/*-------------------------------------------------------------------------
 *
 * dbcommands.c
 *
 *
 * Portions Copyright (c) 1996-2000, PostgreSQL, Inc
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $Header: /cvsroot/pgsql/src/backend/commands/dbcommands.c,v 1.52 2000/03/26 18:32:28 petere Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
#include "commands/dbcommands.h"

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

#include "access/heapam.h"
#include "access/htup.h"
#include "access/skey.h"
#include "access/xact.h"
#include "catalog/catname.h"
#include "catalog/indexing.h"
#include "catalog/pg_database.h"
#include "catalog/pg_shadow.h"
#include "commands/comment.h"
#include "miscadmin.h"
#include "storage/bufmgr.h"        /* for DropBuffers */
#include "storage/fd.h"            /* for closeAllVfds */
#include "storage/sinval.h"        /* for DatabaseHasActiveBackends */
#include "utils/builtins.h"
#include "utils/elog.h"
#include "utils/palloc.h"
#include "utils/rel.h"
#include "utils/syscache.h"


/* non-export function prototypes */
static bool
get_user_info(const char *name, int4 *use_sysid, bool *use_super, bool *use_createdb);

static bool
get_db_info(const char *name, char *dbpath, Oid *dbIdP, int4 *ownerIdP);



/*
 * CREATE DATABASE
 */

void
createdb(const char *dbname, const char *dbpath, int encoding)
{
	char		buf[2 * MAXPGPATH + 100];
	char	   *loc;
    char        locbuf[512];
	int4		user_id;
    bool        use_super, use_createdb;
	Relation	pg_database_rel;
	HeapTuple	tuple;
    TupleDesc   pg_database_dsc;
    Datum       new_record[Natts_pg_database];
    char        new_record_nulls[Natts_pg_database] = { ' ', ' ', ' ', ' ' };

    if (!get_user_info(GetPgUserName(), &user_id, &use_super, &use_createdb))
        elog(ERROR, "current user name is invalid");

    if (!use_createdb && !use_super)
        elog(ERROR, "CREATE DATABASE: permission denied");

    if (get_db_info(dbname, NULL, NULL, NULL))
        elog(ERROR, "CREATE DATABASE: database \"%s\" already exists", dbname);

    /* don't call this in a transaction block */
	if (IsTransactionBlock())
        elog(ERROR, "CREATE DATABASE: may not be called in a transaction block");

	/* Generate directory name for the new database */
    if (dbpath == NULL || strcmp(dbpath, dbname)==0)
        strcpy(locbuf, dbname);
    else
        snprintf(locbuf, sizeof(locbuf), "%s/%s", dbpath, dbname);

    loc = ExpandDatabasePath(locbuf);

	if (loc == NULL)
		elog(ERROR,
             "The database path '%s' is invalid. "
			 "This may be due to a character that is not allowed or because the chosen "
             "path isn't permitted for databases", dbpath);

	/* close virtual file descriptors so the kernel has more available for
       the system() calls */
	closeAllVfds();

    /*
     * Insert a new tuple into pg_database
     */
	pg_database_rel = heap_openr(DatabaseRelationName, AccessExclusiveLock);
	pg_database_dsc = RelationGetDescr(pg_database_rel);

    /* Form tuple */
    new_record[Anum_pg_database_datname-1] = NameGetDatum(namein(dbname));
    new_record[Anum_pg_database_datdba-1] = Int32GetDatum(user_id);
    new_record[Anum_pg_database_encoding-1] = Int32GetDatum(encoding);
    new_record[Anum_pg_database_datpath-1] = PointerGetDatum(textin(locbuf));

    tuple = heap_formtuple(pg_database_dsc, new_record, new_record_nulls);

    /*
     * Update table
     */
    heap_insert(pg_database_rel, tuple);

    /*
     * Update indexes (there aren't any currently)
     */
#ifdef Num_pg_database_indices
    if (RelationGetForm(pg_database_rel)->relhasindex) {
        Relation idescs[Num_pg_database_indices];
      
