require[[strict]]
local p={}

function p.main(frame)
    local parent = frame.getParent(frame) or {}
    local explist = {}
    local fnname, varlist
    local vars = {}
    for k, v in pairs(_G) do
        vars[k] = v -- transfer every global directly to our variable table
    end
    for k, v in pairs(parent.args or {}) do
        vars[k] = tonumber(v) or v -- transfer every parameter directly to our variable table
    end
    for k, v in pairs(frame.args or {}) do
        vars[k] = tonumber(v) or v -- transfer every parameter directly to our variable table
    end
     --- Alas Scribunto does NOT implement coroutines, according to
     --- https://www.mediawiki.org/wiki/Extension:Scribunto/Lua_reference_manual#string.format
     --- this will not stop us from trying to implement one single lousy function call
    if vars[1] then
        fnname, varlist = mw.ustring.match(vars[1], "^%s*(%a[^%s%(]*)%(([^%)]*)%)%s*$")
    end
    if varlist then
        local expn = 0
        repeat
            expn = expn + 1
            explist[expn] = vars[mw.ustring.match(varlist, "([^%,]+)")]
            varlist = mw.ustring.match(varlist, "[^%,]+,(.*)$")
        until not varlist
    end
    local scopetab = vars
    while mw.ustring.match(fnname, "%.") do
        local scopekey
        scopekey, fnname = mw.ustring.match(fnname, "^(%a[^%.]*)%.(.*)$")
        scopetab = scopetab[scopekey]
    end
    local fn = scopetab[fnname]
    if type(fn) ~= "function" then --XXX: What about callable tables?
        return tostring(fn)
    else 
    	local output = {fn(unpack(explist))}
        return output[vars.reserved_return or 1]
    end
end

local function tonumberOrString(v)
	return tonumber(v) or v:gsub("^\\", "", 1)
end

local function callWithTonumberOrStringOnPairs(f, ...)
	local args = {}
	for _, v in ... do
		table.insert(args, tonumberOrString(v))
	end
	return (f(unpack(args)))
end

--[[
------------------------------------------------------------------------------------
-- ipairsAtOffset

-- This is an iterator for arrays. It can be used like ipairs, but with
-- specified i as first index to iterate. i is an offset from 1
--
------------------------------------------------------------------------------------
--]]
local function ipairsAtOffset(t, i)
	local f, s, i0 = ipairs(t)
	return f, s, i0+i
end

local function get(s)
	local G = _G; for _ in mw.text.gsplit(
		mw.text.trim(s, '%s'), '%s*%.%s*'
	) do
		G = G[_]
	end
	return G
end

--[[
------------------------------------------------------------------------------------
-- call
--
-- This function is usually useful for debugging template parameters.
-- Prefix parameter with backslash (\) to force interpreting parameter as string.
-- The leading backslash will be removed before passed to Lua function.
--
-- Example:
--    {{#invoke:Lua call|call|mw.log|a|1|2|3}} will return results of mw.log('a', 1, 2, 3)
--    {{#invoke:Lua call|call|mw.logObject|\a|321|\321| \321 }} will return results of mw.logObject('a', 321, '321', ' \\321 ')
--
-- This example show the debugging to see which Unicode characters are allowed in template parameters,
--    {{#invoke:Lua call|call|mw.ustring.codepoint|{{#invoke:Lua call|call|mw.ustring.char|0x0061}}}} return 97
--    {{#invoke:Lua call|call|mw.ustring.codepoint|{{#invoke:Lua call|call|mw.ustring.char|0x0000}}}} return 65533
--    {{#invoke:Lua call|call|mw.ustring.codepoint|{{#invoke:Lua call|call|mw.ustring.char|0x0001}}}} return 65533
--    {{#invoke:Lua call|call|string.format|0x%04x|{{#invoke:Lua call|call|mw.ustring.codepoint|{{#invoke:Lua call|call|mw.ustring.char|0x0002}}}}}} return 0xfffd
--    {{#invoke:Lua call|call|string.format|0x%04x|{{#invoke:Lua call|call|mw.ustring.codepoint|{{#invoke:Lua call|call|mw.ustring.char|0x007e}}}}}} return 0x007e
--    {{#invoke:Lua call|call|string.format|0x%04x|{{#invoke:Lua call|call|mw.ustring.codepoint|{{#invoke:Lua call|call|mw.ustring.char|0x007f}}}}}} return 0x007f
--    {{#invoke:Lua call|call|string.format|0x%04x|{{#invoke:Lua call|call|mw.ustring.codepoint|{{#invoke:Lua call|call|mw.ustring.char|0x0080}}}}}} return 0x0080
--    {{#invoke:Lua call|call|string.format|0x%04x|{{#invoke:Lua call|call|mw.ustring.codepoint|{{#invoke:Lua call|call|mw.ustring.char|0x00a0}}}}}} return 0x00a0
--
------------------------------------------------------------------------------------
--]]
function p.call(frame)
	return callWithTonumberOrStringOnPairs(get(frame.args[1]),
		ipairsAtOffset(frame.args, 1)
	)
end

--local TableTools = require('Module:TableTools')
--[[
------------------------------------------------------------------------------------
-- get
--
-- Example:
--    {{#invoke:Lua call|get| math.pi }} will return value of math.pi
--    {{#invoke:Lua call|get|math|pi}} will return value of math.pi
--    {{#invoke:Lua call|get| math |pi}} will return value of _G[' math '].pi
--    {{#invoke:Lua call|get|_G| math.pi }} will return value of _G[' math.pi ']
--    {{#invoke:Lua call|get|obj.a.5.c}} will return value of obj.a['5'].c
--    {{#invoke:Lua call|get|obj|a|5|c}} will return value of obj.a[5].c
--
------------------------------------------------------------------------------------
--]]
function p.get(frame)
	-- #frame.args always return 0, regardless of number of unnamed
	-- template parameters, so check manually instead
	if frame.args[2] == nil then
		-- not do tonumber() for this args style,
		-- always treat it as string,
		-- so 'obj.1' will mean obj['1'] rather obj[1]
		return get(frame.args[1])
	else
		local G = _G
		for _, v in ipairs(frame.args) do
			G = G[tonumberOrString(v)]
		end
		return G
	end
end

--[[
------------------------------------------------------------------------------------
-- invoke
--
-- This function is used by Template:Invoke
--
------------------------------------------------------------------------------------
--]]
function p.invoke(frame)
	local pframe, usedpargs = frame:getParent(), {}
	-- get module and function names from parent args if not provided
	local pfargs = setmetatable({frame.args[1], frame.args[2]}, {__index = table})
	if not pfargs[1] then
		pfargs[1], usedpargs[1] = pframe.args[1], true
		if not pfargs[2] then
			pfargs[2], usedpargs[2] = pframe.args[2], true
		end
	elseif not pfargs[2] then
		pfargs[2], usedpargs[1] = pframe.args[1], true
	end
	-- repack sequential args
	for i, v in ipairs(pframe.args) do
		if not usedpargs[i] then
			pfargs:insert(v)
			usedpargs[i] = true
		end
	end
	-- copy other args
	for k, v in pairs(pframe.args) do
		if not pfargs[k] and not usedpargs[k] then
			pfargs[k], usedpargs[k] = v, true
		end
	end
	-- #invoke off parent frame so the new frame has the same parent
	return pframe:callParserFunction{name = '#invoke', args = pfargs}
end

return p