/* -*- indent-tabs-mode: nil; tab-width: 4; c-basic-offset: 4; -*-

   obt/mainloop.c for the Openbox window manager
   Copyright (c) 2006        Mikael Magnusson
   Copyright (c) 2003-2007   Dana Jansens

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   See the COPYING file for a copy of the GNU General Public License.
*/

#include "obt/mainloop.h"
#include "obt/display.h"
#include "obt/util.h"

#ifdef HAVE_STDIO_H
#include <stdio.h>
#endif
#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
#ifdef HAVE_SYS_SELECT_H
#include <sys/select.h>
#endif
#ifdef HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif
#ifdef HAVE_SIGNAL_H
#include <signal.h>
#endif

typedef struct _ObtMainLoopTimer             ObtMainLoopTimer;
typedef struct _ObtMainLoopSignal            ObtMainLoopSignal;
typedef struct _ObtMainLoopSignalHandlerType ObtMainLoopSignalHandlerType;
typedef struct _ObtMainLoopXHandlerType      ObtMainLoopXHandlerType;
typedef struct _ObtMainLoopFdHandlerType     ObtMainLoopFdHandlerType;

/* this should be more than the number of possible signals on any
   architecture... */
#define NUM_SIGNALS 99

/* all created ObtMainLoops. Used by the signal handler to pass along
   signals */
static GSList *all_loops;

/* signals are global to all loops */
static struct {
    guint installed; /* a ref count */
    struct sigaction oldact;
} all_signals[NUM_SIGNALS];

/* a set of all possible signals */
static sigset_t all_signals_set;

/* signals which cause a core dump, these can't be used for callbacks */
static gint core_signals[] =
{
    SIGABRT,
    SIGSEGV,
    SIGFPE,
    SIGILL,
    SIGQUIT,
    SIGTRAP,
    SIGSYS,
    SIGBUS,
    SIGXCPU,
    SIGXFSZ
};
#define NUM_CORE_SIGNALS (sizeof(core_signals) / sizeof(core_signals[0]))

static void sighandler(gint sig);
static void timer_dispatch(ObtMainLoop *loop, GTimeVal **wait);
static void fd_handler_destroy(gpointer data);
static void calc_max_fd(ObtMainLoop *loop);

struct _ObtMainLoop
{
    gint ref;
    Display *display;

    gboolean run;     /* do keep running */
    gboolean running; /* is still running */

    GSList *x_handlers;

    gint fd_x; /* The X fd is a special case! */
    gint fd_max;
    GHashTable *fd_handlers;
    fd_set fd_set;

    GSList *timers;
    GTimeVal now;
    GTimeVal ret_wait;

    gboolean signal_fired;
    guint signals_fired[NUM_SIGNALS];
    GSList *signal_handlers[NUM_SIGNALS];
};

struct _ObtMainLoopTimer
{
    gulong delay;
    GSourceFunc func;
    gpointer data;
    GEqualFunc equal;
    GDestroyNotify destroy;

    /* The timer needs to be freed */
    gboolean del_me;
    /* The time the last fire should've been at */
    GTimeVal last;
    /* When this timer will next trigger */
    GTimeVal timeout;

    /* Only allow a timer's function to fire once per run through the list,
       so that it doesn't get locked in there forever */
    gboolean fired;
};

struct _ObtMainLoopSignalHandlerType
{
    ObtMainLoop *loop;
    gint signal;
    gpointer data;
    ObtMainLoopSignalHandler func;
    GDestroyNotify destroy;
};

struct _ObtMainLoopXHandlerType
{
    ObtMainLoop *loop;
    gpointer data;
    ObtMainLoopXHandler func;
    GDestroyNotify destroy;
};

struct _ObtMainLoopFdHandlerType
{
    ObtMainLoop *loop;
    gint fd;
    gpointer data;
    ObtMainLoopFdHandler func;
    GDestroyNotify destroy;
};

