/* WirePlumber
 *
 * Copyright © 2022 Collabora Ltd.
 *    @author George Kiagiadakis <george.kiagiadakis@collabora.com>
 *
 * SPDX-License-Identifier: MIT
 */

#define G_LOG_DOMAIN "wp-event-dispatcher"

#include "event-dispatcher.h"
#include "event-hook.h"
#include "private/registry.h"
#include "log.h"

#include <spa/support/plugin.h>
#include <spa/support/system.h>

typedef struct _WpEventHookData WpEventHookData;
struct _WpEventHookData
{
  WpEvent *event;
  WpEventHook *hook;
};

static void
wp_hook_data_unref (WpEventHookData *self)
{
  g_clear_pointer (&self->event, wp_event_unref);
  g_clear_object (&self->hook);
  g_slice_free (WpEventHookData, self);
}

struct _WpEvent
{
  grefcount ref;

  /* immutable fields */
  gint priority;
  WpProperties *properties;
  GObject *source;
  GObject *subject;
  GCancellable *cancellable;

  /* managed by the dispatcher */
  GList *hooks;
  gchar *hooks_chain;
  gchar *name;
  WpEventHookData *current_hook_in_async;
};

G_DEFINE_BOXED_TYPE (WpEvent, wp_event, wp_event_ref, wp_event_unref)

static gchar *
form_event_name (WpEvent *e)
{
  WpProperties *props = e->properties;
  const gchar *type = wp_properties_get (props, "event.type");
  const gchar *subject_type = wp_properties_get (props, "event.subject.type");
  const gchar *metadata_name = wp_properties_get (props, "metadata.name");
  const gchar *param = wp_properties_get (props, "event.subject.param-id");

  return g_strdup_printf ("<%p>%s%s%s%s%s%s%s", e, (type ? type : ""),
    ((type && subject_type) ? "@" : ""),
    (subject_type ? subject_type : ""),
    ((subject_type && metadata_name) ? "@" : ""),
    (metadata_name ? metadata_name : ""),
    ((param && subject_type) ? "@" : ""),
    (param ? param : "")
    );
}

static void
on_proxy_destroyed (GObject* self, WpEvent* e)
{
  if (e->subject == self) {
    const gchar* type = wp_properties_get (e->properties, "event.type");
    /* object removal needs to be processed by hooks */
    if (g_str_equal (type, "object-removed"))
      wp_properties_set (e->properties, "pw-proxy-destroyed", "true");
    else
      g_cancellable_cancel (e->cancellable);
  }
}

/*!
 * \brief Creates a new event
 * \ingroup wpevent
 * \param type the type of the event
 * \param priority the priority of the event
 * \param properties (transfer full)(nullable): properties of the event
 * \param source (transfer none): the source of the event
 * \param subject (transfer none)(nullable): the object that the event is about
 * \return (transfer full): the newly constructed event
 */
WpEvent *
wp_event_new (const gchar * type, gint priority, WpProperties * properties,
    GObject * source, GObject * subject)
{
  WpEvent * self = g_slice_new0 (WpEvent);
  g_ref_count_init (&self->ref);

  self->priority = priority;
  self->properties = properties ?
      wp_properties_ensure_unique_owner (properties) :
      wp_properties_new_empty ();

  self->source = source ? g_object_ref (source) : NULL;
  self->subject = subject ? g_object_ref (subject) : NULL;
  self->cancellable = g_cancellable_new ();

  if (self->subject) {
    /* merge properties from subject */
    /* PW properties */
    GParamSpec *pspec = g_object_class_find_property (
        G_OBJECT_GET_CLASS (self->subject), "properties");
    if (pspec && G_PARAM_SPEC_VALUE_TYPE (pspec) == WP_TYPE_PROPERTIES) {
      g_autoptr (WpProperties) subj_props = NULL;
      g_object_get (self->subject, "properties", &subj_props, NULL);
      if (subj_props) {
        wp_properties_update (self->properties, subj_props);
      }
    }

    /* global properties */
    pspec = g_object_class_find_property ( G_OBJECT_GET_CLASS (self->subject),
        "global-properties");
    if (pspec && G_PARAM_SPEC_VALUE_TYPE (pspec) == WP_TYPE_PROPERTIES) {
      g_autoptr (WpProperties) subj_props = NULL;
      g_object_get (self->subject, "global-properties", &subj_props, NULL);
      if (subj_props) {
        wp_properties_update (self->properties, subj_props);
      }
    }

