#!/bin/bash

# alfplayer
# 2014-06-12
#
# Mirror the whole Parabola repository using rsync and keep snapshots

set -e

script_filename="$(basename "$0")"

# Default configuration values.
# They can be overridden by setting the variables in the calling environment.
# 1 to set, 0 to unset
: ${repo:=rsync://repo.parabola.nu:875/repos}
: ${base_dir:=/srv/http}
: ${parabola_dir:=${base_dir}/parabola}
: ${oldest_version:=10}    # snapshots older than this one will be deleted (see also no_delete above)
#: ${date_exclude:=2014.06.19}    # disable running this script this date (see next line)
: ${forcerun:=0}    # force running on excluded date
#: ${terminal:=1}    # outputs to stdout using rsync --progress (and logs to a file)
: ${no_delete:=0}    # disable deletion of oldest snapshots
#: ${TZ:=UTC}      # set time zone

export TZ

# Lock with flock (provided by util-linux)
LOCKFILE="/var/lock/${script_filename}"
LOCKFD=99

_lock()             { flock -$1 $LOCKFD; }

_no_more_locking()  {
    set +e

    # Save exit status
    es=$?

    if [[ -e ${parabola_dir}.tmp ]] ; then
	echo "=> WARNING: Directory with partial transfer ${LOCAL}.tmp remains in file system"
    fi

    if [[ $es != 0 ]] ; then
        echo "=> ERROR: Unsuccessful script termination. Exit status: $es"
        fi
    fi

    _lock u
    _lock xn && \
	rm -f $LOCKFILE
}

_prepare_locking()  { eval "exec $LOCKFD>\"$LOCKFILE\""; trap _no_more_locking EXIT; }

_prepare_locking

# Lock now. The lock is disabled automatically when the script exits (with any error code).
if ! _lock xn ; then
    echo "=> ERROR: Could not obtain lock. Exiting." >&2
    exit 1
fi

date="$(date +%Y.%m.%d)"
current="${parabola_dir}-${date}"
local_useful=0


if [[ ${date_exclude} && ${forcerun} != 1 ]] ; then
    if [[ $DATE == ${date_exclude} ]] ; then
	echo "Manually disabled: ${date}. Exiting."
	exit 0
    fi
fi

# Test if ${parabola_dir} is an existing symlink pointing to an existing directory
if [[ -h ${parabola_dir} ]] ; then
  last_path="$(readlink -f "${parabola_dir}")"
  if [[ -d ${last_path} ]] ; then
    last="${last_path##*/}"
    local_useful=1
  else
    echo "=> ERROR: ${parabola_dir} is a symlink which does not point to an existing directory." >&2
    exit 1
  fi
else
  echo "=> ERROR: ${parabola_dir} does not exist or is not a symlink." >&2
  exit 1
fi


echo
echo "=> Creating snapshot for date ${date}"

if [[ -e "${current}" ]] ; then
  echo "${current} already exists. Exiting." >&2
  exit 1
fi

if [[ -e "${parabola_dir}".tmp ]] ; then
  echo "${parabola_dir}.tmp already exists. Resuming."
else
  cp -al "${last_path}" "${parabola_dir}".tmp
fi


rsync "${repo}"/ -rtvlH ${terminal:+--progress} --safe-links --delete --link-dest="$base_dir"/archlinux/ --link-dest="$parabola_dir" "$parabola_dir".tmp

cd "$base_dir"

echo "=> Delete versions older than the ${oldest_version} oldest version"
delete_list=( $(for dir in parabola-* ; do echo "$(find "$dir" -type f -printf '%T@\n' | sort -n | tail -1) $dir" ; done | awk '{print $2}' | head -n -"${oldest_version}") )

for dir in ${delete_list[@]} ; do
    if [[ ${no_delete} != 1 ]] ; then
        echo "$dir"
        rm -rf "$dir"
    else
	echo "DRY-RUN: rm -rf $dir"
    fi
done

echo "=> Start serving the new repository version"
mv "${parabola_dir}.tmp" "${current}"

if [[ ${local_useful} == 1 ]] ; then
    echo "  => Deleting ${parabola_dir} symlink"
    rm -rf "${parabola_dir}"
fi

# Create symlink
echo "  => Creating symlink ${current} to ${parabola_dir}"
ln -s ${current##*/} ${parabola_dir}

echo "=> Disk space report"
df -h "${base_dir}"

echo "=> ${script_filename} finished successfully. Finish time: $(date --rfc-3339=seconds)"