From 8a61361eae582669d163e1cdd032a314a012a365 Mon Sep 17 00:00:00 2001
From: XmiliaH <45106915+XmiliaH@users.noreply.github.com>
Date: Mon, 15 Jan 2024 17:41:55 +0100
Subject: Add fuzzer (#58)

* Add fuzzer

* Add fuzzer

---------

Co-authored-by: Cliff Click <cliffc@acm.org>
---
 .../java/com/seaofnodes/simple/Fuzzer08Test.java   | 154 +++++++++++
 .../test/java/com/seaofnodes/simple/Reducer.java   | 119 ++++++++
 .../com/seaofnodes/simple/ScriptGenerator.java     | 305 +++++++++++++++++++++
 3 files changed, 578 insertions(+)
 create mode 100644 chapter08/src/test/java/com/seaofnodes/simple/Fuzzer08Test.java
 create mode 100644 chapter08/src/test/java/com/seaofnodes/simple/Reducer.java
 create mode 100644 chapter08/src/test/java/com/seaofnodes/simple/ScriptGenerator.java

diff --git a/chapter08/src/test/java/com/seaofnodes/simple/Fuzzer08Test.java b/chapter08/src/test/java/com/seaofnodes/simple/Fuzzer08Test.java
new file mode 100644
index 00000000..d8f10eef
--- /dev/null
+++ b/chapter08/src/test/java/com/seaofnodes/simple/Fuzzer08Test.java
@@ -0,0 +1,154 @@
+package com.seaofnodes.simple;
+
+import com.seaofnodes.simple.node.Node;
+import com.seaofnodes.simple.node.StopNode;
+import org.junit.Ignore;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.Random;
+
+import static org.junit.Assert.assertTrue;
+
+public class Fuzzer08Test {
+
+    private final ArrayList<Throwable> exceptions = new ArrayList<>();
+
+    public static StopNode parse(String script, boolean disablePeeps) {
+        var parser = new Parser(script);
+        Node._disablePeephole = disablePeeps;
+        return parser.parse();
+    }
+
+    private static boolean sameException(Throwable e1, Throwable e2) {
+        if (e1 == null || e2 == null) return e1 == e2;
+        if (e1.getClass() != e2.getClass()) return false;
+        if (e1.getMessage() != null && e2.getMessage() != null && !e1.getMessage().equals(e2.getMessage())) return false;
+        var s1 = e1.getStackTrace();
+        var s2 = e2.getStackTrace();
+        if (s1 != null && s1.length > 0 && s2 != null && s2.length > 0 && !s1[0].equals(s2[0])) return false;
+        if (!sameException(e1.getCause(), e2.getCause())) return false;
+        var o1 = e1.getSuppressed();
+        var o2 = e2.getSuppressed();
+        if (o1 == null || o2 == null || o1.length != o2.length) return o1 == o2;
+        for (int i=0; i<o1.length; i++) {
+            if (!sameException(o1[i], o2[i])) return false;
+        }
+        return true;
+    }
+
+    private void recordException(Throwable e, String script) {
+        for (var ex : exceptions) {
+            if (sameException(ex, e)) return;
+        }
+        exceptions.add(e);
+        System.out.println("===========================");
+        System.out.println("========== Stack ==========");
+        System.out.flush();
+        e.printStackTrace(System.err);
+        System.err.flush();
+        System.out.println("========== Code ===========");
+        System.out.println(script);
+        System.out.println("========= Reduced =========");
+        System.out.println(Reducer.reduce(script, false));
+        System.out.flush();
+    }
+
+    private void checkGraphs(StopNode stop1, StopNode stop2, long in, String script) {
+        long e1;
+        try {
+            e1 = GraphEvaluator.evaluate(stop1, in);
+        } catch (RuntimeException e) {
+            if (!e.getMessage().equals("Timeout")) recordException(e, script);
+            return;
+        }
+        long e2;
+        try {
+            e2 = GraphEvaluator.evaluate(stop2, in);
+        } catch (RuntimeException e) {
+            if (!e.getMessage().equals("Timeout")) recordException(e, script);
+            return;
+        }
+        if (e1 != e2) {
+            recordException(new RuntimeException("Different calculations " + e1 + " vs " + e2), script);
+        }
+    }
+
+    private void check(String script, boolean valid) {
+        StopNode stop1;
+        try {
+            stop1 = parse(script, true);
+        } catch (Throwable e1) {
+            try {
+                parse(script, false);
+                var rt = new RuntimeException("Exception only without peeps " + e1.getMessage());
