/* GSL - Generic Sound Layer
 * Copyright (C) 2001-2002 Tim Janik
 * Copyright (C) 2004 Stefan Westerfeld
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General
 * Public License along with this library; if not, write to the
 * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 */
#include "gsldatacache.h"

#include "gslcommon.h"
#include "gsldatahandle.h"

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <time.h>


/* --- macros --- */
#define	NODEP_INDEX(dcache, node_p)	((node_p) - (dcache)->nodes)
#define	UPPER_POWER2(n)			(gsl_alloc_upper_power2 (MAX (n, 4)))
#define	CONFIG_NODE_SIZE()		(gsl_get_config ()->dcache_block_size)
#define AGE_EPSILON                     (3)     /* must be < smallest sweep */
#define LOW_PERSISTENCY_SWEEP           (5)

/* we use one global lock to protect the dcache list, the list
 * count (length) and the number of aged (unused) nodes.
 * also, each dcache has its own mutext to protect updates in
 * the reference count, nodes or node data blocks.
 * in order to avoid deadlocks, if both locks need
 * to be held, they always have to be acquired in the order
 * 1) global lock, 2) dcache lock.
 * asyncronous data block filling for a new node occours without
 * the dcache lock being held (as most calls to GslDataHandle
 * functions).
 * however, assignment of the newly acquired data is again
 * protected by the dcache lock. concurrent API entries
 * which require demand loading of such data will wait on
 * a global condition which is always signaled once a new data
 * block read has been completed. using one global condition
 * is considered sufficient until shown otherwise by further
 * profiling/debugging measures.
 */


/* --- prototypes --- */
static void			dcache_free		(GslDataCache	  *dcache);
static GslDataCacheNode*	data_cache_new_node_L	(GslDataCache	  *dcache,
							 gsize		   offset,
							 guint		   pos,
							 gboolean	   demand_load);


/* --- variables --- */
static GslMutex	   global_dcache_mutex = { 0, };
static GslCond	   global_dcache_cond_node_filled = { 0, };
static GslRing	  *global_dcache_list = NULL;
static guint	   global_dcache_count = 0;
static guint       global_dcache_n_aged_nodes = 0;


/* --- functions --- */
void
_gsl_init_data_caches (void)
{
  static gboolean initialized = FALSE;

  g_assert (initialized == FALSE);
  initialized++;

  g_assert (AGE_EPSILON < LOW_PERSISTENCY_SWEEP);
  gsl_cond_init (&global_dcache_cond_node_filled);
  gsl_mutex_init (&global_dcache_mutex);
}

GslDataCache*
gsl_data_cache_new (GslDataHandle *dhandle,
		    guint	   padding)
{
  guint node_size = CONFIG_NODE_SIZE () / sizeof (GslDataType);
  GslDataCache *dcache;

  g_return_val_if_fail (dhandle != NULL, NULL);
  g_return_val_if_fail (padding > 0, NULL);
  g_return_val_if_fail (dhandle->name != NULL, NULL);
  g_assert (node_size == gsl_alloc_upper_power2 (node_size));
  g_return_val_if_fail (padding < node_size / 2, NULL);

  /* allocate new closed dcache if necessary */
  dcache = gsl_new_struct (GslDataCache, 1);
  dcache->dhandle = gsl_data_handle_ref (dhandle);
  dcache->open_count = 0;
  gsl_mutex_init (&dcache->mutex);
  dcache->ref_count = 1;
  dcache->node_size = node_size;
  dcache->padding = padding;
  dcache->max_age = 0;
  dcache->low_persistency = FALSE; /* FIXME: !gsl_data_handle_needs_cache (dcache->dhandle); */
  dcache->n_nodes = 0;
  dcache->nodes = g_renew (GslDataCacheNode*, NULL, UPPER_POWER2 (dcache->n_nodes));

  GSL_SPIN_LOCK (&global_dcache_mutex);
  global_dcache_list = gsl_ring_append (global_dcache_list, dcache);
  global_dcache_count++;
  GSL_SPIN_UNLOCK (&global_dcache_mutex);

  return dcache;
}

void
gsl_data_cache_open (GslDataCache *dcache)
{
  g_return_if_fail (dcache != NULL);
  g_return_if_fail (dcache->ref_count > 0);

