#!/bin/bash

# Outputs or writes to file a JSON snippet of the last time files were backed
# up (created by backup-tool.sh; .pgp) in the specified users' home directories.
# Usage: last-backups [output file]

USERS=(backups-vaultwarden backups-gitea backups-mystats backups-media)

lastForDir() {
        # Alternative datetime format: '%TY-%Tm-%Td %TT', tho sort has to be used differently in that case
        datetime="$(find "/home/$1" -name '*.pgp' -type f -printf '%T@\n' | sort -nr | grep -m  1 '')"
        echo $'\t'"\"$1\": $datetime,"
}

for user in ${USERS[@]}; do
        output+="$(lastForDir $user)\n"
done

# Remove last comma
output="${output::-3}\n"

# Print to stdout if no output file was provided
if [ -z "$1" ]; then
        echo -e "{\n$output}"
        exit 0
fi

# Write to file if not exists
if [ ! -f "$1" ]; then
        echo -e "{\n$output}" > "$1"
        exit 0
fi

# Calc md5 for old file and new output
old=$(md5sum "$1" | cut -d' ' -f1)
new=$(echo -e "{\n$output}" | md5sum | cut -d' ' -f1)

# Compare md5 to only write to output if updated
if [[ "$old" != "$new" ]]; then
        echo -e "{\n$output}" > "$1"
fi