    /* watch for subject pw-proxy-destroyed and cancel event */
    if (g_type_is_a (G_OBJECT_TYPE (self->subject), WP_TYPE_PROXY)) {
      g_signal_connect (self->subject, "pw-proxy-destroyed",
        (GCallback) on_proxy_destroyed, self);
    }
  }

  wp_properties_set (self->properties, "event.type", type);
  self->name = form_event_name (self);

  wp_trace ("event(%s) created", self->name);
  return self;
}

static void
wp_event_free (WpEvent * self)
{
  g_clear_pointer (&self->properties, wp_properties_unref);
  g_clear_object (&self->source);
  g_clear_object (&self->subject);
  g_clear_object (&self->cancellable);
  g_clear_pointer (&self->current_hook_in_async, wp_hook_data_unref);
  g_free (self->hooks_chain);
  g_free (self->name);
}

WpEvent *
wp_event_ref (WpEvent * self)
{
  g_ref_count_inc (&self->ref);
  return self;
}

void
wp_event_unref (WpEvent * self)
{
  if (g_ref_count_dec (&self->ref))
    wp_event_free (self);
}

/*!
 * \brief Gets the properties of the Event
 * \ingroup wpevent
 * \param self the handle
 * \return (transfer full): the properties of the event
 */
WpProperties *
wp_event_get_properties (WpEvent * self)
{
  g_return_val_if_fail(self != NULL, NULL);
  return wp_properties_ref (self->properties);
}

/*!
 * \brief Gets the Source Object of the Event
 * \ingroup wpevent
 * \param self the handle
 * \return (transfer full): the source of the event
 */
GObject *
wp_event_get_source (WpEvent * self)
{
  g_return_val_if_fail(self != NULL, NULL);
  return self->source ? g_object_ref (self->source) : NULL;
}

/*!
 * \brief Gets the Subject Object of the Event
 * \ingroup wpevent
 * \param self the handle
 * \return (transfer full): the subject of the event
 */
GObject *
wp_event_get_subject (WpEvent * self)
{
  g_return_val_if_fail(self != NULL, NULL);
  return self->subject ? g_object_ref (self->subject) : NULL;
}

void
wp_event_stop_processing (WpEvent * self)
{
  g_return_if_fail (self != NULL);
  wp_debug ("stopping event(%s)", self->name);
  g_cancellable_cancel (self->cancellable);
}

struct _WpEventDispatcher
{
  GObject parent;

  GWeakRef core;
  GPtrArray *hooks; /* registered hooks */
  GSource *source;  /* the event loop source */
  GList *events;    /* the events stack */
  gchar *events_chain; /* chain of events for an event run */
  WpEvent *rescan_event;
  struct spa_system *system;
  int eventfd;
};

G_DEFINE_TYPE (WpEventDispatcher, wp_event_dispatcher, G_TYPE_OBJECT)

#define WP_EVENT_SOURCE_DISPATCHER(x) \
    WP_EVENT_DISPATCHER (((WpEventSource *) x)->dispatcher)

typedef struct _WpEventSource WpEventSource;
struct _WpEventSource
{
  GSource parent;
  WpEventDispatcher *dispatcher;
};

static gboolean
wp_event_source_check (GSource * s)
{
  WpEventDispatcher *d = WP_EVENT_SOURCE_DISPATCHER (s);
  return d && d->events &&
      !((WpEvent *) g_list_first (d->events)->data)->current_hook_in_async;
}

static void
on_event_hook_done (WpEventHook * hook, GAsyncResult * res, WpEvent * event)
{
  g_autoptr (GError) error = NULL;
  g_autoptr (WpEventDispatcher) dispatcher =
      wp_event_hook_get_dispatcher (hook);

  g_assert (event->current_hook_in_async->hook == hook);

  if (!wp_event_hook_finish (hook, res, &error) && error &&
      error->domain != G_IO_ERROR && error->code != G_IO_ERROR_CANCELLED)
    wp_message_object (hook, "failed: %s", error->message);

  g_clear_pointer (&event->current_hook_in_async, wp_hook_data_unref);
  spa_system_eventfd_write (dispatcher->system, dispatcher->eventfd, 1);
}

static gchar *
build_chain (const gchar *link, gint link_priority, gchar *chain)
{
  gchar *temp = g_strdup_printf ("%s%s%s(%d)", (chain ? chain : ""),
    (chain ? " -> " : ""), link, link_priority);
  g_free (chain);
  chain = temp;

  return chain;
}

static gboolean
wp_event_source_dispatch (GSource * s, GSourceFunc callback, gpointer user_data)
{
  WpEventDispatcher *d = WP_EVENT_SOURCE_DISPATCHER (s);
  uint64_t count;

