package org.simantics.scl.compiler.elaboration.chr;

import java.util.ArrayList;
import java.util.HashMap;

import org.simantics.scl.compiler.compilation.CompilationContext;
import org.simantics.scl.compiler.elaboration.chr.plan.CHRSearchPlan;
import org.simantics.scl.compiler.elaboration.chr.planning.QueryPlanningContext;
import org.simantics.scl.compiler.elaboration.chr.relations.CHRConstraint;
import org.simantics.scl.compiler.elaboration.contexts.SimplificationContext;
import org.simantics.scl.compiler.elaboration.contexts.TranslationContext;
import org.simantics.scl.compiler.elaboration.contexts.TypingContext;
import org.simantics.scl.compiler.elaboration.expressions.EAsPattern;
import org.simantics.scl.compiler.elaboration.expressions.EVariable;
import org.simantics.scl.compiler.elaboration.expressions.Expression;
import org.simantics.scl.compiler.elaboration.expressions.ExpressionVisitor;
import org.simantics.scl.compiler.elaboration.expressions.Variable;
import org.simantics.scl.compiler.elaboration.expressions.printing.ExpressionToStringVisitor;
import org.simantics.scl.compiler.elaboration.expressions.visitors.StandardExpressionVisitor;
import org.simantics.scl.compiler.errors.Locations;
import org.simantics.scl.compiler.internal.parsing.Symbol;
import org.simantics.scl.compiler.types.Types;
import org.simantics.scl.compiler.types.kinds.Kinds;

import gnu.trove.map.hash.TObjectIntHashMap;
import gnu.trove.set.hash.TIntHashSet;

public class CHRRule extends Symbol {
    public CHRRuleset parentRuleset;
    public int priority;
    public CHRQuery head;
    public CHRQuery body;
    public Variable[] existentialVariables;
    
    // Analysis
    //public int firstPriorityExecuted;
    public int lastPriorityExecuted;
    
    // Plans
    public ArrayList<CHRSearchPlan> plans = new ArrayList<CHRSearchPlan>();
    
    // Code generation, move to CHRPriority
    public String containerClassName;
    
    public CHRRule(long location, CHRQuery head, CHRQuery body, Variable[] existentialVariables) {
        this.location = location;
        this.head = head;
        this.body = body;
        this.existentialVariables = existentialVariables;
    }
    
    public CHRRule(long location, CHRQuery head, CHRQuery body) {
        this(location, head, body, null);
    }

    public void resolve(TranslationContext context) {
        context.pushExistentialFrame();
        head.resolve(context);
        context.disallowNewExistentials();
        body.resolve(context);
        existentialVariables = context.popExistentialFrame();
        
        warnForExistentialsUsedOnlyOnce(context);
    }

    private static final Object NEVER_USED = new Object();
    
    private void warnForExistentialsUsedOnlyOnce(TranslationContext context) {
        // Initialize the hash map
        HashMap<Variable, Object> usageCount = new HashMap<>(existentialVariables.length);
        for(Variable var : existentialVariables)
            if(!var.getName().equals("_"))
                usageCount.put(var, NEVER_USED);
    
        // Collect variable uses
        ExpressionVisitor visitor = new StandardExpressionVisitor() {
            private void handle(Expression expression, Variable variable) {
                Object object = usageCount.remove(variable);
                if(object == NEVER_USED)
                    usageCount.put(variable, expression);
            }
            @Override
            public void visit(EVariable expression) {
                if(expression.variable != null)
                    handle(expression, expression.variable);
            }
            @Override
            public void visit(EAsPattern expression) {
                expression.pattern.accept(this);
                handle(expression, expression.var);
            }
        };
        head.accept(visitor);
        body.accept(visitor);
        
        // Report as warnings
        usageCount.forEach((variable, expression_) -> {
            if(!(expression_ instanceof Expression))
                return; // Should never happen
            Expression expression = (Expression)expression_;
            if(context.isExpandedFromWildcard(expression))
                return;
            
            context.getErrorLog().logWarning(expression.location,
                    "Existential variable " + variable.getName() + " is referred only once. Replace by _ if this is a wildcard.");
        });
        
    }

    public void checkType(TypingContext context) {
        for(Variable variable : existentialVariables)
            variable.setType(Types.metaVar(Kinds.STAR));
        head.checkType(context);
        body.checkType(context);
    }
    
    public void collectVars(TObjectIntHashMap<Variable> allVars, TIntHashSet vars) {
        head.collectVars(allVars, vars);
        body.collectVars(allVars, vars);
    }

    public void setLocationDeep(long loc) {
        if(location == Locations.NO_LOCATION) {
            this.location = loc;
            head.setLocationDeep(loc);
            body.setLocationDeep(loc);
        }
    }
    
    public void simplify(SimplificationContext context) {
        head.simplify(context);
        body.simplify(context);
    }

    public void compile(CompilationContext compilationContext, CHRConstraint initConstraint) {
        boolean hasLocalActiveLiteral = false;
        for(int i=0;i<head.literals.length;++i) {
            CHRLiteral literal = head.literals[i];
            if(literal.passive)
                continue;
            CHRConstraint constraint = (CHRConstraint)literal.relation;
            
            Variable activeFact = new Variable("activeFact", constraint.factType);
            QueryPlanningContext context = new QueryPlanningContext(compilationContext, existentialVariables);
            if(!head.createQueryPlan(context, new EVariable(activeFact), i, initConstraint))
                return;
            body.createEnforcePlan(context, priority);
            addPlan(new CHRSearchPlan(constraint, activeFact, context.getPlanOps()));
            
            if(constraint.parentRuleset == parentRuleset)
                hasLocalActiveLiteral = true;
        }
        if(!hasLocalActiveLiteral) {
            Variable activeFact = new Variable("activeFact", initConstraint.factType);
            QueryPlanningContext context = new QueryPlanningContext(compilationContext, existentialVariables);
            if(!head.createQueryPlan(context, new EVariable(activeFact), -1, initConstraint))
                return;
            body.createEnforcePlan(context, priority);
            /*System.out.println(this);
            for(PlanOp planOp : context.getPlanOps())
                System.out.println("    " + planOp);*/
            addPlan(new CHRSearchPlan(initConstraint, activeFact, context.getPlanOps()));
        }
    }
    
    private void addPlan(CHRSearchPlan plan) {
        plans.add(plan);
    }

    public String toString() {
        StringBuilder b = new StringBuilder();
        ExpressionToStringVisitor visitor = new ExpressionToStringVisitor(b);
        visitor.visit(this);
        return b.toString();
    }
    
}