#!/bin/bash

textfile_dir={{ node_exporter_textfile_dir }}

metric_job=""
metric_started=0
metric_bytes=0
metric_signalled=""

metric_on_signal() {
    metric_signalled=$1
    exit $((128 + $1))
}

metric_install_traps() {
    trap 'metric_on_signal 1' HUP
    trap 'metric_on_signal 2' INT
    trap 'metric_on_signal 15' TERM
}

metric_status() {
    if [ -n "${metric_signalled}" ]
    then
        echo $((128 + metric_signalled))
    else
        echo "$1"
    fi
}

log() {
    echo "[$(date --rfc-3339=seconds)] ${metric_job}: $*"
}

metric_previous_success() {
    local file=${textfile_dir}/backup_${metric_job}.prom

    if [ -r "${file}" ]
    then
        grep "^backup_last_success_timestamp_seconds{backup_job=\"${metric_job}\"} " "${file}" | awk '{ print $2 }'
    fi
}

metric_init() {
    metric_job=$1
    metric_started=$(date +%s)
    mkdir -p ${textfile_dir}
    metric_install_traps
    log "start"
}

metric_archive() {
    metric_bytes=$(stat -c %s "$1" 2>/dev/null || echo 0)
}

metric_finish() {
    local status=$1
    local now
    local success
    local previous
    local file=${textfile_dir}/backup_${metric_job}.prom
    local tmp=${file}.$$

    now=$(date +%s)
    previous=$(metric_previous_success)

    if [ "${status}" -eq 0 ]
    then
        success=${now}
        log "done in $((now - metric_started))s"
    else
        success=${previous:-0}
        log "FAILED with status ${status} after $((now - metric_started))s"
    fi

    cat > "${tmp}" <<EOF
# HELP backup_last_run_timestamp_seconds Unix time of the last run of this backup job.
# TYPE backup_last_run_timestamp_seconds gauge
backup_last_run_timestamp_seconds{backup_job="${metric_job}"} ${now}
# HELP backup_last_success_timestamp_seconds Unix time of the last successful run of this backup job.
# TYPE backup_last_success_timestamp_seconds gauge
backup_last_success_timestamp_seconds{backup_job="${metric_job}"} ${success}
# HELP backup_last_duration_seconds Duration of the last run of this backup job.
# TYPE backup_last_duration_seconds gauge
backup_last_duration_seconds{backup_job="${metric_job}"} $((now - metric_started))
# HELP backup_last_status Exit status of the last run of this backup job, 1 is success.
# TYPE backup_last_status gauge
backup_last_status{backup_job="${metric_job}"} $([ "${status}" -eq 0 ] && echo 1 || echo 0)
# HELP backup_last_archive_bytes Size of the archive produced by the last run of this backup job.
# TYPE backup_last_archive_bytes gauge
backup_last_archive_bytes{backup_job="${metric_job}"} ${metric_bytes}
EOF

    chmod 0644 "${tmp}"
    mv "${tmp}" "${file}"
}

metric_guard() {
    local raw=$?
    local status

    status=$(metric_status ${raw})
    metric_finish ${status}
    exit ${status}
}