        CatalogOpenIndices(Num_pg_database_indices, 
                           Name_pg_database_indices, idescs);
        CatalogIndexInsert(idescs, Num_pg_database_indices, pg_database_rel, 
                           tuple);
        CatalogCloseIndices(Num_pg_database_indices, idescs);
    }
#endif

	heap_close(pg_database_rel, NoLock);

    /* Copy the template database to the new location */

	if (mkdir(loc, S_IRWXU) != 0) {
		elog(ERROR, "CREATE DATABASE: unable to create database directory '%s': %s", loc, strerror(errno));
    }

	snprintf(buf, sizeof(buf), "cp %s%cbase%ctemplate1%c* '%s'",
			 DataDir, SEP_CHAR, SEP_CHAR, SEP_CHAR, loc);
	if (system(buf) != 0) {
        int ret;
        snprintf(buf, sizeof(buf), "rm -rf '%s'", loc);
        ret = system(buf);
        if (ret == 0)
            elog(ERROR, "CREATE DATABASE: could not initialize database directory");
        else
            elog(ERROR, "CREATE DATABASE: Could not initialize database directory. Delete failed as well");
    }
}



/*
 * DROP DATABASE
 */

void
dropdb(const char *dbname)
{
	int4		user_id, db_owner;
    bool        use_super;
	Oid			db_id;
	char	   *path,
				dbpath[MAXPGPATH],
				buf[MAXPGPATH + 100];
	Relation	pgdbrel;
	HeapScanDesc pgdbscan;
	ScanKeyData	key;
	HeapTuple	tup;

    AssertArg(dbname);

	if (strcmp(dbname, "template1") == 0)
		elog(ERROR, "DROP DATABASE: May not be executed on the template1 database");

	if (strcmp(dbname, DatabaseName) == 0)
		elog(ERROR, "DROP DATABASE: Cannot be executed on the currently open database");

	if (IsTransactionBlock())
        elog(ERROR, "DROP DATABASE: May not be called in a transaction block");

    if (!get_user_info(GetPgUserName(), &user_id, &use_super, NULL))
        elog(ERROR, "Current user name is invalid");

    if (!get_db_info(dbname, dbpath, &db_id, &db_owner))
        elog(ERROR, "DROP DATABASE: Database \"%s\" does not exist", dbname);

    if (user_id != db_owner && !use_super)
        elog(ERROR, "DROP DATABASE: Permission denied");

	path = ExpandDatabasePath(dbpath);
	if (path == NULL)
		elog(ERROR,
             "The database path '%s' is invalid. "
			 "This may be due to a character that is not allowed or because the chosen "
             "path isn't permitted for databases", path);

	/* close virtual file descriptors so the kernel has more available for
       the system() calls */
	closeAllVfds();

	/*
	 * Obtain exclusive lock on pg_database.  We need this to ensure
	 * that no new backend starts up in the target database while we
	 * are deleting it.  (Actually, a new backend might still manage to
	 * start up, because it will read pg_database without any locking
	 * to discover the database's OID.  But it will detect its error
	 * in ReverifyMyDatabase and shut down before any serious damage
	 * is done.  See postinit.c.)
	 */
	pgdbrel = heap_openr(DatabaseRelationName, AccessExclusiveLock);

	/*
	 * Check for active backends in the target database.
	 */
	if (DatabaseHasActiveBackends(db_id)) {
		heap_close(pgdbrel, AccessExclusiveLock);
		elog(ERROR, "DROP DATABASE: Database \"%s\" is being accessed by other users", dbname);
    }

	/*
	 * Find the database's tuple by OID (should be unique, we trust).
	 */
	ScanKeyEntryInitialize(&key, 0, ObjectIdAttributeNumber,
						   F_OIDEQ, ObjectIdGetDatum(db_id));

	pgdbscan = heap_beginscan(pgdbrel, 0, SnapshotNow, 1, &key);

	tup = heap_getnext(pgdbscan, 0);
	if (!HeapTupleIsValid(tup))
	{
		heap_close(pgdbrel, AccessExclusiveLock);
        /* This error should never come up since the existence of the
           database is checked earlier */
		elog(ERROR, "DROP DATABASE: Database \"%s\" doesn't exist despite earlier reports to the contrary",
			 dbname);
	}