  GSL_SPIN_LOCK (&dcache->mutex);
  if (!dcache->open_count)
    {
      GslErrorType error;

      error = gsl_data_handle_open (dcache->dhandle);
      if (error)
	{
	  /* FIXME: this is pretty fatal, throw out zero blocks now? */
	  gsl_message_send (GSL_MSG_DATA_CACHE, "Open",
			    error,
			    "failed to open \"%s\": %s",
			    dcache->dhandle->name,
			    gsl_strerror (error));
	}
      else
	{
	  dcache->open_count = 1;
	  dcache->ref_count++;
	}
    }
  else
    dcache->open_count++;
  GSL_SPIN_UNLOCK (&dcache->mutex);
}

void
gsl_data_cache_close (GslDataCache *dcache)
{
  gboolean need_unref;

  g_return_if_fail (dcache != NULL);
  g_return_if_fail (dcache->ref_count > 0);
  g_return_if_fail (dcache->open_count > 0);

  GSL_SPIN_LOCK (&dcache->mutex);
  dcache->open_count--;
  need_unref = !dcache->open_count;
  if (!dcache->open_count)
    gsl_data_handle_close (dcache->dhandle);
  GSL_SPIN_UNLOCK (&dcache->mutex);
  if (need_unref)
    gsl_data_cache_unref (dcache);
}

GslDataCache*
gsl_data_cache_ref (GslDataCache *dcache)
{
  g_return_val_if_fail (dcache != NULL, NULL);
  g_return_val_if_fail (dcache->ref_count > 0, NULL);

  /* we might get invoked with global_dcache_mutex locked */
  GSL_SPIN_LOCK (&dcache->mutex);
  dcache->ref_count++;
  GSL_SPIN_UNLOCK (&dcache->mutex);

  return dcache;
}

static void
dcache_free (GslDataCache *dcache)
{
  guint i;

  g_return_if_fail (dcache->ref_count == 0);
  g_return_if_fail (dcache->open_count == 0);

  gsl_data_handle_unref (dcache->dhandle);
  gsl_mutex_destroy (&dcache->mutex);
  for (i = 0; i < dcache->n_nodes; i++)
    {
      GslDataCacheNode *node = dcache->nodes[i];
      guint size;

      size = dcache->node_size + (dcache->padding << 1);
      gsl_delete_structs (GslDataType, size, node->data - dcache->padding);
      gsl_delete_struct (GslDataCacheNode, node);
    }
  g_free (dcache->nodes);
  gsl_delete_struct (GslDataCache, dcache);
}

void
gsl_data_cache_unref (GslDataCache *dcache)
{
  g_return_if_fail (dcache != NULL);
 restart:
  g_return_if_fail (dcache->ref_count > 0);

  if (dcache->ref_count == 1)	/* possible destruction, need global lock */
    {
      g_return_if_fail (dcache->open_count == 0);

      GSL_SPIN_LOCK (&global_dcache_mutex);
      GSL_SPIN_LOCK (&dcache->mutex);
      if (dcache->ref_count != 1)
	{
	  /* damn, some other thread trapped in, restart */
	  GSL_SPIN_UNLOCK (&dcache->mutex);
	  GSL_SPIN_UNLOCK (&global_dcache_mutex);
	  goto restart;
	}
      dcache->ref_count = 0;
      global_dcache_list = gsl_ring_remove (global_dcache_list, dcache);
      GSL_SPIN_UNLOCK (&dcache->mutex);
      global_dcache_count--;
      global_dcache_n_aged_nodes -= dcache->n_nodes;
      GSL_SPIN_UNLOCK (&global_dcache_mutex);
      dcache_free (dcache);
    }
  else
    {
      GSL_SPIN_LOCK (&dcache->mutex);
      if (dcache->ref_count < 2)
	{
	  /* damn, some other thread trapped in, restart */
	  GSL_SPIN_UNLOCK (&dcache->mutex);
	  goto restart;
	}
      dcache->ref_count--;
      GSL_SPIN_UNLOCK (&dcache->mutex);
    }
}

static inline GslDataCacheNode**
data_cache_lookup_nextmost_node_L (GslDataCache *dcache,
				   gsize         offset)
{
  if (dcache->n_nodes > 0)
    {
      GslDataCacheNode **check, **nodes = dcache->nodes;
      guint n_nodes = dcache->n_nodes, node_size = dcache->node_size;

