Text Diff Tool (java, written by Claude Code)

--- /dev/null
+++ b/src/main/java/TextDiff.java
@@ -0,0 +1,397 @@
+import com.github.difflib.DiffUtils;
+import com.github.difflib.UnifiedDiffUtils;
+import com.github.difflib.patch.AbstractDelta;
+import com.github.difflib.patch.DeltaType;
+import com.github.difflib.patch.Patch;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializationFeature;
+import com.fasterxml.jackson.databind.node.ObjectNode;
+
+import java.io.*;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.util.*;
+
+/**
+ * Text Diff Tool - Compares text files showing additions, deletions, and modifications.
+ * Supports unified, side-by-side, and HTML output formats.
+ * Uses java-diff-utils for diff computation and Jackson for JSON output.
+ */
+public class TextDiff {
+
+    private final List<String> file1Lines;
+    private final List<String> file2Lines;
+    private final String file1Path;
+    private final String file2Path;
+    private final Patch<String> patch;
+    private final int contextLines;
+    private final ObjectMapper mapper;
+
+    public TextDiff(String file1Path, String file2Path, int contextLines) throws IOException {
+        this.file1Path = file1Path;
+        this.file2Path = file2Path;
+        this.contextLines = contextLines;
+        this.file1Lines = Files.readAllLines(Paths.get(file1Path), StandardCharsets.UTF_8);
+        this.file2Lines = Files.readAllLines(Paths.get(file2Path), StandardCharsets.UTF_8);
+        this.patch = DiffUtils.diff(file1Lines, file2Lines);
+        this.mapper = new ObjectMapper().enable(SerializationFeature.INDENT_OUTPUT);
+    }
+
+    /**
+     * Generate unified diff output.
+     */
+    public List<String> getUnifiedDiff() {
+        return UnifiedDiffUtils.generateUnifiedDiff(
+                file1Path, file2Path, file1Lines, patch, contextLines
+        );
+    }
+
+    /**
+     * Display unified diff with ANSI color codes.
+     */
+    public void displayUnified(PrintStream out) {
+        List<String> unifiedDiff = getUnifiedDiff();
+        if (unifiedDiff.isEmpty()) {
+            out.println("\u001B[32mFiles are identical.\u001B[0m");
+            return;
+        }
+        out.println("=== Unified Diff ===");
+        for (String line : unifiedDiff) {
+            if (line.startsWith("+++") || line.startsWith("---")) {
+                out.println("\u001B[1m" + line + "\u001B[0m");
+            } else if (line.startsWith("@@")) {
+                out.println("\u001B[36m" + line + "\u001B[0m");
+            } else if (line.startsWith("+")) {
+                out.println("\u001B[32m" + line + "\u001B[0m");
+            } else if (line.startsWith("-")) {
+                out.println("\u001B[31m" + line + "\u001B[0m");
+            } else {
+                out.println(line);
+            }
+        }
+    }
+
+    /**
+     * Display side-by-side diff.
+     */
+    public void displaySideBySide(PrintStream out, int width) {
+        int colWidth = (width - 7) / 2;
+        String separator = " | ";
+        String headerFmt = "%-" + colWidth + "s" + separator + "%-" + colWidth + "s";
+        String divider = "-".repeat(colWidth) + "-+-" + "-".repeat(colWidth);
+
+        out.println("=== Side-by-Side Diff ===");
+        out.printf("%-5s " + headerFmt + "%n", "Line",
+                truncate(Paths.get(file1Path).getFileName().toString(), colWidth),
+                truncate(Paths.get(file2Path).getFileName().toString(), colWidth));
+        out.println("      " + divider);
+
+        int lineNum1 = 0;
+        int lineNum2 = 0;
+        List<AbstractDelta<String>> deltas = patch.getDeltas();
+        int deltaIdx = 0;
+
+        while (lineNum1 < file1Lines.size() || lineNum2 < file2Lines.size()) {
+            if (deltaIdx < deltas.size()) {
+                AbstractDelta<String> delta = deltas.get(deltaIdx);
+                int srcPos = delta.getSource().getPosition();
+                int tgtPos = delta.getTarget().getPosition();
+
+                while (lineNum1 < srcPos && lineNum2 < tgtPos) {
+                    String left = truncate(file1Lines.get(lineNum1), colWidth);
+                    String right = truncate(file2Lines.get(lineNum2), colWidth);
+                    out.printf("%5d  %-" + colWidth + "s" + separator + "%-" + colWidth + "s%n",