	/* Delete any comments associated with the database */
	DeleteComments(db_id);

	/* Remove the database's tuple from pg_database */
	heap_delete(pgdbrel, &tup->t_self, NULL);

	heap_endscan(pgdbscan);

	/*
	 * Close pg_database, but keep exclusive lock till commit to ensure
	 * that any new backend scanning pg_database will see the tuple dead.
	 */
	heap_close(pgdbrel, NoLock);

	/*
	 * Drop pages for this database that are in the shared buffer cache.
	 * This is important to ensure that no remaining backend tries to
	 * write out a dirty buffer to the dead database later...
	 */
	DropBuffers(db_id);

	/*
	 * Remove the database's subdirectory and everything in it.
	 */
	snprintf(buf, sizeof(buf), "rm -rf '%s'", path);
	if (system(buf) != 0)
        elog(NOTICE, "DROP DATABASE: The database directory '%s' could not be removed", path);
}



/*
 * Helper functions
 */

static bool
get_db_info(const char *name, char *dbpath, Oid *dbIdP, int4 *ownerIdP)
{
	Relation	relation;
	HeapTuple	tuple;
	ScanKeyData scanKey;
    HeapScanDesc scan;

    AssertArg(name);

	relation = heap_openr(DatabaseRelationName, AccessExclusiveLock/*???*/);

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

	scan = heap_beginscan(relation, 0, SnapshotNow, 1, &scanKey);
	if (!HeapScanIsValid(scan))
		elog(ERROR, "Cannot begin scan of %s.", DatabaseRelationName);

	tuple = heap_getnext(scan, 0);

	if (HeapTupleIsValid(tuple))
	{
        text	   *tmptext;
        bool        isnull;
    
        /* oid of the database */
        if (dbIdP)
            *dbIdP = tuple->t_data->t_oid;
        /* uid of the owner */
        if (ownerIdP)
        {
            *ownerIdP = (int4) heap_getattr(tuple,
                                            Anum_pg_database_datdba,
                                            RelationGetDescr(relation),
                                            &isnull);
            if (isnull)
                *ownerIdP = -1; /* hopefully no one has that id already ;) */
        }
        /* database path (as registered in pg_database) */
        if (dbpath)
        {
            tmptext = (text *) heap_getattr(tuple,
                                            Anum_pg_database_datpath,
                                            RelationGetDescr(relation),
                                            &isnull);

            if (!isnull)
            {
                Assert(VARSIZE(tmptext) - VARHDRSZ < MAXPGPATH);

                strncpy(dbpath, VARDATA(tmptext), VARSIZE(tmptext) - VARHDRSZ);
                *(dbpath + VARSIZE(tmptext) - VARHDRSZ) = '\0';
            }
            else
                strcpy(dbpath, "");
        }
	}
	else
    {
        if (dbIdP)
            *dbIdP = InvalidOid;
    }

	heap_endscan(scan);

	/* We will keep the lock on the relation until end of transaction. */
	heap_close(relation, NoLock);

    return HeapTupleIsValid(tuple);
}



static bool
get_user_info(const char * name, int4 *use_sysid, bool *use_super, bool *use_createdb)
{
    HeapTuple   utup;

	AssertArg(name);
	utup = SearchSysCacheTuple(SHADOWNAME,
							   PointerGetDatum(name),
							   0, 0, 0);

    if (!HeapTupleIsValid(utup))
        return false;

    if (use_sysid)
        *use_sysid =    ((Form_pg_shadow) GETSTRUCT(utup))->usesysid;
    if (use_super)
        *use_super =    ((Form_pg_shadow) GETSTRUCT(utup))->usesuper;
    if (use_createdb)
        *use_createdb = ((Form_pg_shadow) GETSTRUCT(utup))->usecreatedb;

    return true;
}
