-module(pog_ffi).

-export([query/3, connect/1, disconnect/1, coerce/1, null/0, transaction/2]).

-record(pog_pool, {name, pid}).

-include_lib("pog/include/pog_Config.hrl").
-include_lib("pg_types/include/pg_types.hrl").

null() ->
    null.

coerce(Value) ->
    Value.

%% Use correct defaults for SSL connections when SSL is enabled.
%% Peers have to be verified & cacerts are fetched directly from the system.
%%
%% `server_name_indication` should be set to the value of the Host, because the
%% connection to Postgres uses a TCP connection that get upgraded to TLS, and
%% the TLS socket is sent as is, meaning the Hostname is lost when ssl module
%% get the socket. server_name_indication overrides that behaviour and send
%% the correct Hostname to the ssl module.
%% `customize_hostname_check` should be set to with the verify hostname match
%% with HTTPS, because otherwise wildcards certificaties (i.e. *.example.com)
%% will not be handled correctly.
default_ssl_options(Host, Ssl) ->
  case Ssl of
    false -> [];
    true -> [
      {verify, verify_peer},
      {cacerts, public_key:cacerts_get()},
      {server_name_indication, binary_to_list(Host)},
      {customize_hostname_check, [
        {match_fun, public_key:pkix_verify_hostname_match_fun(https)}
      ]}
    ]
  end.

connect(Config) ->
    Id = integer_to_list(erlang:unique_integer([positive])),
    PoolName = list_to_atom("pog_pool_" ++ Id),
    #config{
        host = Host,
        port = Port,
        database = Database,
        user = User,
        password = Password,
        ssl = Ssl,
        connection_parameters = ConnectionParameters,
        pool_size = PoolSize,
        queue_target = QueueTarget,
        queue_interval = QueueInterval,
        idle_interval = IdleInterval,
        trace = Trace,
        ip_version = IpVersion,
        rows_as_map = RowsAsMap
    } = Config,
    SslOptions = default_ssl_options(Host, Ssl),
    Options1 = #{
        host => Host,
        port => Port,
        database => Database,
        user => User,
        ssl => Ssl,
        ssl_options => SslOptions,
        connection_parameters => ConnectionParameters,
        pool_size => PoolSize,
        queue_target => QueueTarget,
        queue_interval => QueueInterval,
        idle_interval => IdleInterval,
        trace => Trace,
        decode_opts => [{return_rows_as_maps, RowsAsMap}],
        socket_options => case IpVersion of
            ipv4 -> [];
            ipv6 -> [inet6]
        end
    },
    Options2 = case Password of
        {some, Pw} -> maps:put(password, Pw, Options1);
        none -> Options1
    end,
    {ok, Pid} = pgo_pool:start_link(PoolName, Options2),
    #pog_pool{name = PoolName, pid = Pid}.

disconnect(#pog_pool{pid = Pid}) ->
    erlang:exit(Pid, normal),
    nil.

transaction(#pog_pool{name = Name} = Conn, Callback) ->
    F = fun() ->
        case Callback(Conn) of
            {ok, T} -> {ok, T};
            {error, Reason} -> error({pog_rollback_transaction, Reason})
        end
    end,
    try
        pgo:transaction(Name, F, #{})
    catch
        error:{pog_rollback_transaction, Reason} ->
            {error, {transaction_rolled_back, Reason}}
    end.


query(#pog_pool{name = Name}, Sql, Arguments) ->
    case pgo:query(Sql, Arguments, #{pool => Name}) of
        #{rows := Rows, num_rows := NumRows} ->
            {ok, {NumRows, Rows}};

        {error, Error} ->
            {error, convert_error(Error)}
    end.

convert_error(none_available) ->
    connection_unavailable;
convert_error({pgo_protocol, {parameters, Expected, Got}}) ->
    {unexpected_argument_count, Expected, Got};
convert_error({pgsql_error, #{
    message := Message,
    constraint := Constraint,
    detail := Detail
}}) ->
    {constraint_violated, Message, Constraint, Detail};
convert_error({pgsql_error, #{code := Code, message := Message}}) ->
    Constant = case pog:error_code_name(Code) of
        {ok, X} -> X;
        {error, nil} -> <<"unknown">>
    end,
    {postgresql_error, Code, Constant, Message};
convert_error(#{
    error := badarg_encoding,
    type_info := #type_info{name = Expected},
    value := Value
}) ->
    Got = list_to_binary(io_lib:format("~p", [Value])),
    {unexpected_argument_type, Expected, Got}.