Support for inline elements, initial support for links...

src/markdown.erl

@@ -0,0 +1,137 @@
+%% Copyright (c) 2009 Will Larson <lethain@gmail.com>
+%% <insert MIT License here>
+-module(markdown).
+-author("Will Larson <lethain@gmail.com>").
+-version("0.0.1").
+-export([markdown/1]).
+-export([toggle_tag/3, exclusive_insert_tag/3]).
+-export([parse_link/2, parse_link_text/2]).
+
+markdown(Text) when is_list(Text) ->
+    markdown(list_to_binary(Text));
+markdown(Binary) when is_binary(Binary) ->
+    markdown(Binary, [], [], []).
+
+markdown(<<"">>, OpenTags, Acc, _Context) ->
+    ClosedTags = lists:foldr(fun(Tag, Acc2) ->
+				     [<<"</",Tag/binary,">">> | Acc2]
+			     end, Acc, lists:reverse(OpenTags)),
+    % markdown is gathered in reverse order
+    Reversed = lists:reverse(ClosedTags),
+    list_to_binary(lists:append(lists:map(fun(X) -> binary_to_list(X) end, Reversed)));
+
+markdown(<<"#####", Rest/binary>>, OpenTags, Acc, Context) ->
+    {OpenTags2, Acc2} = exclusive_insert_tag(<<"h5">>, OpenTags, Acc),
+    markdown(Rest, OpenTags2, Acc2, Context);
+markdown(<<"####", Rest/binary>>, OpenTags, Acc, Context) ->
+    {OpenTags2, Acc2} = exclusive_insert_tag(<<"h4">>, OpenTags, Acc),
+    markdown(Rest, OpenTags2, Acc2, Context);
+markdown(<<"###", Rest/binary>>, OpenTags, Acc, Context) ->
+    {OpenTags2, Acc2} = exclusive_insert_tag(<<"h3">>, OpenTags, Acc),
+    markdown(Rest, OpenTags2, Acc2, Context);
+markdown(<<"##", Rest/binary>>, OpenTags, Acc, Context) ->
+    {OpenTags2, Acc2} = exclusive_insert_tag(<<"h2">>, OpenTags, Acc),
+    markdown(Rest, OpenTags2, Acc2, Context);
+markdown(<<"#", Rest/binary>>, OpenTags, Acc, Context) ->
+    {OpenTags2, Acc2} = exclusive_insert_tag(<<"h1">>, OpenTags, Acc),
+    markdown(Rest, OpenTags2, Acc2, Context);
+markdown(<<"**", Rest/binary>>, OpenTags, Acc, Context) ->
+    {OpenTags2, Acc2} = toggle_tag(<<"strong">>, OpenTags, Acc),
+    markdown(Rest, OpenTags2, Acc2, Context);
+markdown(<<"*", Rest/binary>>, OpenTags, Acc, Context) ->
+    {OpenTags2, Acc2} = exclusive_insert_tag(<<"em">>, OpenTags, Acc),
+    markdown(Rest, OpenTags2, Acc2, Context);
+markdown(<<"``", Rest/binary>>, OpenTags, Acc, Context) ->
+    {OpenTags2, Acc2} = exclusive_insert_tag(<<"code">>, OpenTags, Acc),
+    markdown(Rest, OpenTags2, Acc2, Context);
+markdown(<<"`", Rest/binary>>, OpenTags, Acc, Context) ->
+    {OpenTags2, Acc2} = exclusive_insert_tag(<<"code">>, OpenTags, Acc),
+    markdown(Rest, OpenTags2, Acc2, Context);
+markdown(<<"![", Rest/binary>>, OpenTags, Acc, Context) ->
+    case parse_link(<<"[", Rest/binary>>, Context) of
+	{link, Rest2, Href, Text, undefined} ->
+	    Img = <<"<img src=\"", Href/binary, "\" alt=\"", Text/binary, "\">">>,
+	    markdown(Rest2, OpenTags, [Img | Acc], Context);
+	{link, Rest2, Href, Text, Title} ->
+	    Img = <<"<img src=\"", Href/binary, "\" alt=\"", Text/binary, "\" title=\"", Title/binary, "\">">>,
