/*-------------------------------------------------------------------------
 *
 * genfile.c
 *		Functions for direct access to files
 *
 *
 * Copyright (c) 2004-2010, PostgreSQL Global Development Group
 *
 * Author: Andreas Pflug <pgadmin@pse-consulting.de>
 *
 * IDENTIFICATION
 *	  src/backend/utils/adt/genfile.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <sys/file.h>
#include <sys/stat.h>
#include <unistd.h>
#include <dirent.h>

#include "catalog/pg_type.h"
#include "funcapi.h"
#include "mb/pg_wchar.h"
#include "miscadmin.h"
#include "postmaster/syslogger.h"
#include "storage/fd.h"
#include "utils/builtins.h"
#include "utils/memutils.h"
#include "utils/timestamp.h"

typedef struct
{
	char	   *location;
	DIR		   *dirdesc;
} directory_fctx;


/*
 * Convert a "text" filename argument to C string, and check it's allowable.
 *
 * Filename may be absolute or relative to the DataDir, but we only allow
 * absolute paths that match DataDir or Log_directory.
 */
static char *
convert_and_check_filename(text *arg)
{
	char	   *filename;

	filename = text_to_cstring(arg);
	canonicalize_path(filename);	/* filename can change length here */

	/* Disallow ".." in the path */
	if (path_contains_parent_reference(filename))
		ereport(ERROR,
				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
			(errmsg("reference to parent directory (\"..\") not allowed"))));

	if (is_absolute_path(filename))
	{
		/* Allow absolute references within DataDir */
		if (path_is_prefix_of_path(DataDir, filename))
			return filename;
		/* The log directory might be outside our datadir, but allow it */
		if (is_absolute_path(Log_directory) &&
			path_is_prefix_of_path(Log_directory, filename))
			return filename;

		ereport(ERROR,
				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
				 (errmsg("absolute path not allowed"))));
		return NULL;			/* keep compiler quiet */
	}
	else
	{
		return filename;
	}
}


/*
 * Read a section of a file, returning it as text
 */
Datum
pg_read_file(PG_FUNCTION_ARGS)
{
	text	   *filename_t = PG_GETARG_TEXT_P(0);
	int64		seek_offset = PG_GETARG_INT64(1);
	int64		bytes_to_read = PG_GETARG_INT64(2);
	char	   *buf;
	size_t		nbytes;
	FILE	   *file;
	char	   *filename;

	if (!superuser())
		ereport(ERROR,
				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
				 (errmsg("must be superuser to read files"))));

	filename = convert_and_check_filename(filename_t);

	if ((file = AllocateFile(filename, PG_BINARY_R)) == NULL)
		ereport(ERROR,
				(errcode_for_file_access(),
				 errmsg("could not open file \"%s\" for reading: %m",
						filename)));

	if (fseeko(file, (off_t) seek_offset,
			   (seek_offset >= 0) ? SEEK_SET : SEEK_END) != 0)
		ereport(ERROR,
				(errcode_for_file_access(),
				 errmsg("could not seek in file \"%s\": %m", filename)));

	if (bytes_to_read < 0)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("requested length cannot be negative")));

	/* not sure why anyone thought that int64 length was a good idea */
	if (bytes_to_read > (MaxAllocSize - VARHDRSZ))
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("requested length too large")));

	buf = palloc((Size) bytes_to_read + VARHDRSZ);

	nbytes = fread(VARDATA(buf), 1, (size_t) bytes_to_read, file);

	if (ferror(file))
		ereport(ERROR,
				(errcode_for_file_access(),
				 errmsg("could not read file \"%s\": %m", filename)));

	/* Make sure the input is valid */
	pg_verifymbstr(VARDATA(buf), nbytes, false);

	SET_VARSIZE(buf, nbytes + VARHDRSZ);

	FreeFile(file);
	pfree(filename);

