ComputerCraft Lua String Utils

function string:contains(sub)
    return self:find(sub, 1, true) ~= nil
end

function string:startswith(start)
    return self:sub(1, #start) == start
end

function string:endswith(ending)
    return ending == "" or self:sub(-#ending) == ending
end

function string:replace(old, new)
    local s = self
    local searchStartIdx = 1

    while true do
        local startIdx, endIdx = s:find(old, searchStartIdx, true)
        if (not startIdx) then
            break
        end

        local postfix = s:sub(endIdx + 1)
        s = s:sub(1, (startIdx - 1)) .. new .. postfix

        searchStartIdx = -1 * postfix:len()
    end

    return s
end

function string:insert(pos, text)
    return self:sub(1, pos - 1) .. text .. self:sub(pos)
end

local function lstrip_whitespace(s)
    local _, pos = s:find("^%s+")
    if pos then
        s = s:sub(pos + 1)
    end
    return s
end

local function rstrip_whitespace(s)
    pos = s:find("%s+$")
    if pos then
        s = s:sub(1, pos - 1)
    end
    return s
end

function string:strip()
    local s = self
    if s == "" then
        return ""
    end

    s = lstrip_whitespace(s)
    s = rstrip_whitespace(s)

    return s
end

function string:strip_prefix(prefix)
    if prefix == nil then
        return lstrip_whitespace(self)
    end

    local s = self
    local len = #s
    local pLen = #prefix
    if len == 0 or pLen == 0 or len < pLen then
        return s
    elseif s == prefix then
        return ""
    elseif s:sub(1, pLen) == prefix then
        return s:sub(pLen + 1)
    end

    return s
end

function string:strip_suffix(suffix)
    if suffix == nil then
        return rstrip_whitespace(self)
    end

    local s = self
    local len = #s
    local sLen = #suffix
    if len == 0 or sLen == 0 or len < sLen then
        return s
    elseif s == suffix then
        return ""
    elseif s:sub(-sLen) == suffix then
        return s:sub(1, len - sLen)
    end

    return s
end