#!/usr/bin/env bash
# Periodic pg_dump of the roboco DB (interim backup — no PITR/WAL archiving).
# Runs once on start, then every BACKUP_INTERVAL_SECONDS (default 24h). A
# failed dump logs and is retried next cycle; the loop itself never exits.
# ponytail: a plain sleep loop, not a cron daemon — good enough for a fixed
# 24h cadence, swap for a scheduler only if finer granularity is ever needed.
set -u

BACKUP_DIR="${BACKUP_DIR:-/backups}"
KEEP="${BACKUP_KEEP:-14}"
INTERVAL_SECONDS="${BACKUP_INTERVAL_SECONDS:-86400}"
# Off-disk mirror: unset (the default) disables it. Compose sets this only
# when ROBOCO_BACKUP_MIRROR_DIR is set in .env, and that host path should
# live on a DIFFERENT disk (external/remote mount) — a same-disk mirror
# protects nothing.
MIRROR_DIR="${BACKUP_MIRROR_DIR:-}"

# pg_dump reads these natively — no need to pass -h/-p/-U/-d by hand.
export PGHOST="${POSTGRES_HOST:-roboco-postgres}"
export PGPORT="${POSTGRES_PORT:-5432}"
export PGUSER="${POSTGRES_USER:-roboco}"
export PGPASSWORD="${POSTGRES_PASSWORD:-roboco}"
export PGDATABASE="${POSTGRES_DB:-roboco}"

mkdir -p "$BACKUP_DIR"

mirror_backup() {
  # Copy a fresh dump to the off-disk mirror (tmp+rename, same crash safety
  # as the primary write) and prune the mirror to the same $KEEP. Best-effort:
  # an unmounted/unwritable mirror logs and skips — never blocks the primary.
  local dump="$1" name
  [ -n "$MIRROR_DIR" ] || return 0
  name="$(basename "$dump")"
  if ! mkdir -p "$MIRROR_DIR" 2>/dev/null || [ ! -w "$MIRROR_DIR" ]; then
    echo "[backup] $(date -u -Iseconds) mirror dir ${MIRROR_DIR} not writable — skipping" >&2
    return 0
  fi
  rm -f "${MIRROR_DIR}"/roboco-*.dump.tmp
  if cp "$dump" "${MIRROR_DIR}/${name}.tmp" && mv "${MIRROR_DIR}/${name}.tmp" "${MIRROR_DIR}/${name}"; then
    echo "[backup] $(date -u -Iseconds) mirrored: ${MIRROR_DIR}/${name}"
  else
    rm -f "${MIRROR_DIR}/${name}.tmp"
    echo "[backup] $(date -u -Iseconds) mirror FAILED — this dump stays unmirrored (each cycle mirrors only its own dump)" >&2
    return 0
  fi
  # shellcheck disable=SC2012
  ls -1t "${MIRROR_DIR}"/roboco-*.dump 2>/dev/null | tail -n "+$((KEEP + 1))" | while IFS= read -r old; do
    rm -f "$old"
  done
}

run_backup() {
  local ts dest
  # Any .tmp here is a crash orphan (one dump at a time, unique names, and
  # the prune glob never matches them) — sweep before starting.
  rm -f "${BACKUP_DIR}"/roboco-*.dump.tmp
  ts="$(date -u +%Y%m%dT%H%M%SZ)"
  dest="${BACKUP_DIR}/roboco-${ts}.dump"
  echo "[backup] $(date -u -Iseconds) starting pg_dump -> ${dest}"
  if pg_dump -Fc -f "${dest}.tmp"; then
    mv "${dest}.tmp" "${dest}"
    echo "[backup] $(date -u -Iseconds) OK: ${dest}"
    mirror_backup "${dest}"
  else
    rm -f "${dest}.tmp"
    echo "[backup] $(date -u -Iseconds) FAILED — will retry next cycle" >&2
  fi

  # Prune to the newest $KEEP dumps. Filenames are our own fixed timestamp
  # format (no spaces/globs to worry about), so plain `ls -t` is enough.
  # shellcheck disable=SC2012
  ls -1t "${BACKUP_DIR}"/roboco-*.dump 2>/dev/null | tail -n "+$((KEEP + 1))" | while IFS= read -r old; do
    rm -f "$old"
  done
}

while true; do
  run_backup
  sleep "$INTERVAL_SECONDS"
done