RedMew/utils/list_utils.lua

-- Functions that perform actions on tables

local function assert_argument_valid(a, arg_type)
    arg_type = arg_type or 'table'
    if type(a) ~= arg_type then
        error("bad argument #1 to '" .. debug.getinfo(2, 'n').name .. "' (table expected, got " .. type(a) .. ')', 3)
    end
end

table.remove_element = function(t, element)
    assert_argument_valid(t)
    for k, v in pairs(t) do
        if v == element then
            table.remove(t, k)
            break
        end
    end
end

table.add_all = function(t1, t2)
    assert_argument_valid(t1)
    assert_argument_valid(t2)
    for k, v in pairs(t2) do
        if tonumber(k) then
            table.insert(t1, v)
        else
            t1[k] = v
        end
    end
end

table.size = function(t)
    assert_argument_valid(t)
    local size = 0
    for _ in pairs(t) do
        size = size + 1
    end
    return size
end

table.index_of = function(t, e)
    assert_argument_valid(t)
    local i = 1
    for _, v in pairs(t) do
        if v == e then
            return i
        end
        i = i + 1
    end
    return -1
end

table.contains = function(t, e)
    assert_argument_valid(t)
    return table.index_of(t, e) > -1
end

table.set = function(t, index, element)
    assert_argument_valid(t)
    assert_argument_valid(index, 'number')
    local i = 1
    for k in pairs(t) do
        if i == index then
            t[k] = element
            return nil
        end
        i = i + 1
    end
    error('Index out of bounds', 2)
end

table.get = function(t, index)
    assert_argument_valid(t)
    assert_argument_valid(index, 'number')
    local i = 1
    for k in pairs(t) do
        if i == index then
            return t[k]
        end
        i = i + 1
    end
    error('Index out of bounds', 2)
end

-- Chooses a random entry from a table
table.get_random = function(this_table)
    return this_table[math.random(#this_table)]
end

--- Chooses a random entry from a weighted table
-- @param weight_table a table of tables with items and their weights
-- @param item_index the index of the items
-- @param weight_index the index of the weights
-- @returns a random item with weighting
-- @see features.chat_triggers.hodor
table.get_random_weighted = function(weighted_table, item_index, weight_index)
    local total_weight = 0

    for _, w in pairs(weighted_table) do
        total_weight = total_weight + w[weight_index]
    end

    local index = math.random(total_weight)
    local weight_sum = 0
    for _, w in pairs(weighted_table) do
        weight_sum = weight_sum + w[weight_index]
        if weight_sum >= index then
            return w[item_index]
        end
    end
end

--[[
  Returns the index where t[index] == target.
  If there is no such index, returns a negative vaule such that bit32.bnot(value) is
  the index that the vaule should be inserted to keep the list ordered.
  t must be a list in ascending order for the return value to be valid.

  Usage example:
  local t = {1,3,5,7,9}
  local x = 5
  local index = table.binary_search(t, x)
  if index < 0 then
    game.print("value not found, smallest index where t[index] > x is: " .. bit32.bnot(index))
  else
    game.print("value found at index: " .. index)
  end
]]
table.binary_search =
    function(t, target)
    --For some reason bit32.bnot doesn't return negative numbers so I'm using ~x = -1 - x instead.
    assert_argument_valid(t)
    assert_argument_valid(target, 'number')

    local lower = 1
    local upper = #t

    if upper == 0 then
        return -2 -- ~1
    end

    repeat
        local mid = math.floor((lower + upper) / 2)
        local value = t[mid]
        if value == target then
            return mid
        elseif value < target then
            lower = mid + 1
        else
            upper = mid - 1
        end
    until lower > upper

    return -1 - lower -- ~lower
end