TEST_PG_PORT_MASTER=5433
TEST_PG_PORT_REPLICA=5434

TEST_PG_DIR_MASTER=~/postgres_data_master
TEST_PG_DIR_REPLICA=~/postgres_data_replica


# Setup master
mkdir $TEST_PG_DIR_MASTER

pg_ctl -D $TEST_PG_DIR_MASTER initdb

sed -i "s/#listen_addresses = 'localhost'/listen_addresses = '*'/g" $TEST_PG_DIR_MASTER/postgresql.conf
sed -i "s/#port = 5432/port = $TEST_PG_PORT_MASTER/g" $TEST_PG_DIR_MASTER/postgresql.conf

pg_ctl -D $TEST_PG_DIR_MASTER -l logfile start

# Setup replica
pg_basebackup -h localhost --checkpoint=fast -D $TEST_PG_DIR_REPLICA -R -X stream --port=$TEST_PG_PORT_MASTER
sed -i "s/#listen_addresses = 'localhost'/listen_addresses = '*'/g" $TEST_PG_DIR_REPLICA/postgresql.conf
sed -i "s/port = $TEST_PG_PORT_MASTER/port = $TEST_PG_PORT_REPLICA/g" $TEST_PG_DIR_REPLICA/postgresql.conf

pg_ctl -D $TEST_PG_DIR_REPLICA -l logfile_replica start

# Check replication is working
psql postgres --port=$TEST_PG_PORT_MASTER -c "
create table t (
  a integer,
  b text,
  d timestamp without time zone
);
insert into t select i, 'test-master-2-replica'||i , now() from generate_series(1, 5)i;
"
sleep 2
psql postgres --port=$TEST_PG_PORT_REPLICA -c "select * from t;";

# Shutdown master and switch to replica
pg_ctl -D $TEST_PG_DIR_MASTER stop

# enable test changes that will postpone CreateEndOfRecoveryRecord()
touch $TEST_PG_DIR_REPLICA/delay_recovery.signal

psql postgres --port=$TEST_PG_PORT_REPLICA -c "SELECT pg_promote();" &

# Shutdown immediately Postgres (in real life that could be an accident power loss, or any other system level problem...)
sleep 5 # sleep a while to ensure that history file was created
pg_ctl -D $TEST_PG_DIR_REPLICA stop -m i
sleep 5
# cleanup - we do not need the file anymore
rm $TEST_PG_DIR_REPLICA/delay_recovery.signal
# start replica again
pg_ctl -D $TEST_PG_DIR_REPLICA  -l logfile_replica start
# after this point replica is started, and working, but the timeline is still 1 !!!
# it can be checked with `pg_controldata $TEST_PG_DIR_REPLICA`
# and we will get problems later once we switch the replica back to its original role (refer to steps below).

# Bring back master as replica
touch $TEST_PG_DIR_MASTER/standby.signal
sed -i "s/#primary_conninfo = ''/primary_conninfo = 'host=localhost port=$TEST_PG_PORT_REPLICA'/g" $TEST_PG_DIR_MASTER/postgresql.conf
pg_ctl -D $TEST_PG_DIR_MASTER -l logfile start

# Check replication is working
psql postgres --port=$TEST_PG_PORT_REPLICA -c "
create table t2 (
  a integer,
  b text,
  d timestamp without time zone
);
insert into t2 select i, 'test-replica-2-master'||i , now() from generate_series(1, 5)i;
"
sleep 2
psql postgres --port=$TEST_PG_PORT_MASTER -c "select * from t2;";

# Switch back
pg_ctl -D $TEST_PG_DIR_REPLICA stop

psql postgres --port=$TEST_PG_PORT_MASTER -c "SELECT pg_promote();"

touch $TEST_PG_DIR_REPLICA/standby.signal
pg_ctl -D $TEST_PG_DIR_REPLICA -l logfile_replica start

# attempt to start replica here will result in:
# 	'pg_ctl: could not start server'
# 	'Examine the log output.'
# and in the log:
#	2025-01-16 17:30:27.174 +10 [4806] FATAL:  requested timeline 2 is not a child of this server's history
#	2025-01-16 17:30:27.174 +10 [4806] DETAIL:  Latest checkpoint is at 0/303FF90 on timeline 1, but in the history of the requested timeline, the server forked off from that timeline at 0/3023538.
#