local math_mod = require('Module:Math')

local traceText
local Value
Value = {
	lang = mw.getContentLanguage(),
	getDisplay = function (self, second)
		if not self:isValid() then
			return nil
		end
		local display = self.string
		if display == 'trace' then
			if second then
				-- If a cell displays "cm (inch)", show "trace" not "trace (trace)".
				return nil
			end
			return traceText or 'trace'
		end
		if math.abs(self.number) >= 1000 then
			display = self.lang:formatNum(math.abs(self.number))
			if self.number < 0 then
				display = '−' .. display
			end
		elseif self.number < 0 then
			display = '−' .. display:sub(2)
		end
		return display
	end,
	getPrecision = function (self)
		local result = rawget(self, 'precision')
		if not result then
			if self:isValid() then
				result = math.max(0, math_mod._precision(self.string))
			else
				result = 0
			end
			rawset(self, 'precision', result)
		end
		return result
	end,
	isValid = function (self)
		return self.number ~= nil and self.number ~= -9999
	end,
	new = function (v)
		local val, str, precision
		if type(v) == 'string' then
			if v == 'trace' then
				val, str, precision = 0, 'trace', 0
			else
				val, str = math_mod._cleanNumber(v)
			end
		elseif type(v) == 'number' then
			val, str = v, tostring(v)
		end
		if not val then
			val, str = -9999, ''
		end
		return setmetatable({
			number = val,
			string = str,
			precision = precision,
		}, Value)
	end,
	converts = {
		in2cm = { factor = 2.54              },
		in2mm = { factor = 25.4              },
		cm2in = { factor = 1/2.54, p2max = 1 },
		mm2in = { factor = 1/25.4, p2max = 0 },
	},
	setConvert = function (self, invalue, units)
		-- Use method modified from [[Module:Convert]] to determine precision.
		if invalue.string == 'trace' then
			self.number, self.string, self.precision = 0, 'trace', 0
			return
		end
		local convert = self.converts[units] or error('Unknown units')
		local outnum = invalue.number * convert.factor
		local precision = invalue:getPrecision()
		if outnum > 0 then
			local adjust = math.log10(1/convert.factor) + math.log10(2)
			local p1 = math.floor(precision + adjust)
			local p2 = 1 - math.floor(math.log10(outnum))
			if convert.p2max then
				p2 = math.min(p2, convert.p2max)
			end
			precision = math.max(p1, p2)
		end
		self:setNumberRounded(outnum, precision)
	end,
	setNumberRounded = function (self, number, precision)
		if precision > 2 then
			precision = 2
		end
		self.number = math_mod._round(number, precision)
		if precision < 0 then
			self.string = tostring(self.number)
		else
			local fmt = '%.' .. string.format('%d', precision) .. 'f'
			self.string = string.format(fmt, self.number)
		end
	end,
}
Value.__index = Value

local function checkFlag(flag, default)
	if flag == nil then
		return default
	elseif type(flag) == 'boolean' then
		return flag
	elseif type(flag) == 'string' then
		flag = flag:lower()
		if flag == '0' or flag == 'false' or
				flag == '' or flag == 'no' or
				flag == 'n' then
			return false
		else
			return true
		end
	else
		return error('Flag type not valid')
	end
end

local function makeLine(label, first_values, second_values, color_values)
	local result = {'|- style="text-align: center;"\n! scope="row" style="height: 16px;" | ', label, "\n"}
	for i = 1, 13 do
		local color_str = color_values[i]
		if i == 13 then
			table.insert(result, table.concat( {'|style="', color_str, ' border-left-width:medium" class="notheme"| '} ))
		else
			table.insert(result, table.concat( {'|style="', color_str, '" class="notheme"| '} ))
		end
		local display = first_values[i]:getDisplay()
		if display then
			table.insert(result, display)
			if second_values ~= nil then
				display = second_values[i]:getDisplay(true)
				if display then
					table.insert(result, "<br />(" .. display .. ")")
				end
			end
		else
			table.insert(result, '—')
		end
		table.insert(result, "\n")
	end
	return table.concat(result)
end

local function getInputs(args, group_name, suffix, include_space)
	local month_names = { 'Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun',
		'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec', 'year' }
	local str
	local values = {}
	if suffix == nil then
		for i, mon in ipairs(month_names) do
			if include_space then
				str = args[ mon .. ' ' .. group_name ] or ''
			else
				str = args[ mon .. group_name ] or ''
			end
			values[i] = Value.new(str)
		end
	else
		for i, mon in ipairs(month_names) do
			local value, updated
			for var, suf in ipairs(suffix) do
				if include_space then
					str = args[ mon .. ' ' .. group_name .. ' ' .. suf ]
				else
					str = args[ mon .. group_name .. ' ' .. suf ]
				end
				if str ~= nil and str ~= '' then
					value = Value.new(str)
					value.variant = var
					updated = true
					break
				end
			end
			if not updated then
				value = Value.new()
				value.variant = 0
			end
			values[i] = value
		end
	end
	return values
end