+                rt.addSuppressed(e1);
+                recordException(rt, script);
+                return;
+            } catch (Throwable e2) {
+                if (e1.getClass() == e2.getClass() && e1.getMessage().equals(e2.getMessage())) {
+                    if (valid || e1.getClass() != RuntimeException.class) recordException(e1, script);
+                    return;
+                }
+                var rt = new RuntimeException("Bad different exceptions " + e1.getMessage() + " & " + e2.getMessage());
+                rt.addSuppressed(e1);
+                rt.addSuppressed(e2);
+                recordException(rt, script);
+                return;
+            }
+        }
+        StopNode stop2;
+        try {
+            stop2 = parse(script, false);
+        } catch (Throwable e2) {
+            var rt = new RuntimeException("Exception only with peeps " + e2.getMessage());
+            rt.addSuppressed(e2);
+            recordException(rt, script);
+            return;
+        }
+        checkGraphs(stop1, stop2, 0, script);
+        checkGraphs(stop1, stop2, 1, script);
+        checkGraphs(stop1, stop2, 10, script);
+    }
+
+    private void checkParsing(String script) {
+        try {
+            parse(script, false);
+        } catch (Throwable e) {
+            recordException(e, script);
+        }
+    }
+
+    public void fuzzParser(long seed) {
+        var rand = new Random(seed);
+        var sb = new StringBuilder();
+        new ScriptGenerator(rand, sb, true).genProgram();
+        checkParsing(sb.toString());
+    }
+
+    public void fuzzPeeps(long seed) {
+        var rand = new Random(seed);
+        var sb = new StringBuilder();
+        var valid = new ScriptGenerator(rand, sb, false).genProgram();
+        check(sb.toString(), valid);
+    }
+
+    @Test
+    @Ignore
+    public void fuzzParser() {
+        var fuzzer = new Fuzzer08Test();
+        for (int i=0; i<1000000; i++)
+            fuzzer.fuzzParser(i);
+        assertTrue(fuzzer.exceptions.isEmpty());
+    }
+
+    @Test
+    @Ignore
+    public void fuzzPeeps() {
+        var fuzzer = new Fuzzer08Test();
+        for (int i=0; i<1000000; i++)
+            fuzzer.fuzzPeeps(i);
+        assertTrue(fuzzer.exceptions.isEmpty());
+    }
+
+}
diff --git a/chapter08/src/test/java/com/seaofnodes/simple/Reducer.java b/chapter08/src/test/java/com/seaofnodes/simple/Reducer.java
new file mode 100644
index 00000000..38a4502c
--- /dev/null
+++ b/chapter08/src/test/java/com/seaofnodes/simple/Reducer.java
@@ -0,0 +1,119 @@
+package com.seaofnodes.simple;
+
+import com.seaofnodes.simple.node.Node;
+
+import java.util.regex.Pattern;
+
+public class Reducer {
+
+    private record Replace(Pattern p, String r) {}
+
+    private static final Replace[] REPLACEMENTS = {
+            new Replace(Pattern.compile("(?<=[+\\-*/<>=(])--"), ""),
+            new Replace(Pattern.compile("\\b--"), "+"),
+            new Replace(Pattern.compile("\\b\\+-"), "-"),
+            new Replace(Pattern.compile("\\bfalse\\b"), "0"),
+            new Replace(Pattern.compile("\\btrue\\b"), "1"),
+            new Replace(Pattern.compile("-"), ""),
+            new Replace(Pattern.compile("(?<![+\\-*/<>=])(?:-|\\*|/|>=|<=|>|<|!=|==)(?![+\\-*/<>=])"), "+"),
+            new Replace(Pattern.compile("\\{(?:[^{}]|\\{})+}"), "{}"),
+            new Replace(Pattern.compile("\\{((?:[^{}]|\\{})+)}"), "$1"),
+            new Replace(Pattern.compile("\\(([^()]+)\\)"), "$1"),
+            new Replace(Pattern.compile("\\b\\w+\\b"), "1"),
+            new Replace(Pattern.compile("\\b\\w+\\b"), "0"),
+            new Replace(Pattern.compile("\\d+\\+"), ""),
+            new Replace(Pattern.compile("\\+\\d+"), ""),
+            new Replace(Pattern.compile("(?<=\\n|^)[^\\n]*(?=\\n|$)"), "\n"),
+            new Replace(Pattern.compile("\\n+"), "\n"),
+            new Replace(Pattern.compile("^\\n+|\\n+$"), ""),
+            new Replace(Pattern.compile("else "), ""),
+            new Replace(Pattern.compile("\\bif\\([^()]+\\) *"), ""),
+            new Replace(Pattern.compile("\\bwhile\\([^()]+\\) *"), ""),
+    };
