Add a more involved REST example

A pastebin type application that can optionally highlight the output as both text and HTML.
2025-07-14 20:30:23 +00:00 · 2013-02-06 13:09:49 -06:00 · 2013-02-06 13:09:49 -06:00 · d7b83db92e
commit d7b83db92e
parent ae401f7460
11 changed files with 303 additions and 0 deletions
--- a/examples/rest_pastebin/src/toppage_handler.erl
+++ b/examples/rest_pastebin/src/toppage_handler.erl
@ -0,0 +1,132 @@
+%% Feel free to use, reuse and abuse the code in this file.
+
+%% @doc Pastebin handler.
+-module(toppage_handler).
+
+%% REST Callbacks
+-export([init/3]).
+-export([allowed_methods/2]).
+-export([content_types_provided/2]).
+-export([content_types_accepted/2]).
+-export([resource_exists/2]).
+-export([post_is_create/2]).
+-export([create_path/2]).
+
+%% Callback Callbacks
+-export([create_paste/2]).
+-export([paste_html/2]).
+-export([paste_text/2]).
+
+init(_Transport, _Req, []) ->
+	% For the random number generator:
+	{X, Y, Z} = now(),
+	random:seed(X, Y, Z),
+	{upgrade, protocol, cowboy_rest}.
+
+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, Req2} ->
+			{true, Req2, index};
+		{PasteID, Req2} ->
+			case valid_path(PasteID) and file_exists(PasteID) of
+				true -> {true, Req2, PasteID};
+				false -> {false, Req2, PasteID}
+			end
+	end.
+
+post_is_create(Req, State) ->
+	{true, Req, State}.
+
+create_path(Req, State) ->
+	{<<$/, (new_paste_id())/binary>>, Req, State}.
+
+create_paste(Req, State) ->
+	{<<$/, PasteID/binary>>, Req2} = cowboy_req:meta(put_path, Req),
+	{ok, [{<<"paste">>, Paste}], Req3} = cowboy_req:body_qs(Req2),
+	ok = file:write_file(full_path(PasteID), Paste),
+	{true, Req3, State}.
+
+paste_html(Req, index) ->
+	{read_file("index.html"), Req, index};
+paste_html(Req, Paste) ->
+	{Style, Req2} = cowboy_req:qs_val(<<"lang">>, Req, plain),
+	{format_html(Paste, Style), Req2, Paste}.
+
+paste_text(Req, index) ->
+	{read_file("index.txt"), Req, index};
+paste_text(Req, Paste) ->
+	{Style, Req2} = cowboy_req:qs_val(<<"lang">>, Req, plain),
+	{format_text(Paste, Style), Req2, Paste}.
+
+% Private
+
+read_file(Name) ->
+	{ok, Binary} = file:read_file(full_path(Name)),
+	Binary.
+
+full_path(Name) ->
+	{ok, Cwd} = file:get_cwd(),
+	filename:join([Cwd, "priv", 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(<<$., _T/binary>>) -> false;
+valid_path(<<_Char, T/binary>>) -> valid_path(T).
+
+new_paste_id() ->
+	Initial = random:uniform(62) - 1,
+	new_paste_id(<<Initial>>, 7).
+new_paste_id(Bin, 0) ->
+	Chars = <<"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890">>,
+	<< <<(binary_part(Chars, B, 1))/binary>> || <<B>> <= Bin >>;
+new_paste_id(Bin, Rem) ->
+	Next = random:uniform(62) - 1,
+	new_paste_id(<<Bin/binary, Next>>, Rem - 1).
+
+format_html(Paste, plain) ->
+	Text = escape_html_chars(read_file(Paste)),
+	<<"<!DOCTYPE html><html>",
+	"<head><title>paste</title></head>",
+	"<body><pre><code>", Text/binary, "</code></pre></body></html>\n">>;
+format_html(Paste, Lang) ->
+	highlight(full_path(Paste), Lang, "html").
+
+format_text(Paste, plain) ->
+	read_file(Paste);
+format_text(Paste, Lang) ->
+	highlight(full_path(Paste), Lang, "ansi").
+
+highlight(Path, Lang, Type) ->
+	Path1 = binary_to_list(Path),
+	Lang1 = binary_to_list(Lang),
+	os:cmd(["highlight --syntax=", Lang1,
+		" --doc-title=paste ",
+		" --out-format=", Type,
+		" --include-style ", Path1]).
+
+% Escape some HTML characters that might make a fuss
+escape_html_chars(Bin) ->
+	<< <<(escape_html_char(B))/binary>> || <<B>> <= Bin >>.
+
+escape_html_char($<) -> <<"&lt;">>;
+escape_html_char($>) -> <<"&gt;">>;
+escape_html_char($&) -> <<"&amp;">>;
+escape_html_char(C) -> <<C>>.