use alloc::sync::Arc;
use core::cmp::min;
use core::mem::{size_of};
use core::slice;

use bitflags::*;
use device_tree::Node;
use device_tree::util::SliceRead;
use log::*;
use rcore_memory::PAGE_SIZE;
use rcore_memory::paging::PageTable;
use volatile::Volatile;

use rcore_fs::dev::BlockDevice;

use crate::memory::active_table;
use crate::sync::SpinNoIrqLock as Mutex;

use super::super::{DeviceType, Driver, DRIVERS, BLK_DRIVERS};
use super::super::bus::virtio_mmio::*;

pub struct VirtIOBlk {
    interrupt_parent: u32,
    interrupt: u32,
    header: usize,
    queue: VirtIOVirtqueue,
    capacity: usize
}

pub struct VirtIOBlkDriver(Mutex<VirtIOBlk>);


#[repr(C)]
#[derive(Debug)]
struct VirtIOBlkConfig {
    capacity: Volatile<u64>, // number of 512 sectors
}

#[repr(C)]
#[derive(Default)]
struct VirtIOBlkReq {
    req_type: u32,
    reserved: u32,
    sector: u64,
}

#[repr(C)]
struct VirtIOBlkResp {
    data: [u8; VIRTIO_BLK_BLK_SIZE],
    status: u8
}

const VIRTIO_BLK_T_IN: u32 = 0;
const VIRTIO_BLK_T_OUT: u32 = 1;

const VIRTIO_BLK_S_OK: u8 = 0;
const VIRTIO_BLK_S_IOERR: u8 = 1;
const VIRTIO_BLK_S_UNSUPP: u8 = 2;

const VIRTIO_BLK_BLK_SIZE: usize = 512;

bitflags! {
    struct VirtIOBlkFeature : u64 {
        const BARRIER = 1 << 0;
        const SIZE_MAX = 1 << 1;
        const SEG_MAX = 1 << 2;
        const GEOMETRY = 1 << 4;
        const RO = 1 << 5;
        const BLK_SIZE = 1 << 6;
        const SCSI = 1 << 7;
        const FLUSH = 1 << 9;
        const TOPOLOGY = 1 << 10;
        const CONFIG_WCE = 1 << 11;
        const DISCARD = 1 << 13;
        const WRITE_ZEROES = 1 << 14;
        // device independent
        const NOTIFY_ON_EMPTY = 1 << 24; // legacy
        const ANY_LAYOUT = 1 << 27; // legacy
        const RING_INDIRECT_DESC = 1 << 28;
        const RING_EVENT_IDX = 1 << 29;
        const UNUSED = 1 << 30; // legacy
        const VERSION_1 = 1 << 32; // detect legacy
        const ACCESS_PLATFORM = 1 << 33; // since virtio v1.1
        const RING_PACKED = 1 << 34; // since virtio v1.1
        const IN_ORDER = 1 << 35; // since virtio v1.1
        const ORDER_PLATFORM = 1 << 36; // since virtio v1.1
        const SR_IOV = 1 << 37; // since virtio v1.1
        const NOTIFICATION_DATA = 1 << 38; // since virtio v1.1
    }
}

impl Driver for VirtIOBlkDriver {
    fn try_handle_interrupt(&self) -> bool {
        let mut driver = self.0.lock();

        // ensure header page is mapped
        active_table().map_if_not_exists(driver.header as usize, driver.header as usize);
        let header = unsafe { &mut *(driver.header as *mut VirtIOHeader) };
        let interrupt = header.interrupt_status.read();
        if interrupt != 0 {
            header.interrupt_ack.write(interrupt);
            return true;
        }
        return false;
    }

    fn device_type(&self) -> DeviceType {
        DeviceType::Block
    }
}

impl BlockDevice for VirtIOBlkDriver {
    const BLOCK_SIZE_LOG2: u8 = 9; // 512
    fn read_at(&self, block_id: usize, buf: &mut [u8]) -> bool {
        let mut driver = self.0.lock();
        // ensure header page is mapped
        active_table().map_if_not_exists(driver.header as usize, driver.header as usize);

        let mut req = VirtIOBlkReq::default();
        req.req_type = VIRTIO_BLK_T_IN;
        req.reserved = 0;
        req.sector = block_id as u64;
        let input = [0; size_of::<VirtIOBlkResp>()];
        let output = unsafe { slice::from_raw_parts(&req as *const VirtIOBlkReq as *const u8, size_of::<VirtIOBlkReq>()) };
        driver.queue.add_and_notify(&[&input], &[output], 0);
        driver.queue.get_block();
        let resp = unsafe { &*(&input as *const u8 as *const VirtIOBlkResp) };
        if resp.status == VIRTIO_BLK_S_OK {
            let len = min(buf.len(), VIRTIO_BLK_BLK_SIZE);
            buf[..len].clone_from_slice(&resp.data[..len]);
            true
        } else {
            false
        }
    }

    fn write_at(&self, block_id: usize, buf: &[u8]) -> bool {
        unimplemented!()
    }
}

pub fn virtio_blk_init(node: &Node) {
    let reg = node.prop_raw("reg").unwrap();
    let from = reg.as_slice().read_be_u64(0).unwrap();
    let header = unsafe { &mut *(from as *mut VirtIOHeader) };

    header.status.write(VirtIODeviceStatus::DRIVER.bits());

    let device_features_bits = header.read_device_features();
    let device_features = VirtIOBlkFeature::from_bits_truncate(device_features_bits);
    info!("Device features {:?}", device_features);

    // negotiate these flags only
    let supported_features = VirtIOBlkFeature::empty();
    let driver_features = (device_features & supported_features).bits();
    header.write_driver_features(driver_features);

    // read configuration space
    let config = unsafe { &mut *((from + VIRTIO_CONFIG_SPACE_OFFSET) as *mut VirtIOBlkConfig) };
    info!("Config: {:?}", config);
    info!("Found a block device of size {}KB", config.capacity.read() / 2);

    // virtio 4.2.4 Legacy interface
    // configure two virtqueues: ingress and egress
    header.guest_page_size.write(PAGE_SIZE as u32); // one page

    let mut driver = VirtIOBlkDriver(Mutex::new(VirtIOBlk {
        interrupt: node.prop_u32("interrupts").unwrap(),
        interrupt_parent: node.prop_u32("interrupt-parent").unwrap(),
        header: from as usize,
        queue: VirtIOVirtqueue::new(header, 0, 16),
        capacity: config.capacity.read() as usize,
    }));

    header.status.write(VirtIODeviceStatus::DRIVER_OK.bits());

    let driver = Arc::new(driver);
    DRIVERS.write().push(driver.clone());
    BLK_DRIVERS.write().push(driver);
}