package org.simantics.scl.compiler.internal.codegen.optimization;

import org.simantics.scl.compiler.common.names.Name;
import org.simantics.scl.compiler.common.names.Names;
import org.simantics.scl.compiler.constants.SCLConstant;
import org.simantics.scl.compiler.internal.codegen.analysis.StatementBrowser;
import org.simantics.scl.compiler.internal.codegen.references.BoundVar;
import org.simantics.scl.compiler.internal.codegen.references.Val;
import org.simantics.scl.compiler.internal.codegen.references.ValRef;
import org.simantics.scl.compiler.internal.codegen.ssa.SSABlock;
import org.simantics.scl.compiler.internal.codegen.ssa.SSAStatement;
import org.simantics.scl.compiler.internal.codegen.ssa.statements.LetApply;
import org.simantics.scl.compiler.internal.codegen.utils.SSASimplificationContext;

public enum FoldlBuildFusion implements Optimization {
    INSTANCE;
    
    private static class Analysis extends StatementBrowser {
        
        @Override
        protected void unanalyzedBrowse() {
            //System.out.println("- unanalyzedBrowse");
            stopBrowse();
        }
        
        @Override
        protected void handleLoop(SSABlock block,
                SSAStatement recursiveStatement) {
            //System.out.println("- loop");
            stopBrowse();
        }
        
        @Override
        protected void visitStatement(SSAStatement statement) {
            if(statement instanceof LetApply) {
                LetApply apply = (LetApply)statement;
                if(apply.hasEffect()) {
                    //System.out.println("- effectful statement between");
                    stopBrowse();
                }
            }
        }
                
    }
    
    @Override
    public void inline(SSASimplificationContext context, LetApply foldlApplication) {        
        ValRef[] foldlParameters = foldlApplication.getParameters();
        if(foldlParameters.length != 3) // TODO case parameters.length > 3
            return;
        Val list = foldlParameters[2].getBinding();
        if(!(list instanceof BoundVar))
            return;
        if(list.hasMoreThanOneOccurences())
            return;
        BoundVar listVar = (BoundVar)list;
        if(!(listVar.getParent() instanceof LetApply))
            return;
        LetApply buildApplication = (LetApply)listVar.getParent();
                
        { // Check that buildApplication.getFunction() is Prelude.build
            if(buildApplication.getParameters().length != 1)
                return;
            Val buildFunction = buildApplication.getFunction().getBinding();
            if(!(buildFunction instanceof SCLConstant))
                return;
            if(((SCLConstant)buildFunction).getName() != Names.Prelude_build)
                return;
        }

        if(buildApplication.hasEffect() && foldlApplication.hasEffect())
            return;
        
        Analysis analysis = new Analysis();
        analysis.browseBetween(buildApplication, foldlApplication);
        if(analysis.isStopped())
            return;
        
        /*PrintingContext cx = new PrintingContext();
        cx.append("listDef: ");
        listDef.toString(cx);
        cx.append("apply: ");
        apply.toString(cx);*/
                
        foldlApplication.setParameters(new ValRef[] {foldlParameters[1], foldlParameters[0]});
        foldlParameters[2].remove();
        ValRef foldlFunctionRef = foldlApplication.getFunction();
        foldlApplication.setFunction(buildApplication.getParameters()[0].createOccurrence(
                foldlFunctionRef.getTypeParameters()[0], foldlFunctionRef.getTypeParameters()[2]));
        foldlFunctionRef.remove();        
        buildApplication.remove();
        
        /*cx.append("transformed apply: ");
        apply.toString(cx);
        System.out.println(cx.toString());*/
        
        context.markModified("foldl/build");
    }
}