// Copyright (c) Microsoft Corporation.
// Licensed under the MIT License.

//! A shim layer to fuzz responses from an emulated device.
//! This is the primary fuzzer for the host (a.k.a device) ->
//! openhcl attack surface. Do not sanitize any arbitrary data
//! responses in this routine.
use std::sync::Arc;

use crate::arbitrary_data;

use chipset_device::mmio::MmioIntercept;
use chipset_device::pci::PciConfigSpace;
use inspect::Inspect;
use inspect::InspectMut;
use pci_core::msi::MsiConnection;
use user_driver::DeviceBacking;
use user_driver::DmaClient;
use user_driver::interrupt::DeviceInterrupt;
use user_driver_emulated_mock::EmulatedDevice;
use user_driver_emulated_mock::Mapping;

/// An EmulatedDevice fuzzer that requires a working EmulatedDevice backend.
#[derive(Inspect)]
pub struct FuzzEmulatedDevice<T: InspectMut, U> {
    device: EmulatedDevice<T, U>,
}

impl<T: PciConfigSpace + MmioIntercept + InspectMut, U: DmaClient> FuzzEmulatedDevice<T, U> {
    /// Creates a new emulated device, wrapping `device`, using the provided MSI controller.
    pub fn new(device: T, msi_conn: MsiConnection, dma_client: Arc<U>) -> Self {
        let device = EmulatedDevice::new(device, msi_conn, dma_client);

        Self { device }
    }
}

/// Implementation for DeviceBacking trait.
impl<T: 'static + Send + InspectMut + MmioIntercept, U: 'static + DmaClient> DeviceBacking
    for FuzzEmulatedDevice<T, U>
{
    type Registers = Mapping<T>;

    fn id(&self) -> &str {
        self.device.id()
    }

    fn map_bar(&mut self, n: u8) -> anyhow::Result<Self::Registers> {
        self.device.map_bar(n)
    }

    fn dma_client(&self) -> Arc<dyn DmaClient> {
        self.device.dma_client()
    }

    /// Arbitrarily decide to passthrough or return arbitrary value.
    fn max_interrupt_count(&self) -> u32 {
        // Case: Fuzz response
        if let Ok(true) = arbitrary_data::<bool>() {
            // Return an abritrary u32
            if let Ok(num) = arbitrary_data::<u32>() {
                return num;
            }
        }

        // Case: Passthrough
        self.device.max_interrupt_count()
    }

    fn map_interrupt(&mut self, msix: u32, _cpu: u32) -> anyhow::Result<DeviceInterrupt> {
        self.device.map_interrupt(msix, _cpu)
    }
}
