//! Level-triggered interrupt scheduling around the real USB transport operations.
extern crate std;
use super::*;
use crate::f722::usb;
use kaptan_mavlink::{encoder::MavlinkEncoder, generated::kaptan::FILE_DATA_DATA};
use kaptan_tx::FrameClass;
use std::{vec, vec::Vec};
use usb::test_bus as usb_bus;
use usb_bus::{Host, PacketBus, with_link};
use usb_device::bus::PollResult;

fn poll_irq(host: &Host, usb: &mut usb::UsbMavlink<'_, PacketBus>) -> bool {
    usb.with_rx_interrupt_gate(
        |usb| usb.poll(),
        |enabled| host.set_rx_interrupt_enabled(enabled),
    )
}
fn exchange(
    host: &Host,
    usb: &mut usb::UsbMavlink<'_, PacketBus>,
    frame: Option<MavlinkFrame>,
) -> IoBatch {
    exchange_usb(
        usb,
        frame.map(|frame| PendingFrame {
            class: FrameClass::Critical,
            frame,
        }),
        |enabled| host.set_rx_interrupt_enabled(enabled),
    )
}
fn file_frame(length: usize) -> MavlinkFrame {
    let mut data = FILE_DATA_DATA::DEFAULT;
    data.data[..length - 21].fill(0x5a);
    let frame = MavlinkEncoder::new(1, 1).encode(&data);
    assert_eq!(frame.raw_bytes().len(), length);
    frame
}

#[test]
fn register_rmw_changes_only_rxflvlm_and_preserves_adjacent_registers() {
    for bit in 0..32 {
        for initial in [1u32 << bit, !(1u32 << bit)] {
            let mut registers = [0xa5a5_5a5a, initial, 0x5a5a_a5a5];
            for enabled in [false, false, true, true, false] {
                // SAFETY: this aligned RAM word substitutes for the RW register.
                // No concurrent access exists and RAM needs no device barrier.
                unsafe { set_rx_fifo_interrupt_enabled(&mut registers[1], enabled) };
                assert_eq!(registers[1] & !(1 << 4), initial & !(1 << 4));
                assert_eq!(registers[1] & (1 << 4) != 0, enabled);
                assert_eq!(registers[0], 0xa5a5_5a5a);
                assert_eq!(registers[2], 0x5a5a_a5a5);
            }
        }
    }
}

// The asserted, enabled priority-8 vector wins over the priority-7 consumer.
fn step(
    host: &Host,
    usb: &mut usb::UsbMavlink<'_, PacketBus>,
    ready: &mut bool,
    frames: &mut Vec<MavlinkFrame>,
) -> bool {
    if host.enter_irq() {
        *ready |= poll_irq(host, usb);
        false
    } else if core::mem::take(ready) {
        let batch = exchange(host, usb, None);
        *ready |= batch.pending;
        if let Some(frame) = batch.usb {
            frames.push(*frame.raw());
        }
        true
    } else {
        false
    }
}

#[test]
fn level_triggered_burst_starves_legacy_consumer_but_gated_consumer_recovers_exact_frames() {
    for gate in [false, true] {
        with_link(|host, usb| {
            let mut encoder = MavlinkEncoder::new(42, 7);
            let expected = core::array::from_fn::<_, 3, _>(|_| encoder.heartbeat());
            for frame in expected {
                host.write_packet(frame.raw_bytes());
            }
            let mut ready = false;
            let mut frames = Vec::new();
            let mut workers = 0;
            for _ in 0..32 {
                if gate {
                    workers += usize::from(step(host, usb, &mut ready, &mut frames));
                } else if host.enter_irq() {
                    ready |= usb.poll(); // Original handler: no RX source gate.
                } else if core::mem::take(&mut ready) {
                    workers += 1;
                    let batch = exchange(host, usb, None);
                    ready |= batch.pending;
                    if let Some(frame) = batch.usb {
                        frames.push(*frame.raw());
                    }
                }
            }
            if gate {
                assert_eq!(frames, expected);
                assert!(workers > 0);
                assert_eq!(host.receive_backlog(), (0, false));
                assert!(host.rx_interrupt_enabled());
                assert!(host.nvic_enabled());
            } else {
                assert_eq!(
                    workers, 0,
                    "level IRQ prevents the only consumer from running"
                );
                assert!(frames.is_empty());
                assert_eq!(
                    host.receive_backlog(),
                    (1, true),
                    "hardware FIFO and driver buffer are both occupied"
                );
                assert!(
                    host.enter_irq(),
                    "source is still asserted after repeated polls"
                );
            }
        });
    }
}

