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use crate::model::{InletId, OutletId};
use crate::{Model, TractResult};
use bit_set;

#[derive(Debug)]
pub struct PropConst;

impl super::OptimizerPass for PropConst {
    fn pass(&self, model: &mut Model) -> TractResult<bool> {
        let mut replaced = 0;
        let mut done = bit_set::BitSet::with_capacity(model.nodes().len());
        let mut needed: Vec<usize> = vec![];
        for t in model.outputs()?.iter().map(|n| n.node) {
            needed.push(t);
        }
        while let Some(&node) = needed.last() {
            if done.contains(node) {
                needed.pop();
                continue;
            }
            if model.nodes()[node]
                .inputs
                .iter()
                .all(|i| done.contains(i.node))
            {
                needed.pop();
                done.insert(node);
            } else {
                trace!("Looking at node {} inputs", node);
                for ix in 0..model.nodes()[node].inputs.len() {
                    use crate::analyser::types::Fact;
                    let source = model.nodes()[node].inputs[ix];
                    if model.nodes()[source.node].op().name() != "Const"
                        && model.fact(source)?.is_concrete()
                    {
                        use crate::model::ModelDsl;
                        let konst = model.fact(source)?.concretize().unwrap();
                        let id = model.nodes().len();
                        trace!(
                            "   Replacing node {} input {} by a constant instead of {:?}",
                            node,
                            ix,
                            source
                        );
                        let id = model.add_const(format!("Const-{}", id), konst.clone())?;
                        model.add_edge(OutletId::new(id, 0), InletId::new(node, ix))?;
                        model.check_edges()?;
                        model.set_fact(OutletId::new(id, 0), konst.into())?;
                        replaced += 1;
                    } else {
                        needed.push(source.node);
                    }
                }
            }
        }
        debug!("Replaced {} inputs by constants", replaced);
        Ok(replaced > 0)
    }
}