local remind = {}

local utilities = require('utilities')

remind.command = 'remind <duration> <message>'
remind.doc = [[```
	]]..utilities.CMD_PAT..[[remind <duration> <message>
	Repeats a message after a duration of time, in minutes.
	```]]

function remind:init()
	self.database.reminders = self.database.reminders or {}

	remind.triggers = utilities.triggers(self.info.username):t('remind', true).table
end

function remind:action(msg)
	-- Ensure there are arguments. If not, send doc.
	local input = utilities.input(msg.text)
	if not input then
		utilities.send_message(self, msg.chat.id, remind.doc, true, msg.message_id, true)
		return
	end
	-- Ensure first arg is a number. If not, send doc.
	local duration = utilities.get_word(input, 1)
	if not tonumber(duration) then
		utilities.send_message(self, msg.chat.id, remind.doc, true, msg.message_id, true)
		return
	end
	-- Duration must be between one minute and one year (approximately).
	duration = tonumber(duration)
	if duration < 1 then
		duration = 1
	elseif duration > 526000 then
		duration = 526000
	end
	-- Ensure there is a second arg.
	local message = utilities.input(input)
	if not message then
		utilities.send_message(self, msg.chat.id, remind.doc, true, msg.message_id, true)
		return
	end
	-- Make a database entry for the group/user if one does not exist.
	self.database.reminders[msg.chat.id_str] = self.database.reminders[msg.chat.id_str] or {}
	-- Limit group reminders to 10 and private reminders to 50.
	if msg.chat.type ~= 'private' and utilities.table_size(self.database.reminders[msg.chat.id_str]) > 9 then
		utilities.send_reply(self, msg, 'Sorry, this group already has ten reminders.')
		return
	elseif msg.chat.type == 'private' and utilities.table_size(self.database.reminders[msg.chat.id_str]) > 49 then
		utilities.send_reply(msg, 'Sorry, you already have fifty reminders.')
		return
	end
	-- Put together the reminder with the expiration, message, and message to reply to.
	local reminder = {
		time = os.time() + duration * 60,
		message = message
	}
	table.insert(self.database.reminders[msg.chat.id_str], reminder)
	local output = 'I will remind you in ' .. duration
	if duration == 1 then
		output = output .. ' minute!'
	else
		output = output .. ' minutes!'
	end
	utilities.send_reply(self, msg, output)
end

function remind:cron()
	local time = os.time()
	-- Iterate over the group entries in the reminders database.
	for chat_id, group in pairs(self.database.reminders) do
		local new_group = {}
		-- Iterate over each reminder.
		for _, reminder in ipairs(group) do
			-- If the reminder is past-due, send it and nullify it.
			-- Otherwise, add it to the replacement table.
			if time > reminder.time then
				local output = '*Reminder:*\n"' .. utilities.md_escape(reminder.message) .. '"'
				local res = utilities.send_message(self, chat_id, output, true, nil, true)
				-- If the message fails to send, save it for later.
				if not res then
					table.insert(new_group, reminder)
				end
			else
				table.insert(new_group, reminder)
			end
		end
		-- Nullify the original table and replace it with the new one.
		self.database.reminders[chat_id] = new_group
		-- Nullify the table if it is empty.
		if #new_group == 0 then
			self.database.reminders[chat_id] = nil
		end
	end
end

return remind