// Copyright 2020 Xavier Gillard
//
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// this software and associated documentation files (the "Software"), to deal in
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//! This module defines the types used to encode the state of a node in the 
//! SOP problem.

use std::hash::Hash;

use crate::BitSet;

/// This represents a state of the problem
#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq)]
pub struct SopState {
    /// This is the last job in the current sequence
    pub previous: Previous,
    /// These are the jobs still to be scheduled
    pub must_schedule: BitSet,
    /// These are jobs that might still need to be scheduled
    pub maybe_schedule: Option<BitSet>,
    /// This is the 'depth' in the sequence, the number of jobs that have
    /// already been scheduled
    pub depth: usize
}

/// This represents the last job in the current sequence
#[derive(Debug, Clone, Copy, Hash, Eq, PartialEq)]
pub enum Previous {
    /// It can either be at an actual job
    Job(usize),
    /// Or it can be one among a pool of jobs 
    /// (relaxed node == job is Schrödinger's cat)
    Virtual(BitSet),
}