package chunkreader

import (
	"bytes"
	"testing"
)

func TestChunkReaderNextDoesNotReadIfAlreadyBuffered(t *testing.T) {
	server := &bytes.Buffer{}
	r, err := NewChunkReaderEx(server, Options{MinBufLen: 4, BlockLen: 2})
	if err != nil {
		t.Fatal(err)
	}

	src := []byte{1, 2, 3, 4}
	server.Write(src)

	n1, err := r.Next(2)
	if err != nil {
		t.Fatal(err)
	}
	if bytes.Compare(n1, src[0:2]) != 0 {
		t.Fatalf("Expected read bytes to be %v, but they were %v", src[0:2], n1)
	}

	n2, err := r.Next(2)
	if err != nil {
		t.Fatal(err)
	}
	if bytes.Compare(n2, src[2:4]) != 0 {
		t.Fatalf("Expected read bytes to be %v, but they were %v", src[2:4], n2)
	}

	if bytes.Compare(r.buf, src) != 0 {
		t.Fatalf("Expected r.buf to be %v, but it was %v", src, r.buf)
	}
	if r.rp != 4 {
		t.Fatalf("Expected r.rp to be %v, but it was %v", 4, r.rp)
	}
	if r.wp != 4 {
		t.Fatalf("Expected r.wp to be %v, but it was %v", 4, r.wp)
	}
}

func TestChunkReaderNextExpandsBufAsNeeded(t *testing.T) {
	server := &bytes.Buffer{}
	r, err := NewChunkReaderEx(server, Options{MinBufLen: 4, BlockLen: 2})
	if err != nil {
		t.Fatal(err)
	}

	src := []byte{1, 2, 3, 4, 5, 6, 7, 8}
	server.Write(src)

	n1, err := r.Next(5)
	if err != nil {
		t.Fatal(err)
	}
	if bytes.Compare(n1, src[0:5]) != 0 {
		t.Fatalf("Expected read bytes to be %v, but they were %v", src[0:5], n1)
	}
	if len(r.buf) != 6 {
		t.Fatalf("Expected len(r.buf) to be %v, but it was %v", 6, len(r.buf))
	}
}

func TestChunkReaderNextReusesBuf(t *testing.T) {
	server := &bytes.Buffer{}
	r, err := NewChunkReaderEx(server, Options{MinBufLen: 4, BlockLen: 1})
	if err != nil {
		t.Fatal(err)
	}

	src := []byte{1, 2, 3, 4, 5, 6, 7, 8}
	server.Write(src)

	n1, err := r.Next(4)
	if err != nil {
		t.Fatal(err)
	}
	if bytes.Compare(n1, src[0:4]) != 0 {
		t.Fatalf("Expected read bytes to be %v, but they were %v", src[0:4], n1)
	}

	n2, err := r.Next(4)
	if err != nil {
		t.Fatal(err)
	}
	if bytes.Compare(n2, src[4:8]) != 0 {
		t.Fatalf("Expected read bytes to be %v, but they were %v", src[4:8], n2)
	}

	if bytes.Compare(n1, src[4:8]) != 0 {
		t.Fatalf("Expected Next to have reused buf, %v found instead of %v", src[4:8], n1)
	}
}

func TestChunkReaderKeepLastPreventsBufReuse(t *testing.T) {
	server := &bytes.Buffer{}
	r, err := NewChunkReaderEx(server, Options{MinBufLen: 4, BlockLen: 1})
	if err != nil {
		t.Fatal(err)
	}

	src := []byte{1, 2, 3, 4, 5, 6, 7, 8}
	server.Write(src)

	n1, err := r.Next(4)
	if err != nil {
		t.Fatal(err)
	}
	if bytes.Compare(n1, src[0:4]) != 0 {
		t.Fatalf("Expected read bytes to be %v, but they were %v", src[0:4], n1)
	}
	r.KeepLast()

	n2, err := r.Next(4)
	if err != nil {
		t.Fatal(err)
	}
	if bytes.Compare(n2, src[4:8]) != 0 {
		t.Fatalf("Expected read bytes to be %v, but they were %v", src[4:8], n2)
	}

	if bytes.Compare(n1, src[0:4]) != 0 {
		t.Fatalf("Expected KeepLast to prevent Next from overwriting buf, expected %v but it was %v", src[0:4], n1)
	}
}