/*
 * Asterisk
 * 
 * Mark Spencer <markster@marko.net>
 *
 * Copyright(C) Mark Spencer
 * 
 * Distributed under the terms of the GNU General Public License (GPL) Version 2
 *
 * I/O Managment (Derived from Cheops-NG)
 *
 */

#include <stdio.h>
#include <sys/poll.h>
#include <unistd.h>
#include <stdlib.h>
#include <asterisk/io.h>
#include <asterisk/logger.h>

#ifdef DEBUG_IO
#define DEBUG DEBUG_M
#else
#define DEBUG(a) 
#endif

/* 
 * Kept for each file descriptor
 */
struct io_rec {
	ast_io_cb callback;		/* What is to be called */
	void *data; 				/* Data to be passed */
	int *id; 					/* ID number */
};

/* These two arrays are keyed with
   the same index.  it's too bad that
   pollfd doesn't have a callback field
   or something like that.  They grow as
   needed, by GROW_SHRINK_AMOUNT structures
   at once */

#define GROW_SHRINK_SIZE 512

/* Global variables are now in a struct in order to be
   made threadsafe */
struct io_context {
	/* Poll structure */
	struct pollfd *fds;
	/* Associated I/O records */
	struct io_rec *ior;
	/* First available fd */
	unsigned int fdcnt;
	/* Maximum available fd */
	unsigned int maxfdcnt;
	/* Currently used io callback */
	int current_ioc;
};


struct io_context *io_context_create(void)
{
	/* Create an I/O context */
	struct io_context *tmp;
	tmp = malloc(sizeof(struct io_context));
	if (tmp) {
		tmp->fds = NULL;
		tmp->ior =  NULL;
		tmp->fdcnt = 0;
		tmp->maxfdcnt = -1;
		tmp->current_ioc = -1;
	}
	return tmp;
}

void io_context_destroy(struct io_context *ioc)
{
	/* Free associated memory with an I/O context */
	if (ioc->fds)
		free(ioc->fds);
	if (ioc->ior)
		free(ioc->ior);
	free(ioc);
}

static int io_grow(struct io_context *ioc)
{
	/* 
	 * Grow the size of our arrays.  Return 0 on success or
	 * -1 on failure
	 */
	void *tmp;
	DEBUG(ast_log(LOG_DEBUG, "io_grow()\n"));
	ioc->maxfdcnt += GROW_SHRINK_SIZE;
	tmp = realloc(ioc->ior, (ioc->maxfdcnt + 1) * sizeof(struct io_rec));
	if (tmp) {
		ioc->ior = (struct io_rec *)tmp;
		tmp = realloc(ioc->fds, (ioc->maxfdcnt + 1) * sizeof(struct pollfd));
		if (tmp) {
			ioc->fds = tmp;
		} else {
			/*
			 * Not enough memory for the pollfd.  Not really any need
			 * to shrink back the iorec's as we'll probably want to
			 * grow them again soon when more memory is available, and
			 * then they'll already be the right size
			 */
			ioc->maxfdcnt -= GROW_SHRINK_SIZE;
			return -1;
		}
		
	} else {
		/*
		 * Out of memory.  We return to the old size, and return a failure
		 */
		ioc->maxfdcnt -= GROW_SHRINK_SIZE;
		return -1;
	}
	return 0;
}

int *ast_io_add(struct io_context *ioc, int fd, ast_io_cb callback, short events, void *data)
{
	/*
	 * Add a new I/O entry for this file descriptor
	 * with the given event mask, to call callback with
	 * data as an argument.  Returns NULL on failure.
	 */
	DEBUG(ast_log(LOG_DEBUG, "ast_io_add()\n"));
	if (ioc->fdcnt < ioc->maxfdcnt) {
		/* 
		 * We don't have enough space for this entry.  We need to
		 * reallocate maxfdcnt poll fd's and io_rec's, or back out now.
		 */
		if (io_grow(ioc))
			return NULL;
	}