+
+    private static boolean sameException(Throwable e1, Throwable e2) {
+        if (e1 == null || e2 == null) return e1 == e2;
+        if (e1.getClass() != e2.getClass()) return false;
+        if (e1.getMessage() != null && e2.getMessage() != null && !e1.getMessage().equals(e2.getMessage())) return false;
+        var s1 = e1.getStackTrace();
+        var s2 = e2.getStackTrace();
+        if (s1 == null || s1.length == 0 || s2 == null || s2.length == 0) return true;
+        return s1[0].equals(s2[0]);
+    }
+
+    private final boolean disablePeeps;
+
+    private Reducer(boolean disablePeeps) {
+        this.disablePeeps = disablePeeps;
+    }
+
+    private Throwable parse(String script) {
+        try {
+            var parser = new Parser(script);
+            Node._disablePeephole = disablePeeps;
+            parser.parse();
+            return null;
+        } catch (Throwable e) {
+            return e;
+        }
+    }
+
+    private String doReplacement(String script, Throwable ex, Pattern pattern, String with) {
+        var matcher = pattern.matcher(script);
+        var sb = new StringBuilder();
+        int last = 0;
+        while (matcher.find()) {
+            var pos = sb.length();
+            matcher.appendReplacement(sb, with);
+            var tail = sb.length();
+            matcher.appendTail(sb);
+            var ex2 = parse(sb.toString());
+            if (sameException(ex, ex2)) {
+                sb.setLength(tail);
+            } else {
+                sb.setLength(pos);
+                sb.append(script, last, matcher.end());
+            }
+            last = matcher.end();
+        }
+        matcher.appendTail(sb);
+        return sb.toString();
+    }
+
+    private String cleanVariables(String script, Throwable ex) {
+        var matcher = Pattern.compile("\\bint ([0-9a-zA-Z_]+)").matcher(script);
+        int num = 0;
+        while (matcher.find()) {
+            var var = matcher.group(1);
+            if (var.matches("v\\d+")) continue;
+            while (script.contains("v"+num)) num++;
+            var n = script.replaceAll("\\b"+var+"\\b", "v" + num);
+            var ex2 = parse(n);
+            if (sameException(ex, ex2)) {
+                script = n;
+            }
+        }
+        return script;
+    }
+
+    private String doAllReplacements(String script, Throwable ex) {
+        for (var replace: REPLACEMENTS) {
+            script = doReplacement(script, ex, replace.p, replace.r);
+        }
+        return script;
+    }
+
+    public static String reduce(String script, boolean disablePeeps) {
+        var reducer = new Reducer(disablePeeps);
+        var ex = reducer.parse(script);
+        if (ex == null) return "return 0;";
+        String old;
+        do {
+            old = script;
+            script = reducer.doAllReplacements(script, ex);
+            script = reducer.cleanVariables(script, ex);
+        } while (!script.equals(old));
+        return script;
+    }
+
+}
diff --git a/chapter08/src/test/java/com/seaofnodes/simple/ScriptGenerator.java b/chapter08/src/test/java/com/seaofnodes/simple/ScriptGenerator.java
new file mode 100644
index 00000000..8c51089c
--- /dev/null
+++ b/chapter08/src/test/java/com/seaofnodes/simple/ScriptGenerator.java
@@ -0,0 +1,305 @@
+package com.seaofnodes.simple;
+
+import com.seaofnodes.simple.node.ScopeNode;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.Random;
+
+public class ScriptGenerator {
+
+    @SuppressWarnings("unchecked")
+    private static HashSet<String> getKeywords() {
+        try {
+            var field = Parser.class.getDeclaredField("KEYWORDS");
+            field.setAccessible(true);
+            return (HashSet<String>) field.get(new Parser(""));
+        } catch (Throwable e) {
+            throw new ExceptionInInitializerError(e);
+        }
+    }
+
+    private static final int INDENTATION = 4;
+    private static final String VAR_CHARS = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_0123456789";
+    private static final HashSet<String> KEYWORDS = getKeywords();
+
+    private static final int FLAG_STOP = 0x01;
+    private static final int FLAG_IF_WITHOUT_ELSE = 0x02;
