#!/bin/bash
# No way I try to deal with a crippled sh just for POSIX foo.

# Copyright (C) 2009-2016, 2018 Joerg Jaspert <joerg@debian.org>
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License as
# published by the Free Software Foundation; version 2.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

# Homer: Are you saying you're never going to eat any animal again? What
#        about bacon?
# Lisa: No.
# Homer: Ham?
# Lisa: No.
# Homer: Pork chops?
# Lisa: Dad, those all come from the same animal.
# Homer: Heh heh heh. Ooh, yeah, right, Lisa. A wonderful, magical animal.

# exit on errors
set -e
# A pipeline's return status is the value of the last (rightmost)
# command to exit with a non-zero status, or zero if all commands exit
# successfully.
set -o pipefail
# make sure to only use defined variables
set -u
# ERR traps should be inherited from functions too. (And command
# substitutions and subshells and whatnot, but for us the functions is
# the important part here)
set -E

# If the extglob shell option is enabled using the shopt builtin,
# several extended pattern matching operators are recognized. We use
# it for the POSSIBLEARGS and the first case ${ARGS} matching.
shopt -s extglob

# And use one locale, no matter what the caller has set
export LANG=C.UTF-8
export LC_ALL=C.UTF-8

# One arg please
declare -lr ARG=${1:-"meh"}

# program name is the (lower cased) first argument.
PROGRAM="${ARG}"

# import the general variable set. (This will overwrite configdir, but
# it is expected to have the same value)
export SCRIPTVARS=${configdir:?Please define configdir to run this script}/vars
. ${SCRIPTVARS}

# set DEBUG if you want to see a little more logs (needs to be used more)
DEBUG=${DEBUG:-0}

# Check if the argument is a known one. If so, lock us so that only
# one copy of the type of cronscript runs. The $type.tasks file is
# mandantory, so use that for locking.
case ${ARG} in
    ${POSSIBLEARGS})
        # Only one of me should ever run.
        FLOCKER=${FLOCKER:-""}
        [[ ${FLOCKER} != ${configdir}/${PROGRAM}.tasks ]] && exec env FLOCKER="${configdir}/${PROGRAM}.tasks" flock -E 0 -en "${configdir}/${PROGRAM}.tasks" "$0" "$@" || :
        ;;
    *)
        cat - <<EOF
This is the cronscript. It needs an argument or it won't do anything
for you.

Currently accepted Arguments: ${POSSIBLEARGS}

To see what they do, you want to look at the files
\$ARGUMENT.{tasks,functions,variables} in ${configdir}.

EOF
        exit 0
        ;;
esac

function includetasks() {
    local NAME=${1:?}

    _preparetasks ${NAME}
    _runtasks ${NAME}
}

function _preparetasks() {
    local NAME=${1:?}

    # Each "cronscript" may have a variables and a functions file
    # that we source
    for what in variables functions; do
        if [[ -f ${configdir}/${NAME}.${what} ]]; then
            . ${configdir}/${NAME}.${what}
        fi
    done
}

function _runtasks() {
    local NAME=${1:?}

    # Which list of tasks should we run?
    local TASKLIST="${configdir}/${NAME}.tasks"

    # This loop simply wants to be fed by a list of values (see below)
    # made out of 5 columns.
    # The first four are the array values for the stage function, the
    # fifth tells us if we should background the stage call.
    #
    #  - FUNC - the function name to call
    #  - ARGS - Possible arguments to hand to the function. Can be the empty string
    #  - TIME - The timestamp name. Can be the empty string
    #  - ERR  - if this is the string false, then the call will be surrounded by
    #           set +e ... set -e calls, so errors in the function do not exit
    #           the script. Can be the empty string, meaning true.
    #  - BG   - Background the function stage?
    #
    # ATTENTION: Spaces in arguments or timestamp names need to be escaped by \
    #
    # NOTE 1: There are special values for the first column (FUNC).
    #         NOSTAGE - do not call stage function, call the command directly.
    #         RMSTAGE - clean out the stages directory, and as such
    #                   the recording what already ran in an earlier cronscript.
    #                   Note: Only really makes sense at beginning of a tasks file,
    #                   the stages directory gets cleared at successful exit anyways.
    #                   RMSTAGE simply ensures that ALL of the crons tasks ALWAYS run.
    #         INCLUDE - Runs another task list after including corresponding functions

    # Note 2: If you want to hand an empty value to the stage function,
    #         use the word "none" in the list below.
    while read FUNC ARGS TIME ERR BACKGROUND; do
        debug "FUNC: $FUNC ARGS: $ARGS TIME: $TIME ERR: $ERR BG: $BACKGROUND"

        # Empty values in the value list are the string "none" (or the
        # while read loop won't work). Here we ensure that variables that
        # can be empty, are empty if the string none is set for them.
        for var in ARGS TIME; do
            if [[ ${!var} == none ]]; then
                typeset ${var}=''
            fi
        done

        # ERR/BACKGROUND are boolean for all but LOCK/UNLOCK, check that they are.
        for var in ERR BACKGROUND; do
            if [[ ${!var} != false ]] && [[ ${!var} != true ]]; then
                if [[ ${FUNC} != LOCK ]] && [[ ${FUNC} != UNLOCK ]]; then
                    error "Illegal value ${!var} for ${var} (should be true or false), line for function ${FUNC}"
                fi
            fi
        done
        case ${FUNC} in
            NOSTAGE)
                ${ARGS}
                ;;
            RMSTAGE)
                # Make sure we remove our stage files, so all the
                # actions will be done again.
                rm -f ${stagedir}/*
                ;;
            LOCK)
                # We are asked to set a lock, so try to get it.
                # For this we redefine what the columns mean.
                # ARGS: Name of the lockfile
                # TIME: How long to wait for getting the (exclusive) lock
                # ERR: shared == shared lock, may be hold more than once, exclusive == exclusive, only one.

