translit

#!/usr/bin/env escript

%% translit -- map characters
translit([FromSet, ToSet, File]) ->
    Map = mpattern(FromSet, ToSet),
    translit(File, Map, []).

translit([], _, Acc) ->
    ststd:io({output, file}, Acc);
translit([H|T], Map, Acc) ->
    case maps:find(H, Map) of
        {ok, Change} -> translit(T, Map, lists:concat([Acc, [Change]]));
        error -> translit(T, Map, lists:concat([Acc, [H]]))
    end.

%% squashing -- substitute pattern for a single symbol
%%
%% Generate special Map, and reuses translit/3
squashing([FromSet, ToSet, File]) ->
    CharList = lists:map(fun(_) -> ToSet end, lists:seq(1, erlang:length(FromSet))),
    Map = mpattern(FromSet, CharList),
    translit(File, Map, []).

%% deleteall -- delete all occurrences of pattern
%%
%% Generate special Map, and reuses translit/3
deleteall([FromSet, File]) ->
    BlankList = lists:map(fun(_) -> [] end, lists:seq(1, erlang:length(FromSet))),
    Map = mpattern(FromSet, BlankList),
    translit(File, Map, []).

%% mpattern -- transform two Args (chars or lists) into a map
mpattern(FromSet, ToSet) ->
    maps:from_list(lists:zip(FromSet, ToSet)).

%% parse -- detect pattern and return list
parse([Letter|[]]) ->
    [Letter];
parse([Base,45,End|[]]) ->
    List = lists:seq(Base,End),
    List;
parse([Base,45,End|T]) ->
    List = lists:seq(Base, End),
    Tail = parse(T),
    lists:concat([List, Tail]).


%% main -- receive and parse args
main([]) ->
    halt(1);

main([_|[]]) ->
    halt(1);

%% Arg1 = pattern
%% Arg2 = file
%% one pattern means to delete all occurrences on file
main([Arg, File|[]]) ->
    FromSet = parse(Arg),
    Input = ststd:io({input, file}, File),
    deleteall([FromSet, Input]);

%% Arg1 = pattern (fromset)
%% Arg2 = pattern (toset)
%% Arg3 = file
main([Arg1, Arg2, File|[]]) ->
    FromSet = parse(Arg1),
    ToSet = parse(Arg2),
    Input = ststd:io({input, file}, File),
    selector(FromSet, ToSet, Input).

%% transliterate characters from Arg1[i] to Arg2[i]
%% if Arg2 is shorter than Arg1, squash instead
selector(FromSet,ToSet,File) when erlang:length(ToSet) < erlang:length(FromSet) ->
    squashing([FromSet, ToSet, File]);
selector(FromSet, ToSet, File) ->
    translit([FromSet, ToSet, File]).