/*-------------------------------------------------------------------------
 *
 * be-dumpdata.c
 *	  support for collection of returned tuples from an internal
 *	  PQ call into a backend buffer.
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *	$Id: be-dumpdata.c,v 1.24 1999/05/25 16:08:57 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
/*
 * INTERFACE ROUTINES
 *		be_portalinit	 - initialize backend portal administration
 *		be_portalpush	 - add a portal to the top of the portal stack
 *		be_portalpop	 - remove portal on the top of the stack & return it
 *		be_currentportal - return the top portal on the portal stack
 *		be_newportal	 - return a new portal.
 *		be_portalinit	 - initialize backend portal expected to hold results.
 *		be_printtup		 - add a tuple to a backend portal
 *
 * NOTES
 *		Since backend user-defined operators can call queries
 *		which in turn call user-defined operators can call queries...
 *		we have to keep track of portals on a stack.  BeginCommand()
 *		puts portals on the stack and the PQ functions remove them.
 *
 */
#include <string.h>

#include <postgres.h>

#include <lib/dllist.h>
#include <libpq/libpq.h>
#include <access/heapam.h>
#include <access/htup.h>
#include <storage/buf.h>
#include <utils/memutils.h>
#include <fmgr.h>
#include <utils/mcxt.h>
#include <utils/exc.h>
#include <utils/syscache.h>
#include <catalog/pg_type.h>
#include <catalog/catalog.h>
#include <access/printtup.h>

/* ----------------
 *		backend portal stack for recursive PQexec calls
 * ----------------
 */
static Dllist *be_portalstack;

/* ----------------
 *		be_portalinit - initialize backend portal administration
 *
 *		This is called once from InitPostgres() to initialize
 *		the portal stack.
 * ----------------
 */
void
be_portalinit(void)
{
	be_portalstack = DLNewList();
}

/* ----------------
 *		be_portalpush - add a portal to the top of the portal stack
 *
 *		used by BeginCommand()
 * ----------------
 */
void
be_portalpush(PortalEntry *entry)
{
	DLAddTail(be_portalstack, DLNewElem(entry));
}

/* ----------------
 *		be_portalpop - remove the portal on the top of the stack & return it
 *
 *		used by PQexec()
 * ----------------
 */
PortalEntry *
be_portalpop(void)
{
	PortalEntry *p;
	Dlelem	   *elt;

	elt = DLRemTail(be_portalstack);

	p = (elt ? (PortalEntry *) DLE_VAL(elt) : NULL);
	DLFreeElem(elt);
	return p;


}

/* ----------------
 *		be_currentportal - return the top portal on the portal stack
 *
 *		used by be_printtup()
 * ----------------
 */
PortalEntry *
be_currentportal(void)
{
	Dlelem	   *elt;

	elt = DLGetTail(be_portalstack);
	return elt ? (PortalEntry *) DLE_VAL(elt) : NULL;
}

/* ----------------
 *		be_newportal - return a new portal.
 *
 *		If the user-defined function does not specify a portal name,
 *		we generate a unique one.  Names are generated from a combination
 *		of a postgres oid and an integer counter which is incremented
 *		every time we ask for a local portal.
 *
 *		used by BeginCommand()
 * ----------------
 */

static Oid	be_portaloid;
static u_int be_portalcnt = 0;

PortalEntry *
be_newportal(void)
{
	PortalEntry *entry;
	char		buf[PortalNameLength];

	/* ----------------
	 *	generate a new name
	 * ----------------
	 */
	if (be_portalcnt == 0)
		be_portaloid = newoid();
	be_portalcnt++;
	snprintf(buf, PortalNameLength, "be_%u_%d", be_portaloid, be_portalcnt);

	/* ----------------
	 *	initialize the new portal entry and keep track
	 *	of the current memory context for be_printtup().
	 *	This is important - otherwise whatever we allocate
	 *	will go away and the contents of the portal after
	 *	PQexec() returns will be meaningless.
	 * ----------------
	 */
	entry = pbuf_setup(buf);
	entry->portalcxt = (Pointer) CurrentMemoryContext;

	return entry;
}

/* ----------------
 *		be_typeinit - initialize backend portal expected to hold
 *						query results.
 *
 *		used by BeginCommand()
 * ----------------
 */
void
be_typeinit(PortalEntry *entry,
			TupleDesc tupDesc,
			int natts)
{
	PortalBuffer *portal;
	GroupBuffer *group;
	int			i;
	Form_pg_attribute *attrs = tupDesc->attrs;

	/* ----------------
	 *	add a new portal group to the portal
	 * ----------------
	 */
	portal = entry->portal;
	portal->no_groups++;
	portal->groups = group = pbuf_addGroup(portal);
	group->no_fields = natts;

