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%% -*- 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 (C) 2012 Erlware, LLC.
%%%
%%% @doc This provider uses the lib_dir setting of the state. It searches the
%%% Lib Dirs looking for all OTP Applications that are available. When it finds
%%% those OTP Applications it loads the information about them and adds them to
%%% the state of available apps. This implements the rcl_provider behaviour.
-module(rcl_rel_discovery).

-export([do/3,
         format_error/1]).

-include_lib("relcool/include/relcool.hrl").

%%============================================================================
%% API
%%============================================================================

%% @doc recursively dig down into the library directories specified in the state
%% looking for OTP Applications
-spec do(rcl_state:t(), [filename:name()], [rcl_app_info:t()]) ->
                {ok, [rcl_release:t()]} | relcool:error().
do(State, LibDirs, AppMeta) ->
    rcl_log:info(rcl_state:log(State),
                 fun() ->
                         ["Resolving available releases from directories:\n",
                          [[rcl_util:indent(1), LibDir, "\n"] || LibDir <- LibDirs]]
                 end),
    resolve_rel_metadata(State, LibDirs, AppMeta).

-spec format_error([ErrorDetail::term()]) -> iolist().
format_error(ErrorDetails)
  when erlang:is_list(ErrorDetails) ->
    [[format_detail(ErrorDetail), "\n"] || ErrorDetail <- ErrorDetails].

%%%===================================================================
%%% Internal Functions
%%%===================================================================
resolve_rel_metadata(State, LibDirs, AppMeta) ->
    ReleaseMeta0 =
        lists:flatten(ec_plists:map(fun(LibDir) ->
                                            discover_dir([], LibDir, AppMeta)
                                    end, LibDirs)),
    Errors = [case El of
                  {error, Ret} -> Ret;
                  _ -> El
              end
              || El <- ReleaseMeta0,
                 case El of
                     {error, _} ->
                         true;
                     _ ->
                         false
                 end],

    case Errors of
        [] ->
            ReleaseMeta1 = lists:flatten(ReleaseMeta0),
            rcl_log:debug(rcl_state:log(State),
                          fun() ->
                                  ["Resolved the following OTP Releases from the system: \n",
                                   [[rcl_release:format(1, Rel), "\n"] || Rel <- ReleaseMeta1]]
                          end),
            {ok, ReleaseMeta1};
        _ ->
            ?RCL_ERROR(Errors)
    end.

-spec format_detail(ErrorDetail::term()) -> iolist().
format_detail({accessing, File, eaccess}) ->
    io_lib:format("permission denied accessing file ~s", [File]);
format_detail({accessing, File, Type}) ->
    io_lib:format("error (~p) accessing file ~s", [Type, File]).

-spec discover_dir([file:name()], file:name(), [rcl_app_info:t()]) ->
        [rcl_release:t() | {error, Reason::term()}]
      | rcl_release:t()
      | {error, Reason::term()}.
discover_dir(IgnoreDirs, File, AppMeta) ->
    case (not lists:member(File, IgnoreDirs))
        andalso filelib:is_dir(File) of
        true ->
            case file:list_dir(File) of
                {error, Reason} ->
                    {error, {accessing, File, Reason}};
                {ok, List} ->
                    ec_plists:map(fun(LibDir) ->
                                          discover_dir(IgnoreDirs, LibDir, AppMeta)
                                  end,
                                 [filename:join([File, Dir]) || Dir <- List])
            end;
        false ->
            is_valid_release(File, AppMeta)
    end.

-spec is_valid_release(file:name(),
                       [rcl_app_info:t()]) ->
        rcl_release:t()
      | {error, Reason::term()}
      | [].
is_valid_release(File, AppMeta) ->
    case lists:suffix(".rel", File) of
        true ->
            resolve_release(File, AppMeta);
        false ->
            []
    end.

resolve_release(RelFile, AppMeta) ->
    case file:consult(RelFile) of
        {ok, [{release, {RelName, RelVsn},
               {erts, ErtsVsn},
               Apps}]} ->
            build_release(RelName, RelVsn, ErtsVsn, Apps, AppMeta);
        {ok, InvalidRelease} ->
            ?RCL_ERROR({invalid_release_information, InvalidRelease});
        {error, Reason} ->
            ?RCL_ERROR({unable_to_read, RelFile, Reason})
    end.

build_release(RelName, RelVsn, ErtsVsn, Apps, AppMeta) ->
    Release = rcl_release:erts(rcl_release:new(RelName, RelVsn),
                               ErtsVsn),
    resolve_apps(Apps, AppMeta, Release, []).

resolve_apps([], _AppMeta, Release, Acc) ->
    rcl_release:application_details(Release, Acc);
resolve_apps([AppInfo | Apps], AppMeta, Release, Acc) ->
    AppName = erlang:element(1, AppInfo),
    AppVsn = erlang:element(2, AppInfo),
    case find_app(AppName, AppVsn, AppMeta) of
        Error = {error, _} ->
            Error;
        ResolvedApp ->
            resolve_apps(Apps, AppMeta, Release, [ResolvedApp | Acc])
    end.

find_app(AppName, AppVsn, AppMeta) ->
    case ec_lists:find(fun(App) ->
                               NAppName = rcl_app:name(App),
                               NAppVsn = rcl_app:version(App),
                               AppName == NAppName andalso
                                   AppVsn == NAppVsn
                       end, AppMeta) of
        {ok, Head} ->
            Head;
        error ->
            ?RCL_ERROR({could_not_find, {AppName, AppVsn}})
    end.