+	    markdown(Rest2, OpenTags, [Img | Acc], Context)
+    end;
+
+markdown(<<"[", Rest/binary>>, OpenTags, Acc, Context) ->
+    case parse_link(<<"[" , Rest/binary>>, Context) of
+	{link, Rest2, Href, Text, undefined} ->
+	    Link = <<"<a href=\"", Href/binary, ">", Text/binary, "</a>">>,
+	    markdown(Rest2, OpenTags, [Link | Acc], Context);
+	{link, Rest2, Href, Text, Title} ->
+	    Link = <<"<a href=\"", Href/binary, " title=\"", Title/binary, "\" >", Text/binary, "</a>">>,
+	    markdown(Rest2, OpenTags, [Link | Acc], Context);
+	{context, Rest2, Context2} ->
+	    markdown(Rest2, OpenTags, Acc, Context2)
+    end;
+
+
+markdown(<<B:1/binary, Rest/binary>>, OpenTags, Acc, Context) ->
+    markdown(Rest, OpenTags, [B | Acc], Context).
+
+
+%% @doc sub-parser for handling links.
+%%      Handles formats:
+%%        [This is a test](http://test.com/ "The title")
+%%        [This is a test][test]
+%%
+%%     For the second format, you'll need to have previously
+%%     specified the link using the format
+%%        [test]: http://test.com/ "Test Title"
+%%
+%% @spec parse_link() -> link_components() | new_context()
+%%       new_context = {context, binary(), proplist()}
+%%       link_components = {link, binary(), href(), text(), title()}
+%%       href = string()
+%%       text = string()
+%%       title = string() | undefined
+%%       proplist = [{binary(), binary()}]
+parse_link(Binary, Context) ->
+    {Binary2, Text} = parse_link_text(Binary,[]),
+    % stage 2, 
+    ok.
+%% @doc parse the text portion of a link.
+%%      For example, parse "test" from [test][this].
+parse_link_text(<<"[",Binary/binary>>, Acc) ->
+    parse_link_text(Binary, Acc);
+parse_link_text(<<"]",Binary/binary>>, Acc) ->
+    Reversed = lists:reverse(Acc),
+    Text = lists:append(lists:map(fun(X) -> binary_to_list(X) end, Reversed)),				     
+    {Binary, list_to_binary(Text)};
+parse_link_text(<<Char:1/binary, Binary/binary>>, Acc) ->
+    parse_link_text(Binary, [Char | Acc]).
+
+
+
+
+%% @doc close a tag if it is in the open tags stack,
+%%      otherwise open it.
+%% @spec toggle_tag(tag(), tag_stack(), html()) -> {tag_stack(), html()}
+%%       tag = binary()
+%%       tag_stack = [tag()]
+%%       html = [binary()]
+toggle_tag(Tag, OpenTags, Acc) ->
+    case lists:member(Tag, OpenTags) of
+	true ->
+	    {lists:delete(Tag, OpenTags), [<<"</",Tag/binary,">">> | Acc]};
+	false ->
+	    {[Tag | OpenTags], [<<"<",Tag/binary,">">> | Acc]}
+    end.
+
+%% @doc insert tag IFF it isn't already on the
+%%      stack of open tags.
+%% @spec exclusive_insert_tag(tag(), tag_stack(), html()) -> {tag_stack(), html()}
+%%       tag = binary()
+%%       tag_stack = [tag()]
+%%       html = [binary()]
+exclusive_insert_tag(Tag, OpenTags, Acc) ->
+    case lists:member(Tag,OpenTags) of
+	true ->
+	    {OpenTags, Acc};
+	false ->
+	    {[Tag | OpenTags], [<<"<",Tag/binary,">">> | Acc]}
+    end.