#!/bin/bash
#
# A replacement of the logrotate's copytruncate method to use when:
# * we haven't permission to change ownership, so the built-in copytruncate
#   method would fail (this is a bug in logrotate, I think);
# * we haven't permission to reload the service, so the create new log method
#   doesn't work - the service would still write to the already rotated file.
#
# This script, when called as a prerotate script from logrotate configuration:
# * copytruncates a file having $LOGEXT (see below) extesion and compresses it
#   (and returns with 1 exit code, thus, the logrotate will skip this file).
# * does nothing with files having any other extensions - e.g .1, .2 and so on
#   (and returns with 0 exit code, thus, the logrotate can process this file);
#
# In other words, with default settings it simulates the effect of logrotate
# configuration options below:
#   <pathname>/*.log {
#     dateext
#     dateyesterday
#     dateformat %Y-%m-%d.
#     extension log
#     compress
#     copytruncate
#     [...]
#   }
# but doesn't stop if failed to set the permissions during copytruncate.
#
# The script receives the file to process as it's first command line parameter.
# Lack of the parameter it simply does nothing.
#
# Author: Kovács Zoltán <kovacs.zoltan@smartfront.hu>
#         Kovács Zoltán <kovacsz@marcusconsulting.hu>
# License: GNU/GPL v3+ (https://www.gnu.org/licenses/gpl-3.0.en.html)
# 2023-06-18 v1.0
# new: forked from the "SMARTERP_skeleton" repository.
# 2020-11-09 v0.1 Initial release

# Configurable parameters - must be consistent with the logrotate configuration.
#
DATESTRING="$(date "+%Y-%m-%d" -d '1 day ago')"	# Yesterday goes to the filename
LOGEXT="log"					# Processes only *.$LOGEXT files

# Messages.
MSG_MISSINGDEP="Fatal: missing dependency"

# Checks the dependencies.
TR=$(which tr 2>/dev/null)
if [ -z "$TR" ]; then echo "$MSG_MISSINGDEP tr."; exit 1 ; fi
for item in basename cp dirname gzip
do
    if [ -n "$(which $item)" ]
    then export $(echo $item | "$TR" '[:lower:]' '[:upper:]')=$(which $item)
    else echo "$MSG_MISSINGDEP $item." >&2; exit 1; fi
done
# All dependencies are available via "$THECOMMAND" (upper case) call.
#
# An additional bugfix (use "$(which gzip)" instead of "$GZIP"):
# https://www.gnu.org/software/gzip/manual/html_node/Environment.html
GZIP=""

# Lack of the parameter (unlikely) it simply does nothing.
# The script returns an OK status, so the logrotate will continue.
[[ -z "$1" ]] && exit 0
# Parses the parameter.
LOGDIR="$("$DIRNAME" $1)"
LOGFILE="$("$BASENAME" $1)"
NEWFILE="${LOGFILE%.*}.$DATESTRING.${LOGFILE##*.}"

# If the parameter doesn't point to a writeable file it simply does nothing.
[[ ! -w "$LOGDIR/$LOGFILE" ]] && exit 0
# If the log's folder isn't writable it simply does nothing.
[[ ! -w "$LOGDIR" ]] && exit 0
# If the extension doesn't match it simply does nothing.
[[ "${LOGFILE##*.}" != "$LOGEXT" ]] && exit 0
# Cases above must handled by the logrotate itself.
# The script returns an OK status, so the logrotate will continue.

# Doesn't copy if it would overwrite something.
# Returns an error status, so the logrotate won't process this file.
[[ -e "$LOGDIR/$NEWFILE" ]]    && exit 1
[[ -e "$LOGDIR/$NEWFILE.gz" ]] && exit 1
# Tries to copy the current logfile.
"$CP" -p "$LOGDIR/$LOGFILE" "$LOGDIR/$NEWFILE" # >/dev/null 2>&1
# On error returns an error status so the logrotate won't process this file.
[[ ! -r "$LOGDIR/$NEWFILE" ]] && exit 1
# Done with copy. Tries to empty the current logfile. Doesn't check the result.
: >"$LOGDIR/$LOGFILE"
# Compresses the rotated logfile. Doesn't check the result.
"$(which gzip)" "$LOGDIR/$NEWFILE" #>/dev/null 2>&1
# Returns a fake error status to prevent the logrotate to process this file.
exit 1

# That's all, Folks! :)