[Minor] Add preliminary ical support library

diff --git a/lualib/lua_ical.lua b/lualib/lua_ical.lua
new file mode 100644 (file)
index 0000000..4f6b619
--- /dev/null
+++ b/lualib/lua_ical.lua
@@ -0,0 +1,47 @@
+--[[
+Copyright (c) 2019, Vsevolod Stakhov <vsevolod@highsecure.ru>
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+]]--
+
+local l = require 'lpeg'
+
+local wsp = l.P" "
+local crlf = l.P"\r"^-1 * l.P"\n"
+local eol = (crlf * #crlf) + (crlf - (crlf^-1 * wsp))
+local name = l.C((l.P(1) - (l.P":"))^1) / function(v) return (v:gsub("[\n\r]+%s","")) end
+local value = l.C((l.P(1) - eol)^0) / function(v) return (v:gsub("[\n\r]+%s","")) end
+local elt = name * ":" * wsp^0 * value * eol
+
+local exports = {}
+
+local function ical_txt_values(input)
+  local control={n='\n', r='\r'}
+  local escaper = l.Ct((elt / function(_,b) return (b:gsub("\\(.)", control)) end)^1)
+
+  local values = escaper:match(input)
+
+  if not values then
+    return nil
+  end
+
+  return table.concat(values, "\n")
+end
+
+--[[[
+-- @function lua_ical.ical_txt_values(input)
+-- Returns all values from ical as a plain text. Names are completely ignored.
+--]]
+exports.ical_txt_values = ical_txt_values
+
+return exports
\ No newline at end of file