#![no_std]
// A kernel panic takes the whole system down, so kernel code may not
// contain any way to panic. Tests and proofs are exempt.
#![cfg_attr(
    not(any(test, kani)),
    deny(
        clippy::unwrap_used,
        clippy::expect_used,
        clippy::panic,
        clippy::unreachable,
        clippy::todo,
        clippy::unimplemented,
        clippy::indexing_slicing
    )
)]

pub mod abi;
mod board;
mod budget;
mod captree;
pub mod interrupt;
mod memory;
#[cfg(kani)]
pub mod proofs;
mod smp;
pub mod syscall;
mod teardown;

pub use board::{BoardCaps, BoardDevice, BootCaps};
pub use syscall::{SyscallOutcome, SyscallResult};

#[cfg(test)]
#[path = "tests/mod.rs"]
mod tests;

use domain::{
    budget::{Budget, Limits},
    capability::Capability,
    endpoint::EndpointTable,
    error::KernelError,
    irq::IrqRoutingTable,
    memory::{RegionTable, frame::FrameTable},
    notification::NotificationTable,
    process::{MAX_PROCESSES, ProcessTable},
    resource::Resource,
    scheduler::{Scheduler, multi_core::MultiCoreScheduler},
    thread::{MAX_THREADS, ThreadState, ThreadTable},
};
use platform::Platform;
use types::{
    address::PhysicalAddress,
    bounded::{CapSlot, Priority},
    generation::Generation,
    id::{ProcessId, ThreadId},
    permission::{Permission, PermissionSet},
    time::TimeSlice,
};

pub struct Kernel<P: Platform> {
    platform: P,
    processes: ProcessTable,
    threads: ThreadTable,
    endpoints: EndpointTable,
    scheduler: MultiCoreScheduler,
    frames: FrameTable,
    budgets: [Budget; MAX_PROCESSES],
    /// Whose budget each process was carved from (see budget.rs).
    parents: [Option<ProcessId>; MAX_PROCESSES],
    regions: RegionTable,
    irqs: IrqRoutingTable,
    notifications: NotificationTable,
    ipc: [syscall::IpcState; MAX_THREADS],
    pending_results: [Option<SyscallResult>; MAX_THREADS],
    /// The core each thread runs on (see smp.rs).
    homes: [types::id::CoreId; MAX_THREADS],
    /// The capability derivation tree as links (see captree.rs).
    tree: domain::capability::tree::CapTree<{ captree::ALL_CAPS }>,
    /// Where each process's next heap search starts (see memory.rs).
    heap_cursors: [usize; MAX_PROCESSES],
    /// Who to signal when each process dies (see syscall/ipc/events.rs).
    death_watchers: [[Option<domain::timer::Target>; domain::timer::MAX_WATCHERS]; MAX_PROCESSES],
    timers: domain::timer::Timers,
}

impl<P: Platform> Kernel<P> {
    pub fn new(platform: P, pool_base: PhysicalAddress, pool_pages: usize) -> Self {
        let num_cores = platform.num_cores();
        Self {
            platform,
            processes: ProcessTable::new(),
            threads: ThreadTable::new(),
            endpoints: EndpointTable::new(),
            scheduler: MultiCoreScheduler::new(num_cores),
            frames: FrameTable::new(pool_base, pool_pages),
            budgets: [Budget::EMPTY; MAX_PROCESSES],
            parents: [None; MAX_PROCESSES],
            regions: RegionTable::new(),
            irqs: IrqRoutingTable::new(),
            notifications: NotificationTable::new(),
            ipc: [syscall::IpcState::default(); MAX_THREADS],
            pending_results: [const { None }; MAX_THREADS],
            homes: [types::id::CoreId::from_raw(0); MAX_THREADS],
            tree: domain::capability::tree::CapTree::new(),
            heap_cursors: [0; MAX_PROCESSES],
            death_watchers: [[None; domain::timer::MAX_WATCHERS]; MAX_PROCESSES],
            timers: domain::timer::Timers::new(),
        }
    }

