//! Fuzz the `ion` register allocator.

use crate::{checker, fuzzing::func, ion};

use arbitrary::{Arbitrary, Result, Unstructured};

use core::cell::RefCell;

use std::thread_local;

/// `ion`-specific options for generating functions.

const OPTIONS: func::Options = func::Options {

    reused_inputs: true,

    fixed_regs: true,

    fixed_nonallocatable: true,

    clobbers: true,

    reftypes: true,

    callsite_ish_constraints: true,

    ..func::Options::DEFAULT

};

/// A convenience wrapper to generate a [`func::Func`] with `ion`-specific

/// options enabled.

#[derive(Clone, Debug)]

pub struct TestCase {

    func: func::Func,

    annotate: bool,

    check_ssa: bool,

}

impl Arbitrary<'_> for TestCase {

    fn arbitrary(u: &mut Unstructured) -> Result<TestCase> {

        let func = func::Func::arbitrary_with_options(u, &OPTIONS)?;

        let annotate = bool::arbitrary(u)?;

        let check_ssa = bool::arbitrary(u)?;

        Ok(TestCase {

            func,

            annotate,

            check_ssa,

        })

    }

}

/// Test a single function with the `ion` allocator.

///

/// This also:

/// - optionally creates annotations

/// - optionally verifies the incoming SSA

/// - runs the [`checker`].

pub fn check(t: TestCase) {

    let TestCase {

        func,

        annotate,

        check_ssa,

    } = &t;

    log::trace!("func:\n{func:?}");

    let env = func::machine_env();

    thread_local! {

        // We test that ctx is cleared properly between runs.

        static CTX: RefCell<ion::Ctx> = RefCell::default();

    }

    CTX.with(|ctx| {

        ion::run(func, &env, &mut *ctx.borrow_mut(), *annotate, *check_ssa)

            .expect("regalloc did not succeed");

        let mut checker = checker::Checker::new(func, &env);

        checker.prepare(&ctx.borrow().output);

        checker.run().expect("checker failed");

    });

}

#[test]

fn smoke() {

    arbtest::arbtest(|u| {

        let test_case = TestCase::arbitrary(u)?;

        check(test_case);

        Ok(())

    })

    .budget_ms(1_000);

}