package org.jruby.ir.dataflow.analyses;

import java.util.HashSet;
import java.util.ListIterator;
import java.util.Map;
import java.util.Set;
import org.jruby.ir.IRClosure;
import org.jruby.ir.IREvalScript;
import org.jruby.ir.IRScope;
import org.jruby.ir.Operation;
import org.jruby.ir.dataflow.DataFlowConstants;
import org.jruby.ir.dataflow.DataFlowProblem;
import org.jruby.ir.dataflow.FlowGraphNode;
import org.jruby.ir.instructions.BreakInstr;
import org.jruby.ir.instructions.CallBase;
import org.jruby.ir.instructions.ClosureReturnInstr;
import org.jruby.ir.instructions.Instr;
import org.jruby.ir.instructions.ResultInstr;
import org.jruby.ir.instructions.StoreLocalVarInstr;
import org.jruby.ir.operands.ClosureLocalVariable;
import org.jruby.ir.operands.LocalVariable;
import org.jruby.ir.operands.Operand;
import org.jruby.ir.operands.TemporaryVariable;
import org.jruby.ir.operands.Variable;
import org.jruby.ir.operands.WrappedIRClosure;
import org.jruby.ir.representations.BasicBlock;
import org.jruby.ir.util.Edge;

public class StoreLocalVarPlacementNode extends FlowGraphNode {
    public StoreLocalVarPlacementNode(DataFlowProblem prob, BasicBlock n) {
        super(prob, n);
    }

    @Override
    public void init() {
        outDirtyVars = new HashSet<LocalVariable>();

        // For rescue entries, we allocate <in> once and never clear it on each pass.
        if (getBB().isRescueEntry()) inDirtyVars = new HashSet<LocalVariable>();
    }

    public void buildDataFlowVars(Instr i) {
        // Nothing to do -- because we are going to simply use non-closure, non-self, non-block LocalVariables as our data flow variables
        // rather than build a new data flow type for it
    }

    public void initSolnForNode() {
        // For rescue entries, <in> is handled specially
        if (!getBB().isRescueEntry()) inDirtyVars = new HashSet<LocalVariable>();
    }

    public void compute_MEET(Edge e, BasicBlock source, FlowGraphNode pred) {
        StoreLocalVarPlacementNode n = (StoreLocalVarPlacementNode) pred;

        // Ignore rescue entries -- dirty vars are handled specially for these
        if (!source.isRescueEntry()) inDirtyVars.addAll(n.outDirtyVars);
    }

    public boolean applyTransferFunction() {
        IRScope scope = problem.getScope();
        boolean scopeBindingHasEscaped = scope.bindingHasEscaped();

        // Rescue node, if any
        StoreLocalVarPlacementNode rescueNode = (StoreLocalVarPlacementNode)getNonExitBBExceptionTargetNode();

        Set<LocalVariable> dirtyVars = new HashSet<LocalVariable>(inDirtyVars);

        for (Instr i : basicBlock.getInstrs()) {
            // Process calls specially -- these are the sites of binding stores!
            if (i instanceof CallBase) {
                CallBase call = (CallBase) i;
                // At this call site, a binding will get allocated if it has not been already!
                Operand o = call.getClosureArg(null);
                if (o != null && o instanceof WrappedIRClosure) {
                    // In this first pass, the current scope and the call's closure are considered
                    // independent of each other which means any variable that is used by the variable
                    // will get spilled into the binding.  This is clearly conservative, but simplifies
                    // the analysis.
                    IRClosure cl = ((WrappedIRClosure) o).getClosure();

                    // If the call is a dataflow barrier, we have to spill everything here
                    boolean spillAllVars = scopeBindingHasEscaped || call.targetRequiresCallersBinding();

