#!/bin/bash

set -e

OLDDATA=$PGDATA/old_data
NEWDATA=$PGDATA/new_data

echo "Running as $(id)"

# The migration uses $OLDDATA/$NEWDATA as scratch and removes them when it
# finishes; a leftover *empty* one means a run was interrupted before any data
# moved (data still intact at $PGDATA) so we clear it and retry, while a
# *non-empty* one means data may live only there, so we stop for manual recovery.
for scratch in $OLDDATA $NEWDATA; do
  if [ -d "$scratch" ] && [ -n "$(ls -A "$scratch")" ]; then
    echo "FATAL: $scratch exists and is not empty - a previous migration did not"
    echo "complete and the data may only exist there. manual recovery necessary."
    exit 1
  fi
done
rm -rf $OLDDATA $NEWDATA

if [ -f $PGDATA/PG_VERSION ]; then
  DATA_VERSION=$(cat $PGDATA/PG_VERSION)

  if [ -n "$DATA_VERSION" -a "$PG_MAJOR" != "$DATA_VERSION" ]; then
    echo "postgres data version $DATA_VERSION found, but need $PG_MAJOR. Starting migration"
    echo "Installing postgres $DATA_VERSION"
    sed -i "s/$/ $DATA_VERSION/" /etc/apt/sources.list.d/pgdg.list
    apt-get update && apt-get install -y --no-install-recommends \
      postgresql-$DATA_VERSION \
      && rm -rf /var/lib/apt/lists/*
    # pg_upgrade must run as the old cluster's bootstrap superuser (the "install
    # user", oid 10), and the new cluster must be initialised with that same
    # user. It is not necessarily $POSTGRES_USER (e.g. clusters created with the
    # default "postgres" superuser and a separate app role), so read it from the
    # old cluster: briefly start it and ask, connecting as the app role we know.
    PGBIN=/usr/lib/postgresql/$DATA_VERSION/bin
    gosu postgres $PGBIN/pg_ctl -D $PGDATA -w \
      -o "-c listen_addresses= -c unix_socket_directories=/tmp" start
    INSTALL_USER=$(gosu postgres psql -h /tmp -U "$POSTGRES_USER" -d postgres -tAc \
      "select rolname from pg_roles where oid = 10")
    gosu postgres $PGBIN/pg_ctl -D $PGDATA -w stop
    echo "old cluster install user: $INSTALL_USER"
    echo "shuffling around"
    gosu postgres mkdir $OLDDATA $NEWDATA
    chmod 700 $OLDDATA $NEWDATA
    mv $PGDATA/* $OLDDATA/ || true
    echo "running initdb"
    # abuse entrypoint script for initdb by making server error out; initialise
    # the new cluster with the same superuser as the old one so pg_upgrade matches
    gosu postgres bash -c "export PGDATA=$NEWDATA POSTGRES_USER=$INSTALL_USER ; /usr/local/bin/docker-entrypoint.sh --invalid-arg || true"
    echo "running pg_upgrade"
    cd /tmp
    gosu postgres pg_upgrade --link -b /usr/lib/postgresql/$DATA_VERSION/bin -d $OLDDATA -D $NEWDATA -U $INSTALL_USER
    cp $OLDDATA/pg_hba.conf $NEWDATA/
    mv $NEWDATA/* $PGDATA
    rm -rf $OLDDATA
    rmdir $NEWDATA
    echo "migration complete"
  fi
fi

/usr/local/bin/docker-entrypoint.sh postgres