ObtMainLoop *obt_main_loop_new(void)
{
    ObtMainLoop *loop;

    loop = g_slice_new0(ObtMainLoop);
    loop->ref = 1;
    FD_ZERO(&loop->fd_set);
    loop->fd_x = -1;
    loop->fd_max = -1;

    loop->fd_handlers = g_hash_table_new_full(g_int_hash, g_int_equal,
                                              NULL, fd_handler_destroy);

    g_get_current_time(&loop->now);

    /* only do this if we're the first loop created */
    if (!all_loops) {
        guint i;
        struct sigaction action;
        sigset_t sigset;

        /* initialize the all_signals_set */
        sigfillset(&all_signals_set);

        sigemptyset(&sigset);
        action.sa_handler = sighandler;
        action.sa_mask = sigset;
        action.sa_flags = SA_NOCLDSTOP;

        /* grab all the signals that cause core dumps */
        for (i = 0; i < NUM_CORE_SIGNALS; ++i) {
            /* SIGABRT is curiously not grabbed here!! that's because when we
               get one of the core_signals, we use abort() to dump the core.
               And having the abort() only go back to our signal handler again
               is less than optimal */
            if (core_signals[i] != SIGABRT) {
                sigaction(core_signals[i], &action,
                          &all_signals[core_signals[i]].oldact);
                all_signals[core_signals[i]].installed++;
            }
        }
    }

    all_loops = g_slist_prepend(all_loops, loop);

    return loop;
}

void obt_main_loop_ref(ObtMainLoop *loop)
{
    ++loop->ref;
}

void obt_main_loop_unref(ObtMainLoop *loop)
{
    guint i;
    GSList *it, *next;

    if (loop && --loop->ref == 0) {
        g_assert(loop->running == FALSE);

        for (it = loop->x_handlers; it; it = next) {
            ObtMainLoopXHandlerType *h = it->data;
            next = g_slist_next(it);
            obt_main_loop_x_remove(loop, h->func);
        }

        g_hash_table_destroy(loop->fd_handlers);

        for (it = loop->timers; it; it = g_slist_next(it)) {
            ObtMainLoopTimer *t = it->data;
            if (t->destroy) t->destroy(t->data);
            g_slice_free(ObtMainLoopTimer, t);
        }
        g_slist_free(loop->timers);
        loop->timers = NULL;

        for (i = 0; i < NUM_SIGNALS; ++i)
            for (it = loop->signal_handlers[i]; it; it = next) {
                ObtMainLoopSignalHandlerType *h = it->data;
                next = g_slist_next(it);
                obt_main_loop_signal_remove(loop, h->func);
            }

        all_loops = g_slist_remove(all_loops, loop);

        /* only do this if we're the last loop destroyed */
        if (!all_loops) {
            /* grab all the signals that cause core dumps */
            for (i = 0; i < NUM_CORE_SIGNALS; ++i) {
                if (all_signals[core_signals[i]].installed) {
                    sigaction(core_signals[i],
                              &all_signals[core_signals[i]].oldact, NULL);
                    all_signals[core_signals[i]].installed--;
                }
            }
        }

        g_slice_free(ObtMainLoop, loop);
    }
}

static void fd_handle_foreach(gpointer key,
                              gpointer value,
                              gpointer data)
{
    ObtMainLoopFdHandlerType *h = value;
    fd_set *set = data;

    if (FD_ISSET(h->fd, set))
        h->func(h->fd, h->data);
}

void obt_main_loop_run(ObtMainLoop *loop)
{
    XEvent e;
    struct timeval *wait;
    fd_set selset;
    GSList *it;

    loop->run = TRUE;
    loop->running = TRUE;

    while (loop->run) {
        if (loop->signal_fired) {
            guint i;
            sigset_t oldset;