                lock ${ARGS} ${TIME} ${ERR}
                ;;
            UNLOCK)
                unlock ${ARGS}
                ;;
            INCLUDE)
                includetasks ${ARGS}
                ;;
            *)
                GO=(
                    FUNC="${FUNC}"
                    TIME="${TIME}"
                    ARGS="${ARGS}"
                    ERR="${ERR}"
                )
                if [[ ${BACKGROUND} == true ]]; then
                    stage $GO &
                else
                    stage $GO
                fi
                ;;
        esac < /dev/null
    done < <(grep -v '^#' ${TASKLIST} )
}

function lock() {
    local LOCK=${1:-}
    local TIME=${2:-600}
    local TYPE=${3:-exclusive}

    if [[ -z ${LOCK} ]]; then
        log_error "No lockfile name given"
        exit 21
    fi

    local LOCKFILE=

    if [[ $LOCK == /* ]]; then
        LOCKFILE=${LOCK}
    else
        # Prepend LOCK_ to lock name to get to variable name,
        # kind of namespace
        local lvar="LOCK_${LOCK}"
        LOCKFILE=${!lvar}
    fi

    # bash can't open a file read-only, while creating it,
    # so we need to create it ourselves.
    if ! [[ -e $LOCKFILE ]]; then
        install -m 444 /dev/null $LOCKFILE || {
            log_error "Could not create lock ${LOCKFILE}"
            laststeps 2
        }
    fi

    # Get filehandle
    local randomstring
    exec {randomstring}<${LOCKFILE}
    # Store filehandle for later
    LOCKFD[${LOCK}]=${randomstring}

    # "Abusing" the err column, expecting the shared/exclusive value there.
    # Any wrong value means exclusive.
    case ${ERR} in
        shared|exclusive)
            flockparm="--${ERR}"
            ;;
        *)
            flockparm="--exclusive"
            ;;
    esac

    # Deal with time being special, usually it means false or true,
    # but for locks we want a timeout. So if its set to one of the usuals,
    # assume 300
    if [[ ${TIME} == none ]]; then
        TIME=300
    fi
    # Now try to get the lock
    set +e
    flock ${flockparm} --timeout ${TIME} --conflict-exit-code 3 ${LOCKFD[${LOCK}]}
    ret=$?
    set -e
    case ${ret} in
        0)
            return
            ;;
        3)
            log_error "Could not get lock ${LOCKFILE}, timeout"
            laststeps 2
            ;;
        *)
            log_error "Could not get lock ${LOCKFILE}"
            laststeps 2
    esac
}

function unlock() {
    local LOCK=${1:-}
    if [[ -z ${LOCK} ]]; then
        # Warn, but continue, unlock will happen at script end time
        log "No lockfile name given"
    fi

    local randomstring=${LOCKFD[${LOCK}]}
    exec {randomstring}>&-
}

function laststeps() {
    local successval=${1:-0}

    # Redirect output to another file, as we want to compress our logfile
    # and ensure its no longer used
    exec > "$logdir/after${PROGRAM}.log" 2>&1

    # Rotate out old logfiles
    find ${logdir}/${PROGRAM}_*.log.bz2 -mtime +${logkeep} -delete

    # Now, at the very (successful) end of this run, make sure we remove
    # our stage files, so the next script run will do it all again.
    if [[ ${successval} -eq 0 ]]; then
        rm -f ${stagedir}/*
    fi
    bzip2 -9 ${LOGFILE}

    # Logfile should be gone, remove the symlink
    [[ -L ${logdir}/${PROGRAM} ]] && [[ ! -f ${logdir}/${PROGRAM} ]] && rm -f ${logdir}/${PROGRAM} || log "Logfile still exists or symlink gone already? Something fishy going on"

    # FIXME: Mail the log when its non-empty
    [[ -s "${logdir}/after${PROGRAM}.log" ]] || rm "${logdir}/after${PROGRAM}.log"
}

(
    # Where we store lockfile filehandles
    declare -A LOCKFD

    # common functions are "outsourced"
    . "${configdir}/common"

    # Timestamp when we started
    NOW=$(date "+%Y.%m.%d-%H:%M:%S")

    # A logfile for every cron script
    LOGFILE="${logdir}/${PROGRAM}_${NOW}.log"

    # Each "cronscript" may have a variables and a functions file
    # that we source
    _preparetasks ${PROGRAM}

    # Get rid of tempfiles at the end
    trap cleanup EXIT TERM HUP INT QUIT

    # An easy access by name for the current log
    ln -sf ${LOGFILE} ${logdir}/${PROGRAM}

    # And from here, all output to the log please
    exec >> "$LOGFILE" 2>&1

    # The stage function uses this directory
    # This amends the stagedir variable from "vars"
    stagedir="${stagedir}/${PROGRAM}"
    # Ensure the dir exists
    mkdir -p ${stagedir}

    # Run all tasks
    _runtasks ${PROGRAM}

    # we need to wait for the background processes before the end of the cron script
    wait

    # Common to all cron scripts
    log "Cron script successful, all done"

    laststeps 0
)