import System.*
import System.Text.*
import System.Collections.*
import System.Console.*

func RoundTrip(text: string) {
    let bytes: Sequence<byte> = Utf8.Encode(text)
    match Utf8.Decode(bytes) {
        .Ok(let decoded) => {
            if decoded.Equals(text) {
                WriteLine("Round trip")
            }
        }
        .Error(let error) => WriteLine(error.ToString())
    }
}

func Reject(bytes: byte[]) {
    match Utf8.Decode(bytes) {
        .Ok(let text) => WriteLine("Unexpected text")
        .Error(let error) => WriteLine(error.ToString())
    }
}

func Main() {
    RoundTrip("")
    RoundTrip("ASCII")
    RoundTrip("café 🌍")
    RoundTrip("a\u0000b")
    RoundTrip("é")
    RoundTrip("\uFEFFtext")
    let encoded = Utf8.Encode("Aé🌍")
    WriteLine(encoded.Count)
    if encoded[0] == (byte)65 {
        WriteLine("No preamble")
    }
    let source: byte[] = [(byte)65, (byte)66]
    let result = Utf8.Decode(source)
    source[0] = (byte)90
    match result {
        .Ok(let text) => WriteLine(text)
        .Error(let error) => WriteLine(error.ToString())
    }
    Reject([(byte)128])
    Reject([(byte)192, (byte)128])
    Reject([(byte)237, (byte)160, (byte)128])
    Reject([(byte)244, (byte)144, (byte)128, (byte)128])
    Reject([(byte)240, (byte)159, (byte)140])
    Reject([(byte)226, (byte)40, (byte)161])
}