/* Copyright (c) 1993 by Sanjay Ghemawat */

#include <sys/types.h>
#include <sys/file.h>
#include <stdlib.h>

#include <stddef.h>
#include <errno.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <stdio.h>
#include <string.h>

#include "basic.h"
#include "config.h"

#include "calfile.h"
#include "calendar.h"
#include "lexer.h"
#include "misc.h"
#include "statfix.h"
#include "uid.h"

#include <unistd.h>

// Only use "fsync" if it is available.
#ifdef HAVE_FSYNC
extern "C" int fsync(int);
#else
static int fsync(int) {return 0;}
#endif

static char const* sys_error();		// Last system error msg

// Get various file names
static char const* home_backup_file();	// Backup file in home dir
static char const* tmp_backup_file();	// Backup file in tmp dir

static int backup_file(char const* src, char const* dst, long mode);
// effects	Backup file named "src" to file named "dst".
//		Change the mode of "dst" to "mode".
//		Return true iff successful.

const char* CalFile::lastError = "no error";

CalFile::CalFile(int ro, const char* name) {
    readOnly = ro;

    int len = strlen(name);
    char* tmp;

    // Copy file name
    tmp = new char[len+1];
    strcpy(tmp, name);
    fileName = tmp;

    // Copy backup file name
    tmp = new char[len+2];
    sprintf(tmp, "%s~", fileName);
    backupName = tmp;

    // Get directory name for access checks
    char* lastSlash = strrchr(name, '/');
    if (lastSlash == 0) {
	/* Calendar is in current directory */
	tmp = new char[3];
	strcpy(tmp, "./");
    }
    else {
	int dirlen = lastSlash + 1 - name;
	tmp = new char[dirlen+1];
	strncpy(tmp, name, dirlen);
	tmp[dirlen] = '\0';
    }
    dirName = tmp;

    // Get temporary file name.  Make sure it works even
    // on systems with a 14 character file name limit.
    tmp = new char[strlen(dirName)+20];
    sprintf(tmp, "%sical%d~", dirName, getpid());
    tmpName = tmp;

    lastModifyValid = 0;

    calendar = new Calendar;
    calendar->SetReadOnly(readOnly);

    modified = 0;
}

CalFile::~CalFile() {
    delete calendar;
    delete fileName;
    delete backupName;
    delete tmpName;
    delete dirName;
}

void CalFile::Modified() {
    modified = 1;
}

int CalFile::Write() {
    // Get information about the calendar file
    struct stat buf;
    int is_slink = 0;

    int result = lstat(fileName, &buf);
    if ((result >= 0) && S_ISLNK(buf.st_mode)) {
	// Get mode for real referenced file
	is_slink = 1;
	result = stat(fileName, &buf);
    }

    if (result < 0) {
	/* Could not get file mode */
	if (errno == ENOENT) {
	    /* Original file does not even exist - try to write directly */
	    if (WriteTo(calendar, fileName)) {
		written();
		return 1;
	    }
	}
	return 0;
    }

    long mode = buf.st_mode & 07777;

    // See if file is a link, or if the containing directory is write-protected
    if (is_slink || (buf.st_nlink > 1) || (access(dirName, W_OK) < 0)) {
	// Backup by copying to preserve links
	return WriteInPlace(mode);
    }
    else {
	// Backup by renaming old version if possible
	return WriteNew(mode);
    }
}

// Write calendar to temporary location, rename the current version
// to a backup file and then rename the new version to the right
// file name.

int CalFile::WriteNew(long mode) {
    if (! WriteTo(calendar, tmpName)) {
	unlink(tmpName);
	return 0;
    }

    if (chmod(tmpName, mode) < 0) {
	/* Could not set new file mode */
	lastError = sys_error();
	unlink(tmpName);
	return 0;
    }

    // We could conceivably do more sanity checks here.

    // Create backup file.
    // We could check for errors and fail here, but that seems too paranoid.
    unlink(backupName);
    link(fileName, backupName);

    // Now rename the new version
    if (rename(tmpName, fileName) < 0) {
	lastError = sys_error();
	unlink(tmpName);
	return 0;
    }

    written();
    return 1;
}

// First backup the current stable version of the calendar, and then
// write a new version in place.

int CalFile::WriteInPlace(long mode) {
    // XXX Should we just ignore errors while making a backup?
    CopyBackup(mode);

    if (WriteTo(calendar, fileName)) {
	written();
	return 1;
    }

    return 0;
}

int CalFile::CopyBackup(long mode) {
    // Try backing up in various place until we succeed:
    //
    // * backupName
    // * In home directory
    // * In tmp directory

    if (backup_file(fileName, backupName,	   mode)) return 1;
    if (backup_file(fileName, home_backup_file(),  mode)) return 1;
    if (backup_file(fileName, tmp_backup_file(),   mode)) return 1;

    return 0;
}

int CalFile::Read() {
    Calendar* old = ReRead();
    if (old != 0) {
	delete old;
	return 1;
    }
    return 0;
}