+                            lineNum1 + 1, left, right);
+                    lineNum1++;
+                    lineNum2++;
+                }
+
+                List<String> srcLines = delta.getSource().getLines();
+                List<String> tgtLines = delta.getTarget().getLines();
+                int maxLines = Math.max(srcLines.size(), tgtLines.size());
+
+                for (int i = 0; i < maxLines; i++) {
+                    String leftNum = i < srcLines.size() ? String.valueOf(lineNum1 + i + 1) : "";
+                    String left = i < srcLines.size()
+                            ? "\u001B[31m" + truncate(srcLines.get(i), colWidth) + "\u001B[0m"
+                            : "";
+                    String right = i < tgtLines.size()
+                            ? "\u001B[32m" + truncate(tgtLines.get(i), colWidth) + "\u001B[0m"
+                            : "";
+                    out.printf("%5s  %-" + (colWidth + 9) + "s" + separator + "%-" + (colWidth + 9) + "s%n",
+                            leftNum, left, right);
+                }
+
+                lineNum1 += srcLines.size();
+                lineNum2 += tgtLines.size();
+                deltaIdx++;
+            } else {
+                if (lineNum1 < file1Lines.size() && lineNum2 < file2Lines.size()) {
+                    String left = truncate(file1Lines.get(lineNum1), colWidth);
+                    String right = truncate(file2Lines.get(lineNum2), colWidth);
+                    out.printf("%5d  %-" + colWidth + "s" + separator + "%-" + colWidth + "s%n",
+                            lineNum1 + 1, left, right);
+                    lineNum1++;
+                    lineNum2++;
+                } else {
+                    break;
+                }
+            }
+        }
+    }
+
+    /**
+     * Generate HTML diff report.
+     */
+    public String generateHtml() {
+        DiffStats stats = computeStats();
+        StringBuilder sb = new StringBuilder();
+
+        sb.append("<!DOCTYPE html>\n<html>\n<head>\n");
+        sb.append("<meta charset=\"UTF-8\">\n");
+        sb.append("<title>Diff: ").append(escapeHtml(file1Path))
+                .append(" vs ").append(escapeHtml(file2Path)).append("</title>\n");
+        sb.append("<style>\n");
+        sb.append("body { font-family: 'Courier New', monospace; margin: 20px; }\n");
+        sb.append("table { border-collapse: collapse; width: 100%; }\n");
+        sb.append("td, th { border: 1px solid #ddd; padding: 4px 8px; text-align: left; }\n");
+        sb.append("th { background: #f0f0f0; }\n");
+        sb.append(".add { background: #dfd; }\n");
+        sb.append(".del { background: #fdd; }\n");
+        sb.append(".mod { background: #ffd; }\n");
+        sb.append(".linenum { color: #888; width: 50px; text-align: right; }\n");
+        sb.append(".stats { background: #f8f8f8; padding: 15px; border: 1px solid #ccc; margin-bottom: 20px; }\n");
+        sb.append("</style>\n</head>\n<body>\n");
+
+        sb.append("<div class=\"stats\">\n");
+        sb.append("<h2>Diff Statistics</h2>\n");
+        sb.append("<p>Additions: <strong style=\"color:green;\">+").append(stats.additions).append("</strong></p>\n");
+        sb.append("<p>Deletions: <strong style=\"color:red;\">-").append(stats.deletions).append("</strong></p>\n");
+        sb.append("<p>Modifications: <strong style=\"color:orange;\">~").append(stats.modifications).append("</strong></p>\n");
+        sb.append("</div>\n");
+
+        sb.append("<h2>Side-by-Side Comparison</h2>\n");
+        sb.append("<table>\n<tr><th class=\"linenum\">#</th><th>")
+                .append(escapeHtml(file1Path)).append("</th><th class=\"linenum\">#</th><th>")
+                .append(escapeHtml(file2Path)).append("</th></tr>\n");
+
+        int lineNum1 = 0;
+        int lineNum2 = 0;
+        List<AbstractDelta<String>> deltas = patch.getDeltas();
+        int deltaIdx = 0;
+
+        while (lineNum1 < file1Lines.size() || lineNum2 < file2Lines.size()) {
+            if (deltaIdx < deltas.size()) {
+                AbstractDelta<String> delta = deltas.get(deltaIdx);
+                int srcPos = delta.getSource().getPosition();
+
+                while (lineNum1 < srcPos) {
+                    sb.append("<tr><td class=\"linenum\">").append(lineNum1 + 1).append("</td>");
