local p = {}

--[[
Split

This function Splits a string based on a pattern, returns nth substring based on count.

Usage:
{{#invoke:StringFunc|split|source_string|pattern|count|plain}}

Parameters:
	source:  The string to return a subset of
	pattern: The pattern or string to split on 
	count:   The nth substring based on the pattern to return
	plain:   A flag indicating if the pattern should be understood as plain text, defaults to true.
]]
function p.split( frame )
	local new_args = p._getParameters( frame.args, {'source', 'pattern', 'count', 'plain'} )
	local source_str = new_args['source'] or '';
	local pattern = new_args['pattern'] or '';
	if source_str == '' or pattern == '' then
		return source_str;
	end
	local l_plain = p._getBoolean( new_args['plain'] or true );
	if l_plain then
		pattern = p._escapePattern( pattern );
	end
	local plain = false;
	pattern = "[" .. pattern .. "]" 
	local ret_count = tonumber( new_args['count'] ) or 1;
	local start = 1;
	local iter = mw.ustring.find(source_str, pattern, start, plain);
	if iter == nil then
		return source_str;
	end
	if ret_count == 1 then
		return mw.ustring.sub( source_str, start, iter);
	end
    for i=2, ret_count do
    	start = iter+1;
    	iter = mw.ustring.find(source_str,  pattern, start, plain);
    	if iter == nil then
    		break 
    	end
    end
    return mw.ustring.sub( source_str,start,iter); 
end

-- Argument list helper function, as per Module:String
function p._getParameters( frame_args, arg_list)
	local new_args = {};
	local index = 1;
	local value;
	for i, arg in ipairs( arg_list ) do
		value = frame_args[arg]
		if value == nil then
			value = frame_args[index];
			index = index + 1;
		end
		new_args[arg] = value;
	end
	return new_args;
end

-- Escape Pattern helper function so that all charecters are treated as plain text, as per Module:String
function p._escapePattern( pattern_str)
	return mw.ustring.gsub( pattern_str, "([%(%)%.%%%+%-%*%?%[%^%$%]])", "%%%1" );
end

-- Helper Function to interpret boolean strings, as per Module:String
function p._getBoolean( boolean_str ) 
	local boolean_value;
	
	if type( boolean_str ) == 'string' then
		boolean_str = boolean_str:lower();
		if boolean_str == 'false' or boolean_str == 'no' or boolean_str == 'O' or boolean_str == '' then
			boolean_value = false;
		else
			boolean_value = true;
		end
	elseif type(boolean_str) == 'boolean' then
			boolean_value = boolean_str;
	else
		error( 'No boolean value found' );
	end
	return boolean_value
end

return p