local function getAnnualValue(values, mode)
	if mode == 'avg' or mode == 'sum' then
		local total = 0
		local p1, p2, variant
		p1 = 0
		for i = 1, 12 do
			if not values[i]:isValid() then
				return Value.new()
			end
			if not variant then
				local var = values[i].variant
				if var and var ~= 0 then
					variant = var
				end
			end
			p2 = values[i]:getPrecision()
			if p2 > p1 then
				p1 = p2
			end
			total = total + values[i].number
		end
		local value = Value.new(total)
		if mode == 'avg' then
			value:setNumberRounded(total / 12, p1)
		end
		value.variant = variant
		return value
	elseif mode == 'min' then
		local target
		for i = 1, 12 do
			if values[i]:isValid() then
				if target == nil or values[i].number < target.number then
					target = values[i]
				end
			end
		end
		return target or Value.new()
	elseif mode == 'max' then
		local target
		for i = 1, 12 do
			if values[i]:isValid() then
				if target == nil or values[i].number > target.number then
					target = values[i]
				end
			end
		end
		return target or Value.new()
	else
		error('Unrecognized Annual Mode')
	end
end

local function reconcileTemperature(C_values, F_values)
	for i = 1, 13 do
		local p
		if C_values[i].string == '' then
			if F_values[i]:isValid() then
				p = F_values[i]:getPrecision()
				C_values[i]:setNumberRounded((F_values[i].number - 32)*5/9, p)
			end
		elseif F_values[i].string == '' then
			if C_values[i]:isValid() then
				p = C_values[i]:getPrecision()
				F_values[i]:setNumberRounded(C_values[i].number*9/5 + 32, p)
			end
		end
	end
end

local function reconcilePrecipitation(M_values, I_values, prefer_cm)
	local v_class = 0
	for i = 1, 13 do
		if M_values[i].variant == 1 then
			v_class = 1
		elseif M_values[i].variant == 2 then
			v_class = 2
		end
	end
	if v_class == 0 then
		if prefer_cm then
			v_class = 1
		else
			v_class = 2
		end
	end
	for i = 1, 13 do
		local units
		if M_values[i].string == '' then
			if I_values[i]:isValid() then
				if v_class == 1 then
					units = 'in2cm'
				else
					units = 'in2mm'
				end
				M_values[i]:setConvert(I_values[i], units)
				M_values[i].variant = v_class
			end
		elseif I_values[i].string == '' then
			if M_values[i]:isValid() then
				if M_values[i].variant == 1 then
					units = 'cm2in'
				else
					units = 'mm2in'
				end
				I_values[i]:setConvert(M_values[i], units)
			end
		end
	end
end

local function _buildRow(definition, args, options)
	options = options or {}
	local wbc = require('Module:Weather box/colors' .. (options.sandbox or ''))
	local mode = (definition.mode or 'basic'):lower()
	local group_name = definition.group_name
	local first_values, second_values
	local color_values
	local color_scheme = definition.color_scheme or 't'
	local scale_factor = math_mod._cleanNumber(definition.scale_factor) or 1
	local date_mode = checkFlag(definition.date_mode, false)
	local label = definition.label or ''
	local annual_mode = (definition.annual_mode or 'avg'):lower()
	local include_space = checkFlag(definition.include_space, true)
	local second_line = checkFlag(definition.second_line, false)
	local prefer_cm = checkFlag(definition.prefer_cm, false)
	local imperial_first = checkFlag(args['imperial first'])
	local metric_first = checkFlag(args['metric first'])
	local wantSingleLine = options.wantSingleLine or checkFlag(args['single line'])
	local trace = args.trace
	if trace and trace ~= '' then
		traceText = trace
	end
	if imperial_first == nil then
		imperial_first = metric_first == nil and true or not metric_first
	end
	if mode == 'basic' then
		first_values = getInputs(args, group_name, nil, include_space)
		second_values = nil
	elseif mode == 'temperature' then
		first_values = getInputs(args, group_name, {'C'}, include_space)
		second_values = getInputs(args, group_name, {'F'}, include_space)
		reconcileTemperature(first_values, second_values)
	elseif mode == "precipitation" then
		first_values = getInputs(args, group_name, {'cm', 'mm'}, include_space)
		second_values = getInputs(args, group_name, {'inch'}, include_space)
		reconcilePrecipitation(first_values, second_values, prefer_cm)
	else
		error('Requested mode not recognized')
	end
	local good = false
	for i = 1, 13 do
		if first_values[i].string ~= '' then
			good = true
			break
		end
	end
	if not good then
		return ''
	end
	if first_values[13].string == '' then
		first_values[13] = getAnnualValue(first_values, annual_mode)
	end
	if second_values ~= nil then
		if second_values[13].string == '' then
			second_values[13] = getAnnualValue(second_values, annual_mode)
		end
	end
	color_scheme = wbc.interpret_color_code(color_scheme)
	color_values = {}
	local month_adj = { 31/30, 28.25/30, 31/30, 1, 31/30, 1,
		31/30, 31/30, 1, 31/30, 1, 31/30, 365.25/30 }
	for i = 1, 13 do
		if first_values[i]:isValid() then
			local adj = scale_factor
			if date_mode then
				adj = adj / month_adj[i]
			end
			if mode == "precipitation" then
				if first_values[i].variant == 1 then
					adj = adj * 10
				end
			end
			table.insert(color_values, color_scheme(first_values[i].number * adj))
		else
			table.insert(color_values, color_scheme(nil))
		end
	end
	if imperial_first and second_values ~= nil then
		first_values, second_values = second_values, first_values
	end
	if not wantSingleLine then
		if second_line and second_values ~= nil then
			first_values = second_values
		end
		second_values = nil
	end
	return makeLine(label, first_values, second_values, color_values)
end

local function buildRow(frame)
	return _buildRow(frame.args, frame:getParent().args)  -- row definition, template parameters
end

return {
	buildRow = buildRow,
	_buildRow = _buildRow,
}