{ cluster, ... }:

let
  createNode = index: { pkgs, ... }:
    {

      networking.firewall.allowedTCPPorts = [ 5432 8008 5010 ];

      environment.systemPackages = [ pkgs.jq ];

      services.patroni = {

        enable = true;

        softwareWatchdog = true;

        settings = {
          bootstrap = {
            dcs = {
              ttl = 30;
              loop_wait = 10;
              retry_timeout = 10;
              maximum_lag_on_failover = 1048576;
            };
            initdb = [
              { encoding = "UTF8"; }
              "data-checksums"
            ];
          };

          postgresql = {
            use_pg_rewind = true;
            use_slots = true;
            authentication = {
              replication = {
                username = "replicator";
              };
              superuser = {
                username = "postgres";
              };
              rewind = {
                username = "rewind";
              };
            };
            parameters = {
              wal_level = "replica";
              hot_standby_feedback = "on";
              unix_socket_directories = "/tmp";
            };
            pg_hba = [
              "host replication replicator 192.168.1.0/24 md5"
              # Unsafe, do not use for anything other than tests
              "host all all 0.0.0.0/0 trust"
            ];
          };

          etcd3 = {
            host = "192.168.1.4:2379";
          };
        };

        environmentFiles = {
          PATRONI_REPLICATION_PASSWORD = pkgs.writeText "replication-password" "postgres";
          PATRONI_SUPERUSER_PASSWORD = pkgs.writeText "superuser-password" "postgres";
          PATRONI_REWIND_PASSWORD = pkgs.writeText "rewind-password" "postgres";
        };
      };

      # We always want to restart so the tests never hang
      systemd.services.patroni.serviceConfig.StartLimitIntervalSec = 0;
    };

  clusterName = "poseidon";
  link = cluster.config.links.patroni-pg-access;
in
{
  defaults = { depot, pkgs, ... }: {
    environment.systemPackages = [
      pkgs.jq
      depot.packages.postgresql
    ];
    services.patroni.settings.postgresql.pg_hba = [
      "host all all 0.0.0.0/0 trust"
    ];
  };

  # taken from https://github.com/phfroidmont/nixpkgs/blob/patroni-module/nixos/tests/patroni.nix
  testScript = ''
    import json
    nodeNames = json.loads('${builtins.toJSON cluster.config.services.patroni.nodes.worker}')
    clientNames = json.loads('${builtins.toJSON cluster.config.services.patroni.nodes.haproxy}')
    nodes = [ n for n in machines if n.name in nodeNames ]
    clients = [ n for n in machines if n.name in clientNames ]

    def wait_for_all_nodes_ready(expected_replicas=2):
        booted_nodes = filter(lambda node: node.booted, nodes)
        for node in booted_nodes:
            print(node.succeed("patronictl list ${clusterName}"))
            node.wait_until_succeeds(f"[ $(patronictl list -f json ${clusterName} | jq 'length') == {expected_replicas + 1} ]")
            node.wait_until_succeeds("[ $(patronictl list -f json ${clusterName} | jq 'map(select(.Role | test(\"^Leader$\"))) | map(select(.State | test(\"^running$\"))) | length') == 1 ]")
            node.wait_until_succeeds(f"[ $(patronictl list -f json ${clusterName} | jq 'map(select(.Role | test(\"^Replica$\"))) | map(select(.State | test(\"^streaming$\"))) | length') == {expected_replicas} ]")
            print(node.succeed("patronictl list ${clusterName}"))
        for client in clients:
            client.wait_until_succeeds("psql -h ${link.ipv4} -p ${link.portStr} -U postgres --command='select 1;'")

    def run_dummy_queries():
        for client in clients:
            client.succeed("psql -h ${link.ipv4} -p ${link.portStr} -U postgres --pset='pager=off' --tuples-only --command='insert into dummy(val) values (101);'")
            client.succeed("test $(psql -h ${link.ipv4} -p ${link.portStr} -U postgres --pset='pager=off' --tuples-only --command='select val from dummy where val = 101;') -eq 101")
            client.succeed("psql -h ${link.ipv4} -p ${link.portStr} -U postgres --pset='pager=off' --tuples-only --command='delete from dummy where val = 101;'")

    start_all()

    with subtest("should bootstrap a new patroni cluster"):
        wait_for_all_nodes_ready()

    with subtest("should be able to insert and select"):
        clients[0].succeed("psql -h ${link.ipv4} -p ${link.portStr} -U postgres --command='create table dummy as select * from generate_series(1, 100) as val;'")
        for client in clients:
            client.succeed("test $(psql -h ${link.ipv4} -p ${link.portStr} -U postgres --pset='pager=off' --tuples-only --command='select count(distinct val) from dummy;') -eq 100")

    with subtest("should restart after all nodes are crashed"):
        for node in nodes:
            node.crash()
        for node in nodes:
            node.start()
        wait_for_all_nodes_ready()

    with subtest("should be able to run queries while any one node is crashed"):
        masterNodeName = nodes[0].succeed("patronictl list -f json ${clusterName} | jq '.[] | select(.Role | test(\"^Leader$\")) | .Member' -r").strip()
        masterNodeIndex = next((i for i, v in enumerate(nodes) if v.name == masterNodeName), None)

        # Move master node at the end of the list to avoid multiple failovers (makes the test faster and more consistent)
        nodes.append(nodes.pop(masterNodeIndex))

        for node in nodes:
            node.crash()
            wait_for_all_nodes_ready(1)

            # Execute some queries while a node is down.
            run_dummy_queries()

            # Restart crashed node.
            node.start()
            wait_for_all_nodes_ready()

            # Execute some queries with the node back up.
            run_dummy_queries()
  '';
}