                    // - If all variables have to be spilled, then those variables will no longer be dirty after the call site
                    // - If a variable is used in the closure (FIXME: Strictly only those vars that are live at the call site -- 
                    //   but we dont have this info!), it has to be spilt. So, these variables are no longer dirty after the call site.
                    // - If a variable is (re)defined in the closure, it will always be loaded after the call. So, we have to always
                    //   spill it before the call in the scenario that the closure never gets executed! So, it won't be dirty after
                    //   the call site.
                    Set<LocalVariable> newDirtyVars = new HashSet<LocalVariable>(dirtyVars);
                    for (LocalVariable v : dirtyVars) {
                        if (spillAllVars || cl.usesLocalVariable(v) || cl.definesLocalVariable(v)) {
                            newDirtyVars.remove(v);
                        }
                    }
                    dirtyVars = newDirtyVars;
                } else if (scopeBindingHasEscaped || call.targetRequiresCallersBinding()) { // Call has no closure && it requires stores
                    dirtyVars.clear();
                } else {
                    // All variables not local to the current scope have to be always spilled because of
                    // multi-threading scenarios where some other scope could load this variable concurrently.
                    //
                    // Allocate a new hash-set and modify it to get around ConcurrentModificationException on dirtyVars
                    Set<LocalVariable> newDirtyVars = new HashSet<LocalVariable>(dirtyVars);
                    for (LocalVariable v : dirtyVars) {
                        if ((v instanceof ClosureLocalVariable) && ((ClosureLocalVariable)v).definingScope != scope) {
                            newDirtyVars.remove(v);
                        }
                    }
                    dirtyVars = newDirtyVars;
                }
            }

            if (scopeBindingHasEscaped && (i.getOperation() == Operation.PUT_GLOBAL_VAR)) {
                // global-var tracing can execute closures set up in previous trace-var calls
                // in which case we would have the 'scopeBindingHasEscaped' flag set to true
                dirtyVars.clear();
            }

            // If this instruction can raise an exception and we are going to be rescued,
            // spill all dirty vars before the instruction!
            if (i.canRaiseException() && (rescueNode != null)) {
                dirtyVars.clear();
            }

            if (i instanceof ResultInstr) {
                Variable v = ((ResultInstr) i).getResult();

                // %self is local to every scope and never crosses scope boundaries and need not be spilled/refilled
                if (v instanceof LocalVariable && !((LocalVariable) v).isSelf()) dirtyVars.add((LocalVariable) v);
            }

            if (i.getOperation().isReturn()) dirtyVars.clear();
        }

        if (outDirtyVars.equals(dirtyVars)) return false;

        outDirtyVars = dirtyVars;

        return true;
    }

    @Override
    public String toString() {
        return "";
    }

    private TemporaryVariable getLocalVarReplacement(LocalVariable v, IRScope scope, Map<Operand, Operand> varRenameMap) {
         TemporaryVariable value = (TemporaryVariable)varRenameMap.get(v);
         if (value == null) {
             value = scope.getNewTemporaryVariable("%t_" + v.getName());
             varRenameMap.put(v, value);
         }
         return value;
    }

    private boolean addClosureExitStoreLocalVars(IRScope scope, ListIterator<Instr> instrs, Set<LocalVariable> dirtyVars, Map<Operand, Operand> varRenameMap) {
        boolean addedStores  = false;
        boolean isEvalScript = scope instanceof IREvalScript;
        for (LocalVariable v : dirtyVars) {
            if (isEvalScript || !(v instanceof ClosureLocalVariable) || (scope != ((ClosureLocalVariable)v).definingScope)) {
                addedStores = true;
                instrs.add(new StoreLocalVarInstr(getLocalVarReplacement(v, scope, varRenameMap), scope, v));
            }
        }
        return addedStores;
    }

    public boolean addStores(Map<Operand, Operand> varRenameMap, Set<LocalVariable> excTargetDirtyVars) {
        StoreLocalVarPlacementProblem bsp = (StoreLocalVarPlacementProblem) problem;
        IRScope scope = bsp.getScope();

        boolean addedStores            = false;
        boolean isEvalScript           = scope instanceof IREvalScript;
        boolean scopeBindingHasEscaped = scope.bindingHasEscaped();