    /// Builds the kernel in place, one table at a time, to stay off the boot stack.
    ///
    /// # Safety
    /// `slot` must be valid for writes and aligned; the old value is overwritten without drop.
    pub unsafe fn init_in_place(
        slot: *mut Self,
        platform: P,
        pool_base: PhysicalAddress,
        pool_pages: usize,
    ) {
        use core::ptr::addr_of_mut;
        let num_cores = platform.num_cores();
        // SAFETY: the caller guarantees `slot` is valid and aligned; each
        // field is written exactly once.
        unsafe {
            addr_of_mut!((*slot).platform).write(platform);
            addr_of_mut!((*slot).processes).write(ProcessTable::new());
            addr_of_mut!((*slot).threads).write(ThreadTable::new());
            addr_of_mut!((*slot).endpoints).write(EndpointTable::new());
            addr_of_mut!((*slot).scheduler).write(MultiCoreScheduler::new(num_cores));
            addr_of_mut!((*slot).frames).write(FrameTable::new(pool_base, pool_pages));
            addr_of_mut!((*slot).budgets).write([Budget::EMPTY; MAX_PROCESSES]);
            addr_of_mut!((*slot).parents).write([None; MAX_PROCESSES]);
            addr_of_mut!((*slot).regions).write(RegionTable::new());
            addr_of_mut!((*slot).irqs).write(IrqRoutingTable::new());
            addr_of_mut!((*slot).notifications).write(NotificationTable::new());
            addr_of_mut!((*slot).ipc).write([syscall::IpcState::default(); MAX_THREADS]);
            addr_of_mut!((*slot).pending_results).write([const { None }; MAX_THREADS]);
            addr_of_mut!((*slot).homes).write([types::id::CoreId::from_raw(0); MAX_THREADS]);
            addr_of_mut!((*slot).tree).write(domain::capability::tree::CapTree::new());
            addr_of_mut!((*slot).heap_cursors).write([0; MAX_PROCESSES]);
            addr_of_mut!((*slot).death_watchers)
                .write([[None; domain::timer::MAX_WATCHERS]; MAX_PROCESSES]);
            addr_of_mut!((*slot).timers).write(domain::timer::Timers::new());
        }
    }

    pub fn boot(
        &mut self,
        priority: Priority,
        time_slice: TimeSlice,
    ) -> Result<(ProcessId, ThreadId), KernelError> {
        // Init holds every frame and every kernel object to start with.
        let everything = Limits {
            pages: self.frames.free_count(),
            endpoints: domain::endpoint::MAX_ENDPOINTS,
            notifications: domain::notification::MAX_NOTIFICATIONS,
            regions: domain::memory::MAX_REGIONS,
        };
        let pid = self.new_process(None, everything)?;
        let tid = self.threads.spawn(pid, priority, time_slice, None)?;
        self.processes.get_mut(pid)?.add_thread(tid)?;

        let cap = Capability::new(
            Resource::ProcessCreate,
            PermissionSet::empty().with(Permission::Execute),
            Generation::initial(),
        );
        self.insert_derived(pid, cap, None)?;

        let core = self.platform.core_id();
        self.set_home(tid, core);
        self.scheduler.add(tid, priority, core);
        self.scheduler.next(core);
        self.threads.get_mut(tid)?.set_running(core)?;
        Ok((pid, tid))
    }

    pub fn platform_mut(&mut self) -> &mut P {
        &mut self.platform
    }

    pub fn pending_result(&self, thread: ThreadId) -> Option<&SyscallResult> {
        self.pending_results.get(thread.raw() as usize)?.as_ref()
    }

    pub fn take_pending_result(&mut self, thread: ThreadId) -> Option<SyscallResult> {
        self.pending_results.get_mut(thread.raw() as usize)?.take()
    }

    pub fn set_thread_running(
        &mut self,
        tid: ThreadId,
        core: types::id::CoreId,
    ) -> Result<(), domain::error::KernelError> {
        self.threads.get_mut(tid)?.set_running(core)
    }

    pub fn process_exists(&self, pid: ProcessId) -> bool {
        self.processes.get(pid).is_ok()
    }

    pub fn thread_context(&self, tid: ThreadId) -> Option<&domain::thread::SavedContext> {
        self.threads.get(tid).ok().map(|t| t.saved_context())
    }