            /* block signals so that we can do this without the data changing
               on us */
            sigprocmask(SIG_SETMASK, &all_signals_set, &oldset);

            for (i = 0; i < NUM_SIGNALS; ++i) {
                while (loop->signals_fired[i]) {
                    for (it = loop->signal_handlers[i];
                            it; it = g_slist_next(it)) {
                        ObtMainLoopSignalHandlerType *h = it->data;
                        h->func(i, h->data);
                    }
                    loop->signals_fired[i]--;
                }
            }
            loop->signal_fired = FALSE;

            sigprocmask(SIG_SETMASK, &oldset, NULL);
        } else if (loop->display && XPending(loop->display)) {
            do {
                XNextEvent(loop->display, &e);

                if (e.type == MappingNotify)
                    XRefreshKeyboardMapping(&e.xmapping);

                for (it = loop->x_handlers; it; it = g_slist_next(it)) {
                    ObtMainLoopXHandlerType *h = it->data;
                    h->func(&e, h->data);
                }
            } while (XPending(loop->display) && loop->run);
        } else {
            /* this only runs if there were no x events received */

            timer_dispatch(loop, (GTimeVal**)&wait);

            selset = loop->fd_set;
            /* there is a small race condition here. if a signal occurs
               between this if() and the select() then we will not process
               the signal until 'wait' expires. possible solutions include
               using GStaticMutex, and having the signal handler set 'wait'
               to 0 */
            if (!loop->signal_fired)
                select(loop->fd_max + 1, &selset, NULL, NULL, wait);

            /* handle the X events with highest prioirity */
            if (FD_ISSET(loop->fd_x, &selset))
                continue;

            g_hash_table_foreach(loop->fd_handlers,
                                 fd_handle_foreach, &selset);
        }
    }

    loop->running = FALSE;
}

void obt_main_loop_exit(ObtMainLoop *loop)
{
    loop->run = FALSE;
}

/*** XEVENT WATCHERS ***/

void obt_main_loop_x_add(ObtMainLoop *loop,
                         ObtMainLoopXHandler handler,
                         gpointer data,
                         GDestroyNotify notify)
{
    ObtMainLoopXHandlerType *h;

    h = g_slice_new(ObtMainLoopXHandlerType);
    h->loop = loop;
    h->func = handler;
    h->data = data;
    h->destroy = notify;

    if (!loop->x_handlers) {
        g_assert(obt_display); /* is the display open? */

        loop->display = obt_display;
        loop->fd_x = ConnectionNumber(loop->display);
        FD_SET(loop->fd_x, &loop->fd_set);
        calc_max_fd(loop);
    }

    loop->x_handlers = g_slist_prepend(loop->x_handlers, h);
}

void obt_main_loop_x_remove(ObtMainLoop *loop,
                            ObtMainLoopXHandler handler)
{
    GSList *it, *next;

    for (it = loop->x_handlers; it; it = next) {
        ObtMainLoopXHandlerType *h = it->data;
        next = g_slist_next(it);
        if (h->func == handler) {
            loop->x_handlers = g_slist_delete_link(loop->x_handlers, it);
            if (h->destroy) h->destroy(h->data);
            g_slice_free(ObtMainLoopXHandlerType, h);
        }
    }

    if (!loop->x_handlers) {
        FD_CLR(loop->fd_x, &loop->fd_set);
        calc_max_fd(loop);
    }
}

/*** SIGNAL WATCHERS ***/

static void sighandler(gint sig)
{
    GSList *it;
    guint i;

    g_return_if_fail(sig < NUM_SIGNALS);

    for (i = 0; i < NUM_CORE_SIGNALS; ++i)
        if (sig == core_signals[i]) {
            /* XXX special case for signals that default to core dump.
               but throw some helpful output here... */

            fprintf(stderr, "How are you gentlemen? All your base are"
                    " belong to us. (Openbox received signal %d)\n", sig);

            /* die with a core dump */
            abort();
        }

    for (it = all_loops; it; it = g_slist_next(it)) {
        ObtMainLoop *loop = it->data;
        loop->signal_fired = TRUE;
        loop->signals_fired[sig]++;
    }
}

void obt_main_loop_signal_add(ObtMainLoop *loop,
                              gint signal,
                              ObtMainLoopSignalHandler handler,
                              gpointer data,
                              GDestroyNotify notify)
{
    ObtMainLoopSignalHandlerType *h;

    g_return_if_fail(signal < NUM_SIGNALS);

    h = g_slice_new(ObtMainLoopSignalHandlerType);
    h->loop = loop;
    h->signal = signal;
    h->func = handler;
    h->data = data;
    h->destroy = notify;
    loop->signal_handlers[h->signal] =
        g_slist_prepend(loop->signal_handlers[h->signal], h);

