package fragment

import (
	"bytes"
	"io"
	"testing"
)

type readSeekCloser struct {
	*bytes.Reader
	closed bool
}

func (r *readSeekCloser) Close() error {
	r.closed = true
	return nil
}

func TestReaderReadsFragmentsWithoutOwningEOF(t *testing.T) {
	reader := NewReader(bytes.NewReader([]byte("abcdef")), []Fragment{
		{Offset: 1, Length: 2},
		{Offset: 4, Length: 2},
	})

	buf := make([]byte, 4)
	n, err := reader.Read(buf)
	if err != nil {
		t.Fatalf("first read failed: %v", err)
	}
	if got := string(buf[:n]); got != "bc" {
		t.Fatalf("first read = %q, want %q", got, "bc")
	}

	n, err = reader.Read(buf)
	if err != nil {
		t.Fatalf("second read failed: %v", err)
	}
	if got := string(buf[:n]); got != "ef" {
		t.Fatalf("second read = %q, want %q", got, "ef")
	}

	n, err = reader.Read(buf)
	if err != io.EOF {
		t.Fatalf("third read error = %v, want %v", err, io.EOF)
	}
	if n != 0 {
		t.Fatalf("third read count = %d, want 0", n)
	}
}

func TestReaderCloseClosesUnderlyingCloser(t *testing.T) {
	src := &readSeekCloser{Reader: bytes.NewReader([]byte("abcdef"))}
	reader := NewReader(src, []Fragment{{Offset: 0, Length: 2}})

	if err := reader.Close(); err != nil {
		t.Fatalf("Close failed: %v", err)
	}
	if !src.closed {
		t.Fatal("underlying closer was not closed")
	}
}