#!/bin/bash

# Postgres backup/restore hook for the discourse `db` service. Invoked by backupbot-two via:
#   backupbot.backup.pre-hook                     = "/pg_backup.sh backup"
#   backupbot.backup.volumes.postgresql_data.path = "backup.sql"
#   backupbot.restore.post-hook                   = "/pg_backup.sh restore"
# Backup dumps the DB to backup.sql (gzip) inside the postgresql_data volume; backupbot archives it.
# Restore reimports it. Discourse (the rails app + sidekiq) keeps many TCP connections open to the DB
# and reconnects within milliseconds, so a one-shot pg_terminate_backend is NOT enough: restore must
# first block all non-local connections at the pg_hba level (so the app cannot reconnect and interfere
# mid-reimport), then FORCE-drop, recreate, and deterministically reimport the dump, then restore
# pg_hba. (Mirrors the proven matrix-synapse restore hook.) The previous recipe shipped a pg_dump
# backup but NO restore hook — a file-level restore did not reload into the running postgres, so a
# restored backup silently kept the live (un-restored) state. cc-ci caught this: a seeded ci_marker row
# was gone after restore. Same pattern as the immich / mattermost-lts / ghost recipe-PRs.

set -e

BACKUP_FILE='/var/lib/postgresql/data/backup.sql'
export PGPASSWORD=$(cat "${POSTGRES_PASSWORD_FILE:-/run/secrets/db_password}")
DB_USER="${POSTGRES_USER:-discourse}"
DB_NAME="${POSTGRES_DB:-discourse}"

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

function restore {
  cd /var/lib/postgresql/data/

  # Block all non-local connections so the running discourse app + sidekiq cannot reconnect and
  # interfere with the drop/recreate/reimport (a one-shot pg_terminate_backend is not enough — the
  # app reconnects within ms over TCP). Restored on exit.
  restore_hba() {
    cat pg_hba.conf.bak > pg_hba.conf
    rm -f pg_hba.conf.bak
    su postgres -c 'pg_ctl reload'
  }
  cp pg_hba.conf pg_hba.conf.bak
  echo 'local all all trust' > pg_hba.conf
  su postgres -c 'pg_ctl reload'
  trap restore_hba EXIT INT TERM

  # Terminate lingering local sessions, then FORCE-drop + recreate + deterministic reimport.
  psql -U "$DB_USER" -d postgres -c \
    "SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE datname='${DB_NAME}' AND pid<>pg_backend_pid();"
  psql -U "$DB_USER" -d postgres -c "DROP DATABASE ${DB_NAME} WITH (FORCE);"
  createdb -U "$DB_USER" "$DB_NAME"
  gunzip -c "$BACKUP_FILE" | psql -U "$DB_USER" -d "$DB_NAME" -1 -v ON_ERROR_STOP=1 -f -
}

$@