        ListIterator<Instr> instrs    = basicBlock.getInstrs().listIterator();
        Set<LocalVariable>  dirtyVars = new HashSet<LocalVariable>(inDirtyVars);

        // Rescue node, if any
        StoreLocalVarPlacementNode rescueNode = (StoreLocalVarPlacementNode)getNonExitBBExceptionTargetNode();

        // If this is the exit BB, we need a binding store on exit only for vars that are both:
        //
        //   (a) dirty,
        //   (b) live on exit from the closure
        //       condition reqd. because the variable could be dirty but not used outside.
        //         Ex: s=0; a.each { |i| j = i+1; sum += j; }; puts sum
        //       i,j are dirty inside the block, but not used outside

        boolean amExitBB = basicBlock == scope.cfg().getExitBB();

        if (amExitBB) {
            LiveVariablesProblem lvp = (LiveVariablesProblem)scope.getDataFlowSolution(DataFlowConstants.LVP_NAME);
            java.util.Collection<LocalVariable> liveVars = lvp.getVarsLiveOnScopeExit();
            if (liveVars != null) {
                dirtyVars.retainAll(liveVars); // Intersection with variables live on exit from the scope
            } else {
                dirtyVars.clear();
            }
        }

        while (instrs.hasNext()) {
            Instr i = instrs.next();

            if (i instanceof CallBase) {
                CallBase call = (CallBase) i;
                Operand o = call.getClosureArg(null);
                if (o != null && o instanceof WrappedIRClosure) {
                    IRClosure cl = ((WrappedIRClosure) o).getClosure();

                    // Add before call -- hence instrs.previous & instrs.next
                    instrs.previous();

                    // If the call is a dataflow barrier, we have to spill everything here
                    boolean spillAllVars = scopeBindingHasEscaped || call.targetRequiresCallersBinding();

                    // Unless we have to spill everything, spill only those dirty variables that are:
                    // - used in the closure (FIXME: Strictly only those vars that are live at the call site -- but we dont have this info!)
                    Set<LocalVariable> newDirtyVars = new HashSet<LocalVariable>(dirtyVars);
                    for (LocalVariable v : dirtyVars) {
                        // We have to spill the var that is defined in the closure as well because the load var pass
                        // will attempt to load the var always.  So, if the call doesn't actually call the closure,
                        // we'll be in trouble in that scenario!
                        if (spillAllVars || cl.usesLocalVariable(v) || cl.definesLocalVariable(v)) {
                            addedStores = true;
                            instrs.add(new StoreLocalVarInstr(getLocalVarReplacement(v, scope, varRenameMap), scope, v));
                            newDirtyVars.remove(v);
                        }
                    }
                    dirtyVars = newDirtyVars;
                    instrs.next();
                } else if (scopeBindingHasEscaped || call.targetRequiresCallersBinding()) { // Call has no closure && it requires stores
                    // Add before call -- hence instrs.previous & instrs.next
                    instrs.previous();
                    for (LocalVariable v : dirtyVars) {
                        addedStores = true;
                        instrs.add(new StoreLocalVarInstr(getLocalVarReplacement(v, scope, varRenameMap), scope, v));
                    }
                    instrs.next();
                    dirtyVars.clear();
                } else {
                    instrs.previous();