+                    sb.append("<td>").append(escapeHtml(file1Lines.get(lineNum1))).append("</td>");
+                    sb.append("<td class=\"linenum\">").append(lineNum2 + 1).append("</td>");
+                    sb.append("<td>").append(escapeHtml(file2Lines.get(lineNum2))).append("</td></tr>\n");
+                    lineNum1++;
+                    lineNum2++;
+                }
+
+                List<String> srcLines = delta.getSource().getLines();
+                List<String> tgtLines = delta.getTarget().getLines();
+                String cssClass = delta.getType() == DeltaType.DELETE ? "del"
+                        : delta.getType() == DeltaType.INSERT ? "add" : "mod";
+
+                int maxLines = Math.max(srcLines.size(), tgtLines.size());
+                for (int i = 0; i < maxLines; i++) {
+                    sb.append("<tr>");
+                    if (i < srcLines.size()) {
+                        sb.append("<td class=\"linenum\">").append(lineNum1 + i + 1).append("</td>");
+                        sb.append("<td class=\"").append(cssClass).append("\">")
+                                .append(escapeHtml(srcLines.get(i))).append("</td>");
+                    } else {
+                        sb.append("<td class=\"linenum\"></td><td></td>");
+                    }
+                    if (i < tgtLines.size()) {
+                        sb.append("<td class=\"linenum\">").append(lineNum2 + i + 1).append("</td>");
+                        sb.append("<td class=\"").append(cssClass).append("\">")
+                                .append(escapeHtml(tgtLines.get(i))).append("</td>");
+                    } else {
+                        sb.append("<td class=\"linenum\"></td><td></td>");
+                    }
+                    sb.append("</tr>\n");
+                }
+
+                lineNum1 += srcLines.size();
+                lineNum2 += tgtLines.size();
+                deltaIdx++;
+            } else {
+                if (lineNum1 < file1Lines.size() && lineNum2 < file2Lines.size()) {
+                    sb.append("<tr><td class=\"linenum\">").append(lineNum1 + 1).append("</td>");
+                    sb.append("<td>").append(escapeHtml(file1Lines.get(lineNum1))).append("</td>");
+                    sb.append("<td class=\"linenum\">").append(lineNum2 + 1).append("</td>");
+                    sb.append("<td>").append(escapeHtml(file2Lines.get(lineNum2))).append("</td></tr>\n");
+                    lineNum1++;
+                    lineNum2++;
+                } else {
+                    break;
+                }
+            }
+        }
+
+        sb.append("</table>\n</body>\n</html>");
+        return sb.toString();
+    }
+
+    public void saveHtml(String outputPath) throws IOException {
+        String html = generateHtml();
+        Files.writeString(Paths.get(outputPath), html, StandardCharsets.UTF_8);
+        System.out.println("HTML diff saved to: " + outputPath);
+    }
+
+    public DiffStats computeStats() {
+        DiffStats stats = new DiffStats();
+        for (AbstractDelta<String> delta : patch.getDeltas()) {
+            switch (delta.getType()) {
+                case INSERT:
+                    stats.additions += delta.getTarget().getLines().size();
+                    break;
+                case DELETE:
+                    stats.deletions += delta.getSource().getLines().size();
+                    break;
+                case CHANGE:
+                    stats.modifications += Math.max(
+                            delta.getSource().getLines().size(),
+                            delta.getTarget().getLines().size()
+                    );
+                    break;
+            }
+        }
+        stats.file1Lines = file1Lines.size();
+        stats.file2Lines = file2Lines.size();
+        return stats;
+    }
+
+    public void displayStats(PrintStream out) {
+        DiffStats stats = computeStats();
+        out.println("=== Diff Statistics ===");
+        out.println("Additions:     \u001B[32m+" + stats.additions + "\u001B[0m");
+        out.println("Deletions:     \u001B[31m-" + stats.deletions + "\u001B[0m");
+        out.println("Modifications: \u001B[33m~" + stats.modifications + "\u001B[0m");
+        out.println("File 1 lines:  " + stats.file1Lines);
+        out.println("File 2 lines:  " + stats.file2Lines);
