#!/bin/bash

# Postgres backup/restore hook for the immich `database` service (VectorChord/pgvecto.rs image).
# Invoked by backupbot-two via the deploy labels:
#   backupbot.backup.pre-hook              = "/pg_backup.sh backup"
#   backupbot.backup.volumes.postgres.path = "backup.sql"
#   backupbot.restore.post-hook            = "/pg_backup.sh restore"
# Backup dumps the immich DB to backup.sql (gzip) inside the postgres volume; backupbot archives that
# file. Restore reads it back and reimports it.
#
# Two things make the immich DB tricky to restore, and BOTH are handled below:
#
# 1. VectorChord/pgvecto.rs search_path. A plain pg_dump emits
#      SELECT pg_catalog.set_config('search_path', '', false);
#    near the top; on reimport that empty search_path leaves the vector/vchord types + operator
#    classes unresolvable, so the first statement that references them errors. immich's official
#    restore (docs.immich.app/administration/backup-and-restore) rewrites that line to put
#    `public, pg_catalog` back on the search_path BEFORE the import. We do the same.
#
# 2. The app races the restore. immich-server keeps a TCP connection pool to the DB and reconnects
#    within milliseconds of being dropped, re-running its OWN startup migrations. If it does that
#    while our single-transaction import is running, the two conflict (duplicate CREATE/relation
#    errors) and ON_ERROR_STOP aborts our transaction — the import rolls back and nothing is
#    restored, while the app finishes its migration and looks "healthy" on an empty DB. A one-shot
#    pg_terminate_backend does NOT prevent the reconnect. So, like the (green) matrix-synapse hook,
#    we replace pg_hba.conf with a LOCAL-trust-only policy and reload: postgres then REJECTS every
#    TCP connection, locking the app out for the duration of the restore. We restore pg_hba (via an
#    EXIT trap, so it always runs) once the import is done, and the app reconnects to the fully
#    restored DB. Our own psql/createdb use the local socket (trust), so they are unaffected.

set -e

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

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

function restore {
  restore_hba() {
    if [ -f "${HBA}.ccci.bak" ]; then
      cat "${HBA}.ccci.bak" > "$HBA"
      rm -f "${HBA}.ccci.bak"
      psql -U "$DB_USER" -d postgres -c "SELECT pg_reload_conf();" >/dev/null 2>&1 || true
    fi
  }
  trap restore_hba EXIT INT TERM

  # Lock the networked immich-server OUT for the duration of the restore (see header note 2):
  # local-trust-only pg_hba + reload makes postgres reject all TCP connections, then terminate the
  # connections the app already holds so DROP DATABASE can proceed.
  cp "$HBA" "${HBA}.ccci.bak"
  printf 'local all all trust\n' > "$HBA"
  psql -U "$DB_USER" -d postgres -c "SELECT pg_reload_conf();"
  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" "$DB_NAME"
  # Rewrite the empty search_path the VectorChord dump sets (header note 1), then import alone.
  gunzip -c "$BACKUP_FILE" \
    | sed "s/SELECT pg_catalog.set_config('search_path', '', false);/SELECT pg_catalog.set_config('search_path', 'public, pg_catalog', true);/g" \
    | psql -U "$DB_USER" -d "$DB_NAME" --single-transaction --set ON_ERROR_STOP=on

  restore_hba
  trap - EXIT INT TERM
}

$@