	/*
	 * At this point, we've got sufficiently large arrays going
	 * and we can make an entry for it in the pollfd and io_r
	 * structures.
	 */
	ioc->fds[ioc->fdcnt].fd = fd;
	ioc->fds[ioc->fdcnt].events = events;
	ioc->ior[ioc->fdcnt].callback = callback;
	ioc->ior[ioc->fdcnt].data = data;
	ioc->ior[ioc->fdcnt].id = (int *)malloc(sizeof(int));
	/* Bonk if we couldn't allocate an int */
	if (!ioc->ior[ioc->fdcnt].id)
		return NULL;
	*ioc->ior[ioc->fdcnt].id = ioc->fdcnt;
	return ioc->ior[ioc->fdcnt++].id;
}

int *ast_io_change(struct io_context *ioc, int *id, int fd, ast_io_cb callback, short events, void *data)
{
	if (*id < ioc->fdcnt) {
		if (fd > -1)
			ioc->fds[*id].fd = fd;
		if (callback)
			ioc->ior[*id].callback = callback;
		if (events)
			ioc->fds[*id].events = events;
		if (data)
			ioc->ior[*id].data = data;
		return id;
	} else return NULL;
}

static int io_shrink(struct io_context *ioc, int which)
{
	/* 
	 * Bring the fields from the very last entry to cover over
	 * the entry we are removing, then decrease the size of the 
	 * arrays by one.
	 */
	ioc->fdcnt--;

	/* Free the int */
	free(ioc->ior[which].id);
	
	/* If we're not deleting the last one, move the last one to
	   the current position */
	if (which != ioc->fdcnt) {
		ioc->fds[which] = ioc->fds[ioc->fdcnt];
		ioc->ior[which] = ioc->ior[ioc->fdcnt];
		*ioc->ior[which].id = which;
	}
	/* FIXME: We should free some memory if we have lots of unused
	   io structs */
	return 0;
}

int ast_io_remove(struct io_context *ioc, int *id)
{
	if (ioc->current_ioc == *id) {
		ast_log(LOG_NOTICE, "Callback for %d tried to remove itself\n", *id);
	} else
	
	if (*id < ioc->fdcnt) {
		return io_shrink(ioc, *id);
	} else 
		ast_log(LOG_NOTICE, "Unable to remove unknown id %d\n", *id);

	return -1;
}

int ast_io_wait(struct io_context *ioc, int howlong)
{
	/*
	 * Make the poll call, and call
	 * the callbacks for anything that needs
	 * to be handled
	 */
	int res;
	int x;
	DEBUG(ast_log(LOG_DEBUG, "ast_io_wait()\n"));
	res = poll(ioc->fds, ioc->fdcnt, howlong);
	if (res > 0) {
		/*
		 * At least one event
		 */
		for(x=0;x<ioc->fdcnt;x++) {
			if (ioc->fds[x].revents) {
				/* There's an event waiting */
				ioc->current_ioc = *ioc->ior[x].id;
				if (!ioc->ior[x].callback(ioc->ior[x].id, ioc->fds[x].fd, ioc->fds[x].revents, ioc->ior[x].data)) {
					/* Time to delete them since they returned a 0 */
					io_shrink(ioc, x);
				}
				ioc->current_ioc = -1;
			}
		}
	}
	return res;
}

void ast_io_dump(struct io_context *ioc)
{
	/*
	 * Print some debugging information via
	 * the logger interface
	 */
	int x;
	ast_log(LOG_DEBUG, "Asterisk IO Dump: %d entries, %d max entries\n", ioc->fdcnt, ioc->maxfdcnt);
	ast_log(LOG_DEBUG, "================================================\n");
	ast_log(LOG_DEBUG, "| ID    FD     Callback    Data        Events  |\n");
	ast_log(LOG_DEBUG, "+------+------+-----------+-----------+--------+\n");
	for (x=0;x<ioc->fdcnt;x++) {
		ast_log(LOG_DEBUG, "| %.4d | %.4d | %p | %p | %.6x |\n", 
				*ioc->ior[x].id,
				ioc->fds[x].fd,
				ioc->ior[x].callback,
				ioc->ior[x].data,
				ioc->fds[x].events);
	}
	ast_log(LOG_DEBUG, "================================================\n");
}