package varint

import (
	"bytes"
	"testing"
)

// TestRoundTrip covers the boundary values where the terminal-byte encoding
// changes width.
func TestRoundTrip(t *testing.T) {
	vals := []uint64{0, 1, 126, 127, 128, 254, 255, 16383, 16384, 1 << 31, 1 << 62}
	for _, v := range vals {
		var buf bytes.Buffer
		Encode(&buf, v)
		got, err := Decode(&buf)
		if err != nil {
			t.Fatal(err)
		}
		if got != v {
			t.Fatalf("roundtrip: got %d want %d", got, v)
		}
		if buf.Len() != 0 {
			t.Fatalf("Decode left %d bytes", buf.Len())
		}
	}
}

// TestStream decodes values written back to back: the reader must stop at the
// terminal byte and leave the next value in place.
func TestStream(t *testing.T) {
	var buf bytes.Buffer
	Encode(&buf, uint64(300))
	Encode(&buf, uint64(7))
	a, err := Decode(&buf)
	if err != nil || a != 300 {
		t.Fatal("first value")
	}
	b, err := Decode(&buf)
	if err != nil || b != 7 {
		t.Fatal("second value")
	}
}

func TestDecodeEmpty(t *testing.T) {
	var buf bytes.Buffer
	if _, err := Decode(&buf); err == nil {
		t.Fatal("Decode of an empty reader should fail")
	}
}