//! A place in a CPN.

use std::hash::{Hash, Hasher};
use std::ops::AddAssign;

/// Token capacity of a `Place`.
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub enum Capacity {
    /// The `Place` can only hold this many tokens.
    Limited(usize),

    /// The `Place` can hold an arbitrary number of tokens.
    Infinite,
}

impl AddAssign<usize> for Capacity {
    fn add_assign(&mut self, n: usize) {
        if let Self::Limited(cap) = self {
            *cap += n;
        }
    }
}

/// A place in a CPN.
///
/// A place has a name, and a capacity. If not explicitly set using `with_capacity`, the capacity
/// defaults to infinite.
#[derive(Debug, Clone)]
pub struct Place {
    name: String,
    capacity: Capacity,
}

impl Place {
    /// Construct a new place with the given name, and infinite capacity.
    pub fn new<S>(name: S) -> Self
    where
        S: Into<String>,
    {
        Self {
            name: name.into(),
            capacity: Capacity::Infinite,
        }
    }

    /// Limit the capacity of this place to `cap` tokens.
    ///
    /// # Panics
    ///
    /// Panics if `cap` is 0.
    pub fn with_capacity(mut self, cap: usize) -> Self {
        assert!(cap > 0, "A capacity of 0 makes no sense!");
        self.capacity = Capacity::Limited(cap);
        self
    }

    /// Get a reference to the name of this place.
    pub fn name(&self) -> &str {
        &self.name
    }

    /// Get the capacity of this place.
    pub fn capacity(&self) -> Capacity {
        self.capacity
    }
}

impl PartialEq for Place {
    fn eq(&self, other: &Self) -> bool {
        self.name == other.name
    }
}

impl Eq for Place {}

impl Hash for Place {
    fn hash<H>(&self, state: &mut H)
    where
        H: Hasher,
    {
        state.write(self.name.as_bytes());
    }
}

impl From<&str> for Place {
    fn from(s: &str) -> Self {
        Self::new(s)
    }
}

impl From<String> for Place {
    fn from(s: String) -> Self {
        Self {
            name: s,
            capacity: Capacity::Infinite,
        }
    }
}