function WebDavApi.urlEncode(str)
    if not str then return nil end

    -- RFC 3986 defines "unreserved" characters:
    -- ALPHA (A-Z, a-z), DIGIT (0-9), '-', '.', '_', '~'
    -- The pattern below matches any character that is NOT an unreserved character.
    -- %w includes ALPHA and DIGIT.
    -- The set [^%w%.%-%_%~] matches characters NOT in the unreserved set.
    
    return string.gsub(str, "([^%w%.%-%_%~])", function(c)
        -- Get the byte value of the matched character
        local byte_val = string.byte(c)
        
        -- Special handling for SPACE (32) and other common reserved characters
        -- For full compliance, any character not in the "unreserved" set is encoded.
        -- We encode the byte value as a two-digit hex string prefixed with %.
        return string.format("%%%02X", byte_val)
    end)
end