  /* clear the eventfd */
  spa_system_eventfd_read (d->system, d->eventfd, &count);

  /* get the highest priority event */
  GList *levent = g_list_first (d->events);
  while (levent) {
    WpEvent *event = (WpEvent *) (levent->data);

    /* event hook is still in progress, we will continue later */
    if (event->current_hook_in_async)
      return G_SOURCE_CONTINUE;

    /* remove the remaining hooks if the event was cancelled */
    if (g_cancellable_is_cancelled (event->cancellable) && event->hooks) {
      wp_debug_object (d, "event(%s) cancelled remove it", event->name);
      g_list_free_full (g_steal_pointer (&event->hooks),
        (GDestroyNotify) wp_hook_data_unref);
    } else
    /* avoid duplicate entries in chain */
    if (!d->events_chain || !strstr (d->events_chain, event->name)) {
      d->events_chain = build_chain (event->name, event->priority,
        d->events_chain);
      wp_debug_object (d, "dispatching event (%s)" WP_OBJECT_FORMAT " priority(%d)",
          event->name, WP_OBJECT_ARGS (event->subject), event->priority);
    }
    /* get the highest priority hook */
    GList *lhook = g_list_first (event->hooks);
    if (lhook) {
      WpEventHookData *hook_data = (WpEventHookData *) (lhook->data);
      WpEventHook *hook = hook_data->hook;
      const gchar *name = wp_event_hook_get_name (hook);
      gint priority = wp_event_hook_get_priority (hook);
      WpEventHookExecType type = wp_event_hook_get_exec_type (hook);

      event->current_hook_in_async = hook_data;
      event->hooks = g_list_delete_link (event->hooks,
            g_steal_pointer (&lhook));

      event->hooks_chain = build_chain (name, priority, event->hooks_chain);
      wp_trace_object (d, "running hook <%p>(%s)", hook, name);

      if ((event == d->rescan_event) &&
          (type == WP_EVENT_HOOK_EXEC_TYPE_AFTER_EVENTS_WITH_EVENT)) {
        WpEvent *hook_event = hook_data->event;
        wp_trace_object (d, "after-events-with-event with event %s", hook_event->name);

        if (g_cancellable_is_cancelled (hook_event->cancellable)) {
          wp_debug_object (d, "skip running hook(%s) as its trigger event(%s)"
            " is cancelled", name, hook_event->name);
          event->current_hook_in_async = NULL;
        }
        else
          wp_event_hook_run (hook, hook_event, event->cancellable,
              (GAsyncReadyCallback) on_event_hook_done, event);
      }
      else
        /* execute the hook, possibly async */
        wp_event_hook_run (hook, event, event->cancellable,
            (GAsyncReadyCallback) on_event_hook_done, event);
    }

    /* clear the event after all hooks are done */
    if (!event->hooks && !event->current_hook_in_async) {
      d->events = g_list_delete_link (d->events, g_steal_pointer (&levent));
      if (event == d->rescan_event)
        d->rescan_event = NULL;
      g_clear_pointer (&event, wp_event_unref);
    }

    /* get the next event */
    levent = g_list_first (d->events);
  }

  /* an event run completed reset the events_chain */
  g_free (d->events_chain);
  d->events_chain = NULL;

  return G_SOURCE_CONTINUE;
}

static GSourceFuncs source_funcs = {
  NULL,
  wp_event_source_check,
  wp_event_source_dispatch,
  NULL
};

static void
wp_event_dispatcher_init (WpEventDispatcher * self)
{
  g_weak_ref_init (&self->core, NULL);
  self->hooks = g_ptr_array_new_with_free_func (g_object_unref);

  self->source = g_source_new (&source_funcs, sizeof (WpEventSource));
  ((WpEventSource *) self->source)->dispatcher = self;