#[test]
fn split_coalesced_bad_crc_and_zlp_packets_preserve_rx_and_live_tx_boundaries() {
    with_link(|host, usb| {
        let incoming = file_frame(130);
        let mut encoder = MavlinkEncoder::new(42, 7);
        let first = encoder.heartbeat();
        let mut corrupt = encoder.heartbeat().raw_bytes().to_vec();
        *corrupt.last_mut().unwrap() ^= 1;
        let last = encoder.heartbeat();
        host.write_packet(&incoming.raw_bytes()[..64]);
        host.write_packet(&[]); // An OUT ZLP must not mask a partial MAVLink frame.
        host.write_packet(&incoming.raw_bytes()[64..128]);
        host.write_packet(
            &[
                &incoming.raw_bytes()[128..],
                first.raw_bytes(),
                &corrupt,
                last.raw_bytes(),
            ]
            .concat(),
        );

        let outgoing = file_frame(128);
        let after = encoder.heartbeat();
        assert!(exchange(host, usb, Some(outgoing)).accepted);
        assert!(host.enter_irq());
        assert!(poll_irq(host, usb));
        assert!(!host.rx_interrupt_enabled());
        assert!(host.nvic_enabled());
        let mut packets = vec![host.take_packet().unwrap()];
        assert!(
            host.enter_irq(),
            "IN completion interrupts while RX is masked"
        );
        assert!(poll_irq(host, usb));
        packets.push(host.take_packet().unwrap());
        assert_eq!(packets.iter().map(Vec::len).collect::<Vec<_>>(), [64, 64]);
        assert!(host.enter_irq());
        assert!(poll_irq(host, usb));
        packets.push(host.take_packet().unwrap());
        assert_eq!(packets[2], [], "TX ZLP progresses without the RX consumer");

        let sent = exchange(host, usb, Some(after));
        assert!(sent.accepted);
        assert!(
            !sent.pending,
            "TX admission's IoBatch flag is not the IRQ policy"
        );
        assert!(
            !host.rx_interrupt_enabled(),
            "TX must preserve the actual unread RX gate"
        );
        if let Some(packet) = host.take_packet() {
            packets.push(packet);
        }

        let partial = exchange(host, usb, None);
        assert!(partial.usb.is_none());
        assert!(!partial.pending);
        assert!(
            host.rx_interrupt_enabled(),
            "the partial framer is waiting for more bytes, not the worker"
        );

        let mut ready = false;
        let mut frames = Vec::new();
        for _ in 0..64 {
            step(host, usb, &mut ready, &mut frames);
            if let Some(packet) = host.take_packet() {
                packets.push(packet);
            }
        }
        assert_eq!(frames, [incoming, first, last]);
        assert_eq!(
            packets.iter().map(Vec::len).collect::<Vec<_>>(),
            [64, 64, 0, 13]
        );
        assert_eq!(
            packets.concat(),
            [outgoing.raw_bytes(), after.raw_bytes()].concat()
        );
        assert!(host.nvic_enabled());
    });
}

#[test]
fn final_poll_refill_stays_masked_and_rearm_preserves_already_pending_irq() {
    with_link(|host, usb| {
        let frame = MavlinkEncoder::new(42, 7).heartbeat();
        host.write_packet(&frame.raw_bytes()[..8]);
        assert!(host.enter_irq());
        usb.with_rx_interrupt_gate(
            |usb| {
                assert!(usb.poll());
                // Latch NVIC pending just before masking the peripheral source.
                host.write_packet(&frame.raw_bytes()[8..]);
            },
            |enabled| host.set_rx_interrupt_enabled(enabled),
        );
        let partial = exchange(host, usb, None);
        assert!(partial.usb.is_none());
        assert!(partial.pending, "the final poll refilled rx_remaining");
        assert!(!host.rx_interrupt_enabled());
        assert!(host.nvic_enabled());
        let complete = exchange(host, usb, None);
        assert_eq!(complete.usb.unwrap().raw(), &frame);
        assert!(!complete.pending);
        assert_eq!(host.receive_backlog(), (0, false));
        assert!(
            host.enter_irq(),
            "RX rearm preserves latched NVIC pending even after polling consumed the source"
        );
        assert!(!poll_irq(host, usb));
    });
}

#[test]
fn arrivals_on_either_side_of_rearm_are_not_lost() {
    for before in [true, false] {
        with_link(|host, usb| {
            let mut encoder = MavlinkEncoder::new(42, 7);
            let first = encoder.heartbeat();
            let next = encoder.heartbeat();
            host.write_packet(first.raw_bytes());
            assert!(host.enter_irq());
            assert!(poll_irq(host, usb));
            let batch = exchange_usb(usb, None, |enabled| {
                assert!(enabled);
                if before {
                    host.write_packet(next.raw_bytes());
                }
                host.set_rx_interrupt_enabled(enabled);
                if !before {
                    host.write_packet(next.raw_bytes());
                }
            });
            assert_eq!(batch.usb.unwrap().raw(), &first);
            assert!(!batch.pending);
            assert!(host.enter_irq());
            assert!(poll_irq(host, usb));
            assert_eq!(exchange(host, usb, None).usb.unwrap().raw(), &next);
        });
    }
}

