/*-------------------------------------------------------------------------
 *
 * dbcommands.c--
 *
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $Header: /cvsroot/pgsql/src/backend/commands/dbcommands.c,v 1.28 1998/12/15 12:45:55 vadim Exp $
 *
 *-------------------------------------------------------------------------
 */
#include <stdio.h>
#include <string.h>
#include <signal.h>
#include <sys/stat.h>

#include "postgres.h"

#include "access/heapam.h"
#include "access/htup.h"
#include "access/relscan.h"
#include "catalog/catname.h"
#include "catalog/pg_database.h"
#include "catalog/pg_shadow.h"
#include "commands/dbcommands.h"
#include "fmgr.h"
#include "miscadmin.h"			/* for DataDir */
#include "storage/bufmgr.h"
#include "storage/fd.h"
#include "storage/lmgr.h"
#include "tcop/tcopprot.h"
#include "utils/rel.h"
#include "utils/syscache.h"


/* non-export function prototypes */
static void check_permissions(char *command, char *dbpath, char *dbname,
				  Oid *dbIdP, int4 *userIdP);
static HeapTuple get_pg_dbtup(char *command, char *dbname, Relation dbrel);
static void stop_vacuum(char *dbpath, char *dbname);

void
createdb(char *dbname, char *dbpath, int encoding)
{
	Oid			db_id;
	int4		user_id;
	char		buf[512];
	char		*lp,
					loc[512];

	/*
	 * If this call returns, the database does not exist and we're allowed
	 * to create databases.
	 */
	check_permissions("createdb", dbpath, dbname, &db_id, &user_id);

	/* close virtual file descriptors so we can do system() calls */
	closeAllVfds();

	/* Now create directory for this new database */
	if ((dbpath != NULL) && (strcmp(dbpath, dbname) != 0))
	{
		if (*(dbpath + strlen(dbpath) - 1) == SEP_CHAR)
			*(dbpath + strlen(dbpath) - 1) = '\0';
		snprintf(loc, 512, "%s%c%s", dbpath, SEP_CHAR, dbname);
	}
	else
		strcpy(loc, dbname);

	lp = ExpandDatabasePath(loc);

	if (lp == NULL)
		elog(ERROR, "Unable to locate path '%s'"
			 "\n\tThis may be due to a missing environment variable"
			 " in the server", loc);

	if (mkdir(lp, S_IRWXU) != 0)
		elog(ERROR, "Unable to create database directory '%s'", lp);

	snprintf(buf, 512, "%s %s%cbase%ctemplate1%c* %s",
			COPY_CMD, DataDir, SEP_CHAR, SEP_CHAR, SEP_CHAR, lp);
	system(buf);

	snprintf(buf, 512, 
			"insert into pg_database (datname, datdba, encoding, datpath)"
			" values ('%s', '%d', '%d', '%s');", dbname, user_id, encoding, loc);

	pg_exec_query(buf);
}

void
destroydb(char *dbname)
{
	int4		user_id;
	Oid			db_id;
	char		*path,
					dbpath[MAXPGPATH + 1],
					buf[512];

	/*
	 * If this call returns, the database exists and we're allowed to
	 * remove it.
	 */
	check_permissions("destroydb", dbpath, dbname, &db_id, &user_id);

	if (!OidIsValid(db_id))
		elog(FATAL, "pg_database instance has an invalid OID");

	/* stop the vacuum daemon */
	stop_vacuum(dbpath, dbname);

	path = ExpandDatabasePath(dbpath);
	if (path == NULL)
		elog(ERROR, "Unable to locate path '%s'"
			 "\n\tThis may be due to a missing environment variable"
			 " in the server", dbpath);

	/*
	 * remove the pg_database tuple FIRST, this may fail due to
	 * permissions problems
	 */
	snprintf(buf, 512, 
			"delete from pg_database where pg_database.oid = \'%d\'::oid", db_id);
	pg_exec_query(buf);

	/*
	 * remove the data directory. If the DELETE above failed, this will
	 * not be reached
	 */

	snprintf(buf, 512, "rm -r %s", path);
	system(buf);

	/* drop pages for this database that are in the shared buffer cache */
	DropBuffers(db_id);
}

static HeapTuple
get_pg_dbtup(char *command, char *dbname, Relation dbrel)
{
	HeapTuple	dbtup;
	HeapTuple	tup;
	HeapScanDesc scan;
	ScanKeyData scanKey;

	ScanKeyEntryInitialize(&scanKey, 0, Anum_pg_database_datname,
						   F_NAMEEQ, NameGetDatum(dbname));

	scan = heap_beginscan(dbrel, 0, SnapshotNow, 1, &scanKey);
	if (!HeapScanIsValid(scan))
		elog(ERROR, "%s: cannot begin scan of pg_database", command);

