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Diffstat (limited to 'src/rlx_provider.erl')
-rw-r--r-- | src/rlx_provider.erl | 117 |
1 files changed, 117 insertions, 0 deletions
diff --git a/src/rlx_provider.erl b/src/rlx_provider.erl new file mode 100644 index 0000000..b0de178 --- /dev/null +++ b/src/rlx_provider.erl @@ -0,0 +1,117 @@ +%% -*- erlang-indent-level: 4; indent-tabs-mode: nil; fill-column: 80 -*- +%%% Copyright 2012 Erlware, LLC. All Rights Reserved. +%%% +%%% This file is provided to you under the Apache License, +%%% Version 2.0 (the "License"); you may not use this file +%%% except in compliance with the License. You may obtain +%%% a copy of the License at +%%% +%%% http://www.apache.org/licenses/LICENSE-2.0 +%%% +%%% Unless required by applicable law or agreed to in writing, +%%% software distributed under the License is distributed on an +%%% "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +%%% KIND, either express or implied. See the License for the +%%% specific language governing permissions and limitations +%%% under the License. +%%%------------------------------------------------------------------- +%%% @author Eric Merritt <[email protected]> +%%% @copyright 2011 Erlware, LLC. +%%% @doc +%%% A module that supports providing state manipulation services to the system. +%%% @end +%%%------------------------------------------------------------------- +-module(rlx_provider). + +%% API +-export([new/2, + do/2, + impl/1, + format_error/1, + format_error/2, + format/1]). + +-export_type([t/0]). + +-include_lib("relx/include/relx.hrl"). + +%%%=================================================================== +%%% Types +%%%=================================================================== + +-opaque t() :: {?MODULE, module()}. + + +-ifdef(have_callback_support). + +-callback init(rlx_state:t()) -> {ok, rlx_state:t()} | relx:error(). +-callback do(rlx_state:t()) -> {ok, rlx_state:t()} | relx:error(). +-callback format_error(Reason::term()) -> iolist(). + +-else. + +%% In the case where R14 or lower is being used to compile the system +%% we need to export a behaviour info +-export([behaviour_info/1]). +-spec behaviour_info(atom()) -> [{atom(), arity()}] | undefined. +behaviour_info(callbacks) -> + [{init, 1}, + {do, 1}, + {format_error, 1}]; +behaviour_info(_) -> + undefined. + +-endif. + +%%%=================================================================== +%%% API +%%%=================================================================== + +%% @doc create a new provider object from the specified module. The +%% module should implement the provider behaviour. +%% +%% @param ModuleName The module name. +%% @param State0 The current state of the system +-spec new(module(), rlx_state:t()) -> + {t(), {ok, rlx_state:t()}} | relx:error(). +new(ModuleName, State0) when is_atom(ModuleName) -> + State1 = ModuleName:init(State0), + case code:which(ModuleName) of + non_existing -> + ?RLX_ERROR({non_existing, ModuleName}); + _ -> + {{?MODULE, ModuleName}, State1} + end. + +%% @doc Manipulate the state of the system, that new state +%% +%% @param Provider the provider object +%% @param State the current state of the system +-spec do(Provider::t(), rlx_state:t()) -> + {ok, rlx_state:t()} | relx:error(). +do({?MODULE, Mod}, State) -> + Mod:do(State). + +%%% @doc get the name of the module that implements the provider +%%% @param Provider the provider object +-spec impl(Provider::t()) -> module(). +impl({?MODULE, Mod}) -> + Mod. + +%% @doc format an error produced from a provider. +-spec format_error(Reason::term()) -> iolist(). +format_error({non_existing, ModuleName}) -> + io_lib:format("~p does not exist in the system", [ModuleName]). + +%% @doc format an error produced from a provider. +-spec format_error(t(), Reason::term()) -> iolist(). +format_error({?MODULE, Mod}, Error) -> + Mod:format_error(Error). + +%% @doc print the provider module name +%% +%% @param T - The provider +%% @return An iolist describing the provider +-spec format(t()) -> iolist(). +format({?MODULE, Mod}) -> + erlang:atom_to_list(Mod). |