//! Common functionality used by the mock implementations.

use std::fmt::Debug;
use std::sync::{Arc, Mutex};

/// Generic Mock implementation
///
/// This supports the specification and evaluation of expectations to allow automated testing of hal drivers.
/// Mismatches between expectations will cause runtime assertions to assist in locating the source of the fault.
///
/// Note that the implementation uses an `Arc<Mutex<...>>` internally, so a
/// cloned instance of the mock can be used to check the expectations of the
/// original instance that has been moved into a driver.
#[derive(Debug)]
pub struct Generic<T: Clone + Debug + PartialEq> {
    expected: Arc<Mutex<(usize, Vec<T>)>>,
}

impl<'a, T: 'a> Generic<T>
where
    T: Clone + Debug + PartialEq,
{
    /// Create a new mock interface
    ///
    /// This creates a new generic mock interface with initial expectations
    pub fn new<E>(expected: E) -> Generic<T>
    where
        E: IntoIterator<Item = &'a T>,
    {
        let mut g = Generic {
            expected: Arc::new(Mutex::new((0, vec![]))),
        };

        g.expect(expected);

        g
    }

    /// Set expectations on the interface
    ///
    /// This is a list of transactions to be executed in order
    /// Note that setting this will overwrite any existing expectations
    pub fn expect<E>(&mut self, expected: E)
    where
        E: IntoIterator<Item = &'a T>,
    {
        let v: Vec<T> = expected.into_iter().map(|v| v.clone()).collect();
        let mut e = self.expected.lock().unwrap();
        e.0 = 0;
        e.1 = v;
    }

    /// Assert that all expectations on a given Mock have been met
    pub fn done(&mut self) {
        let e = self.expected.lock().unwrap();
        assert_eq!(
            e.0,
            e.1.len(),
            "Mock call number(left) and expectations(right) do not match"
        );
    }
}

/// Clone allows a single mock to be duplicated for control and evaluation
impl<T> Clone for Generic<T>
where
    T: Clone + Debug + PartialEq,
{
    fn clone(&self) -> Self {
        Generic {
            expected: self.expected.clone(),
        }
    }
}

/// Iterator impl for use in mock impls
impl<T> Iterator for Generic<T>
where
    T: Clone + Debug + PartialEq,
{
    type Item = T;
    fn next(&mut self) -> Option<Self::Item> {
        let mut e = self.expected.lock().unwrap();
        e.0 += 1;
        e.1.get(e.0 - 1).map(|v| v.clone())
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_generic_mock() {
        let expectations = [0u8, 1u8];
        let mut mock: Generic<u8> = Generic::new(&expectations);

        assert_eq!(mock.next(), Some(0u8));
        assert_eq!(mock.next(), Some(1u8));
        assert_eq!(mock.next(), None);
    }
}