+
+    private final Random random;
+    private int indentation = 0;
+    private final StringBuilder sb;
+    private int loopDepth = 0;
+    private int currScopeStart = 0;
+    private int depth = 0;
+    private int exprDepth = 3;
+    private final ArrayList<String> variables = new ArrayList<>();
+    private final boolean generateValid;
+    private boolean maybeInvalid = false;
+
+    public ScriptGenerator(Random random, StringBuilder sb, boolean generateValid) {
+        this.random = random;
+        this.sb = sb;
+        this.generateValid = generateValid;
+    }
+
+    private int randLog(int max) {
+        max--;
+        int n = 1 << max;
+        var num = random.nextInt(n);
+        for(int i=max-1; i>=0; i--) {
+            if ((num & (1 << i))!=0) return max-i-1;
+        }
+        return max;
+    }
+
+    private StringBuilder printIndentation() {
+        return sb.repeat(' ', indentation);
+    }
+
+    public boolean genProgram() {
+        this.maybeInvalid = false;
+        variables.add(ScopeNode.ARG0);
+        depth = random.nextInt(9) + 1;
+        currScopeStart = variables.size();
+        if ((genStatements() & FLAG_STOP) != 0)
+            genReturn();
+        return !this.maybeInvalid;
+    }
+
+    public int genStatements() {
+        var num = random.nextInt(10);
+        for (int i=0; i<num; i++) {
+            printIndentation();
+            var stop = genStatement();
+            sb.append("\n");
+            if ((stop & FLAG_STOP) != 0) return stop;
+        }
+        return 0;
+    }
+
+    public int genStatement() {
+        return switch (random.nextInt(10)) {
+            case 1 -> genBlock();
+            case 2 -> genIf();
+            case 3 -> genWhile();
+            case 4, 5 -> genDecl();
+            case 6, 7, 8 -> genAssignment();
+            default -> genExit();
+        };
+    }
+
+    public int genStatementBlock() {
+        indentation += INDENTATION;
+        int res;
+        if (depth == 0) {
+            res = random.nextBoolean() ? genAssignment() : genExit();
+        } else {
+            depth--;
+            res = switch (random.nextInt(10)) {
+                case 1, 2, 3, 4, 5 -> {
+                    depth++;
+                    indentation -= INDENTATION;
+                    var ret = genBlock();
+                    indentation += INDENTATION;
+                    depth--;
+                    yield ret;
+                }
+                case 6 -> genIf();
+                case 7 -> genWhile();
+                case 8 -> genAssignment();
+                default -> genExit();
+            };
+            depth++;
+        }
+        indentation -= INDENTATION;
+        return res;
+    }
+
+    public int genExit() {
+        if (loopDepth == 0 && generateValid) return genReturn();
+        return switch (random.nextInt(7)) {
+            case 0,1,2 -> {
+                if (loopDepth == 0) maybeInvalid = true;
+                sb.append("continue;");
+                yield FLAG_STOP;
+            }
+            case 3,4,5 -> {
+                if (loopDepth == 0) maybeInvalid = true;
+                sb.append("break;");
+                yield FLAG_STOP;
+            }
+            default -> genReturn();
+        };
+    }
+
+    public int genBlock() {
+        if (depth == 0) {
+            sb.append("{}");
+            return 0;
+        }
+        depth--;
+        int oldCSS = currScopeStart;
+        currScopeStart = variables.size();
+        sb.append("{\n");
+        indentation += INDENTATION;
+        var stop = genStatements();
+        indentation -= INDENTATION;
+        printIndentation().append("}");
+        while (variables.size() > currScopeStart)
+            variables.removeLast();
+        currScopeStart = oldCSS;
+        depth++;
+        return stop & ~FLAG_IF_WITHOUT_ELSE;
+    }
+
+    public int genIf() {
+        sb.append("if(");
+        genExpression();
+        sb.append(") ");
+        var stop = genStatementBlock();
+        if ((stop & FLAG_IF_WITHOUT_ELSE) == 0 && random.nextInt(10) > 3) {
+            sb.append("\n");
+            printIndentation().append("else ");