      /* caller has to figure himself whether we return nextmost vs. exact match */
      nodes -= 1;
      do
	{
	  gint cmp;
	  guint i;
	  
	  i = (n_nodes + 1) >> 1;
	  check = nodes + i;
	  cmp = offset < (*check)->offset ? -1 : offset >= (*check)->offset + node_size;
	  if (cmp == 0)
	    return check;	/* exact match */
	  else if (cmp > 0)
	    {
	      n_nodes -= i;
	      nodes = check;
	    }
	  else /* if (cmp < 0) */
	    n_nodes = i - 1;
	}
      while (n_nodes);
      
      return check; /* nextmost */
    }
  return NULL;
}

static inline GslDataCacheNode*
data_cache_new_node_L (GslDataCache     *dcache,
		       gsize	         offset,
		       guint	         pos,
		       gboolean	         demand_load)
{
  GslDataCacheNode **node_p, *dnode;
  GslDataCacheNode *left_node;
  GslDataType *data, *node_data;
  guint new_node_array_size, old_node_array_size = UPPER_POWER2 (dcache->n_nodes);
  GslLong dhandle_length;
  guint i, size;
  gint result;

  i = dcache->n_nodes++;
  new_node_array_size = UPPER_POWER2 (dcache->n_nodes);
  if (old_node_array_size != new_node_array_size)
    dcache->nodes = g_renew (GslDataCacheNode*, dcache->nodes, new_node_array_size);
  node_p = dcache->nodes + pos;
  g_memmove (node_p + 1, node_p, (i - pos) * sizeof (*node_p));
  dnode = gsl_new_struct (GslDataCacheNode, 1);
  (*node_p) = dnode;
  dnode->offset = offset & ~(dcache->node_size - 1);
  dnode->ref_count = 1;
  dnode->age = 0;
  dnode->data = NULL;
  GSL_SPIN_UNLOCK (&dcache->mutex);

  size = dcache->node_size + (dcache->padding << 1);
  data = gsl_new_struct (GslDataType, size);
  node_data = data + dcache->padding;
  offset = dnode->offset;
  if (dcache->padding > offset)		/* pad out bytes before data start */
    {
      guint short_pad = dcache->padding - offset;

      memset (data, 0, short_pad * sizeof (GslDataType));
      size -= short_pad;
      data += short_pad;
      offset -= (dcache->padding - short_pad); /* should always result in offset=0 */
    }
  else
    offset -= dcache->padding;
  if (!demand_load)
    g_message (G_STRLOC ":FIXME: lazy data loading not yet supported");

  /* if we have a left node, and it contains data that we need, copy it */
  left_node = pos ? dcache->nodes[pos - 1] : NULL;
  if (left_node)
    {
      guint left_node_size = dcache->node_size;
      gint left_node_offset = left_node->offset;
      GslDataType *left_node_data = left_node->data;

      /* padding around left_node */
      left_node_size += (dcache->padding << 1);
      left_node_offset -= dcache->padding;
      left_node_data -= dcache->padding;

      if (offset < left_node_offset + left_node_size)
	{
	  guint left_node_copy = left_node_offset + left_node_size - offset;

	  memcpy (data, left_node_data + offset - left_node_offset,
	                left_node_copy * sizeof (GslDataType));

	  offset += left_node_copy;
	  size -= left_node_copy;
	  data += left_node_copy;
	}
    }
  dhandle_length = gsl_data_handle_length (dcache->dhandle);
  do
    {
      if (offset >= dhandle_length)
	break;
      size = MIN (size, dhandle_length - offset);
      result = gsl_data_handle_read (dcache->dhandle, offset, size, data);
      if (result < 0)
	{
	  gsl_message_send (GSL_MSG_DATA_CACHE, "ReadAhead",
			    GSL_ERROR_READ_FAILED,
			    "reading from \"%s\"", dcache->dhandle->name);
	  break;
	}
      else
	{
	  offset += result;
	  size -= result;
	  data += result;
	}
    }
  while (size && result > 0);
  memset (data, 0, size * sizeof (data[0]));

  GSL_SPIN_LOCK (&dcache->mutex);
  dnode->data = node_data;
  gsl_cond_broadcast (&global_dcache_cond_node_filled);
  
  return dnode;
}

GslDataCacheNode*
gsl_data_cache_ref_node (GslDataCache       *dcache,
			 gsize               offset,
			 GslDataCacheRequest load_request)
{
  GslDataCacheNode **node_p, *node;
  guint insertion_pos;

  g_return_val_if_fail (dcache != NULL, NULL);
  g_return_val_if_fail (dcache->ref_count > 0, NULL);
  g_return_val_if_fail (dcache->open_count > 0, NULL);
  g_return_val_if_fail (offset < gsl_data_handle_length (dcache->dhandle), NULL);

