--
-- Minetest asyncio: Lua 5.1 workarounds
--


local rawequal = rawequal
minetest.log('warning', '[asyncio] LuaJIT not installed, asyncio.iter() ' ..
    'will be less efficient.')

-- Helper functions
local function pack_len(...)
    local res = {...}
    res.length = select('#', ...)
    return res
end

local function unpack_len(t, i)
    i = i or 1
    if i <= t.length then
        return t[i], unpack_len(t, i + 1)
    end
end

-- A workaround for non-LuaJIT Lua 5.1
-- Lua 5.1 does not allow coroutine.yield() inside iterators.
function asyncio.iter(func, ...)
    local iter = asyncio._iter_start(func, ...)

    -- Fetch all values first
    local t = {}
    while true do
        local msg = pack_len(iter())
        if msg[1] == nil then break end
        table.insert(t, msg)
    end
    iter = nil

    -- Get the values
    return function()
        local msg = table.remove(t, 1)
        if type(msg) == 'table' then
            return unpack_len(msg)
        end
    end
end

-- A pcall() workaround/hack.
local last_error = ...
assert(type(last_error) == 'table')
local function pcall_hack(func, ...)
    asyncio.yield(last_error, pack_len(func(...)))
end

function last_error.cleanup() last_error.msg = nil end
local old_pcall = pcall
function pcall(func, ...)
    if not asyncio.running then return old_pcall(func, ...) end
    local l, msg = asyncio._iter_start(pcall_hack, func, ...)()
    if l == last_error then
        return true, unpack_len(msg)
    elseif l ~= nil then
        return false, 'asyncio.yield() called outside of async iterator.'
    end
    return false, last_error.msg
end