  /* this is higher than normal "idle" operations but lower than the default
     priority, which is used for events from the PipeWire socket and timers */
  g_source_set_priority (self->source, G_PRIORITY_HIGH_IDLE);
}

static void
clear_event (WpEvent * event)
{
  g_cancellable_cancel (event->cancellable);
  g_list_free_full (g_steal_pointer (&event->hooks), g_object_unref);
  wp_event_unref (event);
}

static void
wp_event_dispatcher_finalize (GObject * object)
{
  WpEventDispatcher *self = WP_EVENT_DISPATCHER (object);

  g_list_free_full (g_steal_pointer (&self->events),
      (GDestroyNotify) clear_event);

  ((WpEventSource *) self->source)->dispatcher = NULL;
  g_source_destroy (self->source);
  g_clear_pointer (&self->source, g_source_unref);

  close (self->eventfd);

  g_clear_pointer (&self->hooks, g_ptr_array_unref);
  g_weak_ref_clear (&self->core);
  g_free (self->events_chain);

  G_OBJECT_CLASS (wp_event_dispatcher_parent_class)->finalize (object);
}

static void
wp_event_dispatcher_class_init (WpEventDispatcherClass * klass)
{
  GObjectClass *object_class = (GObjectClass *) klass;

  object_class->finalize = wp_event_dispatcher_finalize;
}

/*!
 * \brief Returns the event dispatcher instance that is associated with the
 * given core.
 *
 * This method will also create the instance and register it with the core,
 * if it had not been created before.
 *
 * \ingroup wpeventdispatcher
 * \param core the core
 * \return (transfer full): the event dispatcher instance
 */
WpEventDispatcher *
wp_event_dispatcher_get_instance (WpCore * core)
{
  WpRegistry *registry = wp_core_get_registry (core);
  WpEventDispatcher *dispatcher = wp_registry_find_object (registry,
      (GEqualFunc) WP_IS_EVENT_DISPATCHER, NULL);

  if (G_UNLIKELY (!dispatcher)) {
    dispatcher = g_object_new (WP_TYPE_EVENT_DISPATCHER, NULL);
    g_weak_ref_set (&dispatcher->core, core);

    struct pw_context *context = wp_core_get_pw_context (core);
    uint32_t n_support;
    const struct spa_support *support =
        pw_context_get_support (context, &n_support);
    dispatcher->system =
        spa_support_find (support, n_support, SPA_TYPE_INTERFACE_System);

    dispatcher->eventfd = spa_system_eventfd_create (dispatcher->system, 0);
    g_source_add_unix_fd (dispatcher->source, dispatcher->eventfd, G_IO_IN);

    g_source_attach (dispatcher->source, wp_core_get_g_main_context (core));
    wp_registry_register_object (registry, g_object_ref (dispatcher));
  }

  return dispatcher;
}

static gint
event_cmp_func (const WpEvent *a, const WpEvent *b)
{
  return b->priority - a->priority;
}

static gint
hook_cmp_func (const WpEventHookData *new_hook, const WpEventHookData *listed_hook)
{
  return wp_event_hook_get_priority ((WpEventHook *) listed_hook->hook) -
         wp_event_hook_get_priority ((WpEventHook *) new_hook->hook);
}

static gint
after_events_hook_cmp_func (const WpEventHookData *new_hook,
    const WpEventHookData *listed_hook)
{
  if (new_hook->event != listed_hook->event)
    return G_MININT;
  else
    return hook_cmp_func (new_hook, listed_hook);
}


static gint
is_hook_present (const WpEventHookData *hook_data, const WpEventHook *hook)
{
  return !(hook == hook_data->hook);
}

/*!
 * \brief Pushes a new event onto the event stack for dispatching only if there
 * are any hooks are available for it.
 * \ingroup wpeventdispatcher
 *
 * \param self the dispatcher
 * \param event (transfer full): the new event
 */
void
wp_event_dispatcher_push_event (WpEventDispatcher * self, WpEvent * event)
{
  g_return_if_fail (WP_IS_EVENT_DISPATCHER (self));
  g_return_if_fail (event != NULL);
  gboolean hooks_added = FALSE;
  gboolean rescan_hooks_added = FALSE;

  if (!self->rescan_event)
    self->rescan_event = wp_event_new ("rescan", G_MININT16, NULL, NULL, NULL);

