package edu.rice.hj.example.comp322.assignments.hw4;

import edu.rice.hj.api.SuspendableException;

import java.util.Iterator;

import static edu.rice.hj.Module1.finish;

public class ConstraintSatisfaction {
    IConstraintSystem problem;
    FVT fvt;
    int thresholdSize = 1;

    public ConstraintSatisfaction(IConstraintSystem inputProblem) {
        problem = inputProblem;
    }

    public void solve() {
        double t1 = System.nanoTime() / 1e9;

        //System.out.println(problem.getInitialFvt());
        // Start the parallel search
        search(problem.getInitialState(), 0, problem.getInitialFvt());

        double t2 = System.nanoTime() / 1e9;
        java.text.DecimalFormat df = new java.text.DecimalFormat("#.##");

        // Print out the final output
        System.out.println("Time = " + df.format(t2 - t1) + " sec");
    }

    public void search(ProblemState state, int curVar, FVT fvt) {
        if (curVar == fvt.getNumVars()) {
            problem.addSolution(state);
            //System.out.println(state);
            //System.exit(0);

        } else {
            Iterator<Integer> itr = fvt.getValues(curVar).iterator();
            while (itr.hasNext()) {
                Integer v = itr.next();
                ProblemState newState = state.copy();
                newState.setValue(curVar, v);
                FVT newFvt = forwardCheck(curVar, v, fvt);
                if (newFvt != null) {
                    search(newState, curVar + 1, newFvt);
                }
            }
        }

    }

    public void parallelSolve() throws SuspendableException {
        double t1 = System.nanoTime() / 1e9;

        // Start the parallel search
        finish(() -> {
            parallelSearch(problem.getInitialState(), 0, problem.getInitialFvt());
        });
        double t2 = System.nanoTime() / 1e9;
        java.text.DecimalFormat df = new java.text.DecimalFormat("#.##");

        // Print out the final output
        System.out.println("Time = " + df.format(t2 - t1) + " sec");
    }

    public void parallelSearch(ProblemState state, int curVar, FVT fvt) {
        /* TODO: Create a parallel implementation of the constraint solver search() */
    }

    public FVT forwardCheck(int curVar, Integer curVal, FVT fvt) {
        FVT newFvt = new FVT(fvt.getNumVars());
        for (int freeVar = curVar + 1; freeVar < fvt.getNumVars(); freeVar++) {
            Iterator<Integer> itr = fvt.getValues(freeVar).iterator();
            while (itr.hasNext()) {
                Integer v = itr.next();
                if (problem.isConsistent(curVar, curVal, freeVar, v)) {
                    newFvt.addValue(freeVar, v);
                }
            }
            if (newFvt.getValues(freeVar).size() == 0) {
                return null;
            }
        }
        return newFvt;
    }
}