    if (!all_signals[signal].installed) {
        struct sigaction action;
        sigset_t sigset;

        sigemptyset(&sigset);
        action.sa_handler = sighandler;
        action.sa_mask = sigset;
        action.sa_flags = SA_NOCLDSTOP;

        sigaction(signal, &action, &all_signals[signal].oldact);
    }

    all_signals[signal].installed++;
}

void obt_main_loop_signal_remove(ObtMainLoop *loop,
                                 ObtMainLoopSignalHandler handler)
{
    guint i;
    GSList *it, *next;

    for (i = 0; i < NUM_SIGNALS; ++i) {
        for (it = loop->signal_handlers[i]; it; it = next) {
            ObtMainLoopSignalHandlerType *h = it->data;

            next = g_slist_next(it);

            if (h->func == handler) {
                g_assert(all_signals[h->signal].installed > 0);

                all_signals[h->signal].installed--;
                if (!all_signals[h->signal].installed) {
                    sigaction(h->signal, &all_signals[h->signal].oldact, NULL);
                }

                loop->signal_handlers[i] =
                    g_slist_delete_link(loop->signal_handlers[i], it);
                if (h->destroy) h->destroy(h->data);

                g_slice_free(ObtMainLoopSignalHandlerType, h);
            }
        }
    }

}

/*** FILE DESCRIPTOR WATCHERS ***/

static void max_fd_func(gpointer key, gpointer value, gpointer data)
{
    ObtMainLoop *loop = data;

    /* key is the fd */
    loop->fd_max = MAX(loop->fd_max, *(gint*)key);
}

static void calc_max_fd(ObtMainLoop *loop)
{
    loop->fd_max = loop->fd_x;

    g_hash_table_foreach(loop->fd_handlers, max_fd_func, loop);
}

void obt_main_loop_fd_add(ObtMainLoop *loop,
                          gint fd,
                          ObtMainLoopFdHandler handler,
                          gpointer data,
                          GDestroyNotify notify)
{
    ObtMainLoopFdHandlerType *h;

    h = g_slice_new(ObtMainLoopFdHandlerType);
    h->loop = loop;
    h->fd = fd;
    h->func = handler;
    h->data = data;
    h->destroy = notify;

    g_hash_table_replace(loop->fd_handlers, &h->fd, h);
    FD_SET(h->fd, &loop->fd_set);
    calc_max_fd(loop);
}

static void fd_handler_destroy(gpointer data)
{
    ObtMainLoopFdHandlerType *h = data;

    FD_CLR(h->fd, &h->loop->fd_set);

    if (h->destroy)
        h->destroy(h->data);
    g_slice_free(ObtMainLoopFdHandlerType, h);
}

void obt_main_loop_fd_remove(ObtMainLoop *loop,
                             gint fd)
{
    g_hash_table_remove(loop->fd_handlers, &fd);
    calc_max_fd(loop);
}

/*** TIMEOUTS ***/

#define NEAREST_TIMEOUT(loop) \
    (((ObtMainLoopTimer*)(loop)->timers->data)->timeout)

static glong timecompare(GTimeVal *a, GTimeVal *b)
{
    glong r;
    if ((r = a->tv_sec - b->tv_sec)) return r;
    return a->tv_usec - b->tv_usec;
}

static void insert_timer(ObtMainLoop *loop, ObtMainLoopTimer *ins)
{
    GSList *it;
    for (it = loop->timers; it; it = g_slist_next(it)) {
        ObtMainLoopTimer *t = it->data;
        if (timecompare(&ins->timeout, &t->timeout) <= 0) {
            loop->timers = g_slist_insert_before(loop->timers, it, ins);
            break;
        }
    }
    if (it == NULL) /* didnt fit anywhere in the list */
        loop->timers = g_slist_append(loop->timers, ins);
}

void obt_main_loop_timeout_add(ObtMainLoop *loop,
                               gulong microseconds,
                               GSourceFunc handler,
                               gpointer data,
                               GEqualFunc cmp,
                               GDestroyNotify notify)
{
    ObtMainLoopTimer *t = g_slice_new(ObtMainLoopTimer);

