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use rand::Rng;
use wfc::{PropagateError, RunBorrow, RunOwn, Wave};
use wrap::Wrap;

pub trait RetryOwn: Copy + private::Sealed {
    type Return;
    fn retry<'a, W, R>(&mut self, run: RunOwn<'a, W>, rng: &mut R) -> Self::Return
    where
        W: Wrap,
        R: Rng;
}

#[derive(Debug, Clone, Copy)]
pub struct Forever;

impl RetryOwn for Forever {
    type Return = Wave;
    fn retry<'a, W, R>(&mut self, mut run: RunOwn<'a, W>, rng: &mut R) -> Self::Return
    where
        W: Wrap,
        R: Rng,
    {
        loop {
            match run.collapse(rng) {
                Ok(()) => (),
                Err(PropagateError::Contradiction) => continue,
            }
            return run.into_wave();
        }
    }
}

#[derive(Debug, Clone, Copy)]
pub struct NumTimes(pub usize);

impl RetryOwn for NumTimes {
    type Return = Result<Wave, PropagateError>;
    fn retry<'a, W, R>(&mut self, mut run: RunOwn<'a, W>, rng: &mut R) -> Self::Return
    where
        W: Wrap,
        R: Rng,
    {
        loop {
            match run.collapse(rng) {
                Ok(()) => return Ok(run.into_wave()),
                Err(e) => {
                    if self.0 == 0 {
                        return Err(e);
                    } else {
                        self.0 -= 1;
                    }
                }
            }
        }
    }
}

pub trait RetryBorrow: Copy + private::Sealed {
    type Return;
    fn retry<'a, W, R>(
        &mut self,
        run: &mut RunBorrow<'a, W>,
        rng: &mut R,
    ) -> Self::Return
    where
        W: Wrap,
        R: Rng;
}

impl RetryBorrow for Forever {
    type Return = ();
    fn retry<'a, W, R>(&mut self, run: &mut RunBorrow<'a, W>, rng: &mut R) -> Self::Return
    where
        W: Wrap,
        R: Rng,
    {
        loop {
            match run.collapse(rng) {
                Ok(()) => break,
                Err(PropagateError::Contradiction) => continue,
            }
        }
    }
}

impl RetryBorrow for NumTimes {
    type Return = Result<(), PropagateError>;
    fn retry<'a, W, R>(&mut self, run: &mut RunBorrow<'a, W>, rng: &mut R) -> Self::Return
    where
        W: Wrap,
        R: Rng,
    {
        loop {
            match run.collapse(rng) {
                Ok(()) => return Ok(()),
                Err(e) => {
                    if self.0 == 0 {
                        return Err(e);
                    } else {
                        self.0 -= 1;
                    }
                }
            }
        }
    }
}

mod private {
    use super::*;

    pub trait Sealed {}

    impl Sealed for Forever {}
    impl Sealed for NumTimes {}
}