-- tbl_weight = { 
-- 	[xx] = { id = xx, weight = xx },
-- 	...
-- }

-- https://github.com/kinbei/lua-misc/blob/master/weighted_random.lua

return function(tbl_weight, random_func, id, weight)
    random_func = random_func or math.random
    id = id or "id"
    weight = weight or "weight"

    local t = {}
    local total_index = #tbl_weight
    local total_weight = 0

    for _, v in pairs(tbl_weight) do
        assert(type(v[weight]) == "number")

        total_weight = total_weight + v[weight]
        table.insert(t, {
            [id] = v[id],
            [weight] = v[weight],
        })
    end

    return function()
        local rand_index

        while true do
            rand_index = random_func(1, total_index)
            if random_func(1, total_weight) < t[rand_index].weight then
                return t[rand_index][id]
            end
        end
    end
end

-- ----------------------------------------------------------------------------------------
-- math.randomseed( os.time() )

-- local function test_case_1()
-- 	print("test_case_1")

-- 	local t = {}
-- 	table.insert(t, { id = 1, weight = 400 } )
-- 	table.insert(t, { id = 2, weight = 30  } )
-- 	table.insert(t, { id = 3, weight = 100 } )
-- 	table.insert(t, { id = 4, weight = 8   } )
-- 	table.insert(t, { id = 5, weight = 30  } )
-- 	table.insert(t, { id = 6, weight = 500 } )
-- 	table.insert(t, { id = 7, weight = 20  } )
-- 	table.insert(t, { id = 8, weight = 200 } )
-- 	table.insert(t, { id = 9, weight = 40  } )
-- 	table.insert(t, { id = 10, weight = 70  } )
-- 	table.insert(t, { id = 11, weight = 300 } )
-- 	table.insert(t, { id = 12, weight = 500 } )
-- 	table.insert(t, { id = 13, weight = 350 } )
-- 	table.insert(t, { id = 14, weight = 20  } )
-- 	table.insert(t, { id = 15, weight = 480 } )
-- 	table.insert(t, { id = 16, weight = 250 } )
-- 	table.insert(t, { id = 17, weight = 500 } )
-- 	table.insert(t, { id = 18, weight = 50  } )
-- 	table.insert(t, { id = 19, weight = 300 } )
-- 	table.insert(t, { id = 20, weight = 500 } )

-- 	local f = weighted_random(t)

-- 	local result = {}
-- 	for i = 1, 4648 do
-- 		local id = f()
-- 		result[id] = result[id] or 0
-- 		result[id] = result[id] + 1
-- 	end

-- 	local r = {}
-- 	for k, v in pairs(result) do
-- 		table.insert(r, { id = k, times = v })
-- 	end

-- 	table.sort(r, function(a, b) return a.times > b.times end)
-- 	for _, v in ipairs(r) do
-- 		print(v.id, v.times)
-- 	end
-- end

-- local function test_case_2()
-- 	print("test_case_2")

-- 	local t = {}
-- 	t[1] = { weight = 2000, id = 1 }
-- 	t[2] = { weight = 2000, id = 2 }
-- 	t[3] = { weight = 30, id = 3 }
-- 	t[4] = { weight = 40, id = 4 }
-- 	t[5] = { weight = 50, id = 5 }

--         local f = weighted_random(t)

--         local result = {}
--         for i = 1, 4120 do
--                 local id = f()
--                 result[id] = result[id] or 0
--                 result[id] = result[id] + 1
--         end

--         local r = {}
--         for k, v in pairs(result) do
--                 table.insert(r, { id = k, times = v })
--         end

--         table.sort(r, function(a, b) return a.times > b.times end)
--         for _, v in ipairs(r) do
--                 print(v.id, v.times)
--         end
-- end

-- test_case_1()
-- test_case_2()