#[test]
fn backpressure_keeps_reset_suspend_and_resume_interrupts_serviceable() {
    for reset in [true, false] {
        with_link(|host, usb| {
            let frame = file_frame(130);
            assert!(exchange(host, usb, Some(frame)).accepted);
            for _ in 0..3 {
                host.write_packet(&frame.raw_bytes()[..8]);
            }
            assert!(host.enter_irq());
            assert!(poll_irq(host, usb));
            assert!(host.enter_irq(), "one already-pending exception is allowed");
            assert!(poll_irq(host, usb));
            assert_eq!(host.receive_backlog(), (1, true));
            assert!(!host.enter_irq());
            let (_, original_mask) = host.interrupt_status();
            host.event(if reset {
                PollResult::Reset
            } else {
                PollResult::Suspend
            });
            assert!(host.enter_irq());
            poll_irq(host, usb);
            assert!(!usb.is_open());
            assert!(host.events_empty());
            assert!(host.nvic_enabled());
            assert_eq!(
                host.interrupt_status().1 & !(1 << 4),
                original_mask & !(1 << 4)
            );
            if reset {
                assert!(host.rx_interrupt_enabled());
                assert_eq!(host.receive_backlog(), (0, false));
                host.configure(usb, true);
                host.dtr(usb, true);
                assert!(
                    host.collect_packets(usb).is_empty(),
                    "reset discarded the old TX queue"
                );
            } else {
                assert!(!host.rx_interrupt_enabled(), "suspend retains unread RX");
                assert_eq!(host.receive_backlog(), (1, true));
                host.event(PollResult::Resume);
                assert!(host.enter_irq());
                poll_irq(host, usb);
                assert!(usb.is_open());
                assert_eq!(host.collect_packets(usb).concat(), frame.raw_bytes());
            }
        });
    }
}

#[test]
fn ep0_setup_cannot_bypass_a_blocked_bulk_fifo_head() {
    with_link(|host, usb| {
        let frame = MavlinkEncoder::new(42, 7).heartbeat();
        assert!(exchange(host, usb, Some(frame)).accepted);
        for _ in 0..3 {
            host.write_packet(frame.raw_bytes());
        }
        assert!(host.enter_irq());
        poll_irq(host, usb);
        assert!(host.enter_irq());
        poll_irq(host, usb);
        assert_eq!(host.receive_backlog(), (1, true));
        assert!(!host.enter_irq());
        host.queue_control([0x21, 0x22, 0, 0, 0, 0, 0, 0]); // DTR close behind bulk
        assert_eq!(host.receive_backlog(), (2, true));
        assert!(
            !host.enter_irq(),
            "EP0 arrival also uses the masked RX source"
        );
        let (raw, mask) = host.interrupt_status();
        assert_ne!(raw & (1 << 4), 0);
        assert_eq!(raw & mask, 0);
        host.take_packet().unwrap(); // IN completion can interrupt and poll raw RX.
        assert!(host.enter_irq());
        poll_irq(host, usb);
        assert_eq!(host.receive_backlog(), (2, true));
        assert!(
            usb.is_open(),
            "SETUP cannot jump over the blocked FIFO head"
        );
        assert_eq!(exchange(host, usb, None).usb.unwrap().raw(), &frame);
        exchange(host, usb, None);
        assert!(!usb.is_open(), "consumer progress finally allows DTR close");
        assert!(host.rx_interrupt_enabled());
        assert!(host.nvic_enabled());
    });
}

#[test]
fn full_fifo_backpressures_host_then_consumer_progress_allows_retry() {
    with_link(|host, usb| {
        let frame = file_frame(64);
        for _ in 0..3 {
            assert!(host.try_write_packet(frame.raw_bytes()));
        }
        assert!(!host.try_write_packet(frame.raw_bytes()));
        let mut ready = false;
        let mut frames = Vec::new();
        for _ in 0..32 {
            step(host, usb, &mut ready, &mut frames);
        }
        assert_eq!(frames, [frame; 3]);
        assert!(host.try_write_packet(frame.raw_bytes()));
        for _ in 0..16 {
            step(host, usb, &mut ready, &mut frames);
        }
        assert_eq!(frames, [frame; 4]);
        assert_eq!(host.receive_backlog(), (0, false));
        assert!(host.rx_interrupt_enabled());
        assert!(host.nvic_enabled());
    });
}