%% Feel free to use, reuse and abuse the code in this file.
%% @doc Pastebin handler.
-module(toppage_h).
%% Standard callbacks.
-export([init/2]).
-export([allowed_methods/2]).
-export([content_types_provided/2]).
-export([content_types_accepted/2]).
-export([resource_exists/2]).
%% Custom callbacks.
-export([create_paste/2]).
-export([paste_html/2]).
-export([paste_text/2]).
init(Req, Opts) ->
{cowboy_rest, Req, Opts}.
allowed_methods(Req, State) ->
{[<<"GET">>, <<"POST">>], Req, State}.
content_types_provided(Req, State) ->
{[
{{<<"text">>, <<"plain">>, []}, paste_text},
{{<<"text">>, <<"html">>, []}, paste_html}
], Req, State}.
content_types_accepted(Req, State) ->
{[{{<<"application">>, <<"x-www-form-urlencoded">>, '*'}, create_paste}],
Req, State}.
resource_exists(Req, _State) ->
case cowboy_req:binding(paste_id, Req) of
undefined ->
{true, Req, index};
PasteID ->
case valid_path(PasteID) and file_exists(PasteID) of
true -> {true, Req, PasteID};
false -> {false, Req, PasteID}
end
end.
create_paste(Req, State) ->
PasteID = new_paste_id(),
{ok, [{<<"paste">>, Paste}], Req2} = cowboy_req:read_urlencoded_body(Req),
ok = file:write_file(full_path(PasteID), Paste),
case cowboy_req:method(Req2) of
<<"POST">> ->
{{true, <<$/, PasteID/binary>>}, Req2, State};
_ ->
{true, Req2, State}
end.
paste_html(Req, index) ->
{read_file("index.html"), Req, index};
paste_html(Req, Paste) ->
#{lang := Lang} = cowboy_req:match_qs([{lang, [fun lang_constraint/2], plain}], Req),
{format_html(Paste, Lang), Req, Paste}.
paste_text(Req, index) ->
{read_file("index.txt"), Req, index};
paste_text(Req, Paste) ->
#{lang := Lang} = cowboy_req:match_qs([{lang, [fun lang_constraint/2], plain}], Req),
{format_text(Paste, Lang), Req, Paste}.
% Private
lang_constraint(forward, Bin) ->
case re:run(Bin, "^[a-z0-9_]+$", [{capture, none}]) of
match -> {ok, Bin};
nomatch -> {error, bad_lang}
end;
lang_constraint(format_error, {bad_lang, _}) ->
"Invalid lang parameter.".
read_file(Name) ->
{ok, Binary} = file:read_file(full_path(Name)),
Binary.
full_path(Name) ->
filename:join([code:priv_dir(rest_pastebin), Name]).
file_exists(Name) ->
case file:read_file_info(full_path(Name)) of
{ok, _Info} -> true;
{error, _Reason} -> false
end.
valid_path(<<>>) -> true;
valid_path(<<$., _T/binary>>) -> false;
valid_path(<<$/, _T/binary>>) -> false;
valid_path(<<_Char, T/binary>>) -> valid_path(T).
new_paste_id() ->
Initial = rand:uniform(62) - 1,
new_paste_id(<<Initial>>, 7).
new_paste_id(Bin, 0) ->
Chars = <<"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890">>,
<< <<(binary_part(Chars, B, 1))/binary>> || <<B>> <= Bin >>;
new_paste_id(Bin, Rem) ->
Next = rand:uniform(62) - 1,
new_paste_id(<<Bin/binary, Next>>, Rem - 1).
format_html(Paste, plain) ->
Text = escape_html_chars(read_file(Paste)),
<<"<!DOCTYPE html><html>",
"<head><title>paste</title></head>",
"<body><pre><code>", Text/binary, "</code></pre></body></html>\n">>;
format_html(Paste, Lang) ->
highlight(full_path(Paste), Lang, "html").
format_text(Paste, plain) ->
read_file(Paste);
format_text(Paste, Lang) ->
highlight(full_path(Paste), Lang, "ansi").
highlight(Path, Lang, Type) ->
Path1 = binary_to_list(Path),
Lang1 = binary_to_list(Lang),
os:cmd(["highlight --syntax=", Lang1,
" --doc-title=paste ",
" --out-format=", Type,
" --include-style ", Path1]).
% Escape some HTML characters that might make a fuss
escape_html_chars(Bin) ->
<< <<(escape_html_char(B))/binary>> || <<B>> <= Bin >>.
escape_html_char($<) -> <<"<">>;
escape_html_char($>) -> <<">">>;
escape_html_char($&) -> <<"&">>;
escape_html_char(C) -> <<C>>.
