f = {
	args_default = {
		bracket_left = "",
		bracket_right = "",
		bracket_year_left = "",
		bracket_year_right = "",
		postscript = "",
		page = "",
		pages = "",
		location = "",
		article = "",
		page_sep = ", p. ",
		pages_sep = ", pp. ",
		ref = "",
		P1 = "",
		P2 = "",
		P3 = "",
		P4 = "",
		P5 = ""
	}
};

function trim( str )
	if str == nil then
		return nil;
	end
	return str:match( "^%s*(.-)%s*$");
end    

local function is_year (param)
	return param:match ('^%d%d%d%d?%l?$') or param:match ('^n%.d%.%l?$') or param:match ('^nd%l?$') or param:match ('^c%. %d%d%d%d?%l?$') or param:match ('^%d%d%d%d–%d%d%d%d%l?$');
end

function core( args )
	local result;

	if args.P5 ~= "" then
		if is_year (args.P5) then
			result = table.concat ({args.P1, ' et al. ', args.bracket_year_left, args.P5, args.bracket_year_right});
		else
			args.P5 = '';														-- when P5 not a year don't include in anchor
			result = table.concat ({args.P1, ' et al.'});						-- and don't render it
		end

	elseif args.P4 ~= "" then
		if is_year (args.P4) then
			result = table.concat ({args.P1, ', ', args.P2, ' & ', args.P3, ' ', args.bracket_year_left, args.P4, args.bracket_year_right});	-- three names and a year
		else
			result = table.concat ({args.P1, ' et al.'});						-- four names
		end

	elseif args.P3 ~= "" then
		if is_year (args.P3) then
			result = table.concat ({args.P1, ' & ', args.P2, ' ', args.bracket_year_left, args.P3, args.bracket_year_right});	-- two names and a year
		else
			result = table.concat ({args.P1, ', ', args.P2, ' ', ' & ', args.P3});	-- three names
		end
			
	elseif args.P2 ~= "" then
		if is_year (args.P2) then
			result = table.concat ({args.P1, ' ', args.bracket_year_left, args.P2, args.bracket_year_right});	-- one name and year
		else
			result = table.concat ({args.P1, ' & ', args.P2});				-- two names
		end
		
	else
		result = args.P1;														-- one name
	end
																				-- when author-date result ends with a dot (typically when the last positional parameter holds 'n.d.')
																				-- and when no in-source location (no |p=, |pp=, or |loc=)
																				-- and when the first or only character in args.postscript is a dot
																				-- remove the author-date result trailing dot
																				-- the author-date result trailing dot will be replaced later with the content of args.postscript (usually a dot)
	if ('.' == result:sub(-1)) and ('.' == args.postscript:sub(1)) and ('' == args.page) and ('' == args.pages) and ('' == args.location) then
		result = result:gsub ('%.$', '');
	end
	
	if args.ref ~= 'none' then
		if args.ref ~= "" then
			result = "[[" .. args.article .. "#" .. mw.uri.anchorEncode(args.ref) .. "|" .. result .. "]]";
		else
			result = "[[" .. args.article .. "#CITEREF" .. mw.uri.anchorEncode(args.P1 .. args.P2 .. args.P3 .. args.P4 .. args.P5) .. "|" .. result .. "]]";
		end
	end

	if args.page ~= "" then
		result = result .. args.page_sep .. args.page;
	elseif args.pages ~= "" then
		result = result .. args.pages_sep .. args.pages;
	end      

	if args.location ~= "" then
		result = result .. ", " .. args.location;
	end

	result = table.concat ({args.bracket_left, result, args.bracket_right, args.postscript}):gsub ('%s+', ' ');		-- strip redundant spaces
	return result;
end

function f.harvard_core( frame )
	local args = {};
	local pframe = frame:getParent();

