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//! Observers give insights about runs of a target, such as coverage, timing, stack depth, and more.

pub mod map;
pub use map::*;

pub mod cmp;
pub use cmp::*;

pub mod concolic;

use alloc::string::{String, ToString};
use core::time::Duration;
use serde::{Deserialize, Serialize};

use crate::{
    bolts::{
        current_time,
        tuples::{MatchName, Named},
    },
    Error,
};

/// Observers observe different information about the target.
/// They can then be used by various sorts of feedback.
pub trait Observer<I, S>: Named {
    /// The testcase finished execution, calculate any changes.
    /// Reserved for future use.
    #[inline]
    fn flush(&mut self) -> Result<(), Error> {
        Ok(())
    }

    /// Called right before exexution starts
    #[inline]
    fn pre_exec(&mut self, _state: &mut S, _input: &I) -> Result<(), Error> {
        Ok(())
    }

    /// Called right after execution finished.
    #[inline]
    fn post_exec(&mut self, _state: &mut S, _input: &I) -> Result<(), Error> {
        Ok(())
    }
}

/// A haskell-style tuple of observers
pub trait ObserversTuple<I, S>: MatchName {
    /// This is called right before the next execution.
    fn pre_exec_all(&mut self, state: &mut S, input: &I) -> Result<(), Error>;

    /// This is called right after the last execution
    fn post_exec_all(&mut self, state: &mut S, input: &I) -> Result<(), Error>;
}

impl<I, S> ObserversTuple<I, S> for () {
    fn pre_exec_all(&mut self, _state: &mut S, _input: &I) -> Result<(), Error> {
        Ok(())
    }

    fn post_exec_all(&mut self, _state: &mut S, _input: &I) -> Result<(), Error> {
        Ok(())
    }
}

impl<Head, Tail, I, S> ObserversTuple<I, S> for (Head, Tail)
where
    Head: Observer<I, S>,
    Tail: ObserversTuple<I, S>,
{
    fn pre_exec_all(&mut self, state: &mut S, input: &I) -> Result<(), Error> {
        self.0.pre_exec(state, input)?;
        self.1.pre_exec_all(state, input)
    }

    fn post_exec_all(&mut self, state: &mut S, input: &I) -> Result<(), Error> {
        self.0.post_exec(state, input)?;
        self.1.post_exec_all(state, input)
    }
}

/// A simple observer, just overlooking the runtime of the target.
#[derive(Serialize, Deserialize, Debug, Clone)]
pub struct TimeObserver {
    name: String,
    start_time: Duration,
    last_runtime: Option<Duration>,
}

impl TimeObserver {
    /// Creates a new [`TimeObserver`] with the given name.
    #[must_use]
    pub fn new(name: &'static str) -> Self {
        Self {
            name: name.to_string(),
            start_time: Duration::from_secs(0),
            last_runtime: None,
        }
    }

    /// Gets the runtime for the last execution of this target.
    #[must_use]
    pub fn last_runtime(&self) -> &Option<Duration> {
        &self.last_runtime
    }
}

impl<I, S> Observer<I, S> for TimeObserver {
    fn pre_exec(&mut self, _state: &mut S, _input: &I) -> Result<(), Error> {
        self.last_runtime = None;
        self.start_time = current_time();
        Ok(())
    }

    fn post_exec(&mut self, _state: &mut S, _input: &I) -> Result<(), Error> {
        self.last_runtime = current_time().checked_sub(self.start_time);
        Ok(())
    }
}

impl Named for TimeObserver {
    fn name(&self) -> &str {
        &self.name
    }
}

#[cfg(feature = "std")]
#[cfg(test)]
mod tests {

    use crate::{
        bolts::tuples::{tuple_list, tuple_list_type, Named},
        observers::{StdMapObserver, TimeObserver},
    };

    static mut MAP: [u32; 4] = [0; 4];

    #[test]
    fn test_observer_serde() {
        let obv = tuple_list!(
            TimeObserver::new("time"),
            StdMapObserver::new("map", unsafe { &mut MAP })
        );
        let vec = postcard::to_allocvec(&obv).unwrap();
        println!("{:?}", vec);
        let obv2: tuple_list_type!(TimeObserver, StdMapObserver<u32>) =
            postcard::from_bytes(&vec).unwrap();
        assert_eq!(obv.0.name(), obv2.0.name());
    }
}