+    }
+
+    /**
+     * Export stats as JSON using Jackson.
+     */
+    public String statsToJson() throws Exception {
+        DiffStats stats = computeStats();
+        ObjectNode node = mapper.createObjectNode();
+        node.put("file1", file1Path);
+        node.put("file2", file2Path);
+        node.put("additions", stats.additions);
+        node.put("deletions", stats.deletions);
+        node.put("modifications", stats.modifications);
+        node.put("total_changes", stats.additions + stats.deletions + stats.modifications);
+        node.put("file1_lines", stats.file1Lines);
+        node.put("file2_lines", stats.file2Lines);
+        return mapper.writeValueAsString(node);
+    }
+
+    private static String truncate(String s, int maxLen) {
+        if (s == null) return "";
+        return s.length() > maxLen ? s.substring(0, maxLen - 3) + "..." : s;
+    }
+
+    private static String escapeHtml(String s) {
+        return s.replace("&", "&amp;").replace("<", "&lt;")
+                .replace(">", "&gt;").replace("\"", "&quot;");
+    }
+
+    static class DiffStats {
+        int additions = 0;
+        int deletions = 0;
+        int modifications = 0;
+        int file1Lines = 0;
+        int file2Lines = 0;
+    }
+
+    public static void main(String[] args) {
+        if (args.length < 2) {
+            System.err.println("Usage: java TextDiff <file1> <file2> [options]");
+            System.err.println("Options:");
+            System.err.println("  --format <unified|side-by-side|html|json|all>  Output format (default: unified)");
+            System.err.println("  --context <n>          Context lines (default: 3)");
+            System.err.println("  --html-output <path>   HTML output file path");
+            System.err.println("  --width <n>            Column width for side-by-side (default: 120)");
+            System.err.println("  --stats                Show statistics");
+            System.exit(1);
+        }
+
+        String file1 = args[0];
+        String file2 = args[1];
+        String format = "unified";
+        int contextLines = 3;
+        int width = 120;
+        String htmlOutput = "diff_report.html";
+        boolean showStats = false;
+
+        for (int i = 2; i < args.length; i++) {
+            switch (args[i]) {
+                case "--format":
+                    format = args[++i];
+                    break;
+                case "--context":
+                    contextLines = Integer.parseInt(args[++i]);
+                    break;
+                case "--html-output":
+                    htmlOutput = args[++i];
+                    break;
+                case "--width":
+                    width = Integer.parseInt(args[++i]);
+                    break;
+                case "--stats":
+                    showStats = true;
+                    break;
+            }
+        }
+
+        try {
+            TextDiff diff = new TextDiff(file1, file2, contextLines);
+
+            if (showStats || format.equals("all")) {
+                diff.displayStats(System.out);
+                System.out.println();
+            }
+
+            switch (format) {
+                case "unified":
+                    diff.displayUnified(System.out);
+                    break;
+                case "side-by-side":
+                    diff.displaySideBySide(System.out, width);
+                    break;
+                case "html":
+                    diff.saveHtml(htmlOutput);
+                    break;
+                case "json":
+                    System.out.println(diff.statsToJson());
+                    break;
+                case "all":
+                    diff.displayUnified(System.out);
+                    System.out.println();
+                    diff.displaySideBySide(System.out, width);
+                    System.out.println();
+                    diff.saveHtml(htmlOutput);
+                    System.out.println();
+                    System.out.println(diff.statsToJson());
+                    break;
+                default:
+                    System.err.println("Unknown format: " + format);
+                    System.exit(1);
+            }
+        } catch (Exception e) {
+            System.err.println("Error: " + e.getMessage());
+            System.exit(1);
+        }
+    }
+}

