"""Tests for packet scheduler and congestion control."""

import pytest


class TestRetransmitTimer:
    def test_initial_rto(self):
        from i2p_streaming.scheduler import RetransmitTimer
        timer = RetransmitTimer()
        assert timer.rto == 3000  # Initial RTO: 3 seconds

    def test_update_rtt(self):
        from i2p_streaming.scheduler import RetransmitTimer
        timer = RetransmitTimer()
        timer.update_rtt(100)  # 100ms RTT
        assert timer.rto > 0
        assert timer.rto < 3000  # Should be less than initial

    def test_backoff(self):
        from i2p_streaming.scheduler import RetransmitTimer
        timer = RetransmitTimer()
        rto1 = timer.rto
        timer.backoff()
        assert timer.rto == rto1 * 2

    def test_max_backoff(self):
        from i2p_streaming.scheduler import RetransmitTimer
        timer = RetransmitTimer()
        for _ in range(20):
            timer.backoff()
        assert timer.rto <= 60000  # Max 60 seconds

    def test_update_rtt_smoothing(self):
        from i2p_streaming.scheduler import RetransmitTimer
        timer = RetransmitTimer()
        timer.update_rtt(100)
        rto1 = timer.rto
        timer.update_rtt(200)
        rto2 = timer.rto
        # RTO should change but be smoothed
        assert rto2 != rto1


class TestCongestionWindow:
    def test_initial_window(self):
        from i2p_streaming.scheduler import CongestionWindow
        cw = CongestionWindow(initial_size=6)
        assert cw.size == 6

    def test_slow_start_increase(self):
        from i2p_streaming.scheduler import CongestionWindow
        cw = CongestionWindow(initial_size=1, ssthresh=16)
        cw.on_ack()
        assert cw.size == 2  # Doubles in slow start

    def test_congestion_avoidance(self):
        from i2p_streaming.scheduler import CongestionWindow
        cw = CongestionWindow(initial_size=16, ssthresh=16)
        cw.on_ack()
        # In congestion avoidance, increase is additive (~1/size per ACK)
        assert cw.size > 16
        assert cw.size <= 17

    def test_on_loss(self):
        from i2p_streaming.scheduler import CongestionWindow
        cw = CongestionWindow(initial_size=20, ssthresh=32)
        cw.on_loss()
        # AIMD: halve the window
        assert cw.size == 10
        assert cw.ssthresh == 10

    def test_minimum_window(self):
        from i2p_streaming.scheduler import CongestionWindow
        cw = CongestionWindow(initial_size=1, ssthresh=16)
        cw.on_loss()
        assert cw.size >= 1  # Never go below 1

    def test_max_window(self):
        from i2p_streaming.scheduler import CongestionWindow
        cw = CongestionWindow(initial_size=1, ssthresh=16, max_size=128)
        for _ in range(200):
            cw.on_ack()
        assert cw.size <= 128


class TestPacketScheduler:
    def test_can_send_within_window(self):
        from i2p_streaming.scheduler import PacketScheduler
        sched = PacketScheduler(window_size=10)
        assert sched.can_send()

    def test_cannot_send_window_full(self):
        from i2p_streaming.scheduler import PacketScheduler
        sched = PacketScheduler(window_size=2)
        sched.on_packet_sent(seq=0)
        sched.on_packet_sent(seq=1)
        assert not sched.can_send()

    def test_ack_frees_window(self):
        from i2p_streaming.scheduler import PacketScheduler
        sched = PacketScheduler(window_size=1)
        sched.on_packet_sent(seq=0)
        assert not sched.can_send()
        sched.on_ack(seq=0)
        assert sched.can_send()

    def test_outstanding_count(self):
        from i2p_streaming.scheduler import PacketScheduler
        sched = PacketScheduler(window_size=10)
        sched.on_packet_sent(seq=0)
        sched.on_packet_sent(seq=1)
        assert sched.outstanding == 2
        sched.on_ack(seq=0)
        assert sched.outstanding == 1