#![no_main]
use gc::{self, gc_ref::GcRef, test_utils::GotDropped, trace::GCTrace};
use libfuzzer_sys::fuzz_target;
use std::cell::RefCell;

use libfuzzer_sys::arbitrary;

#[derive(arbitrary::Arbitrary, Debug)]
struct ChildIDx(usize);

impl ChildIDx {
	fn choose<'a, T>(&self, choices: &'a [T]) -> Option<&'a T> {
		let idx = self.choose_index(choices.len())?;
		Some(choices.get(idx).unwrap())
	}

	fn choose_index(&self, len: usize) -> Option<usize> {
		(len != 0).then(|| self.0 % len)
	}
}

#[derive(arbitrary::Arbitrary, Debug)]
enum GraphExplore {
	ExploreChild(ChildIDx, Box<GraphExplore>),
	Stop,
}

#[derive(arbitrary::Arbitrary, Debug)]
enum Op {
	AddLink(GraphExplore, Option<GraphExplore>),
	RemoveChild(GraphExplore, ChildIDx),
	CollectGarbage,
}

#[derive(GCTrace, Default)]
struct Node {
	children: Vec<GCNode>,
}

type GCNode = GcRef<RefCell<Node>>;

impl Node {
	fn explore(node: GCNode, instructions: GraphExplore) -> GCNode {
		match instructions {
			GraphExplore::ExploreChild(child_idx, child_instructions) => {
				let child = child_idx
					.choose(&*node.borrow().children)
					.map(|v| v.clone());
				child
					.map(|c| Node::explore(c, *child_instructions))
					.unwrap_or(node)
			}
			GraphExplore::Stop => node,
		}
	}
}

fuzz_target!(|ops: Vec<Op>| {
	let mut allocator = gc::allocator::GCAllocator::default();
	let root: GCNode = allocator.alloc(RefCell::default());
	for op in ops {
		match op {
			Op::AddLink(parent_path, child_path) => {
				let child = child_path
					.map(|c| Node::explore(root.clone(), c))
					.unwrap_or_else(|| allocator.alloc(RefCell::default()));

				let parent = Node::explore(root.clone(), parent_path);
				parent.borrow_mut().children.push(child);
			}
			Op::RemoveChild(parent_path, child_idx) => {
				let parent = Node::explore(root.clone(), parent_path);
				let children = &mut parent.borrow_mut().children;
				let idx = child_idx.choose_index(children.len());
				if let Some(idx) = idx {
					children.remove(idx);
				}
			}
			Op::CollectGarbage => unsafe { allocator.gc(&root) },
		}
	}
	unsafe { allocator.gc(&()) };
});