/*

 * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

import com.sun.source.tree.BinaryTree;

import com.sun.source.tree.ClassTree;

import com.sun.source.tree.CompilationUnitTree;

import com.sun.source.tree.IdentifierTree;

import com.sun.source.tree.LiteralTree;

import com.sun.source.tree.PrimitiveTypeTree;

import com.sun.source.tree.Tree;

import com.sun.source.tree.VariableTree;

import com.sun.source.util.TreeScanner;

import java.util.HashSet;

import java.util.Locale;

import java.util.Set;

public class CodeBuilder {

    public static String buildCodeToGenerate(Tree t, String builder) {

        StringBuilder result = new StringBuilder();

        new TreeScanner<Void, Void>() {

            private final Set<String> usedNames = new HashSet<>();

            private String currentBuilder = builder;

            @Override

            public Void visitClass(ClassTree node, Void p) {

                result.append(currentBuilder() + "._class(\"" + node.getSimpleName() + "\", ");

                doScan("C", () -> super.visitClass(node, p));

                result.append(")");

                return null;

            }

            @Override

            public Void visitCompilationUnit(CompilationUnitTree node, Void p) {

                result.append(currentBuilder() + ".createCompilationUnitTree(");

                doScan("U", () -> super.visitCompilationUnit(node, p));

                result.append(")");

                return null;

            }

            @Override

            public Void visitVariable(VariableTree node, Void p) {

                result.append(currentBuilder() + ".field(\"" + node.getName() + "\", "); //XXX: field/vs local variable!

                doScan("T", node.getType());

                result.append(", ");

                doScan("F", () -> {

                    //TODO: modifiers....

                    if (node.getInitializer() != null) {

                        result.append(currentBuilder() + ".init(");

                        doScan("E", node.getInitializer());

                        result.append(")");

                    }

                });

                result.append(")");

                return null;

            }

            @Override

            public Void visitPrimitiveType(PrimitiveTypeTree node, Void p) {

                result.append(currentBuilder() + "._" + node.getPrimitiveTypeKind().name().toLowerCase(Locale.ROOT) + "()");

                return null;

            }

            @Override

            public Void visitLiteral(LiteralTree node, Void p) {

                result.append(currentBuilder() + ".literal(" + node.getValue() + ")");

                return null;

            }

            @Override

            public Void visitBinary(BinaryTree node, Void p) {

                switch (node.getKind()) {

                    case PLUS:

                        result.append(currentBuilder() + ".plus(");

                        doScan("E", node.getLeftOperand());

                        result.append(", ");

                        doScan("E", node.getRightOperand());

                        result.append(")");

                        break;

                    default: throw new IllegalStateException("Not handled: " + node.getKind());

                }

                return null;

            }

            @Override

            public Void visitIdentifier(IdentifierTree node, Void p) {

                result.append(currentBuilder() + ".ident(\"" + node.getName() + "\")");

                return null;

            }

            private String currentBuilder() {

                if (currentBuilder != null) {

                    String res = currentBuilder;

                    currentBuilder = null;

                    return res;

                }

                return "";

            }

            private void doScan(String preferredBuilderName, Tree... subTreesToScan) {

                doScan(preferredBuilderName, () -> {

                    for (Tree tree : subTreesToScan) {

                        scan(tree, null);

                    }

                });

            }

            private void doScan(String preferredBuilderName, Runnable scan) {

                String prevBuilder = currentBuilder;

                String builder = inferBuilderName(preferredBuilderName);

                try {

                    result.append(builder + " -> ");

                    int len = result.length();

                    currentBuilder = builder;

                    scan.run();

                    if (result.length() == len) {

                        result.append("{}");

                    }

                } finally {

                    currentBuilder = prevBuilder;

                    usedNames.remove(builder);

                }

            }

            private String inferBuilderName(String preferredBuilderName) {

                Integer idx = null;

                while (true) {

                    String thisBuilder = preferredBuilderName + (idx != null ? idx : "");

                    if (usedNames.add(thisBuilder)) {

                        return thisBuilder;

                    }

                    idx = idx != null ? idx + 1 : 1;

                }

            }

        }.scan(t, null);

        return result.toString();

    }

}