Claude Code wrote this java project from the task below. It does not run on a clean Ubuntu 22.04 machine as written.

Task given to the agent:

TASK: Text Diff Tool

Write a program that compares two text files and produces a detailed diff showing additions, deletions, and modifications with configurable output formats and context control.

FUNCTIONAL REQUIREMENTS:
- Accept two file paths as command-line arguments (original and modified)
- Compute the longest common subsequence (LCS) based diff to identify added, deleted, and changed lines
- Support multiple output formats via --format flag: unified diff (default, similar to git diff), side-by-side (two-column view), inline (changes marked within lines), and html (visual diff as an HTML page)
- Support configurable context lines around changes via --context flag (default: 3 lines of unchanged context around each change)
- Detect and highlight intra-line changes: when a line is modified, show exactly which words or characters changed within the line
- Support ignoring whitespace differences via --ignore-whitespace flag
- Support ignoring case differences via --ignore-case flag
- Support ignoring blank lines via --ignore-blank-lines flag
- Compute and display diff statistics: total lines in each file, lines added, lines deleted, lines modified, and a similarity percentage
- Support comparing directories via --recursive flag: compare all matching files in two directory trees and report which files are added, deleted, modified, or identical
- Apply color coding in console output: green for additions, red for deletions, yellow for modifications
- Save the diff output to a file via --output flag
- If no input files are given, generate two sample text files (original and modified version with insertions, deletions, modifications, and moved blocks), then compute and display the diff in all supported formats
- Handle errors: binary files (detect and skip with warning), missing files, encoding mismatches, and very large files

Create a complete Java project for a clean Ubuntu 22.04 machine with only JDK 17+ installed. Include:
- Source code
- pom.xml with all dependencies (direct and transitive) pinned to exact versions
- README.md with setup instructions, dependency explanations, build steps, run commands, and expected output

[
  {
    "category": "misspecification",
    "rule": "signature.build_layout_mismatch",
    "source": "failure_signature",
    "excerpt": "error: no classes were compiled"
  }
]

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.textdiff</groupId>
    <artifactId>text-diff-tool</artifactId>
    <version>1.0.0</version>
    <packaging>jar</packaging>

    <name>Text Diff Tool</name>
    <description>Compares text files showing additions, deletions, and modifications in multiple formats</description>

    <properties>
        <maven.compiler.source>17</maven.compiler.source>
        <maven.compiler.target>17</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>io.github.java-diff-utils</groupId>
            <artifactId>java-diff-utils</artifactId>
            <version>4.12</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.16.1</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-jar-plugin</artifactId>
                <version>3.3.0</version>
                <configuration>
                    <archive>
                        <manifest>
                            <mainClass>TextDiff</mainClass>
                        </manifest>
                    </archive>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

import com.github.difflib.DiffUtils;
import com.github.difflib.UnifiedDiffUtils;
import com.github.difflib.patch.AbstractDelta;
import com.github.difflib.patch.DeltaType;
import com.github.difflib.patch.Patch;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.databind.node.ObjectNode;

import java.io.*;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.*;

/**
 * Text Diff Tool - Compares text files showing additions, deletions, and modifications.
 * Supports unified, side-by-side, and HTML output formats.
 * Uses java-diff-utils for diff computation and Jackson for JSON output.
 */
public class TextDiff {

    private final List<String> file1Lines;
    private final List<String> file2Lines;
    private final String file1Path;
    private final String file2Path;
    private final Patch<String> patch;
    private final int contextLines;
    private final ObjectMapper mapper;

    public TextDiff(String file1Path, String file2Path, int contextLines) throws IOException {
        this.file1Path = file1Path;
        this.file2Path = file2Path;
        this.contextLines = contextLines;
        this.file1Lines = Files.readAllLines(Paths.get(file1Path), StandardCharsets.UTF_8);
        this.file2Lines = Files.readAllLines(Paths.get(file2Path), StandardCharsets.UTF_8);
        this.patch = DiffUtils.diff(file1Lines, file2Lines);
        this.mapper = new ObjectMapper().enable(SerializationFeature.INDENT_OUTPUT);
    }

    /**
     * Generate unified diff output.
     */
    public List<String> getUnifiedDiff() {
        return UnifiedDiffUtils.generateUnifiedDiff(
                file1Path, file2Path, file1Lines, patch, contextLines
        );
    }

    /**
     * Display unified diff with ANSI color codes.
     */
    public void displayUnified(PrintStream out) {
        List<String> unifiedDiff = getUnifiedDiff();
        if (unifiedDiff.isEmpty()) {
            out.println("\u001B[32mFiles are identical.\u001B[0m");
            return;
        }
        out.println("=== Unified Diff ===");
        for (String line : unifiedDiff) {
            if (line.startsWith("+++") || line.startsWith("---")) {
                out.println("\u001B[1m" + line + "\u001B[0m");
            } else if (line.startsWith("@@")) {
                out.println("\u001B[36m" + line + "\u001B[0m");
            } else if (line.startsWith("+")) {
                out.println("\u001B[32m" + line + "\u001B[0m");
            } else if (line.startsWith("-")) {
                out.println("\u001B[31m" + line + "\u001B[0m");
            } else {
                out.println(line);
            }
        }
    }