	PG_RETURN_TEXT_P(buf);
}

/*
 * stat a file
 */
Datum
pg_stat_file(PG_FUNCTION_ARGS)
{
	text	   *filename_t = PG_GETARG_TEXT_P(0);
	char	   *filename;
	struct stat fst;
	Datum		values[6];
	bool		isnull[6];
	HeapTuple	tuple;
	TupleDesc	tupdesc;

	if (!superuser())
		ereport(ERROR,
				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
				 (errmsg("must be superuser to get file information"))));

	filename = convert_and_check_filename(filename_t);

	if (stat(filename, &fst) < 0)
		ereport(ERROR,
				(errcode_for_file_access(),
				 errmsg("could not stat file \"%s\": %m", filename)));

	/*
	 * This record type had better match the output parameters declared for me
	 * in pg_proc.h.
	 */
	tupdesc = CreateTemplateTupleDesc(6, false);
	TupleDescInitEntry(tupdesc, (AttrNumber) 1,
					   "size", INT8OID, -1, 0);
	TupleDescInitEntry(tupdesc, (AttrNumber) 2,
					   "access", TIMESTAMPTZOID, -1, 0);
	TupleDescInitEntry(tupdesc, (AttrNumber) 3,
					   "modification", TIMESTAMPTZOID, -1, 0);
	TupleDescInitEntry(tupdesc, (AttrNumber) 4,
					   "change", TIMESTAMPTZOID, -1, 0);
	TupleDescInitEntry(tupdesc, (AttrNumber) 5,
					   "creation", TIMESTAMPTZOID, -1, 0);
	TupleDescInitEntry(tupdesc, (AttrNumber) 6,
					   "isdir", BOOLOID, -1, 0);
	BlessTupleDesc(tupdesc);

	memset(isnull, false, sizeof(isnull));

	values[0] = Int64GetDatum((int64) fst.st_size);
	values[1] = TimestampTzGetDatum(time_t_to_timestamptz(fst.st_atime));
	values[2] = TimestampTzGetDatum(time_t_to_timestamptz(fst.st_mtime));
	/* Unix has file status change time, while Win32 has creation time */
#if !defined(WIN32) && !defined(__CYGWIN__)
	values[3] = TimestampTzGetDatum(time_t_to_timestamptz(fst.st_ctime));
	isnull[4] = true;
#else
	isnull[3] = true;
	values[4] = TimestampTzGetDatum(time_t_to_timestamptz(fst.st_ctime));
#endif
	values[5] = BoolGetDatum(S_ISDIR(fst.st_mode));

	tuple = heap_form_tuple(tupdesc, values, isnull);

	pfree(filename);

	PG_RETURN_DATUM(HeapTupleGetDatum(tuple));
}


/*
 * List a directory (returns the filenames only)
 */
Datum
pg_ls_dir(PG_FUNCTION_ARGS)
{
	FuncCallContext *funcctx;
	struct dirent *de;
	directory_fctx *fctx;

	if (!superuser())
		ereport(ERROR,
				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
				 (errmsg("must be superuser to get directory listings"))));

	if (SRF_IS_FIRSTCALL())
	{
		MemoryContext oldcontext;

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

		fctx = palloc(sizeof(directory_fctx));
		fctx->location = convert_and_check_filename(PG_GETARG_TEXT_P(0));

		fctx->dirdesc = AllocateDir(fctx->location);

		if (!fctx->dirdesc)
			ereport(ERROR,
					(errcode_for_file_access(),
					 errmsg("could not open directory \"%s\": %m",
							fctx->location)));

		funcctx->user_fctx = fctx;
		MemoryContextSwitchTo(oldcontext);
	}

	funcctx = SRF_PERCALL_SETUP();
	fctx = (directory_fctx *) funcctx->user_fctx;

	while ((de = ReadDir(fctx->dirdesc, fctx->location)) != NULL)
	{
		if (strcmp(de->d_name, ".") == 0 ||
			strcmp(de->d_name, "..") == 0)
			continue;

		SRF_RETURN_NEXT(funcctx, CStringGetTextDatum(de->d_name));
	}

	FreeDir(fctx->dirdesc);

	SRF_RETURN_DONE(funcctx);
}
