use types::{badge::Badge, bounded::CapSlot, generation::Generation, permission::PermissionSet};

pub mod authority;

use crate::{error::KernelError, resource::Resource};

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

// Sized so that every representable `CapSlot` indexes a real slot.
pub const MAX_CAPS_PER_PROCESS: usize = CapSlot::MAX as usize + 1;

#[derive(Clone)]
pub struct Capability {
    resource: Resource,
    permissions: PermissionSet,
    generation: Generation,
    badge: Badge,
}

impl Capability {
    pub fn new(resource: Resource, permissions: PermissionSet, generation: Generation) -> Self {
        Self {
            resource,
            permissions,
            generation,
            badge: Badge::NONE,
        }
    }

    /// The same capability with `badge` stamped on it.
    pub fn with_badge(mut self, badge: Badge) -> Self {
        self.badge = badge;
        self
    }

    pub fn badge(&self) -> Badge {
        self.badge
    }

    pub fn resource(&self) -> &Resource {
        &self.resource
    }

    pub fn permissions(&self) -> &PermissionSet {
        &self.permissions
    }

    pub fn generation(&self) -> &Generation {
        &self.generation
    }
}

pub struct CapabilityTable {
    slots: [Option<Capability>; MAX_CAPS_PER_PROCESS],
}

impl CapabilityTable {
    pub fn new() -> Self {
        Self {
            slots: [const { None }; MAX_CAPS_PER_PROCESS],
        }
    }

    pub fn get(&self, slot: CapSlot) -> Result<&Capability, KernelError> {
        let idx = slot.value() as usize;
        self.slots[idx]
            .as_ref()
            .ok_or(KernelError::InvalidSlot(slot))
    }

    pub fn insert(&mut self, cap: Capability) -> Result<CapSlot, KernelError> {
        let idx = self
            .slots
            .iter()
            .position(|s| s.is_none())
            .ok_or(KernelError::NoFreeSlot)?;

        self.slots[idx] = Some(cap);
        CapSlot::new(idx as u8).ok_or(KernelError::NoFreeSlot)
    }

    pub fn remove(&mut self, slot: CapSlot) -> Result<(), KernelError> {
        let idx = slot.value() as usize;
        if self.slots[idx].is_none() {
            return Err(KernelError::InvalidSlot(slot));
        }
        self.slots[idx] = None;
        Ok(())
    }
}

impl Default for CapabilityTable {
    fn default() -> Self {
        Self::new()
    }
}