TableUtils

local api = {}

function api.isTable(o)
    return type(o) == "table"
end

function api.hasKey(tbl, target)
    if tbl[target] ~= nil then
        return true
    end

    -- key might exist but set to nil value
    for key, _ in pairs(tbl) do
        if key == target then
            return true
        end
    end

    return false
end

function api.hasValue(tbl, target)
    for _, value in pairs(tbl) do
        if value == target then
            return true
        end
    end

    return false
end

function api.size(tbl)
    count = 0
    for _ in pairs(tbl) do count = count + 1 end
    return count
end

function api.print(tbl, level)
    level = (type(level) == "number") and level or 1
    if api.isTable(tbl) then
        local s = "{"
        if api.size(tbl) > 0 then
            for k, v in pairs(tbl) do
                if not api.isTable(k) then
                    k = "\""..(k ~= nil and tostring(k) or "nil").."\""
                else
                    k = api.print(k, level + 1)
                end
                s = s.."\n"..(string.rep("\t", level))..""..k.." = "..api.print(v, level + 1)..","
            end
        else
            return "{}"
        end

        return s.."\n"..(string.rep("\t", level - 1)).."}"
    else
        return tostring(tbl)
    end
end

local index = {}
local metatable = {
    __index = function(t, k)
        -- print("*access to element "..tostring(k))
        return t[index][k]
    end,
    __newindex = function(t, k, v)
        -- print("*update of element "..tostring(k).." to "..tostring(v))
        t[index][k] = v
    end
}

function api.proxy(tbl)
    local proxy = {}
    proxy[index] = tbl
    setmetatable(proxy, metatable)
    return proxy, metatable
end

return api