feat(objectionary#284): add first implementation for If node

src/main/java/org/eolang/opeo/ast/If.java

@@ -0,0 +1,138 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016-2023 Objectionary.com
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package org.eolang.opeo.ast;
+
+import java.util.List;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+import lombok.EqualsAndHashCode;
+import lombok.ToString;
+import org.eolang.jeo.representation.xmir.XmlNode;
+import org.objectweb.asm.Opcodes;
+import org.xembly.Directive;
+import org.xembly.Directives;
+
+/**
+ * If ast node.
+ * @since 0.2
+ */
+@ToString
+@EqualsAndHashCode
+public final class If implements AstNode {
+
+    /**
+     * First value to compare.
+     */
+    private final AstNode first;
+
+    /**
+     * Second value to compare.
+     */
+    private final AstNode second;
+
+    /**
+     * Where to jump if the comparison is true.
+     */
+    private final Label target;
+
+    /**
+     * Constructor.
+     * @param node XMIR node.
+     */
+    public If(final XmlNode node, Function<XmlNode, AstNode> search) {
+        this(If.xfirst(node, search), If.xsecond(node, search), If.xtarget(node));
+    }
+
+    /**
+     * Constructor.
+     * @param first First value.
+     * @param second Second value.
+     * @param target Target label.
+     */
+    public If(
+        final AstNode first,
+        final AstNode second,
+        final Label target
+    ) {
+        this.first = first;
+        this.second = second;
+        this.target = target;
+    }
+
+    @Override
+    public List<AstNode> opcodes() {
+        return Stream.concat(
+            Stream.concat(
+                this.first.opcodes().stream(),
+                this.second.opcodes().stream()
+            ),
+            Stream.of(new Opcode(Opcodes.IF_ICMPGT, this.target))
+        ).collect(Collectors.toList());
+    }
+
+    @Override
+    public Iterable<Directive> toXmir() {
+        return new Directives()
+            .add("o").attr("base", ".if")
+            .add("o").attr("base", ".gt")
+            .append(this.first.toXmir())
+            .append(this.second.toXmir())
+            .up()
+            .append(this.target.toXmir())
+            .add("o").attr("base", "nop").up()
+            .up();
+    }
+
+    /**
+     * Extracts the first value.
+     * @param node XMIR node where to extract the value.
+     * @return Value.
+     */
+    private static AstNode xfirst(final XmlNode node, Function<XmlNode, AstNode> search) {
+        return search.apply(node.child("base", ".gt").firstChild());
+    }
+
+    /**
+     * Extracts the second value.
+     * @param node XMIR node where to extract the value.
+     * @return Value.
+     */
+    private static AstNode xsecond(final XmlNode node, Function<XmlNode, AstNode> search) {
+        final List<XmlNode> children = node.child("base", ".gt").children()
+            .collect(Collectors.toList());
+        return search.apply(children.get(children.size() - 1));
+
+    }
+
+    /**
+     * Extracts the target label.
+     * @param node XMIR node where to extract the label.
+     * @return Label.
+     */
+    private static Label xtarget(final XmlNode node) {
+        return new Label(node.child("base", "label"));
+    }
+
+}

src/main/java/org/eolang/opeo/ast/Label.java

@@ -25,6 +25,8 @@
 
 import java.util.Collections;
 import java.util.List;
+import lombok.EqualsAndHashCode;
+import lombok.ToString;
 import org.eolang.jeo.representation.directives.DirectivesData;
 import org.eolang.jeo.representation.xmir.AllLabels;
 import org.eolang.jeo.representation.xmir.HexString;
@@ -35,6 +37,8 @@
  * Label ast node.
  * @since 0.1
  */
+@ToString
+@EqualsAndHashCode
 public final class Label implements AstNode {
 
     /**

src/main/java/org/eolang/opeo/decompilation/handlers/IfHandler.java

@@ -1,11 +1,31 @@
 package org.eolang.opeo.decompilation.handlers;
 
