#!/bin/bash

# Postgres backup/restore hook for the discourse `db` service (discourse/postgres image).

set -e

# constants 
BACKUP_FILE='/var/lib/postgresql/backup.sql'
DATADIR="${PGDATA:-/var/lib/postgresql/18/docker}"
DB_NAME="${POSTGRES_DB:-discourse}"

# The bootstrap superuser (install user, oid 10) differs between deployments
# (`postgres` on bitnami-origin clusters, `discourse` on others). Detect it at
# runtime over the local trust socket rather than hard-coding a name.
detect_superuser() {
  local u name
  for u in discourse postgres; do
    name="$(psql -U "$u" -d "$DB_NAME" -tAc 'select rolname from pg_roles where oid = 10' 2>/dev/null | tr -d '[:space:]')"
    if [ -n "$name" ]; then echo "$name"; return 0; fi
  done
  echo postgres
}
SU="$(detect_superuser)"

function backup {
  pg_dump -U "$SU" "$DB_NAME" | gzip > "$BACKUP_FILE"
}

function restore {
  cd "$DATADIR"

  # Block all non-local connections so the running discourse app + sidekiq cannot reconnect and
  # interfere with the drop/recreate/reimport. Restored on exit.
  restore_hba() {
    cat pg_hba.conf.bak > pg_hba.conf
    rm -f pg_hba.conf.bak
    su postgres -c "pg_ctl -D '$DATADIR' reload"
  }
  cp pg_hba.conf pg_hba.conf.bak
  echo 'local all all trust' > pg_hba.conf
  su postgres -c "pg_ctl -D '$DATADIR' reload"
  trap restore_hba EXIT INT TERM

  # terminate any lingering local sessions before recreate
  # see https://stackoverflow.com/questions/5108876/kill-a-postgresql-session-connection
  psql -U "$SU" -d postgres -c \
    "SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE datname='${DB_NAME}' AND pid<>pg_backend_pid();"

  # drop database and then recreate it
  psql -U "$SU" -d postgres -c "DROP DATABASE ${DB_NAME} WITH (FORCE);"
  createdb -U "$SU" "$DB_NAME"

  # reimport data
  gunzip -c "$BACKUP_FILE" | psql -U "$SU" -d "$DB_NAME" -1 -v ON_ERROR_STOP=1 -f -
}

$@