/*-------------------------------------------------------------------------
 *
 * database.c
 *    Commands to interact with the database object in a distributed
 *    environment.
 *
 * Copyright (c) Citus Data, Inc.
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "miscadmin.h"

#include "access/htup_details.h"
#include "access/xact.h"
#include "catalog/objectaddress.h"
#include "catalog/pg_database.h"
#include "commands/dbcommands.h"
#include "nodes/parsenodes.h"
#include "utils/syscache.h"

#include "distributed/commands.h"
#include "distributed/commands/utility_hook.h"
#include "distributed/deparser.h"
#include "distributed/metadata/distobject.h"
#include "distributed/metadata_sync.h"
#include "distributed/metadata_utility.h"
#include "distributed/multi_executor.h"
#include "distributed/relation_access_tracking.h"
#include "distributed/worker_transaction.h"

static AlterOwnerStmt * RecreateAlterDatabaseOwnerStmt(Oid databaseOid);
static Oid get_database_owner(Oid db_oid);
static ObjectAddress * GetDatabaseAddressFromDatabaseName(char *databaseName,
														  bool missingOk);
List * PreprocessGrantOnDatabaseStmt(Node *node, const char *queryString,
									 ProcessUtilityContext processUtilityContext);

/* controlled via GUC */
bool EnableAlterDatabaseOwner = true;


/*
 * AlterDatabaseOwnerObjectAddress returns the ObjectAddress of the database that is the
 * object of the AlterOwnerStmt. Errors if missing_ok is false.
 */
List *
AlterDatabaseOwnerObjectAddress(Node *node, bool missing_ok, bool isPostprocess)
{
	AlterOwnerStmt *stmt = castNode(AlterOwnerStmt, node);
	Assert(stmt->objectType == OBJECT_DATABASE);

	Oid databaseOid = get_database_oid(strVal((String *) stmt->object), missing_ok);
	ObjectAddress *address = palloc0(sizeof(ObjectAddress));
	ObjectAddressSet(*address, DatabaseRelationId, databaseOid);

	return list_make1(address);
}


/*
 * DatabaseOwnerDDLCommands returns a list of sql statements to idempotently apply a
 * change of the database owner on the workers so that the database is owned by the same
 * user on all nodes in the cluster.
 */
List *
DatabaseOwnerDDLCommands(const ObjectAddress *address)
{
	Node *stmt = (Node *) RecreateAlterDatabaseOwnerStmt(address->objectId);
	return list_make1(DeparseTreeNode(stmt));
}


/*
 * RecreateAlterDatabaseOwnerStmt creates an AlterOwnerStmt that represents the operation
 * of changing the owner of the database to its current owner.
 */
static AlterOwnerStmt *
RecreateAlterDatabaseOwnerStmt(Oid databaseOid)
{
	AlterOwnerStmt *stmt = makeNode(AlterOwnerStmt);

	stmt->objectType = OBJECT_DATABASE;
	stmt->object = (Node *) makeString(get_database_name(databaseOid));

	Oid ownerOid = get_database_owner(databaseOid);
	stmt->newowner = makeNode(RoleSpec);
	stmt->newowner->roletype = ROLESPEC_CSTRING;
	stmt->newowner->rolename = GetUserNameFromId(ownerOid, false);

	return stmt;
}


/*
 * get_database_owner returns the Oid of the role owning the database
 */
static Oid
get_database_owner(Oid db_oid)
{
	HeapTuple tuple = SearchSysCache1(DATABASEOID, ObjectIdGetDatum(db_oid));
	if (!HeapTupleIsValid(tuple))
	{
		ereport(ERROR, (errcode(ERRCODE_UNDEFINED_DATABASE),
						errmsg("database with OID %u does not exist", db_oid)));
	}

	Oid dba = ((Form_pg_database) GETSTRUCT(tuple))->datdba;

	ReleaseSysCache(tuple);

	return dba;
}


/*
 * PreprocessGrantOnDatabaseStmt is executed before the statement is applied to the local
 * postgres instance.
 *
 * In this stage we can prepare the commands that need to be run on all workers to grant
 * on databases.
 */
List *
PreprocessGrantOnDatabaseStmt(Node *node, const char *queryString,
							  ProcessUtilityContext processUtilityContext)
{
	if (!ShouldPropagate())
	{
		return NIL;
	}

	GrantStmt *stmt = castNode(GrantStmt, node);
	Assert(stmt->objtype == OBJECT_DATABASE);

	List *databaseList = stmt->objects;

	if (list_length(databaseList) == 0)
	{
		return NIL;
	}

	EnsureCoordinator();

	char *sql = DeparseTreeNode((Node *) stmt);

	List *commands = list_make3(DISABLE_DDL_PROPAGATION,
								(void *) sql,
								ENABLE_DDL_PROPAGATION);

	return NodeDDLTaskList(NON_COORDINATOR_NODES, commands);
}


/*
 * PreprocessAlterDatabaseStmt is executed before the statement is applied to the local
 * postgres instance.
 *
 * In this stage we can prepare the commands that need to be run on all workers to grant
 * on databases.
 */
List *
PreprocessAlterDatabaseStmt(Node *node, const char *queryString,
							ProcessUtilityContext processUtilityContext)
{
	AlterDatabaseStmt *stmt = castNode(AlterDatabaseStmt, node);
	bool missingOk = false;
	ObjectAddress *dbAddress = GetDatabaseAddressFromDatabaseName(stmt->dbname,
																  missingOk);
	if (!ShouldPropagate() || !IsAnyObjectDistributed(list_make1(dbAddress)))
	{
		return NIL;
	}

	EnsureCoordinator();

	char *sql = DeparseTreeNode((Node *) stmt);

	List *commands = list_make3(DISABLE_DDL_PROPAGATION,
								(void *) sql,
								ENABLE_DDL_PROPAGATION);

	return NodeDDLTaskList(NON_COORDINATOR_NODES, commands);
}


/*
 * PreprocessAlterDatabaseSetStmt is executed before the statement is applied to the local
 * postgres instance.
 *
 * In this stage we can prepare the commands that need to be run on all workers to grant
 * on databases.
 */
List *
PreprocessAlterDatabaseRefreshCollStmt(Node *node, const char *queryString,
									   ProcessUtilityContext processUtilityContext)
{
	if (!ShouldPropagate())
	{
		return NIL;
	}

	AlterDatabaseRefreshCollStmt *stmt = castNode(AlterDatabaseRefreshCollStmt, node);

	EnsureCoordinator();

	char *sql = DeparseTreeNode((Node *) stmt);

	List *commands = list_make3(DISABLE_DDL_PROPAGATION,
								(void *) sql,
								ENABLE_DDL_PROPAGATION);

	return NodeDDLTaskList(NON_COORDINATOR_NODES, commands);
}


/*
 * GetDatabaseAddressFromDatabaseName gets the database name and returns the ObjectAddress
 * of the database.
 */
static ObjectAddress *
GetDatabaseAddressFromDatabaseName(char *databaseName, bool missingOk)
{
	Oid databaseOid = get_database_oid(databaseName, missingOk);
	ObjectAddress *dbObjectAddress = palloc0(sizeof(ObjectAddress));
	ObjectAddressSet(*dbObjectAddress, DatabaseRelationId, databaseOid);
	return dbObjectAddress;
}