#include "postgres.h"

#include "access/heapam.h"
#include "catalog/pg_type.h"
#include "funcapi.h"
#include "utils/acl.h"
#include "utils/builtins.h"

PG_MODULE_MAGIC;

static const char *
convert_aclright_to_string(int aclright)
{
	switch (aclright)
	{
		case ACL_INSERT:
			return "INSERT";
		case ACL_SELECT:
			return "SELECT";
		case ACL_UPDATE:
			return "UPDATE";
		case ACL_DELETE:
			return "DELETE";
#if defined(ACL_TRUNCATE)
		case ACL_TRUNCATE:
			return "TRUNCATE";
#endif
		case ACL_REFERENCES:
			return "REFERENCES";
		case ACL_TRIGGER:
			return "TRIGGER";
		case ACL_EXECUTE:
			return "EXECUTE";
		case ACL_USAGE:
			return "USAGE";
		case ACL_CREATE:
			return "CREATE";
		case ACL_CREATE_TEMP:
			return "TEMPORARY";
		case ACL_CONNECT:
			return "CONNECT";
		default:
			elog(ERROR, "unrecognized aclright: %d", aclright);
			return NULL;
	}
}


/*----------
 * Convert an aclitem[] to a table.
 *
 * Example:
 *
 * aclexplode('{=r/joe,foo=a*w/joe}'::aclitem[])
 *
 * returns the table
 *
 * {{ OID(joe), 0::OID,   'SELECT', false },
 *	{ OID(joe), OID(foo), 'INSERT', true },
 *	{ OID(joe), OID(foo), 'UPDATE', false }}
 *----------
 */
PG_FUNCTION_INFO_V1(aclexplode);
Datum
aclexplode(PG_FUNCTION_ARGS)
{
	Acl		   *acl = PG_GETARG_ACL_P(0);
	FuncCallContext *funcctx;
	int		   *idx;
	AclItem    *aidat;

	if (SRF_IS_FIRSTCALL())
	{
		TupleDesc	tupdesc;
		MemoryContext oldcontext;

		/* check_acl() */
		if (ARR_ELEMTYPE(acl) != ACLITEMOID)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
					 errmsg("ACL array contains wrong data type")));
		if (ARR_NDIM(acl) != 1)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
					 errmsg("ACL arrays must be one-dimensional")));
		if (ARR_HASNULL(acl))
			ereport(ERROR,
					(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
					 errmsg("ACL arrays must not contain null values")));


		funcctx = SRF_FIRSTCALL_INIT();
		oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

		/*
		 * build tupdesc for result tuples (matches out parameters in pg_proc
		 * entry)
		 */
		tupdesc = CreateTemplateTupleDesc(4, false);
		TupleDescInitEntry(tupdesc, (AttrNumber) 1, "grantor",
						   OIDOID, -1, 0);
		TupleDescInitEntry(tupdesc, (AttrNumber) 2, "grantee",
						   OIDOID, -1, 0);
		TupleDescInitEntry(tupdesc, (AttrNumber) 3, "privilege_type",
						   TEXTOID, -1, 0);
		TupleDescInitEntry(tupdesc, (AttrNumber) 4, "is_grantable",
						   BOOLOID, -1, 0);

		funcctx->tuple_desc = BlessTupleDesc(tupdesc);

		/* allocate memory for user context */
		idx = (int *) palloc(sizeof(int[2]));
		idx[0] = 0;				/* ACL array item index */
		idx[1] = -1;			/* privilege type counter */
		funcctx->user_fctx = (void *) idx;

		MemoryContextSwitchTo(oldcontext);
	}

	funcctx = SRF_PERCALL_SETUP();
	idx = (int *) funcctx->user_fctx;
	aidat = ACL_DAT(acl);

	/* need test here in case acl has no items */
	while (idx[0] < ACL_NUM(acl))
	{
		AclItem    *aidata;
		AclMode		priv_bit;

		idx[1]++;
		if (idx[1] == N_ACL_RIGHTS)
		{
			idx[1] = 0;
			idx[0]++;
			if (idx[0] >= ACL_NUM(acl)) /* done */
				break;
		}
		aidata = &aidat[idx[0]];
		priv_bit = 1 << idx[1];

		if (ACLITEM_GET_PRIVS(*aidata) & priv_bit)
		{
			Datum		result;
			Datum		values[4];
			bool		nulls[4];
			HeapTuple	tuple;

			values[0] = ObjectIdGetDatum(aidata->ai_grantor);
			values[1] = ObjectIdGetDatum(aidata->ai_grantee);
			values[2] = DirectFunctionCall1(textin,
								CStringGetDatum(convert_aclright_to_string(priv_bit)));
			values[3] = BoolGetDatum((ACLITEM_GET_GOPTIONS(*aidata) & priv_bit) != 0);

			MemSet(nulls, 0, sizeof(nulls));

			tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
			result = HeapTupleGetDatum(tuple);

			SRF_RETURN_NEXT(funcctx, result);
		}
	}

	SRF_RETURN_DONE(funcctx);
}