    g_assert(microseconds > 0); /* if it's 0 it'll cause an infinite loop */

    t->delay = microseconds;
    t->func = handler;
    t->data = data;
    t->equal = cmp;
    t->destroy = notify;
    t->del_me = FALSE;
    g_get_current_time(&loop->now);
    t->last = t->timeout = loop->now;
    g_time_val_add(&t->timeout, t->delay);

    insert_timer(loop, t);
}

void obt_main_loop_timeout_remove(ObtMainLoop *loop,
                                  GSourceFunc handler)
{
    GSList *it;

    for (it = loop->timers; it; it = g_slist_next(it)) {
        ObtMainLoopTimer *t = it->data;
        if (t->func == handler)
            t->del_me = TRUE;
    }
}

void obt_main_loop_timeout_remove_data(ObtMainLoop *loop, GSourceFunc handler,
                                       gpointer data, gboolean cancel_dest)
{
    GSList *it;

    for (it = loop->timers; it; it = g_slist_next(it)) {
        ObtMainLoopTimer *t = it->data;
        if (t->func == handler && t->equal(t->data, data)) {
            t->del_me = TRUE;
            if (cancel_dest)
                t->destroy = NULL;
        }
    }
}

/* find the time to wait for the nearest timeout */
static gboolean nearest_timeout_wait(ObtMainLoop *loop, GTimeVal *tm)
{
  if (loop->timers == NULL)
    return FALSE;

  tm->tv_sec = NEAREST_TIMEOUT(loop).tv_sec - loop->now.tv_sec;
  tm->tv_usec = NEAREST_TIMEOUT(loop).tv_usec - loop->now.tv_usec;

  while (tm->tv_usec < 0) {
    tm->tv_usec += G_USEC_PER_SEC;
    tm->tv_sec--;
  }
  tm->tv_sec += tm->tv_usec / G_USEC_PER_SEC;
  tm->tv_usec %= G_USEC_PER_SEC;
  if (tm->tv_sec < 0)
    tm->tv_sec = 0;

  return TRUE;
}

static void timer_dispatch(ObtMainLoop *loop, GTimeVal **wait)
{
    GSList *it, *next;

    gboolean fired = FALSE;

    g_get_current_time(&loop->now);

    for (it = loop->timers; it; it = next) {
        ObtMainLoopTimer *curr;

        next = g_slist_next(it);

        curr = it->data;

        /* since timer_stop doesn't actually free the timer, we have to do our
           real freeing in here.
        */
        if (curr->del_me) {
            /* delete the top */
            loop->timers = g_slist_delete_link(loop->timers, it);
            if (curr->destroy)
                curr->destroy(curr->data);
            g_slice_free(ObtMainLoopTimer, curr);
            continue;
        }

        /* the queue is sorted, so if this timer shouldn't fire, none are
           ready */
        if (timecompare(&NEAREST_TIMEOUT(loop), &loop->now) > 0)
            break;

        /* we set the last fired time to delay msec after the previous firing,
           then re-insert.  timers maintain their order and may trigger more
           than once if they've waited more than one delay's worth of time.
        */
        loop->timers = g_slist_delete_link(loop->timers, it);
        g_time_val_add(&curr->last, curr->delay);
        if (curr->func(curr->data)) {
            g_time_val_add(&curr->timeout, curr->delay);
            insert_timer(loop, curr);
        } else {
            if (curr->destroy)
                curr->destroy(curr->data);
            g_slice_free(ObtMainLoopTimer, curr);
        }

        /* the timer queue has been shuffled, start from the beginning
           (which is the next one to fire) */
        next = loop->timers;

        fired = TRUE;
    }

    if (fired) {
        /* if at least one timer fires, then don't wait on X events, as there
           may already be some in the queue from the timer callbacks.
        */
        loop->ret_wait.tv_sec = loop->ret_wait.tv_usec = 0;
        *wait = &loop->ret_wait;
    } else if (nearest_timeout_wait(loop, &loop->ret_wait))
        *wait = &loop->ret_wait;
    else
        *wait = NULL;
}