ndp.lua

-- ndp - Natural Date Parser library for Lua

-- Copyright (C) 2009 Matthew Wild <mwild1@gmail.com>

-- 

-- This project is MIT/X11 licensed. Please see the

-- COPYING file in the source package for more information.

--

module(..., package.seeall);

require "luarocks.require"

require "lpeg"

-- Add case-insensitive string matching to Lpeg

function lpeg.Pi(s)

	local patt = lpeg.P(true);

	for c in s:gmatch(".") do

		patt = patt * (lpeg.P(c:lower()) + lpeg.P(c:upper()));

	end

	return patt;

end

function lpeg.one_of(list)

	local patt = lpeg.P(false);

	for _, match in ipairs(list) do

		patt = patt + lpeg.Pi(match);

	end

	return patt;

end

local wordsep = lpeg.S" ";

local ordinal = lpeg.P{ lpeg.C(lpeg.R("09")^-2) * (lpeg.Pi("st") + lpeg.Pi("nd") + lpeg.Pi("rd") + lpeg.Pi("th")) + 1 * lpeg.V(1) };

local number = lpeg.R "09"^1

local day_name = lpeg.one_of {'monday',   'tuesday', 'wednesday',

                              'thursday', 'friday',  'saturday', 'sunday'}

local month_name = lpeg.one_of {'january', 'february', 'march', 'april', 'may', 'june', 

                                     'july', 'august', 'september', 'october', 'november', 'december' }

local year = lpeg.R("09") * lpeg.R("09") * lpeg.R("09") * lpeg.R("09");

local unit_of_time = lpeg.one_of { 'second', 'minute', 'hour', 'day', 'week', 'month', 'year' }

local time_of_day = lpeg.one_of { 'morning', 'noon', 'afternoon', 'evening', 'night', 'midnight' }

local time_of_days = { morning = 09, noon = 12, afternoon = 13, evening = 17, night = 21, midnight = 00 }

local quantity;

local quantities = { 

		["a"]        = 1;

		["an"]       = 1;

		["a couple of"] = 2;

		["a few"]    = 3;

		["several"]  = 3;

	};

-- Create 'quantity' to match any of the quantities we know

do

	local quantity_list = {};

	for k in pairs(quantities) do

		quantity_list[#quantity_list+1] = k;

	end

	table.sort(quantity_list, function (a,b) return #a>#b; end);

	quantity = number + lpeg.one_of(quantity_list);

end

seconds_in_a = { second = 1 }

seconds_in_a.minute  = seconds_in_a.second *  60;

seconds_in_a.hour    = seconds_in_a.minute *  60;

seconds_in_a.day     = seconds_in_a.hour   *  24;

seconds_in_a.week    = seconds_in_a.day    *   7;

seconds_in_a.month   = seconds_in_a.week   *   4;

seconds_in_a.year    = seconds_in_a.day    * 365;

local function get_time_part(time, part)

	return os.date("*t", time)[part];

end

local function adjust_time(time, part, value)

	local split_time = os.date("*t", time);

	split_time[part] = value;

	return os.time(split_time);

end

local function find_next_day_by_name(time, day_name)

	day_name = day_name:lower():gsub("^.", string.upper); -- Normalize

	for i=1,8 do

		time = time + seconds_in_a.day;

		if os.date("%A", time) == day_name then

			return time;

		end

	end

	return;

end

local function find_next_month_by_name(time, month_name)

	month_name = month_name:lower():gsub("^.", string.upper); -- Normalize

	local split_time = os.date("*t", time);

	for i=1,13 do

		split_time.month = split_time.month + 1;

		if split_time.month == 13 then split_time.month = 1; end

		time = os.time(split_time);

		if os.date("%B", time) == month_name then

			return time;

		end

	end

	return;

end

local function advance_months(time, n)

	local split_time = os.date("*t", time);

	split_time.month = ((split_time.month-1)+n)%12+1;

	split_time.year = split_time.year + math.floor(n/12);

	return os.time(split_time);

end

local function advance_years(time, n)

	local split_time = os.date("*t", time);

	split_time.year = split_time.year + n;

	return os.time(split_time);

end

function when(str, relative_to)

	local time = relative_to or os.time();

	local P, Pi = lpeg.P, lpeg.Pi;

	local patterns = 

	{ 

		{ Pi"today" };

		{ Pi"tomorrow" /

			function ()

				time = time + seconds_in_a.day;

			end };

		{ (lpeg.one_of{"a ", "the "}+true) * Pi"day after" /

			function ()

				time = time + seconds_in_a.day;

			end };

		{ Pi"next week" /

			function ()

				time = time + seconds_in_a.week;

			end };

		{ Pi"next month" /

			function ()

				time = advance_months(time, 1);

			end };

		{ Pi"next year" /

			function ()

				time = advance_years(time, 1);

			end };

		{ year /

			function (year)

				time = adjust_time(time, "year", tonumber(year));

			end };

		{ (Pi"in " + true) * month_name /

			function (month_name)

				time = find_next_month_by_name(time, month_name:match("%S+$"));

			end };

		{ (Pi"on " + true) * day_name /

			function (day_name)

				time = find_next_day_by_name(time, day_name:match("%S+$"));

			end };

		{ (Pi"in " + true) * ( quantity * P" " * unit_of_time ) * (P"s"^-1) /

			function (number_and_unit)

				local number, unit = number_and_unit:gsub("^in ", ""):match("^(.+)%s+(.-)s?$");

				number = quantities[number] or tonumber(number);

				if unit == "month" then

					time = advance_months(time, number);

				elseif unit == "year" then

					time = advance_years(time, number);

				else

					time = time + seconds_in_a[unit] * number;

				end

			end };

		{ (lpeg.one_of{"this ", "in the ", "at "} + true)* time_of_day /

			function (time_of_day)

					time_of_day = time_of_day:match("%S+$");

					if time_of_day == "morning" and get_time_part(time, "hour") > time_of_days.morning then

						time = time + seconds_in_a.day; -- Morning has passed, so next morning

					end

					time = adjust_time(time, "hour", time_of_days[time_of_day]);

					if time_of_day == "noon" or time_of_day == "midnight" then

						time = adjust_time(time, "min", 00);

					else

						time = adjust_time(time, "min", 30);

					end

			end };

	}

	local ret, min_pos, max_pos;

	local function check_min_pos(start) start = start - 1; if not min_pos or start < min_pos then min_pos = start; end end;

	for _, pattern in pairs(patterns) do

		ret = lpeg.match(lpeg.P{ lpeg.Cp()*pattern[1] + 1 * (1-wordsep)^0 * wordsep * lpeg.V(1) }/check_min_pos, str);

		if ret then

			if not max_pos or ret > max_pos then max_pos = ret; end

			--print("Matches ".._.." until "..ret);

		end

	end

	return time, min_pos, max_pos;

end