  /* attach hooks that run for this event */
  for (guint i = 0; i < self->hooks->len; i++) {
    WpEventHook *hook = g_ptr_array_index (self->hooks, i);

    if (wp_event_hook_runs_for_event (hook, event)) {
      WpEventHookData *hook_data = g_slice_new0 (WpEventHookData);
      WpEventHookExecType hook_type = wp_event_hook_get_exec_type (hook);
      const gchar *name = wp_event_hook_get_name (hook);
      gint priority = wp_event_hook_get_priority (hook);

      hook_data->hook = g_object_ref (hook);
      /* ON_EVENT hooks run at the dispatching of the event */
      if (hook_type == WP_EVENT_HOOK_EXEC_TYPE_ON_EVENT) {
        event->hooks = g_list_insert_sorted (event->hooks, hook_data,
            (GCompareFunc) hook_cmp_func);
        hooks_added = true;

        wp_debug_object (self, "added hook <%p>(%s(%d))", hook, name, priority);
      }
      /* AFTER_EVENTS hooks run after all other events have been dispatched */
      else if (hook_type == WP_EVENT_HOOK_EXEC_TYPE_AFTER_EVENTS_WITH_EVENT) {
        /* this event will be sent to hook when it is being dispatched */
        hook_data->event = wp_event_ref (event);

        self->rescan_event->hooks = g_list_insert_sorted (
          self->rescan_event->hooks, hook_data,
          (GCompareFunc) after_events_hook_cmp_func);
        rescan_hooks_added = true;

        wp_debug_object (self, "added after-events-with-event rescan hook"
          " <%p>(%s(%d)) for event %s", hook, name, priority, event->name);
      }
      /* for after-events retain only one instance per hook */
      else if (!g_list_find_custom (self->rescan_event->hooks, hook,
        (GCompareFunc) is_hook_present)) {
        self->rescan_event->hooks = g_list_insert_sorted (
            self->rescan_event->hooks, hook_data, (GCompareFunc) hook_cmp_func);
        rescan_hooks_added = true;

        wp_debug_object (self, "added rescan hook <%p>(%s(%d))", hook, name, priority);
      }
    }
  }

  if (rescan_hooks_added) {
    if (!g_list_find (self->events, self->rescan_event))
      self->events = g_list_insert_sorted (self->events, self->rescan_event,
        (GCompareFunc) event_cmp_func);

    wp_debug_object (self, "pushed rescan event %p for event(%s)",
        self->rescan_event, event->name);
  }

  if (hooks_added) {
    self->events = g_list_insert_sorted (self->events, event,
      (GCompareFunc) event_cmp_func);
    wp_debug_object (self, "pushed event (%s)" WP_OBJECT_FORMAT " priority(%d)",
      event->name, WP_OBJECT_ARGS (event->subject), event->priority);
  }
  else
    g_clear_pointer (&event, wp_event_unref);

  if (hooks_added || rescan_hooks_added)
    /* wakeup the GSource */
    spa_system_eventfd_write (self->system, self->eventfd, 1);
}

/*!
 * \brief Registers an event hook
 * \ingroup wpeventdispatcher
 *
 * \param self the event dispatcher
 * \param hook (transfer none): the hook to register
 */
void
wp_event_dispatcher_register_hook (WpEventDispatcher * self,
    WpEventHook * hook)
{
  g_return_if_fail (WP_IS_EVENT_DISPATCHER (self));
  g_return_if_fail (WP_IS_EVENT_HOOK (hook));

  g_autoptr (WpEventDispatcher) already_registered_dispatcher =
      wp_event_hook_get_dispatcher (hook);
  g_return_if_fail (already_registered_dispatcher == NULL);

  wp_event_hook_set_dispatcher (hook, self);
  g_ptr_array_add (self->hooks, g_object_ref (hook));
}

/*!
 * \brief Unregisters an event hook
 * \ingroup wpeventdispacher
 *
 * \param self the event dispatcher
 * \param hook (transfer none): the hook to unregister
 */
void
wp_event_dispatcher_unregister_hook (WpEventDispatcher * self,
    WpEventHook * hook)
{
  g_return_if_fail (WP_IS_EVENT_DISPATCHER (self));
  g_return_if_fail (WP_IS_EVENT_HOOK (hook));

  g_autoptr (WpEventDispatcher) already_registered_dispatcher =
      wp_event_hook_get_dispatcher (hook);
  g_return_if_fail (already_registered_dispatcher == self);

  wp_event_hook_set_dispatcher (hook, NULL);
  g_ptr_array_remove_fast (self->hooks, hook);
}