    /**
     * Display side-by-side diff.
     */
    public void displaySideBySide(PrintStream out, int width) {
        int colWidth = (width - 7) / 2;
        String separator = " | ";
        String headerFmt = "%-" + colWidth + "s" + separator + "%-" + colWidth + "s";
        String divider = "-".repeat(colWidth) + "-+-" + "-".repeat(colWidth);

        out.println("=== Side-by-Side Diff ===");
        out.printf("%-5s " + headerFmt + "%n", "Line",
                truncate(Paths.get(file1Path).getFileName().toString(), colWidth),
                truncate(Paths.get(file2Path).getFileName().toString(), colWidth));
        out.println("      " + divider);

        int lineNum1 = 0;
        int lineNum2 = 0;
        List<AbstractDelta<String>> deltas = patch.getDeltas();
        int deltaIdx = 0;

        while (lineNum1 < file1Lines.size() || lineNum2 < file2Lines.size()) {
            if (deltaIdx < deltas.size()) {
                AbstractDelta<String> delta = deltas.get(deltaIdx);
                int srcPos = delta.getSource().getPosition();
                int tgtPos = delta.getTarget().getPosition();

                while (lineNum1 < srcPos && lineNum2 < tgtPos) {
                    String left = truncate(file1Lines.get(lineNum1), colWidth);
                    String right = truncate(file2Lines.get(lineNum2), colWidth);
                    out.printf("%5d  %-" + colWidth + "s" + separator + "%-" + colWidth + "s%n",
                            lineNum1 + 1, left, right);
                    lineNum1++;
                    lineNum2++;
                }

                List<String> srcLines = delta.getSource().getLines();
                List<String> tgtLines = delta.getTarget().getLines();
                int maxLines = Math.max(srcLines.size(), tgtLines.size());

                for (int i = 0; i < maxLines; i++) {
                    String leftNum = i < srcLines.size() ? String.valueOf(lineNum1 + i + 1) : "";
                    String left = i < srcLines.size()
                            ? "\u001B[31m" + truncate(srcLines.get(i), colWidth) + "\u001B[0m"
                            : "";
                    String right = i < tgtLines.size()
                            ? "\u001B[32m" + truncate(tgtLines.get(i), colWidth) + "\u001B[0m"
                            : "";
                    out.printf("%5s  %-" + (colWidth + 9) + "s" + separator + "%-" + (colWidth + 9) + "s%n",
                            leftNum, left, right);
                }

                lineNum1 += srcLines.size();
                lineNum2 += tgtLines.size();
                deltaIdx++;
            } else {
                if (lineNum1 < file1Lines.size() && lineNum2 < file2Lines.size()) {
                    String left = truncate(file1Lines.get(lineNum1), colWidth);
                    String right = truncate(file2Lines.get(lineNum2), colWidth);
                    out.printf("%5d  %-" + colWidth + "s" + separator + "%-" + colWidth + "s%n",
                            lineNum1 + 1, left, right);
                    lineNum1++;
                    lineNum2++;
                } else {
                    break;
                }
            }
        }
    }

    /**
     * Generate HTML diff report.
     */
    public String generateHtml() {
        DiffStats stats = computeStats();
        StringBuilder sb = new StringBuilder();

        sb.append("<!DOCTYPE html>\n<html>\n<head>\n");
        sb.append("<meta charset=\"UTF-8\">\n");
        sb.append("<title>Diff: ").append(escapeHtml(file1Path))
                .append(" vs ").append(escapeHtml(file2Path)).append("</title>\n");
        sb.append("<style>\n");
        sb.append("body { font-family: 'Courier New', monospace; margin: 20px; }\n");
        sb.append("table { border-collapse: collapse; width: 100%; }\n");
        sb.append("td, th { border: 1px solid #ddd; padding: 4px 8px; text-align: left; }\n");
        sb.append("th { background: #f0f0f0; }\n");
        sb.append(".add { background: #dfd; }\n");
        sb.append(".del { background: #fdd; }\n");
        sb.append(".mod { background: #ffd; }\n");
        sb.append(".linenum { color: #888; width: 50px; text-align: right; }\n");
        sb.append(".stats { background: #f8f8f8; padding: 15px; border: 1px solid #ccc; margin-bottom: 20px; }\n");
        sb.append("</style>\n</head>\n<body>\n");