Calendar* CalFile::ReRead() {
    Time newFileTime;
    int gotTime = GetModifyTime(fileName, newFileTime);

    Calendar* cal = ReadFrom(fileName);
    Calendar* old = 0;
    if (cal != 0) {
	old = calendar;
	calendar = cal;
	calendar->SetReadOnly(readOnly);

	PerformAccessCheck();

	modified = 0;

	lastModifyValid = gotTime;
	if (gotTime)
	    lastModifyTime = newFileTime;
    }
    return old;
}

int CalFile::FileHasChanged() {
    PerformAccessCheck();

    Time newModifyTime;
    int newModifyValid = GetModifyTime(fileName, newModifyTime);

    if (newModifyValid != lastModifyValid) {
	/* Ability to read file information changed */
	return 1;
    }

    return (lastModifyValid && (newModifyTime != lastModifyTime));
}

Calendar* CalFile::ReadFrom(const char* name) {
    Calendar* cal = new Calendar;
    Lexer input(name);

    if (! cal->Read(&input)) {
	lastError = input.LastError();
	delete cal;
	cal = 0;
    }

    return cal;
}

int CalFile::WriteTo(Calendar* cal, const char* name) {
    FILE* output = fopen(name, "w");
    if (! output) {
	lastError = "could not open file for writing calendar";
        return 0;
    }

    cal->Write(output);
    fflush(output);
    if (ferror(output) || (fsync(fileno(output)) < 0)) {
	lastError = "error writing calendar file";
        fclose(output);
        return 0;
    }

    fclose(output);
    return 1;
}

int CalFile::GetModifyTime(char const* file, Time& t) {
    struct stat buf;

    int ret = stat(file, &buf);
    if (ret < 0) return 0;

    struct timeval tv;
    tv.tv_sec  = buf.st_mtime;
    tv.tv_usec = 0;

    t = Time(tv);
    return 1;
}

void CalFile::PerformAccessCheck() {
    calendar->SetReadOnly(readOnly);

    if (access(fileName, W_OK) < 0) {
	switch (errno) {
	  case ENOENT:
	    /* File does not exist */
	    break;
	  case EACCES:
	  case EROFS:
	  case ETXTBSY:
	    /* Permission denied */
	    calendar->SetReadOnly(1);
	    break;
	  default:
	    /* Should not happen if we were successfuly able to read cal */
	    break;
	}
    }
}

void CalFile::written() {
    modified = 0;
    lastModifyValid = GetModifyTime(fileName, lastModifyTime);
}

/* How to get U*ix error message */
#ifdef HAVE_STRERROR

#ifndef HAVE_STRERROR_PROTO
extern "C" {
    extern char* strerror(int);
}
#endif

static char const* sys_error() {
    return (strerror(errno));
}

#else /* !HAVE_STRERROR */

#ifndef HAVE_SYS_ERRLIST_PROTO

extern "C" {
    extern char* sys_errlist[];
}

#endif /* HAVE_SYS_ERRLIST_PROTO */

static char const* sys_error() {
    return sys_errlist[errno];
}

#endif /* !HAVE_STRERROR */

static int backup_file(char const* src, char const* dst, long mode) {
    if (dst == 0) return 0;
    if (!copy_file(src, dst)) return 0;

    // XXX Ignoring error while changing mode of backup file
    chmod(dst, mode);
    return 1;
}

static char const* home_backup_file() {
    static char const* part_name = "icalbak~";
    static char const* full_name = 0;
    static int inited = 0;

    // Make sure we initialize only once
    if (!inited) {
	inited = 1;
	char const* home = getenv("HOME");
	if (home != 0) {
	    char* copy = new char[strlen(home) + strlen(part_name) + 2];
	    sprintf(copy, "%s/%s", home, part_name);
	    full_name = copy;
	}
    }

    return full_name;
}

static char const* tmp_backup_file() {
    static char const* prefix = "/tmp/ical_";
    static char const* full_name = 0;
    static int inited = 0;

    // Make sure we initialize only once
    if (!inited) {
	inited = 1;
	char const* uid = my_name();
	if (uid != 0) {
	    char* copy = new char[strlen(prefix) + strlen(uid) + 2];
	    sprintf(copy, "%s%s~", prefix, uid);
	    full_name = copy;
	}
    }

    return full_name;
}