    pub fn thread_context_mut(
        &mut self,
        tid: ThreadId,
    ) -> Option<&mut domain::thread::SavedContext> {
        self.threads
            .get_mut(tid)
            .ok()
            .map(|t| t.saved_context_mut())
    }

    pub fn thread_process(&self, tid: ThreadId) -> Option<ProcessId> {
        self.threads.get(tid).ok().map(|t| t.process())
    }

    pub fn current_thread(&self) -> Option<ThreadId> {
        let core = self.platform.core_id();
        self.scheduler.current(core)
    }

    pub fn pick_next_thread(&mut self) -> Option<ThreadId> {
        use domain::scheduler::Scheduler;
        let core = self.platform.core_id();
        self.scheduler.next(core)
    }

    /// A process for boot code to load, its `limits` carved from `parent`.
    pub fn create_process_internal(
        &mut self,
        parent: ProcessId,
        limits: Limits,
    ) -> Option<ProcessId> {
        self.new_process(Some(parent), limits).ok()
    }

    pub fn spawn_thread_internal(&mut self, pid: ProcessId) -> Option<ThreadId> {
        let tid = self
            .threads
            .spawn(pid, Priority::DEFAULT, TimeSlice::DEFAULT, None)
            .ok()?;
        let _ = self.processes.get_mut(pid).map(|p| p.add_thread(tid));
        self.place(tid);
        self.make_ready(tid, Priority::DEFAULT);
        Some(tid)
    }

    /// Creates an endpoint owned by `owner`; it is destroyed with `owner`.
    pub fn create_endpoint(
        &mut self,
        owner: ProcessId,
    ) -> Result<types::id::EndpointId, KernelError> {
        self.processes.get(owner)?;
        self.charge_object(owner, budget::ENDPOINTS)?;
        self.endpoints
            .create(owner)
            .ok_or(KernelError::NoFreeSlot)
            .inspect_err(|_| self.uncharge_object(owner, budget::ENDPOINTS))
    }

    pub fn grant_capability(
        &mut self,
        to: ProcessId,
        resource: Resource,
        permissions: PermissionSet,
    ) -> Result<CapSlot, KernelError> {
        self.grant_cap(to, resource, permissions)
    }

    fn caller(&self) -> Result<(ThreadId, ProcessId), KernelError> {
        let core = self.platform.core_id();
        let tid = self
            .scheduler
            .current(core)
            .ok_or(KernelError::WouldBlock)?;
        let thread = self.threads.get(tid)?;
        match thread.state() {
            ThreadState::Running(_) => Ok((tid, thread.process())),
            _ => Err(KernelError::WouldBlock),
        }
    }

    fn check_cap(
        &self,
        owner: ProcessId,
        slot: CapSlot,
        needed: Permission,
    ) -> Result<&Capability, KernelError> {
        let process = self.processes.get(owner)?;
        let cap = process.capabilities().get(slot)?;
        if !cap.permissions().allows(needed) {
            return Err(KernelError::PermissionDenied { slot, needed });
        }
        match self.resource_generation(cap.resource()) {
            Some(current) if cap.generation().is_valid_against(&current) => Ok(cap),
            _ => Err(KernelError::RevokedCapability(slot)),
        }
    }

    /// The generation a capability to `resource` must carry, or `None` if
    /// the object no longer exists.
    fn resource_generation(&self, resource: &Resource) -> Option<Generation> {
        match resource {
            Resource::Endpoint(id) => self.endpoints.generation(*id),
            Resource::Memory(id) => self.regions.generation(*id),
            Resource::Notification(id) => self.notifications.generation(*id),
            Resource::Process(pid) => self.processes.generation(*pid),
            Resource::Interrupt(_)
            | Resource::ProcessCreate
            | Resource::SystemControl
            | Resource::Console => Some(Generation::initial()),
        }
    }

    fn grant_cap(
        &mut self,
        to: ProcessId,
        resource: Resource,
        permissions: PermissionSet,
    ) -> Result<CapSlot, KernelError> {
        let generation = self
            .resource_generation(&resource)
            .ok_or(KernelError::NoSuchObject)?;
        let cap = Capability::new(resource, permissions, generation);
        self.insert_derived(to, cap, None)
    }
}