+            stop &= genStatementBlock();
+        } else {
+            stop = FLAG_IF_WITHOUT_ELSE;
+        }
+        return stop;
+    }
+
+    public int genWhile() {
+        sb.append("while(");
+        genExpression();
+        sb.append(") ");
+        loopDepth++;
+        var stop = genStatementBlock();
+        loopDepth--;
+        return stop & FLAG_IF_WITHOUT_ELSE;
+    }
+
+    private StringBuilder getRandomName() {
+        int len = random.nextInt(10) + 1;
+        StringBuilder sb = new StringBuilder(len);
+        sb.append(VAR_CHARS.charAt(random.nextInt(VAR_CHARS.length()-10)));
+        for (int i=1; i<len; i++)
+            sb.append(VAR_CHARS.charAt(random.nextInt(VAR_CHARS.length())));
+        return sb;
+    }
+
+    private String getVarName() {
+        if (currScopeStart > 0 && random.nextInt(10) > 7) {
+            var v = variables.get(random.nextInt(currScopeStart));
+            if (variables.lastIndexOf(v) < currScopeStart) return v;
+            if (!generateValid) {
+                maybeInvalid = true;
+                return v;
+            }
+        }
+        StringBuilder sb = getRandomName();
+        var v = sb.toString();
+        if (!generateValid && (KEYWORDS.contains(v) || variables.lastIndexOf(v) >= currScopeStart)) {
+            maybeInvalid = true;
+            return v;
+        }
+        while (KEYWORDS.contains(v) || variables.lastIndexOf(v) >= currScopeStart) {
+            sb.append(VAR_CHARS.charAt(random.nextInt(VAR_CHARS.length())));
+            v = sb.toString();
+        }
+        return v;
+    }
+
+    public int genDecl() {
+        String name = getVarName();
+        sb.append("int ").append(name).append("=");
+        genExpression();
+        sb.append(";");
+        variables.add(name);
+        return 0;
+    }
+
+    public int genAssignment() {
+        if (variables.isEmpty()) return genDecl();
+        genVariable();
+        sb.append("=");
+        genExpression();
+        sb.append(";");
+        return 0;
+    }
+
+    public int genReturn() {
+        sb.append("return ");
+        genExpression();
+        sb.append(";");
+        return FLAG_STOP;
+    }
+
+    private static final String[] EXPRESSIONS = {"==", "!=", "<", "<=", ">", ">=", "+", "-", "*", "/"};
+    private static final String[] UNARY = {"-"};
+
+    public void genExpression() {
+        var num = randLog(10);
+        while(num-->0) {
+            genUnary();
+            sb.append(EXPRESSIONS[random.nextInt(EXPRESSIONS.length)]);
+        }
+        genUnary();
+    }
+
+    public void genUnary() {
+        var num = randLog(6);
+        while(num-->0) {
+            sb.append(UNARY[random.nextInt(UNARY.length)]);
+        }
+        genPrimary();
+    }
+
+    public void genPrimary() {
+        switch (random.nextInt(10)) {
+            case 0:
+                sb.append("true");
+                break;
+            case 1:
+                sb.append("false");
+                break;
+            case 2:
+                if (exprDepth == 0) {
+                    if (random.nextBoolean()) {
+                        genNumber();
+                    } else {
+                        genVariable();
+                    }
+                } else {
+                    sb.append("(");
+                    exprDepth--;
+                    genExpression();
+                    exprDepth++;
+                    sb.append(")");
+                }
+                break;
+            case 3, 4, 5, 6:
+                genNumber();
+                break;
+            default:
+                genVariable();
+        }
+    }
+
+    public void genNumber() {
+        sb.append(random.nextInt(100));
+    }
+
+    public void genVariable() {
+        if (!generateValid && random.nextInt(100)>97) {
+            sb.append(getRandomName());
+            maybeInvalid = true;
+            return;
+        }
+        if (variables.isEmpty()) {
+            genNumber();
+        } else {
+            sb.append(variables.get(random.nextInt(variables.size())));
+        }
+    }
+
+}
-- 
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