banner_gen.erl

-export([
    init/1
    , content_types_provided/2
    , provide_content/2
]).


-include_lib("webmachine_resource.hrl").
-include_lib("zotonic.hrl").


-define(DEFAULT_LENGTH, 64).
-define(DEFAULT_LABEL, "world ! {self(), erlanger}").

-record(image, {
                type="normal",
                style="light",
                label=?DEFAULT_LABEL,
                url=undefined,
                glyph_dir,
                out_dir,
                out_file,
                path_to_images
                }).


init(Args) -> {ok, Args}.


content_types_provided(ReqData, Context) ->
    {[{"image/png", provide_content}], ReqData, Context}.


provide_content(ReqData, Context) ->
    Context1 = z_context:set_reqdata(ReqData, Context),
    Context2 = z_context:ensure_all(Context1),
    File = get_image(Context2),

    %% http://hg.rabbitmq.com/rabbitmq-server/file/50890ac979ba/src/worker_pool.erl
    %% see article at 
    %% http://www.lshift.net/blog/2010/03/29/on-the-limits-of-concurrency-worker-pools-in-erlang    
    case worker_pool:submit(fun() -> maybe_fetch_object(File) end) of 
    {true, Value} ->
        {Value, ReqData, Context};
    {false, _} ->
        {"none", ReqData, Context}
    end.

get_image(Context) ->     
    {Type, Style, Label, Url} = get_relevant_vars(Context),
    Hash = hash_file(Label, Url, Type, Style),
    
    LibDir = filename:join([z_utils:lib_dir(Context), "lib", "images"]),
    
    GlyphDir = filename:join([LibDir, "glyphs"]),
    OutDir   = filename:join([LibDir, "out"]),
    
    % hash all incoming data
    
    % LabelShort is of type "3xHd5Mug0DLZjxjMeWgPxD2"
    OutFileDir = filename:join([
                               OutDir,
                               lists:sublist(Hash, 1, 1),
                               lists:sublist(Hash, 2, 1),
                               lists:sublist(Hash, 3, 1),
                               lists:sublist(Hash, 4, 2)
                               ]) ++ "/",
    OutFileName = lists:sublist(Hash, 6, length(Hash)) ++ ".png",

    OutFile = filename:join([OutFileDir, OutFileName]),
    
    File = case mod_redis:action({exists, [io_lib:format("image:~s", [Hash])]}, Context) of
        false ->
            %% using redis here, can be any DB at all
            %% используем Redis, можно использовать любую базу

            Inc = z_convert:to_list(mod_redis:action({incr, ["imagecount"]}, Context)),
            
            mod_redis:action({set, [io_lib:format("image:~s", [Hash]), Inc]}, Context),
            
            filelib:ensure_dir(OutFileDir),
            
            gen_image(
                #image{
                    type  = Type,
                    style = Style,
                    label = Label,
                    url   = Url,
                    glyph_dir =  GlyphDir,
                    out_dir   =  OutFileDir,
                    out_file  =  OutFile,
                    path_to_images = LibDir
                }
            ),
            mod_redis:action({set, [io_lib:format("image:file:~s", [Inc]), OutFile]}, Context),
            OutFile;
        _ ->
            Id = mod_redis:action({get, [io_lib:format("image:~s", [Hash])]}, Context),
            F = mod_redis:action({get, [io_lib:format("image:file:~s", [z_convert:to_list(Id)])]}, Context),
            F
    end,
    z_convert:to_list(File).

hash_file(Label, Url, Type, Style) ->
    <<Label2:128/unsigned-integer>> = crypto:md5(unicode:characters_to_binary(Label)),
    <<Url2:128/unsigned-integer>>   = crypto:md5(unicode:characters_to_binary(Url)),
    LabelShort = base62:encode(Label2),
    UrlShort   = base62:encode(Url2),
    lists:flatten([short(Type), short(Style), LabelShort, UrlShort]).


gen_image(#image{type=Type, style=Style, label=Label, out_file=OutFile, glyph_dir=GlyphDir, path_to_images = PathToImages}) ->
    Theme = get_theme(Style),
    Size  = get_size(Type),
    
    Cmd = [
           "cd ", PathToImages, " && python ",
           "draw_text.py",
           " -o ", OutFile,
           " -t ", Theme,
           " -b ", Size,
           " -l ", binary_to_list(unicode:characters_to_binary(mochiweb_util:shell_quote(Label)))
           ],

    worker_pool:submit(fun() -> os:cmd(Cmd) end).


get_theme(Theme) when Theme =:= "light" orelse Theme =:= "dark" ->
    Theme;
get_theme(Theme) ->
    "light".

get_size("big") ->
    "big";
get_size("normal") ->
    "medium";
get_size("medium") ->
    "medium";
get_size("small") ->
    "small";
get_size(_) ->
    "medium".

get_glyph_dir(GlyphDir, Size, Theme) ->
    filename:join([GlyphDir, z_convert:to_list(Size), Theme]).

get_out_path(Context) ->
    filename:join([z_utils:lib_dir(Context), "lib", "out"]).

short(S) ->
    lists:sublist(S, 1).