        sb.append("<div class=\"stats\">\n");
        sb.append("<h2>Diff Statistics</h2>\n");
        sb.append("<p>Additions: <strong style=\"color:green;\">+").append(stats.additions).append("</strong></p>\n");
        sb.append("<p>Deletions: <strong style=\"color:red;\">-").append(stats.deletions).append("</strong></p>\n");
        sb.append("<p>Modifications: <strong style=\"color:orange;\">~").append(stats.modifications).append("</strong></p>\n");
        sb.append("</div>\n");

        sb.append("<h2>Side-by-Side Comparison</h2>\n");
        sb.append("<table>\n<tr><th class=\"linenum\">#</th><th>")
                .append(escapeHtml(file1Path)).append("</th><th class=\"linenum\">#</th><th>")
                .append(escapeHtml(file2Path)).append("</th></tr>\n");

        int lineNum1 = 0;
        int lineNum2 = 0;
        List<AbstractDelta<String>> deltas = patch.getDeltas();
        int deltaIdx = 0;

        while (lineNum1 < file1Lines.size() || lineNum2 < file2Lines.size()) {
            if (deltaIdx < deltas.size()) {
                AbstractDelta<String> delta = deltas.get(deltaIdx);
                int srcPos = delta.getSource().getPosition();

                while (lineNum1 < srcPos) {
                    sb.append("<tr><td class=\"linenum\">").append(lineNum1 + 1).append("</td>");
                    sb.append("<td>").append(escapeHtml(file1Lines.get(lineNum1))).append("</td>");
                    sb.append("<td class=\"linenum\">").append(lineNum2 + 1).append("</td>");
                    sb.append("<td>").append(escapeHtml(file2Lines.get(lineNum2))).append("</td></tr>\n");
                    lineNum1++;
                    lineNum2++;
                }

                List<String> srcLines = delta.getSource().getLines();
                List<String> tgtLines = delta.getTarget().getLines();
                String cssClass = delta.getType() == DeltaType.DELETE ? "del"
                        : delta.getType() == DeltaType.INSERT ? "add" : "mod";

                int maxLines = Math.max(srcLines.size(), tgtLines.size());
                for (int i = 0; i < maxLines; i++) {
                    sb.append("<tr>");
                    if (i < srcLines.size()) {
                        sb.append("<td class=\"linenum\">").append(lineNum1 + i + 1).append("</td>");
                        sb.append("<td class=\"").append(cssClass).append("\">")
                                .append(escapeHtml(srcLines.get(i))).append("</td>");
                    } else {
                        sb.append("<td class=\"linenum\"></td><td></td>");
                    }
                    if (i < tgtLines.size()) {
                        sb.append("<td class=\"linenum\">").append(lineNum2 + i + 1).append("</td>");
                        sb.append("<td class=\"").append(cssClass).append("\">")
                                .append(escapeHtml(tgtLines.get(i))).append("</td>");
                    } else {
                        sb.append("<td class=\"linenum\"></td><td></td>");
                    }
                    sb.append("</tr>\n");
                }

                lineNum1 += srcLines.size();
                lineNum2 += tgtLines.size();
                deltaIdx++;
            } else {
                if (lineNum1 < file1Lines.size() && lineNum2 < file2Lines.size()) {
                    sb.append("<tr><td class=\"linenum\">").append(lineNum1 + 1).append("</td>");
                    sb.append("<td>").append(escapeHtml(file1Lines.get(lineNum1))).append("</td>");
                    sb.append("<td class=\"linenum\">").append(lineNum2 + 1).append("</td>");
                    sb.append("<td>").append(escapeHtml(file2Lines.get(lineNum2))).append("</td></tr>\n");
                    lineNum1++;
                    lineNum2++;
                } else {
                    break;
                }
            }
        }

        sb.append("</table>\n</body>\n</html>");
        return sb.toString();
    }

    public void saveHtml(String outputPath) throws IOException {
        String html = generateHtml();
        Files.writeString(Paths.get(outputPath), html, StandardCharsets.UTF_8);
        System.out.println("HTML diff saved to: " + outputPath);
    }

