Change cosmo '$' escape string in markdown renderer

so that we can put 2 selectors next to each other and still be able to
tell where one ends and the other one begins

renderers/markdown.moon

@@ -1,5 +1,70 @@
 Path = require "sitegen.path"
 
+dollar_temp = "z000sitegen_markdown00dollar0000"
+
+-- a constructor for quote delimited strings
+simple_string = (delim) ->
+  import P from require "lpeg"
+
+  inner = P("\\#{delim}") + "\\\\" + (1 - P delim)
+  inner = inner^0
+  P(delim) * inner * P(delim)
+
+lua_string = ->
+  import P, C, Cmt, Cb, Cg from require "lpeg"
+  check_lua_string = (str, pos, right, left) ->
+    #left == #right
+
+  string_open = P"[" * P"="^0 * "["
+  string_close = P"]" * P"="^0 * "]"
+
+  valid_close = Cmt C(string_close) * Cb"string_open", check_lua_string
+
+  Cg(string_open, "string_open") *
+    (1 - valid_close)^0 * string_close
+
+-- returns a pattern that parses a cosmo template. Can be used to have
+-- pre-processors ignore text that would be handled by cosmo
+parse_cosmo = ->
+  import P, R, Cmt, Cs, V from require "lpeg"
+  curly = P {
+    P"{" * (
+      simple_string("'") +
+      simple_string('"') +
+      lua_string! +
+      V(1) +
+      (P(1) - "}")
+    )^0 * P"}"
+  }
+
+  alphanum = R "az", "AZ", "09", "__"
+  P"$" * alphanum^1 * (curly)^-1
+
+escape_cosmo = (str) ->
+  escapes = {}
+  import P, R, Cmt, Cs, V from require "lpeg"
+
+  counter = 0
+
+  cosmo = parse_cosmo! / (tpl) ->
+    counter += 1
+    key = "#{dollar_temp}.#{counter}"
+    escapes[key] = tpl
+    key
+
+  patt = Cs (cosmo + P(1))^0 * P(-1)
+  str = patt\match(str) or str, escapes
+  str, escapes
+
+unescape_cosmo = (str, escapes) ->
+  import P, R, Cmt, Cs from require "lpeg"
+
+  escape_patt = P(dollar_temp) * P(".") * R("09")^1 / (key) ->
+    escapes[key] or error "bad key for unescape_cosmo"
+
+  patt = Cs (escape_patt + P(1))^0 * P(-1)
+  assert patt\match(str)
+
 needs_shell_escape = (str) -> not not str\match "[^%w_-]"
 shell_escape = (str) -> str\gsub "'", "''"
 
@@ -21,10 +86,13 @@ write_exec = (cmd, content) ->
 
 -- config command like this in site.moon:
 -- require("renderers.markdown").cmd = "pandoc --mathjax >"
-class PandocRenderer extends require "sitegen.renderers.markdown"
+class PandocRenderer extends require "sitegen.renderers.html"
-  unescape_cosmo = @unescape_cosmo
+  @escape_cosmo: escape_cosmo
-  escape_cosmo = @escape_cosmo
+  @unescape_cosmo: unescape_cosmo
+  @parse_cosmo: parse_cosmo
 
+  source_ext: "md"
+  ext: "html"
   cmd: "pandoc --mathjax --lua-filter pygments.lua >"
   pandoc: (content) => Path.read_file write_exec @@cmd, content