	/*
	 * since we want to return the tuple out of this proc, and we're going
	 * to close the relation, copy the tuple and return the copy.
	 */
	tup = heap_getnext(scan, 0);

	if (HeapTupleIsValid(tup))
		dbtup = heap_copytuple(tup);
	else
		dbtup = tup;

	heap_endscan(scan);
	return dbtup;
}

/*
 *	check_permissions() -- verify that the user is permitted to do this.
 *
 *	If the user is not allowed to carry out this operation, this routine
 *	elog(ERROR, ...)s, which will abort the xact.  As a side effect, the
 *	user's pg_user tuple OID is returned in userIdP and the target database's
 *	OID is returned in dbIdP.
 */

static void
check_permissions(char *command,
				  char *dbpath,
				  char *dbname,
				  Oid *dbIdP,
				  int4 *userIdP)
{
	Relation	dbrel;
	HeapTuple	dbtup,
				utup;
	int4		dbowner = 0;
	char		use_createdb;
	bool		dbfound;
	bool		use_super;
	char	   *userName;
	text	   *dbtext;
	char		path[MAXPGPATH + 1];

	userName = GetPgUserName();
	utup = SearchSysCacheTuple(USENAME,
							   PointerGetDatum(userName),
							   0, 0, 0);
	*userIdP = ((Form_pg_shadow) GETSTRUCT(utup))->usesysid;
	use_super = ((Form_pg_shadow) GETSTRUCT(utup))->usesuper;
	use_createdb = ((Form_pg_shadow) GETSTRUCT(utup))->usecreatedb;

	/* Check to make sure user has permission to use createdb */
	if (!use_createdb)
	{
		elog(ERROR, "user '%s' is not allowed to create/destroy databases",
			 userName);
	}

	/* Make sure we are not mucking with the template database */
	if (!strcmp(dbname, "template1"))
		elog(ERROR, "%s: cannot be executed on the template database", command);

	/* Check to make sure database is not the currently open database */
	if (!strcmp(dbname, DatabaseName))
		elog(ERROR, "%s: cannot be executed on an open database", command);

	/* Check to make sure database is owned by this user */

	/*
	 * need the reldesc to get the database owner out of dbtup and to set
	 * a write lock on it.
	 */
	dbrel = heap_openr(DatabaseRelationName);

	if (!RelationIsValid(dbrel))
		elog(FATAL, "%s: cannot open relation \"%-.*s\"",
			 command, DatabaseRelationName);

	/*
	 * Acquire a write lock on pg_database from the beginning to avoid
	 * upgrading a read lock to a write lock.  Upgrading causes long
	 * delays when multiple 'createdb's or 'destroydb's are run simult.
	 * -mer 7/3/91
	 */
	LockRelation(dbrel, AccessExclusiveLock);
	dbtup = get_pg_dbtup(command, dbname, dbrel);
	dbfound = HeapTupleIsValid(dbtup);

	if (dbfound)
	{
		dbowner = (int4) heap_getattr(dbtup,
									  Anum_pg_database_datdba,
									  RelationGetDescr(dbrel),
									  (char *) NULL);
		*dbIdP = dbtup->t_data->t_oid;
		dbtext = (text *) heap_getattr(dbtup,
									   Anum_pg_database_datpath,
									   RelationGetDescr(dbrel),
									   (char *) NULL);

		strncpy(path, VARDATA(dbtext), (VARSIZE(dbtext) - VARHDRSZ));
		*(path + VARSIZE(dbtext) - VARHDRSZ) = '\0';
	}
	else
		*dbIdP = InvalidOid;

	heap_close(dbrel);

	/*
	 * Now be sure that the user is allowed to do this.
	 */

	if (dbfound && !strcmp(command, "createdb"))
	{

		elog(ERROR, "createdb: database '%s' already exists", dbname);

	}
	else if (!dbfound && !strcmp(command, "destroydb"))
	{

		elog(ERROR, "destroydb: database '%s' does not exist", dbname);

	}
	else if (dbfound && !strcmp(command, "destroydb")
			 && dbowner != *userIdP && use_super == false)
	{

		elog(ERROR, "%s: database '%s' is not owned by you", command, dbname);

	}

	if (dbfound && !strcmp(command, "destroydb"))
		strcpy(dbpath, path);
}	/* check_permissions() */

/*
 *	stop_vacuum() -- stop the vacuum daemon on the database, if one is running.
 */
static void
stop_vacuum(char *dbpath, char *dbname)
{
	char		filename[256];
	FILE		*fp;
	int			pid;

	if (strchr(dbpath, SEP_CHAR) != 0)
	{
		snprintf(filename, 256, "%s%cbase%c%s%c%s.vacuum", 
				DataDir, SEP_CHAR, SEP_CHAR, dbname, SEP_CHAR, dbname);
	}
	else
		snprintf(filename, 256, "%s%c%s.vacuum", dbpath, SEP_CHAR, dbname);

	if ((fp = AllocateFile(filename, "r")) != NULL)
	{
		fscanf(fp, "%d", &pid);
		FreeFile(fp);
		if (kill(pid, SIGKILLDAEMON1) < 0)
		{
			elog(ERROR, "can't kill vacuum daemon (pid %d) on '%s'",
				 pid, dbname);
		}
	}
}
