local p = {}

-- reproduced from Module:Convert
local scale = {
	second = 1,
	seconds = 1,
	minute = 60,
	minutes = 60,
	hour = 3600,
	hours = 3600,
	day = 86400,
	days = 86400,
	month = 2629800,
	months = 2629800,
	year = 31557600,
	years = 31557600
}

local cfg = {
	error_positive_number = 'Human readable duration error: First argument must be a positive number ([[Template:Human readable duration|help]])',
	error_time_unit = 'Human readable duration error: Second argument must be a valid time unit ([[Template:Human readable duration|help]])',
}

-- from http://lua-users.org/wiki/SimpleRound
local function round(num, decimal_places)
	local mult = 10^(decimal_places or 0)
	return math.floor(num * mult + 0.5) / mult
end

local function parse_archive_bot_settings(parameter, parsed_page, is_rounded, template_index)
	
	local good_para = false
	for _, v in ipairs({
		'bot', 'age', 'units', 'minthreadsleft', 'min', 'minkeepthreads'
	}) do
		if v == parameter then good_para = true end
		if good_para then break end
	end
	if not good_para then return '' end
	
	local tpv = require('Template parameter value')
	local get_parameter = tpv.getParameter
	local find_template = tpv.getTemplate
	
	if not is_filled(parsed_page) then parsed_page = mw.getCurrentTitle().fulltext end
	
	local miszabot_config = 'User:MiszaBot/config'
	local cb_config = 'User:ClueBot III/ArchiveThis'
	if find_template(parsed_page, miszabot_config) then
		local match = mw.ustring.match
		local age_exists, age = get_parameter(parsed_page, miszabot_config, 'algo')
		local minthreads_exists, minthreads = get_parameter(parsed_page, miszabot_config, 'minthreadsleft')
		
		if parameter == 'bot' then
			return 'Lowercase sigmabot III'
		elseif parameter == 'age' and age_exists then
			return match(age, '^%s*old%s*%((%d+)[dh]?%)%s*$')
		elseif parameter == 'units' and age_exists then
			local units = match(age, '^%s*old%s*%(%d+([dh]?)%)%s*$')
			if units == 'd' then return 'days'
			elseif units == 'h' then return 'hours'
			else return 'seconds' end
		elseif minthreads_exists then -- already took care of the other invalids, so this is just minthreads
			return minthreads
		end
	elseif find_template(parsed_page, cluebot_config) then
		if template_index then
			template_index = tonumber(template_index)
			if template_index == nil then template_index = 1 end
		end
		
		local age_exists, age = get_parameter(
			parsed_page, cluebot_config, 'age', { template_index = template_index }
		)
		local minthreads_exists, minthreads = get_parameter(
			parsed_page, cluebot_config, 'minkeepthreads', { template_index = template_index }
		)
		if not is_filled(is_rounded) then is_rounded = nil end
		
		if parameter == 'bot' then
			return 'User:ClueBot III'
		elseif parameter == 'age' then
			if not is_rounded then return age end
			
			local num_age = tonumber(age)
			if num_age <= 24 then return age end
			
			-- this formula converts from hours to days with half day precision
			-- i.e. it pops out n+0 or n+0.5 days
			-- apparently 7.6 days is undesirable
			local double_days = 2 * num_age / 24
			local rounded_double_days = round(double_days, 0)
			local days_with_halves = rounded_double_days / 2
			return tostring(days_with_halves)
		elseif parameter == 'units' then
			if not is_rounded or tonumber(age) <= 24 then return 'hours' end
			return 'days'
		else -- already took care of the other invalids, so this is just minthreads
			return minthreads
		end
	end
	return ''
end

function p._parse_ext_settings(args)
	
end

function p.parse_ext_settings(frame)
	local args = frame:getParent().args
	return p._parse_archive_bot(args)
end

local function archives_error(specific_class, error_text)
	local format = mw.ustring.format
	return format('<strong class="archives-bots-error %s">%s</strong>', specific_class, error_text)
end

function p._human_readable_duration(args)
	local time = tonumber(args[1])

	if time == nil or time < 0 then
		return archives_error('archives-bots-error-number', cfg.error_positive_number)
	end

	local unit = string.lower(args[2] or "")

	if scale[unit] == nil then
		return archives_error('archives-bots-error-time-unit', cfg.error_time_unit)
	end

	local timeseconds = time * scale[unit]

	if timeseconds < 59.75 then -- rounds to 59.5 seconds or less
		local converted = math.floor(timeseconds * 2 + 0.5) / 2
		return converted .. " second" .. (converted ~= 1 and "s" or "")
	elseif timeseconds < 3585 then -- rounds to 59.5 minutes or less
		local converted = math.floor(timeseconds / scale.minute * 2 + 0.5) / 2
		return converted .. " minute" .. (converted ~= 1 and "s" or "")
	elseif timeseconds < 258300 and timeseconds ~= 86400 and timeseconds ~= 172800 then -- rounds to 71.5 hours or less, excluding 24 and 48 hours exactly
		local converted = math.floor(timeseconds / scale.hour * 2 + 0.5) / 2
		return converted .. " hour" .. (converted ~= 1 and "s" or "")
	elseif timeseconds < 4341600 then -- rounds to 50 days or less
		local converted = math.floor(timeseconds / scale.day * 2 + 0.5) / 2
		return converted .. " day" .. (converted ~= 1 and "s" or "")
	elseif timeseconds < 48651300 then -- rounds to 18 months or less (rounds to nearest integer instead of 0.5)
		local converted = math.floor(timeseconds / scale.month + 0.5)
		return converted .. " month" .. (converted ~= 1 and "s" or "")
	else -- anything over 18 months rounds to nearest 0.5 years
		local converted = math.floor(timeseconds / scale.year * 2 + 0.5) / 2
		return converted .. " year" .. (converted ~= 1 and "s" or "")
	end
	
end

function p.human_readable_duration(frame)
	local args = frame:getParent().args
	return p._human_readable_duration(args)
end

return p