package stario

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

func TestNewStarBufferRejectsZeroCapacity(t *testing.T) {
	buf, err := NewStarBuffer(0)
	if err != ErrStarBufferInvalidCapacity {
		t.Fatalf("unexpected error: %v", err)
	}
	if buf != nil {
		t.Fatal("expected nil buffer when capacity is invalid")
	}
}

func TestStarBufferCloseDrainsThenEOF(t *testing.T) {
	buf, err := NewStarBuffer(4)
	if err != nil {
		t.Fatal(err)
	}
	if _, err := buf.Write([]byte("abcd")); err != nil {
		t.Fatal(err)
	}
	if err := buf.Close(); err != nil {
		t.Fatal(err)
	}

	got := make([]byte, 4)
	n, err := buf.Read(got)
	if err != nil {
		t.Fatal(err)
	}
	if n != 4 || !bytes.Equal(got[:n], []byte("abcd")) {
		t.Fatalf("unexpected payload: n=%d data=%q", n, got[:n])
	}

	n, err = buf.Read(got)
	if n != 0 || err != io.EOF {
		t.Fatalf("expected EOF after draining buffer, got n=%d err=%v", n, err)
	}

	if _, err := buf.Write([]byte("x")); err != ErrStarBufferWriteClosed {
		t.Fatalf("unexpected write error after Close: %v", err)
	}
}

func TestStarBufferAbortAllowsDrain(t *testing.T) {
	buf, err := NewStarBuffer(4)
	if err != nil {
		t.Fatal(err)
	}
	if _, err := buf.Write([]byte("ab")); err != nil {
		t.Fatal(err)
	}
	if err := buf.Abort(); err != nil {
		t.Fatal(err)
	}

	got := make([]byte, 2)
	n, err := buf.Read(got)
	if err != nil {
		t.Fatal(err)
	}
	if n != 2 || !bytes.Equal(got[:n], []byte("ab")) {
		t.Fatalf("unexpected payload after abort: n=%d data=%q", n, got[:n])
	}

	n, err = buf.Read(got)
	if n != 0 || err != io.EOF {
		t.Fatalf("expected EOF after draining aborted buffer, got n=%d err=%v", n, err)
	}

	if _, err := buf.Write([]byte("x")); err != ErrStarBufferClosed {
		t.Fatalf("unexpected write error after Abort: %v", err)
	}
}

func TestStarBufferNilReadIsNoOp(t *testing.T) {
	buf, err := NewStarBuffer(4)
	if err != nil {
		t.Fatal(err)
	}
	if n, err := buf.Read(nil); n != 0 || err != nil {
		t.Fatalf("expected nil read to be a no-op, got n=%d err=%v", n, err)
	}
}

func TestStarBufferNilWriteIsNoOp(t *testing.T) {
	buf, err := NewStarBuffer(4)
	if err != nil {
		t.Fatal(err)
	}
	if n, err := buf.Write(nil); n != 0 || err != nil {
		t.Fatalf("expected nil write to be a no-op, got n=%d err=%v", n, err)
	}
	if _, err := buf.Write([]byte("ab")); err != nil {
		t.Fatalf("nil write must not end the write side, got %v", err)
	}
}