  GSL_SPIN_LOCK (&dcache->mutex);
  node_p = data_cache_lookup_nextmost_node_L (dcache, offset);
  if (node_p)
    {
      node = *node_p;
      if (offset >= node->offset && offset < node->offset + dcache->node_size)
	{
	  gboolean rejuvenate_node = !node->ref_count;

	  if (load_request == GSL_DATA_CACHE_PEEK)
	    {
	      if (node->data)
		node->ref_count++;
	      else
		node = NULL;
	      GSL_SPIN_UNLOCK (&dcache->mutex);
              if (node && rejuvenate_node)
                {
                  GSL_SPIN_LOCK (&global_dcache_mutex); /* different lock */
                  global_dcache_n_aged_nodes--;
                  GSL_SPIN_UNLOCK (&global_dcache_mutex);
                }
	      return node;
	    }

	  node->ref_count++;
	  if (load_request == GSL_DATA_CACHE_DEMAND_LOAD)
	    while (!node->data)
	      gsl_cond_wait (&global_dcache_cond_node_filled, &dcache->mutex);
	  GSL_SPIN_UNLOCK (&dcache->mutex);
	  /* g_printerr ("hit: %d :%d: %d\n", node->offset, offset, node->offset + dcache->node_size); */

	  if (rejuvenate_node)
	    {
	      GSL_SPIN_LOCK (&global_dcache_mutex); /* different lock */
	      global_dcache_n_aged_nodes--;
	      GSL_SPIN_UNLOCK (&global_dcache_mutex);
	    }
	  
	  return node;					/* exact match */
	}
      insertion_pos = NODEP_INDEX (dcache, node_p);	/* insert before neighbour */
      if (offset > node->offset)			/* insert after neighbour */
	insertion_pos += 1;
      /* g_printerr ("mis: %d :%d: %d\n", node->offset, offset, node->offset + dcache->node_size); */
    }
  else
    insertion_pos = 0;	/* insert at start */

  if (load_request != GSL_DATA_CACHE_PEEK)
    node = data_cache_new_node_L (dcache, offset, insertion_pos, load_request == GSL_DATA_CACHE_DEMAND_LOAD);
  else
    node = NULL;

  GSL_SPIN_UNLOCK (&dcache->mutex);

  return node;
}

static gboolean /* still locked */
data_cache_free_olders_Lunlock (GslDataCache *dcache,
                                guint         max_lru)  /* how many lru nodes to keep */
{
  GslDataCacheNode **slot_p;
  guint i, rejuvenate, size;
  guint n_freed = 0;

  g_return_val_if_fail (dcache != NULL, TRUE);

  /* it doesn't make sense to free nodes below the jitter that
   * AGE_EPSILON attempts to prevent.
   */
  max_lru = MAX (AGE_EPSILON, max_lru);
  if (max_lru >= dcache->max_age)
    return TRUE;

  rejuvenate = dcache->max_age - max_lru;
  if (0)
    g_print ("start sweep: dcache (%p) with %u nodes, max_age: %u, rejuvenate: %u (max_lru: %u)\n",
	      dcache, dcache->n_nodes, dcache->max_age, rejuvenate, max_lru);
  size = dcache->node_size + (dcache->padding << 1);
  slot_p = NULL;
  for (i = 0; i < dcache->n_nodes; i++)
    {
      GslDataCacheNode *node = dcache->nodes[i];

      if (!node->ref_count && node->age <= rejuvenate)
	{
	  gsl_delete_structs (GslDataType, size, node->data - dcache->padding);
	  gsl_delete_struct (GslDataCacheNode, node);
	  if (!slot_p)
	    slot_p = dcache->nodes + i;
	  n_freed++;
	}
      else
	{
	  node->age -= MIN (rejuvenate, node->age);
	  if (slot_p)
	    {
	      *slot_p = node;
	      slot_p++;
	    }
	}
    }
  dcache->max_age = max_lru;
  if (slot_p)
    dcache->n_nodes = NODEP_INDEX (dcache, slot_p);
  GSL_SPIN_UNLOCK (&dcache->mutex);

  if (n_freed)
    {
      GSL_SPIN_LOCK (&global_dcache_mutex);
      global_dcache_n_aged_nodes -= n_freed;
      GSL_SPIN_UNLOCK (&global_dcache_mutex);
    }

  if (0)
    g_printerr ("freed %u nodes (%u bytes) remaining %u bytes\n",
		n_freed, n_freed * CONFIG_NODE_SIZE (),
		global_dcache_n_aged_nodes * CONFIG_NODE_SIZE ());
  return FALSE;
}

void
gsl_data_cache_unref_node (GslDataCache     *dcache,
			   GslDataCacheNode *node)
{
  GslDataCacheNode **node_p;
  gboolean check_cache;

  g_return_if_fail (dcache != NULL);
  g_return_if_fail (node != NULL);
  g_return_if_fail (node->ref_count > 0);