	args.bracket_left = pframe.args.BracketLeft or "";
	args.bracket_right = pframe.args.BracketRight or "";
	args.bracket_year_left = pframe.args.BracketYearLeft or "";
	args.bracket_year_right = pframe.args.BracketYearRight or "";
	args.postscript = pframe.args.Postscript or "";
	if 'none' == args.postscript then
		args.postscript = '';
	end

	args.page = pframe.args.Page or "";
	args.pages = pframe.args.Pages or "";
	args.location = pframe.args.Location or "";
	args.page_sep = pframe.args.PageSep or "";
	args.pages_sep = pframe.args.PagesSep or "";
	args.ref = pframe.args.REF or "{{{REF}}}";
	args.P1 = trim( pframe.args.P1 ) or "";
	args.P2 = trim( pframe.args.P2 ) or "";
	args.P3 = trim( pframe.args.P3 ) or "";
	args.P4 = trim( pframe.args.P4 ) or "";
	args.P5 = trim( pframe.args.P5 ) or "";

	return core( args );
end

function f.harvard_citation( frame )
	local args = f.args_default;
	pframe = frame:getParent();

	args.bracket_left = "(";
	args.bracket_right = ")";
	args.page = pframe.args.p or pframe.args.page or "";
	args.pages = pframe.args.pp or pframe.args.pages or "";
	args.location = pframe.args.loc or "";
	args.ref = pframe.args.ref or pframe.args.Ref or "";
	args.P1 = trim( pframe.args[1] ) or "";
	args.P2 = trim( pframe.args[2] ) or "";
	args.P3 = trim( pframe.args[3] ) or "";
	args.P4 = trim( pframe.args[4] ) or "";
	args.P5 = trim( pframe.args[5] ) or "";

	return core( args );
end

function f.harvard_citation_no_bracket( frame )
	local args = f.args_default;
	pframe = frame:getParent();

	args.page = pframe.args.p or pframe.args.page or "";
	args.pages = pframe.args.pp or pframe.args.pages or "";
	args.location = pframe.args.loc or "";
	args.ref = pframe.args.ref or pframe.args.Ref or "";
	args.P1 = trim( pframe.args[1] ) or "";
	args.P2 = trim( pframe.args[2] ) or "";
	args.P3 = trim( pframe.args[3] ) or "";
	args.P4 = trim( pframe.args[4] ) or "";
	args.P5 = trim( pframe.args[5] ) or "";

	return core( args );
end

function f.sfn( frame, args )
	local args = args or f.args_default;
	for k, v in pairs( frame.args ) do											-- for {{sfnp}}, override default with values provided in the #invoke:
		args[k] = v;	   
	end
	
	pframe = frame:getParent();

	args.postscript = pframe.args.postscript or pframe.args.ps or ".";
	if 'none' == args.postscript then
		args.postscript = '';
	end
	args.page = pframe.args.p or pframe.args.page or "";
	args.pages = pframe.args.pp or pframe.args.pages or "";
	args.location = pframe.args.loc or "";
	args.ref = pframe.args.ref or pframe.args.Ref or "";
	args.P1 = trim( pframe.args[1] ) or "";
	args.P2 = trim( pframe.args[2] ) or "";
	args.P3 = trim( pframe.args[3] ) or "";
	args.P4 = trim( pframe.args[4] ) or "";
	args.P5 = trim( pframe.args[5] ) or "";

	local result = core( args );
																				-- put it all together and then strip redundant spaces
	local name = table.concat ({'FOOTNOTE', args.P1, args.P2, args.P3, args.P4, args.P5, args.page, args.pages, args.location}):gsub ('%s+', ' ');

	result = frame:extensionTag{ name = "ref", args = {name=name}, content=result };

	return result;
end

function f.sfnt( frame )
	local args = f.args_default;
	args.article = mw.title.getCurrentTitle().subjectPageTitle.fullText;
	args.article = string.gsub(args.article, "Wikipedia:Articles for deletion/", "", 1);
	return f.sfn(frame, args);
end

return f;