	/* ----------------
	 *	initialize portal group type info
	 * ----------------
	 */
	if (natts > 0)
	{
		group->types = pbuf_addTypes(natts);
		for (i = 0; i < natts; ++i)
		{
			strncpy(group->types[i].name, attrs[i]->attname.data, NAMEDATALEN);
			group->types[i].typid = attrs[i]->atttypid;
			group->types[i].typlen = attrs[i]->attlen;
		}
	}
}

/* ----------------
 *		be_printtup - add a tuple to a backend portal
 *
 *		used indirectly by ExecRetrieve()
 *
 *		This code is pretty much copied from printtup(), dump_type()
 *		and dump_data().  -cim 2/12/91
 * ----------------
 */
void
be_printtup(HeapTuple tuple, TupleDesc typeinfo, DestReceiver * self)
{
	int			i;
	Datum		attr;
	bool		isnull;
	Oid			typoutput,
				typelem;

	PortalEntry *entry = NULL;
	PortalBuffer *portal = NULL;
	GroupBuffer *group = NULL;
	TupleBlock *tuples = NULL;
	char	  **values;
	int		   *lengths;

	MemoryContext savecxt;

	/* ----------------
	 *	get the current portal and group
	 * ----------------
	 */
	entry = be_currentportal();
	portal = entry->portal;
	group = portal->groups;

	/* ----------------
	 *	switch to the portal's memory context so that
	 *	the tuples we allocate are returned to the user.
	 * ----------------
	 */
	savecxt = MemoryContextSwitchTo((MemoryContext) entry->portalcxt);

	/* ----------------
	 *	If no tuple block yet, allocate one.
	 *	If the current block is full, allocate another one.
	 * ----------------
	 */
	if (group->tuples == NULL)
	{
		tuples = group->tuples = pbuf_addTuples();
		tuples->tuple_index = 0;
	}
	else
	{
		tuples = group->tuples;
		/* walk to the end of the linked list of TupleBlocks */
		while (tuples->next)
			tuples = tuples->next;

		/*
		 * now, tuples is the last TupleBlock, check to see if it is full.
		 * If so, allocate a new TupleBlock and add it to the end of the
		 * chain
		 */

		if (tuples->tuple_index == TupleBlockSize)
		{
			tuples->next = pbuf_addTuples();
			tuples = tuples->next;
			tuples->tuple_index = 0;
		}
	}

	/* ----------------
	 *	Allocate space for a tuple.
	 * ----------------
	 */
	tuples->values[tuples->tuple_index] = pbuf_addTuple(tuple->t_data->t_natts);
	tuples->lengths[tuples->tuple_index] = pbuf_addTupleValueLengths(tuple->t_data->t_natts);
	/* ----------------
	 *	copy printable representations of the tuple's attributes
	 *	to the portal.
	 *
	 *	This seems silly, because the user's function which is calling
	 *	PQexec() or PQfn() will probably just convert this back into the
	 *	internal form anyways, but the point here is to provide a uniform
	 *	libpq interface and this is how the fe libpq interface currently
	 *	works.	Pretty soon we'll have to add code to let the fe or be
	 *	select the desired data representation and then deal with that.
	 *	This should not be too hard, as there already exist typrecieve()
	 *	and typsend() procedures for user-defined types (see pg_type.h)
	 *	-cim 2/11/91
	 * ----------------
	 */

	values = tuples->values[tuples->tuple_index];
	lengths = tuples->lengths[tuples->tuple_index];

	for (i = 0; i < tuple->t_data->t_natts; i++)
	{
		attr = heap_getattr(tuple, i + 1, typeinfo, &isnull);
		getTypeOutAndElem((Oid) typeinfo->attrs[i]->atttypid,
						  &typoutput, &typelem);

		lengths[i] = typeinfo->attrs[i]->attlen;

		if (lengths[i] == -1)	/* variable length attribute */
		{
			if (!isnull)
				lengths[i] = VARSIZE(attr) - VARHDRSZ;
			else
				lengths[i] = 0;
		}

		if (!isnull && OidIsValid(typoutput))
			values[i] = fmgr(typoutput, attr, typelem,
							 typeinfo->attrs[i]->atttypmod);
		else
			values[i] = NULL;

	}

	/* ----------------
	 *	increment tuple group counters
	 * ----------------
	 */
	portal->no_tuples++;
	group->no_tuples++;
	tuples->tuple_index++;

	/* ----------------
	 *	return to the original memory context
	 * ----------------
	 */
	MemoryContextSwitchTo(savecxt);
}