    public DiffStats computeStats() {
        DiffStats stats = new DiffStats();
        for (AbstractDelta<String> delta : patch.getDeltas()) {
            switch (delta.getType()) {
                case INSERT:
                    stats.additions += delta.getTarget().getLines().size();
                    break;
                case DELETE:
                    stats.deletions += delta.getSource().getLines().size();
                    break;
                case CHANGE:
                    stats.modifications += Math.max(
                            delta.getSource().getLines().size(),
                            delta.getTarget().getLines().size()
                    );
                    break;
            }
        }
        stats.file1Lines = file1Lines.size();
        stats.file2Lines = file2Lines.size();
        return stats;
    }

    public void displayStats(PrintStream out) {
        DiffStats stats = computeStats();
        out.println("=== Diff Statistics ===");
        out.println("Additions:     \u001B[32m+" + stats.additions + "\u001B[0m");
        out.println("Deletions:     \u001B[31m-" + stats.deletions + "\u001B[0m");
        out.println("Modifications: \u001B[33m~" + stats.modifications + "\u001B[0m");
        out.println("File 1 lines:  " + stats.file1Lines);
        out.println("File 2 lines:  " + stats.file2Lines);
    }

    /**
     * Export stats as JSON using Jackson.
     */
    public String statsToJson() throws Exception {
        DiffStats stats = computeStats();
        ObjectNode node = mapper.createObjectNode();
        node.put("file1", file1Path);
        node.put("file2", file2Path);
        node.put("additions", stats.additions);
        node.put("deletions", stats.deletions);
        node.put("modifications", stats.modifications);
        node.put("total_changes", stats.additions + stats.deletions + stats.modifications);
        node.put("file1_lines", stats.file1Lines);
        node.put("file2_lines", stats.file2Lines);
        return mapper.writeValueAsString(node);
    }

    private static String truncate(String s, int maxLen) {
        if (s == null) return "";
        return s.length() > maxLen ? s.substring(0, maxLen - 3) + "..." : s;
    }

    private static String escapeHtml(String s) {
        return s.replace("&", "&amp;").replace("<", "&lt;")
                .replace(">", "&gt;").replace("\"", "&quot;");
    }

    static class DiffStats {
        int additions = 0;
        int deletions = 0;
        int modifications = 0;
        int file1Lines = 0;
        int file2Lines = 0;
    }

    public static void main(String[] args) {
        if (args.length < 2) {
            System.err.println("Usage: java TextDiff <file1> <file2> [options]");
            System.err.println("Options:");
            System.err.println("  --format <unified|side-by-side|html|json|all>  Output format (default: unified)");
            System.err.println("  --context <n>          Context lines (default: 3)");
            System.err.println("  --html-output <path>   HTML output file path");
            System.err.println("  --width <n>            Column width for side-by-side (default: 120)");
            System.err.println("  --stats                Show statistics");
            System.exit(1);
        }

        String file1 = args[0];
        String file2 = args[1];
        String format = "unified";
        int contextLines = 3;
        int width = 120;
        String htmlOutput = "diff_report.html";
        boolean showStats = false;

        for (int i = 2; i < args.length; i++) {
            switch (args[i]) {
                case "--format":
                    format = args[++i];
                    break;
                case "--context":
                    contextLines = Integer.parseInt(args[++i]);
                    break;
                case "--html-output":
                    htmlOutput = args[++i];
                    break;
                case "--width":
                    width = Integer.parseInt(args[++i]);
                    break;
                case "--stats":
                    showStats = true;
                    break;
            }
        }

        try {
            TextDiff diff = new TextDiff(file1, file2, contextLines);

            if (showStats || format.equals("all")) {
                diff.displayStats(System.out);
                System.out.println();
            }

            switch (format) {
                case "unified":
                    diff.displayUnified(System.out);
                    break;
                case "side-by-side":
                    diff.displaySideBySide(System.out, width);
                    break;
                case "html":
                    diff.saveHtml(htmlOutput);
                    break;
                case "json":
                    System.out.println(diff.statsToJson());
                    break;
                case "all":
                    diff.displayUnified(System.out);
                    System.out.println();
                    diff.displaySideBySide(System.out, width);
                    System.out.println();
                    diff.saveHtml(htmlOutput);
                    System.out.println();
                    System.out.println(diff.statsToJson());
                    break;
                default:
                    System.err.println("Unknown format: " + format);
                    System.exit(1);
            }
        } catch (Exception e) {
            System.err.println("Error: " + e.getMessage());
            System.exit(1);
        }
    }
}