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% Licensed 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.
%% @doc Saves a Key/Value pair to a ini file. The Key consists of a Module
%% and Variable combination. If that combination is found in the ini file
%% the new value replaces the old value. If only the Module is found the
%% Variable and value combination is appended to the Module. If the Module
%% does not yet exist in the ini file, it is added and the Variable/Value
%% pair is appended.
%% @see couch_config
-module(couch_config_writer).
-include("couch_db.hrl").
-export([save_to_file/2]).
%% @spec save_to_file(
%% Config::{{Module::string(), Variable::string()}, Value::string()},
%% File::filename()) -> ok
%% @doc Saves a Module/Key/Value triple to the ini file File::filename()
save_to_file({{Module, Variable}, Value}, File) ->
?LOG_DEBUG("saving to file '~s', Congif: '~p'", [File, {{Module, Variable}, Value}]),
% open file and create a list of lines
{ok, Stream} = file:read_file(File),
OldFileContents = binary_to_list(Stream),
{ok, Lines} = regexp:split(OldFileContents, "\r\n|\n|\r|\032"),
% prepare input variables
ModuleName = "[" ++ Module ++ "]",
VariableList = Variable,
% produce the contents for the config file
NewFileContents =
case NewFileContents2 = save_loop({{ModuleName, VariableList}, Value}, Lines, "", "", []) of
% we didn't change anything, that means we couldn't find a matching
% [ini section] in which case we just append a new one.
OldFileContents ->
append_new_ini_section({{ModuleName, VariableList}, Value}, OldFileContents);
_ ->
NewFileContents2
end,
% do the save, close the config file and get out
save_file(File, NewFileContents),
file:close(Stream),
ok.
%% @doc Iterates over the lines of an ini file and replaces or adds a new
%% configuration directive.
save_loop({{Module, Variable}, Value}, [Line|Rest], OldCurrentModule, Contents, DoneVariables) ->
% if we find a new [ini section] (Module), save that for reference
NewCurrentModule = parse_module(Line, OldCurrentModule),
% if the current Module is the one we want to change, try to match
% each line with the Variable
NewContents = case Module of
NewCurrentModule ->
% see if the current line matches the variable we want to substitute
case parse_variable(Line, Variable, Value) of
% nope, return original line
nomatch ->
DoneVariables2 = DoneVariables,
Line;
% got em! return new line
NewLine ->
DoneVariables2 = [Variable|DoneVariables],
NewLine
end;
% if the variable we want to change couldn't be replaced, we append it
% in the proper module section
OldCurrentModule ->
case lists:member(Variable, DoneVariables) of
false ->
DoneVariables2 = [Variable|DoneVariables],
Variable ++ "=" ++ Value ++ "\n" ++ Line;
true ->
DoneVariables2 = DoneVariables,
Line
end;
% otherwise we just print out the original line
_ ->
DoneVariables2 = DoneVariables,
Line
end,
% clumsy way to only append a newline character
% if the line is not empty. We need this to not
% avoid haveing a newline inserted at the top
% of the target file each time we save it.
Contents2 = case Contents of "" -> ""; _ -> Contents ++ "\n" end,
% go to next line
save_loop({{Module, Variable}, Value}, Rest, NewCurrentModule, Contents2 ++ NewContents, DoneVariables2);
save_loop(_Config, [], _OldModule, NewFileContents, _DoneVariable) ->
% we're out of new lines, just return the new file's contents
NewFileContents.
append_new_ini_section({{ModuleName, Variable}, Value}, OldFileContents) ->
OldFileContents ++ "\n\n" ++ ModuleName ++ "\n" ++ Variable ++ "=" ++ Value ++ "\n".
%% @spec parse_module(Lins::string(), OldModule::string()) -> string()
%% @doc Tries to match a line against a pattern specifying a ini module or
%% section ("[Module]"). Returns OldModule if no match is found.
parse_module(Line, OldModule) ->
case regexp:match(Line, "^\\[([a-zA-Z0-9_-]*)\\]$") of
nomatch ->
OldModule;
{error, Error} ->
io:format("ini file regex error module: '~s'~n", [Error]),
OldModule;
{match, Start, Length} ->
string:substr(Line, Start, Length)
end.
%% @spec parse_variable(Line::string(), Variable::string(), Value::string()) ->
%% string() | nomatch
%% @doc Tries to match a variable assignment in Line. Returns nomatch if the
%% Variable is not found. Returns a new line composed of the Variable and
%% Value otherwise.
parse_variable(Line, Variable, Value) ->
case regexp:match(Line, "^" ++ Variable ++ "=") of
nomatch ->
nomatch;
{error, Error}->
io:format("ini file regex error variable: '~s'~n", [Error]),
nomatch;
{match, _Start, _Length} ->
Variable ++ "=" ++ Value
end.
%% @spec save_file(File::filename(), Contents::string()) ->
%% ok | {error, Reason::string()}
%% @doc Writes Contents to File
save_file(File, Contents) ->
file:write_file(File, list_to_binary(Contents)).
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