin.de>
 */
#include <stdio.h>

#ifdef __MACH__
#define _XOPEN_SOURCE
#endif
#include <ucontext.h>
#ifdef __MACH__
#undef _XOPEN_SOURCE
#endif
#include <err.h>

#ifdef HAVE_VALGRIND_H
#include <valgrind.h>
#define VALGRIND_DEBUG DEBUG
#elif defined(HAVE_VALGRIND_VALGRIND_H)
#include <valgrind/valgrind.h>
#define VALGRIND_DEBUG DEBUG
#else
#define VALGRIND_STACK_REGISTER(...)
#define VALGRIND_DEBUG(...)
#endif

#include <stdlib.h>

#include "kernel_internal.h"
#include "sched.h"

#include "cpu.h"
#include "cpu-conf.h"

#include "native_internal.h"

#define ENABLE_DEBUG (0)
#include "debug.h"

extern volatile tcb_t *active_thread;

ucontext_t end_context;
char __end_stack[SIGSTKSZ];

#ifdef MODULE_UART0
fd_set _native_rfds;
#endif

/**
 * TODO: implement
 */
void thread_print_stack(void)
{
    DEBUG("XXX: thread_print_stack()\n");
    return;
}

char *thread_stack_init(void (*task_func)(void), void *stack_start, int stacksize)
{
    unsigned int *stk;
    ucontext_t *p;

    VALGRIND_STACK_REGISTER(stack_start, stack_start + stacksize);
    VALGRIND_DEBUG("VALGRIND_STACK_REGISTER(%p, %p)\n", stack_start, (void*)((int)stack_start + stacksize));

    DEBUG("thread_stack_init()\n");

    stk = stack_start;

#ifdef NATIVESPONTOP
    p = (ucontext_t *)stk;
    stk += sizeof(ucontext_t) / sizeof(void *);
    stacksize -= sizeof(ucontext_t);
#else
    p = (ucontext_t *)(stk + ((stacksize - sizeof(ucontext_t)) / sizeof(void *)));
    stacksize -= sizeof(ucontext_t);
#endif

    if (getcontext(p) == -1) {
        err(EXIT_FAILURE, "thread_stack_init(): getcontext()");
    }

    p->uc_stack.ss_sp = stk;
    p->uc_stack.ss_size = stacksize;
    p->uc_stack.ss_flags = 0;
    p->uc_link = &end_context;

    if (sigemptyset(&(p->uc_sigmask)) == -1) {
        err(EXIT_FAILURE, "thread_stack_init(): sigemptyset()");
    }

    makecontext(p, task_func, 0);

    return (char *) p;
}

void isr_cpu_switch_context_exit(void)
{
    ucontext_t *ctx;

    DEBUG("XXX: cpu_switch_context_exit()\n");
    if ((sched_context_switch_request == 1) || (active_thread == NULL)) {
        sched_run();
    }

    DEBUG("XXX: cpu_switch_context_exit(): calling setcontext(%s)\n\n", active_thread->name);
    ctx = (ucontext_t *)(active_thread->sp);

    /* the next context will have interrupts enabled due to ucontext */
    DEBUG("XXX: cpu_switch_context_exit: native_interrupts_enabled = 1;\n");
    native_interrupts_enabled = 1;
    _native_in_isr = 0;

    if (setcontext(ctx) == -1) {
        err(EXIT_FAILURE, "cpu_switch_context_exit(): setcontext():");
    }
}

void cpu_switch_context_exit()
{
    if (_native_in_isr == 0) {
        dINT();
        _native_in_isr = 1;
        native_isr_context.uc_stack.ss_sp = __isr_stack;
        native_isr_context.uc_stack.ss_size = SIGSTKSZ;
        native_isr_context.uc_stack.ss_flags = 0;
        makecontext(&native_isr_context, isr_cpu_switch_context_exit, 0);
        if (setcontext(&native_isr_context) == -1) {
            err(EXIT_FAILURE, "cpu_switch_context_exit: swapcontext");
        }
    }
    else {
        isr_cpu_switch_context_exit();
    }
    errx(EXIT_FAILURE, "this should have never been reached!!");
}

void isr_thread_yield()
{
    DEBUG("isr_thread_yield()\n");

    sched_run();
    ucontext_t *ctx = (ucontext_t *)(active_thread->sp);
    DEBUG("isr_thread_yield(): switching to(%s)\n\n", active_thread->name);

    native_interrupts_enabled = 1;
    _native_in_isr = 0;
    if (setcontext(ctx) == -1) {
        err(EXIT_FAILURE, "isr_thread_yield(): setcontext()");
    }
}

void thread_yield()
{
    ucontext_t *ctx = (ucontext_t *)(active_thread->sp);
    if (_native_in_isr == 0) {
        _native_in_isr = 1;
        dINT();
        native_isr_context.uc_stack.ss_sp = __isr_stack;
        native_isr_context.uc_stack.ss_size = SIGSTKSZ;
        native_isr_context.uc_stack.ss_flags = 0;
        makecontext(&native_isr_context, isr_thread_yield, 0);
        if (swapcontext(ctx, &native_isr_context) == -1) {
            err(EXIT_FAILURE, "thread_yield: swapcontext");
        }
        eINT();
    }
    else {
        isr_thread_yield();
    }
}

void native_cpu_init()
{
    if (getcontext(&end_context) == -1) {
        err(EXIT_FAILURE, "end_context(): getcontext()");
    }

    end_context.uc_stack.ss_sp = __end_stack;
    end_context.uc_stack.ss_size = SIGSTKSZ;
    end_context.uc_stack.ss_flags = 0;
    makecontext(&end_context, sched_task_exit, 0);
    VALGRIND_STACK_REGISTER(__end_stack, __end_stack + sizeof(__end_stack));
    VALGRIND_DEBUG("VALGRIND_STACK_REGISTER(%p, %p)\n", __end_stack, (void*)((int)__end_stack + sizeof(__end_stack)));

    DEBUG("RIOT native cpu initialized.");
}
/** @} */