package audio

import (
	"errors"
	"testing"

	"github.com/pion/rtp"
)

func pkt(seq uint16) *rtp.Packet {
	return &rtp.Packet{
		Header:  rtp.Header{SequenceNumber: seq, PayloadType: opusPayloadType},
		Payload: []byte{0x00},
	}
}

func TestPlayoutLateDrop(t *testing.T) {
	p := NewPlayout(2)
	p.Push(pkt(500))
	p.Push(pkt(501))
	// Drain to set the playout head past 500.
	if _, _, err := p.PopOrSkip(); err != nil {
		t.Fatalf("first pop: %v", err)
	}
	if _, _, err := p.PopOrSkip(); err != nil {
		t.Fatalf("second pop: %v", err)
	}
	// A late packet with seq 499 must be dropped (not block, not surface
	// later).
	p.Push(pkt(499))
	if _, _, err := p.PopOrSkip(); !errors.Is(err, ErrEmpty) {
		t.Fatalf("late packet should not have been buffered; got err=%v", err)
	}
}

func TestPlayoutSkipAhead(t *testing.T) {
	p := NewPlayout(2)
	// Push 600, 601 to prime, then drain so playoutHead = 602.
	p.Push(pkt(600))
	p.Push(pkt(601))
	if _, _, err := p.PopOrSkip(); err != nil {
		t.Fatalf("first pop: %v", err)
	}
	if _, _, err := p.PopOrSkip(); err != nil {
		t.Fatalf("second pop: %v", err)
	}
	// Now skip seq 602, 603; deliver 604, 605.
	p.Push(pkt(604))
	p.Push(pkt(605))
	got, gap, err := p.PopOrSkip()
	if err != nil {
		t.Fatalf("skip-ahead pop: %v", err)
	}
	if got.SequenceNumber != 604 {
		t.Errorf("got seq=%d, want 604", got.SequenceNumber)
	}
	if gap != 2 {
		t.Errorf("got gap=%d, want 2 (skipped 602, 603)", gap)
	}
	// Next pop should be 605 with no gap.
	got, gap, err = p.PopOrSkip()
	if err != nil {
		t.Fatalf("follow-up pop: %v", err)
	}
	if got.SequenceNumber != 605 {
		t.Errorf("got seq=%d, want 605", got.SequenceNumber)
	}
	if gap != 0 {
		t.Errorf("follow-up gap=%d, want 0", gap)
	}
}

func TestPlayoutSeqWraparound(t *testing.T) {
	p := NewPlayout(2)
	// Push packets straddling the uint16 boundary: 65534, 65535, 0, 1.
	for _, s := range []uint16{65534, 65535, 0, 1} {
		p.Push(pkt(s))
	}
	// Should pop in correct order despite the wrap.
	wantOrder := []uint16{65534, 65535, 0, 1}
	for _, want := range wantOrder {
		got, gap, err := p.PopOrSkip()
		if err != nil {
			t.Fatalf("Pop want=%d: %v", want, err)
		}
		if got.SequenceNumber != want {
			t.Errorf("got seq=%d, want %d", got.SequenceNumber, want)
		}
		if gap != 0 {
			t.Errorf("seq=%d gap=%d, want 0", want, gap)
		}
	}
}