module validate

// http://bjoern.hoehrmann.de/utf-8/decoder/dfa/

// vfmt off
const utf8d = [
    u8(0), 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1,
    1, 1, 1, 1, 1, 1, 1, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
    7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
    7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 10, 3, 3, 3, 3,
    3, 3, 3, 3, 3, 3, 3, 3, 4, 3, 3, 11, 6, 6, 6, 5, 8, 8, 8, 8, 8, 8, 8,
    8, 8, 8, 8, 0, 12, 24, 36, 60, 96, 84, 12, 12, 12, 48, 72, 12, 12, 12,
    12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 0, 12, 12, 12, 12, 12, 0, 12,
    0, 12, 12, 12, 24, 12, 12, 12, 12, 12, 24, 12, 24, 12, 12, 12, 12, 12,
    12, 12, 12, 12, 24, 12, 12, 12, 12, 12, 24, 12, 12, 12, 12, 12, 12, 12,
    24, 12, 12, 12, 12, 12, 12, 12, 12, 12, 36, 12, 36, 12, 12, 12, 36, 12,
    12, 12, 12, 12, 36, 12, 36, 12, 12, 12, 36, 12, 12, 12, 12, 12, 12, 12,
    12, 12, 12 ]!
// vfmt on

// utf8_string returns true, if the given string `s` consists only of valid UTF-8 runes
pub fn utf8_string(s string) bool {
    return utf8_data(s.str, s.len)
}

// utf8_data returns true, if the given `data` block, with length `len` bytes, consists only of valid UTF-8 runes
@[direct_array_access]
pub fn utf8_data(data &u8, len int) bool {
    mut state := 0

    for i := 0; i < len; i++ {
        b := unsafe { data[i] }
        state = utf8d[256 + state + utf8d[b]]
        if state == 12 {
            return false
        }
    }
    return state == 0
}