  GSL_SPIN_LOCK (&dcache->mutex);
  node_p = data_cache_lookup_nextmost_node_L (dcache, node->offset);
  g_assert (node_p && *node_p == node);	/* paranoid check lookup, yeah! */
  node->ref_count -= 1;
  check_cache = !node->ref_count;
  if (!node->ref_count &&
      (node->age + AGE_EPSILON <= dcache->max_age ||
       dcache->max_age < AGE_EPSILON))
    node->age = ++dcache->max_age;
  GSL_SPIN_UNLOCK (&dcache->mutex);

  if (check_cache)
    {
      guint node_size = CONFIG_NODE_SIZE ();
      guint cache_mem = gsl_get_config ()->dcache_cache_memory;
      guint current_mem;

      /* FIXME: cache sweeping should not be done from _unref_node for high persistency caches */
      GSL_SPIN_LOCK (&global_dcache_mutex);
      global_dcache_n_aged_nodes++;
      current_mem = node_size * global_dcache_n_aged_nodes;
      if (current_mem > cache_mem)
	{
	  guint dcache_count, needs_unlock;
	  dcache = gsl_ring_pop_head (&global_dcache_list);
	  GSL_SPIN_LOCK (&dcache->mutex);
	  dcache->ref_count++;
	  global_dcache_list = gsl_ring_append (global_dcache_list, dcache);
	  dcache_count = global_dcache_count;
	  GSL_SPIN_UNLOCK (&global_dcache_mutex);
	  if (dcache->low_persistency)
	    needs_unlock = data_cache_free_olders_Lunlock (dcache, LOW_PERSISTENCY_SWEEP);
	  else
	    {
	      guint max_lru;
	      /* try to free the actual cache overflow from the
	       * dcache we just picked, but don't free more than
	       * 25% of its nodes yet.
	       * overflow is actual overhang + ~6% of cache size,
	       * so cache sweeps are triggered less frequently.
	       */
	      current_mem -= cache_mem;		/* overhang */
	      current_mem += cache_mem >> 4;	/* overflow = overhang + 6% */
	      current_mem /= node_size;		/* n_nodes to free */
	      current_mem = MIN (current_mem, dcache->n_nodes);
	      max_lru = dcache->n_nodes >> 1;
	      max_lru += max_lru >> 1;		/* 75% of n_nodes */
	      max_lru = MAX (max_lru, dcache->n_nodes - current_mem);
	      needs_unlock = data_cache_free_olders_Lunlock (dcache, MAX (max_lru, LOW_PERSISTENCY_SWEEP));
	    }
	  if (needs_unlock)
	    GSL_SPIN_UNLOCK (&dcache->mutex);
	}
      else
	GSL_SPIN_UNLOCK (&global_dcache_mutex);
    }
}

void
gsl_data_cache_free_olders (GslDataCache *dcache,
			    guint         max_age)
{
  gboolean needs_unlock;
  g_return_if_fail (dcache != NULL);

  GSL_SPIN_LOCK (&dcache->mutex);
  needs_unlock = data_cache_free_olders_Lunlock (dcache, max_age);
  if (needs_unlock)
    GSL_SPIN_UNLOCK (&dcache->mutex);
}

GslDataCache*
gsl_data_cache_from_dhandle (GslDataHandle *dhandle,
			     guint          min_padding)
{
  GslRing *ring;

  g_return_val_if_fail (dhandle != NULL, NULL);

  GSL_SPIN_LOCK (&global_dcache_mutex);
  for (ring = global_dcache_list; ring; ring = gsl_ring_walk (global_dcache_list, ring))
    {
      GslDataCache *dcache = ring->data;

      if (dcache->dhandle == dhandle && dcache->padding >= min_padding)
	{
	  gsl_data_cache_ref (dcache);
	  GSL_SPIN_UNLOCK (&global_dcache_mutex);
	  return dcache;
	}
    }
  GSL_SPIN_UNLOCK (&global_dcache_mutex);

  return gsl_data_cache_new (dhandle, min_padding);
}