#!/bin/bash -e
###########################################################################

if [ ! -x "$1" ]
then
    echo >&2 "Usage: $0 <provisioner script>"
    exit 1
fi

# source the provisioner script
. "$1"

printf 'Starting wireguard-inject: %s - %s\n' "$PROVISIONER_NAME" "$(date)"

# other configuration
RUNDIR='/run/wireguard-inject'
[ -d "$RUNDIR" ] || mkdir -m 0700 "$RUNDIR"
MODFILE="${RUNDIR}/${PROVISIONER_NAME}"

###########################################################################

# loop until at least 5 seconds since the last modification date
while :
do

    declare -A modtimes
    maxmod=0

    # scan for modification dates
    while IFS= read -r file
    do
        [ -n "$file" ] || continue
        mod=$(stat -c "%Y" "$file")
        modtimes[$file]="$mod"
        if [ "$mod" -gt "$maxmod" ]
        then
            maxmod="$mod"
        fi
        
    done <<< "$(list_config_files)"

    # check the time
    now=$(date '+%s')
    date_diff=$(( now - maxmod ))
    [ "$date_diff" -gt 5 ] && break

    # still updates happening, loop around
    echo "- waiting for config to settle: $(date)"
    sleep $(( 6 - date_diff ))
    
done

###########################################################################
# compare against the previous run

declare -A interfaces
declare -A previous_modtimes
declare -A add_interfaces
declare -A remove_interfaces
modcount=0

if [ -f "$MODFILE" ]
then
    # slurp the previous modtimes into a map
    declare -A previous_modtimes
    while IFS='!' read -r file mod
    do
        previous_modtimes[$file]="$mod"
    done < "$MODFILE"
fi

# check for changed files
# also, create a map of interfaces to config files along the way

for file in "${!modtimes[@]}"
do
    base=${file##*/}
    iface=${base%%.*}
    interfaces[$iface]="$file"
    
    if [ -v "previous_modtimes[$file]" ] &&
           [ "${previous_modtimes[$file]}" -eq "${modtimes[$file]}" ]
    then
        continue
    fi

    # if an interface has been modified, remove it then re-add it
    remove_interfaces[$iface]=1
    add_interfaces[$iface]=1

    modcount=$(( modcount + 1 ))
done

###########################################################################
# fetch a list of configured interfaces

declare -A actual_interfaces
while IFS= read -r iface
do
    actual_interfaces[$iface]=1
done <<< "$(list_actual_interfaces)"

###########################################################################
# now we can figure out if interfaces have been added or removed

for iface in "${!actual_interfaces[@]}"
do
    # does actual interface exist in config ?
    if [ ! -v "interfaces[$iface]" ]
    then
        # interface has been removed
        remove_interfaces[$iface]=1
    fi
done

for iface in "${!interfaces[@]}"
do
    # does interface actually exist ?
    if [ ! -v "actual_interfaces[$iface]" ]
    then
        # interface has been added
        add_interfaces[$iface]=1

        # can't remove the interface if it wasn't there in the first place
        unset "remove_interfaces[$iface]"
    fi
done

###########################################################################
# finally in a position to make some changes

echo " - Removing ${#remove_interfaces[@]} tunnels"
for iface in "${!remove_interfaces[@]}"
do
    echo "   _ $iface"
    remove_tunnel "$iface"
done

echo " - Adding ${#add_interfaces[@]} tunnels"
for iface in "${!add_interfaces[@]}"
do
    echo "   + $iface"
    add_tunnel "$iface" "${interfaces[$iface]}"
done

###########################################################################
# all done

# save the modified times if required
if [ "$modcount" -gt 0 ]
then
    exec 3> "$MODFILE"
    for file in "${!modtimes[@]}"
    do
        echo >&3 "${file}!${modtimes[$file]}"
    done
    exec 3>&-
fi

# also signal the provisioner
all_done

echo "Completed changes: $(date)"
###########################################################################
# end of file