-- This module implements {{for loop}}.

local getArgs = require('Module:Arguments').getArgs
local yesno = require('Module:Yesno')
local p = {}

function p.templatemain(frame)
	return p.main(frame:newChild{title = "Template:For_loop"})
end

function p.main(frame)
	local args = getArgs(frame, {
		trim = false,
		removeBlanks = false
	})
	return p._main(args)
end

function p._main(args)
	local template = args['call'] or 'void'
	local calltemplates = yesno(args.substall or "", true) or not mw.isSubsting()
	local variableParam = args.pv
	variableParam = tonumber(variableParam) or variableParam or 1 -- fix for positional parameters
	local variableValPrefix = args.prefix or ''
	local variableValPostfix = args.postfix or ''
	local sep = args[1] or ''
	local constantArgs = p.getConstants(args)
	local variableVals = p.getVariableVals(args)

	local result = ''
	local addSeparator = false;
	for _, v in ipairs(variableVals) do
		v = mw.text.trim(v)
		if #v > 0 or not yesno(args.skipBlanks) then
			if addSeparator then
				result = result .. sep
			end
			addSeparator = true;
			local targs = constantArgs
			targs[variableParam] = variableValPrefix .. v .. variableValPostfix
			if calltemplates then
				local output = p.callTemplate(template, targs)
				if #mw.text.trim(output) == 0 then
					addSeparator = false
				end
				result = result .. output
			else
				local makeTemplate = require('Module:Template invocation').invocation
				result = result .. makeTemplate(template, targs)
			end
		end
	end
	return result
end

function p.getConstants(args)
	local constantArgNums = p.getArgNums(args, 'pc', 'n')
	local constantArgs = {}
	for _, num in ipairs(constantArgNums) do
		local keyArg = 'pc' .. tostring(num) .. 'n'
		local valArg = 'pc' .. tostring(num) .. 'v'
		local key = args[keyArg]
		key = tonumber(key) or key
		local value = args[valArg]
		constantArgs[key] = value
	end
	return constantArgs
end

function p.getVariableVals(args)
	local variableVals = {}
	if args.start or args.stop or args.by then
		if args[2] then
			error("Both start/stop/by and numbered parameters specified")
		end
		local start = tonumber(args.start or 1)
		local stop = tonumber(args.stop or 1)
		local by = tonumber(args.by or 1)
		for i = start, stop, by do
			variableVals [#variableVals + 1] = i
		end
	else
		for i, v in ipairs(args) do
			if i ~= 1 then
				variableVals[i - 1] = v
			end
		end
	end
	return variableVals
end

function p.getArgNums(args, prefix, suffix)
	-- Returns a table containing the numbers of the arguments that exist
	-- for the specified prefix and suffix.
	local nums = {}
	local pattern = '^' .. prefix .. '([1-9]%d*)' .. suffix .. '$'
	for k, _ in pairs(args) do
		local num = tostring(k):match(pattern)
		if num then
			nums[#nums + 1] = tonumber(num)
		end
	end
	table.sort(nums)
	return nums
end

function p.callTemplate(template, targs)
	return mw.getCurrentFrame():expandTemplate{title = template, args = targs}
end

return p