                    // All variables not local to the current scope have to be always spilled because of
                    // multi-threading scenarios where some other scope could load this variable concurrently.
                    //
                    // Allocate a new hash-set and modify it to get around ConcurrentModificationException on dirtyVars
                    Set<LocalVariable> newDirtyVars = new HashSet<LocalVariable>(dirtyVars);
                    for (LocalVariable v : dirtyVars) {
                        if ((v instanceof ClosureLocalVariable) && ((ClosureLocalVariable)v).definingScope != scope) {
                            addedStores = true;
                            instrs.add(new StoreLocalVarInstr(getLocalVarReplacement(v, scope, varRenameMap), scope, v));
                            newDirtyVars.remove(v);
                        }
                    }
                    dirtyVars = newDirtyVars;
                    instrs.next();
                }
            } else if ((i instanceof ClosureReturnInstr) || (i instanceof BreakInstr)) {
                // At closure return and break instructions (both of which are exits from the closure),
                // we need a binding store on exit only for vars that are both:
                //
                //   (a) dirty,
                //   (b) live on exit from the closure
                //       condition reqd. because the variable could be dirty but not used outside.
                //         Ex: s=0; a.each { |i| j = i+1; sum += j; return if j < 5; sum += 1; }; puts sum
                //       i,j are dirty inside the block, but not used outside
                //
                // If this also happens to be exit BB, we would have intersected already earlier -- so no need to do it again!

                if (!amExitBB) {
                    LiveVariablesProblem lvp = (LiveVariablesProblem)scope.getDataFlowSolution(DataFlowConstants.LVP_NAME);
                    java.util.Collection<LocalVariable> liveVars = lvp.getVarsLiveOnScopeExit();
                    if (liveVars != null) {
                        dirtyVars.retainAll(liveVars); // Intersection with variables live on exit from the scope
                    } else {
                        dirtyVars.clear();
                    }
                }

                // Add before call
                instrs.previous();
                boolean f = addClosureExitStoreLocalVars(scope, instrs, dirtyVars, varRenameMap);
                addedStores = addedStores || f;
                instrs.next();

                // Nothing is dirty anymore -- everything that needs spilling has been spilt
                dirtyVars.clear();
            }

            if (scopeBindingHasEscaped && (i.getOperation() == Operation.PUT_GLOBAL_VAR)) {
                // global-var tracing can execute closures set up in previous trace-var calls
                // in which case we would have the 'scopeBindingHasEscaped' flag set to true
                instrs.previous();
                for (LocalVariable v : dirtyVars) {
                    addedStores = true;
                    instrs.add(new StoreLocalVarInstr(getLocalVarReplacement(v, scope, varRenameMap), scope, v));
                }
                instrs.next();
                dirtyVars.clear();
            }

            if (i.canRaiseException()) {
                if (rescueNode != null) {
                    // If exceptions will be rescued, spill every dirty var here
                    // Add before excepting instr -- hence instrs.previous & instrs.next
                    instrs.previous();
                    for (LocalVariable v : dirtyVars) {
                        addedStores = true;
                        instrs.add(new StoreLocalVarInstr(getLocalVarReplacement(v, scope, varRenameMap), scope, v));
                    }
                    instrs.next();
                    dirtyVars.clear();
                } else if (excTargetDirtyVars != null) {
                    // If exceptions won't be rescued, pass them back to be spilled in the global ensure block
                    excTargetDirtyVars.addAll(dirtyVars);
                }
            }

            if (i instanceof ResultInstr) {
                Variable v = ((ResultInstr) i).getResult();

                // %self is local to every scope and never crosses scope boundaries and need not be spilled/refilled
                if (v instanceof LocalVariable && !((LocalVariable) v).isSelf()) {
                    LocalVariable lv = (LocalVariable) v;
                    dirtyVars.add(lv);

                    // Make sure there is a replacement tmp-var allocated for lv
                    getLocalVarReplacement(lv, scope, varRenameMap);
                }
            }             
        }

        // If this is the exit BB, add binding stores for all vars that are still dirty
        if (amExitBB) {
            // Last instr could be a return -- so, move iterator one position back
            if (instrs.hasPrevious()) instrs.previous();
            boolean f = addClosureExitStoreLocalVars(scope, instrs, dirtyVars, varRenameMap);
            addedStores = addedStores || f;
        }

        return addedStores;
    }

    Set<LocalVariable> inDirtyVars;   // On entry to flow graph node:  Variables that need to be stored to the heap binding
    Set<LocalVariable> outDirtyVars;  // On exit from flow graph node: Variables that need to be stored to the heap binding
}
