%% Copyright (c) 2015, SiftLogic LLC
%% Copyright (c) 2015-2020, DNSimple Corporation
%%
%% Permission to use, copy, modify, and/or distribute this software for any
%% purpose with or without fee is hereby granted, provided that the above
%% copyright notice and this permission notice appear in all copies.
%%
%% THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
%% WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
%% MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
%% ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
%% WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
%% ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
%% OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

-module(erldns_storage).

-behaviour(gen_server).

%% inter-module API
-export([start_link/0]).
%% API
-export([
    create/1,
    insert/2,
    delete_table/1,
    delete/2,
    select_delete/2,
    backup_table/1,
    backup_tables/0,
    select/2,
    select/3,
    foldl/3,
    empty_table/1,
    list_table/1,
    load_zones/0,
    load_zones/1
]).
%% gen_server callbacks
-export([
    init/1,
    handle_call/3,
    handle_cast/2,
    handle_info/2,
    terminate/2,
    code_change/3
]).

-record(state, {}).

-define(POLL_WAIT_HOURS, 1).
-define(FILENAME, "zones.json").

%% Gen Server Callbacks
start_link() ->
    gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).

%% @doc Inits the module, and sends a "timeout" to handle_info to start the poller for table backup
init([]) ->
    %%This call to handle_info starts the timer to backup tables in the given interval.
    {ok, #state{}, 0}.

handle_call(_Request, _From, State) ->
    {reply, ok, State, 0}.

handle_cast(_Msg, State) ->
    {noreply, State, 0}.

%% @doc Backups the tables in the given period
handle_info(timeout, State) ->
    Before = erlang:timestamp(),
    {error, not_implemented} = backup_tables(),
    TimeSpentMs = timer:now_diff(erlang:timestamp(), Before) div 1000,
    {noreply, State, max(?POLL_WAIT_HOURS * 60000 - TimeSpentMs, 0)};
handle_info(_Info, State) ->
    {noreply, State, 0}.

terminate(_Reason, _State) ->
    ok.

code_change(_OldVsn, State, _Extra) ->
    {ok, State}.

%% Public API
%% @doc API for a module's function calls. Please note that all crashes should be handled at the
%% lowest level of the API (ex. erldns_storage_json).
%% @end

%% @doc Call to a module's create. Creates a new table.
-spec create(atom()) -> ok | {error, Reason :: term()}.
create(Table) ->
    Module = mod(Table),
    Module:create(Table).

%% @doc Call to a module's insert. Inserts a value into the table.
-spec insert(atom(), tuple()) -> ok | {error, Reason :: term()}.
insert(Table, Value) ->
    Module = mod(Table),
    Module:insert(Table, Value).

%% @doc Call to a module's delete_table. Deletes the entire table.
-spec delete_table(atom()) -> ok | {error, Reason :: term()}.
delete_table(Table) ->
    Module = mod(Table),
    Module:delete_table(Table).

%% @doc Call to a module's delete. Deletes a key value from a table.
-spec delete(atom(), term()) -> ok | {error, Reason :: term()}.
delete(Table, Key) ->
    Module = mod(Table),
    Module:delete(Table, Key).

-spec select_delete(atom(), list()) -> {ok, Count :: integer()} | {error, Reason :: term()}.
select_delete(Table, MatchSpec) ->
    Module = mod(Table),
    Module:select_delete(Table, MatchSpec).

%% @doc Backup the table to the JSON file.
%% @see https://github.com/SiftLogic/erl-dns/issues/3
-spec backup_table(atom()) -> ok | {error, Reason :: term()}.
backup_table(Table) ->
    Module = mod(Table),
    Module:backup_table(Table).

%% @doc Backup the tables to the JSON file.
%% @see https://github.com/SiftLogic/erl-dns/issues/3
-spec backup_tables() -> ok | {error, Reason :: term()}.
backup_tables() ->
    Module = mod(),
    Module:backup_tables().

%% @doc Call to a module's select. Uses table key pair, and can be considered a "lookup" in terms of ets.
-spec select(atom(), term()) -> [tuple()].
select(Table, Key) ->
    Module = mod(Table),
    Module:select(Table, Key).

%% @doc Call to a module's select/3 Uses a matchspec to generate matches.
-spec select(atom(), list(), infinite | integer()) -> [tuple()].
select(Table, MatchSpec, Limit) ->
    Module = mod(Table),
    Module:select(Table, MatchSpec, Limit).

%% @doc Call to a module's foldl.
-spec foldl(fun(), list(), atom()) -> Acc :: term() | {error, Reason :: term()}.
foldl(Fun, Acc, Table) ->
    Module = mod(Table),
    Module:foldl(Fun, Acc, Table).

%% @doc This function emptys the specified table of all values.
-spec empty_table(atom()) -> ok | {error, Reason :: term()}.
empty_table(Table) ->
    Module = mod(Table),
    Module:empty_table(Table).

%% @doc List all elements in a table.
-spec list_table(atom()) -> [] | term() | {error, term()}.
list_table(TableName) ->
    Module = mod(TableName),
    Module:list_table(TableName).

%% @doc Load zones from a file. The default file name is "zones.json".(copied from erldns_zone_loader.erl)
-spec load_zones() -> {ok, integer()} | {err, atom()}.
load_zones() ->
    load_zones(filename()).

%% @doc Load zones from a file. The default file name is "zones.json".(copied from erldns_zone_loader.erl)
-spec load_zones(list()) -> {ok, integer()} | {err, atom()}.
load_zones(Filename) when is_list(Filename) ->
    case file:read_file(Filename) of
        {ok, Binary} ->
            lager:debug("Parsing zones JSON"),

            %% The "object_finish" callback override is here so that we don't return maps
            %% and instead keep the list of decoded information as a keyword list. Maybe we
            %% won't need this behavior in the future, but for now it's a good way to keep
            %% compatibility with what we used before to decode JSON (jsx).
            {JsonZones, ok, _} = json:decode(Binary, ok, #{
                object_finish => fun(Acc, OldAcc) -> {lists:reverse(Acc), OldAcc} end
            }),

            lager:debug("Putting zones into cache"),
            lists:foreach(
                fun(JsonZone) ->
                    Zone = erldns_zone_parser:zone_to_erlang(JsonZone),
                    ok = erldns_zone_cache:put_zone(Zone)
                end,
                JsonZones
            ),
            lager:debug("Loaded zones (count: ~p)", [length(JsonZones)]),
            {ok, length(JsonZones)};
        {error, Reason} ->
            erldns_events:notify({?MODULE, failed_zones_load, Reason}),
            {err, Reason}
    end.

%% Internal API
%% @doc Get file name from env, or return default (copied from erldns_zone_loader.erl)
filename() ->
    case application:get_env(erldns, zones) of
        {ok, Filename} ->
            Filename;
        _ ->
            ?FILENAME
    end.

%% @doc This function retrieves the module name to be used for a given application or table
%% (ex. erldns_storage_json...). Matched tables are always going to use ets because they are either
%% cached, or functionality is optimal in ets.
%% @end
mod() ->
    erldns_config:storage_type().

mod(packet_cache) ->
    erldns_storage_json;
mod(host_throttle) ->
    erldns_storage_json;
mod(handler_registry) ->
    erldns_storage_json;
mod(geolocation) ->
    erldns_storage_mnesia;
mod(lookup_table) ->
    erldns_storage_json;
mod(_Table) ->
    erldns_config:storage_type().