+import org.eolang.opeo.ast.AstNode;
+import org.eolang.opeo.ast.If;
+import org.eolang.opeo.ast.Label;
+import org.eolang.opeo.ast.Opcode;
 import org.eolang.opeo.decompilation.DecompilerState;
 import org.eolang.opeo.decompilation.InstructionHandler;
+import org.eolang.opeo.decompilation.OperandStack;
+import org.objectweb.asm.Opcodes;
 
+/**
+ * If instruction handler.
+ * [value1, value2] → []
+ * If value1 is greater than value2, branch to instruction at branchoffset
+ * (signed short constructed from unsigned bytes branchbyte1 << 8 | branchbyte2)
+ * @since 0.2
+ */
 public final class IfHandler implements InstructionHandler {
     @Override
     public void handle(final DecompilerState state) {
+        if (state.instruction().opcode() == Opcodes.IF_ICMPGT) {
+            final OperandStack stack = state.stack();
+            final AstNode first = stack.pop();
+            final AstNode second = stack.pop();
+            final Label operand = (Label) state.operand(0);
+            stack.push(new If(first, second, operand));
 
+        }
     }
 }

src/test/java/org/eolang/opeo/ast/IfTest.java

@@ -0,0 +1,113 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016-2023 Objectionary.com
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package org.eolang.opeo.ast;
+
+import com.jcabi.xml.XMLDocument;
+import org.eolang.jeo.representation.xmir.XmlNode;
+import org.hamcrest.MatcherAssert;
+import org.hamcrest.Matchers;
+import org.junit.jupiter.api.Test;
+import org.objectweb.asm.Opcodes;
+import org.xembly.ImpossibleModificationException;
+import org.xembly.Xembler;
+
+/**
+ * Test case for {@link If}.
+ * @since 0.2
+ */
+class IfTest {
+
+    /**
+     * Xmir for the 'if' statement.
+     */
+    private static final String XMIR = String.join(
+        "\n",
+        "<?xml version='1.0' encoding='UTF-8'?>",
+        "<o base='.if'>",
+        "   <o base='.gt'>",
+        "      <o base='int' data='bytes'>00 00 00 00 00 00 00 01</o>",
+        "      <o base='int' data='bytes'>00 00 00 00 00 00 00 02</o>",
+        "   </o>",
+        "   <o base='label' data='bytes'>C3 BF</o>",
+        "   <o base='nop'/>",
+        "</o>",
+        ""
+    );
+
+    @Test
+    void convertsIfStatementToXmir() throws ImpossibleModificationException {
+        MatcherAssert.assertThat(
+            "Can convert 'if' statement to correct XMIR",
+            new XMLDocument(
+                new Xembler(
+                    new If(
+                        new Literal(1), new Literal(2), new Label("FF")
+                    ).toXmir()
+                ).xml()
+            ),
+            Matchers.equalTo(new XMLDocument(IfTest.XMIR))
+        );
+    }
+
+    @Test
+    void createsIfStatementFromXmir() {
+        MatcherAssert.assertThat(
+            "Can create 'if' statement from XMIR",
+            new If(new XmlNode(IfTest.XMIR), xml -> {
+                final AstNode result;
+                if (xml.text().contains("1")) {
+                    result = new Literal(1);
+                } else {
+                    result = new Literal(2);
+                }
+                return result;
+            }),
+            Matchers.equalTo(
+                new If(
+                    new Literal(1),
+                    new Literal(2),
+                    new Label("C3 BF")
+                )
+            )
+        );
+    }
+
+    @Test
+    void convertsToOpcodes() {
+        final Label label = new Label("C3 BF");
+        MatcherAssert.assertThat(
+            "Can convert 'if' statement to opcodes",
+            new If(
+                new Literal(1),
+                new Literal(2),
+                label
+            ).opcodes(),
+            Matchers.hasItems(
+                new Opcode(Opcodes.ICONST_1),
+                new Opcode(Opcodes.ICONST_2),
+                new Opcode(Opcodes.IF_ICMPGT, label)
+            )
+        );
+    }
+}