// CodeDiffUtil.java
if (changeType == CodeDiff.ChangeType.DELETE) {
    // 删除的文件：不发 diff 内容，只记录文件路径和行数
    diffContent = null;
} else if (changeType == CodeDiff.ChangeType.ADD) {
    // 新增文件：只预览前 50 行，跳过 import 语句，限制 4000 字符
    diffContent = buildAddedFilePreview(change, virtualFile);
} else if (changeType == CodeDiff.ChangeType.RENAME) {
    // 纯重命名（没有内容变更）：只记录 "moved from A to B"
    diffContent = buildMovedFileSummary(change);
} else {
    // 修改文件：提取真正的 diff
    diffContent = extractDiffResult(change);
}

// CodeDiffUtil.java - generateUnifiedDiffInternal()

// 1. 纯空白字符变更：前后内容去掉空白后一样，跳过
if (isWhitespaceOnlyChange(beforeChanged, afterChanged)) {
    continue;
}

// 2. 纯 import 变更：只改了 import 语句，跳过
if (isImportOnlyChange(beforeChanged, afterChanged)) {
    continue;
}

// 3. 纯注释变更：Java 文件中只改了注释，跳过
if (isJavaFile && isCommentOnlyChange(beforeChanged, afterChanged)) {
    continue;
}

// 4. 纯顺序调整：行内容没变，只是顺序调了，跳过
if (isJavaFile && isReorderOnlyChange(beforeChanged, afterChanged)) {
    continue;
}

// 每个文件最多保留 6 个 diff 块
private static final int MAX_HUNKS_PER_FILE = 6;

// 单个 diff 块最多保留 20 行
private static final int MAX_LINES_PER_HUNK = 20;

// 单行最大 240 字符（超过截断）
private static final int MAX_DIFF_LINE_CHARS = 240;

// 新增文件预览最大 4000 字符
private static final int MAX_ADDED_PREVIEW_CHARS = 4000;

// 单文件 diff 最大 12000 字符（超过直接截断）
private static final int MAX_DIFF_CHARS_PER_FILE = 12000;

// CodeDiffUtil.java - generateUnifiedDiffInternal()
String context = resolveSymbolContext(virtualFile, afterStart, beforeStart);
if (context != null && !context.isEmpty()) {
    diff.append("上下文: ").append(context).append("\n");
}

@Service(Service.Level.PROJECT)
public final class ChangelogService {

    @NotNull
    public String generateChangelog(@NotNull List<String> commitHashes) {
        // 1. 通过 JGit 读取提交记录
        List<CommitInfo> commits = readCommits(commitHashes);

        // 2. 按日期分组，组装 prompt
        String prompt = buildPrompt(commits);

        // 3. 调用 AI 服务
        return callAIService(prompt);
    }

    @NotNull
    public String generateDailyReport(@NotNull List<String> commitHashes) {
        // 使用日报模板
    }

    @NotNull
    public String generateWeeklyReport(@NotNull List<String> commitHashes) {
        // 使用周报模板
    }
}

@NotNull
private List<CommitInfo> readCommits(@NotNull List<String> commitHashes) {
    List<CommitInfo> commits = new ArrayList<>();
    Repository repository = getRepository();

    try (Git git = new Git(repository)) {
        for (String hash : commitHashes) {
            ObjectId commitId = repository.resolve(hash);
            if (commitId != null) {
                RevCommit commit = git.log()
                    .add(commitId)
                    .setMaxCount(1)
                    .call()
                    .iterator()
                    .next();

                commits.add(new CommitInfo(
                    commit.getName(),
                    commit.getShortMessage(),
                    commit.getFullMessage(),
                    new Date(commit.getCommitTime() * 1000L),
                    commit.getAuthorIdent().getName()
                ));
            }
        }
    }
    return commits;
}

@NotNull
public String generateCommitMessageFromDiff(@NotNull Collection<Change> changes) {
    // 1. 提取代码变更信息
    List<CodeDiff> codeDiffs = CodeDiffUtil.extractCodeDiffs(changes);

    if (codeDiffs.isEmpty()) {
        throw new Exception("没有检测到代码变更");
    }

    // 2. 构建 prompt，包含文件路径、变更类型、增删行数、diff 内容
    String prompt = buildPromptFromCodeDiff(codeDiffs);

    // 3. 调用 AI
    return callAIServiceForCommitMessage(prompt);
}

private static boolean isMeaningfulChange(CodeDiff diff) {
    if (diff.addedLines == 0 && diff.deletedLines == 0) {
        return false;
    }
    if (diff.diffContent != null &&
        diff.diffContent.matches("(?s).*^\\s*[+-]\\s*$.*")) {
        return false;
    }
    return true;
}

private static final String CHANGELOG_SYSTEM_PROMPT = """
    你是一位专业的技术文档撰写专家。

    根据 Git 提交记录生成版本更新日志。

    生成原则：
    1. 用户导向：重点说明对用户的价值，不是技术细节
    2. 分类清晰：按功能类型分类
    3. 语言简洁：避免过于技术化的描述
    4. 格式规范：Markdown 格式，适当 emoji

    分类标准：
    - 🎉 重大更新：重要功能发布、架构升级
    - 🚀 新增功能：新功能模块
    - 🐛 问题修复：Bug 修复
    - 🔧 技术改进：性能优化、重构
    - 📚 文档更新：文档相关

    注意：
    - 输出不要用代码块包裹
    - 根据实际情况灵活调整分类
    """;

@NotNull
private String buildPrompt(@NotNull List<CommitInfo> commits) {
    SettingsState settings = SettingsState.getInstance();
    String template = settings.changelogTemplate;
    String commitsText = buildCommitsText(commits);

    return template
        .replace("{version}", "v1.0.0")
        .replace("{commits}", commitsText);
}

@NotNull
private String buildCommitsText(@NotNull List<CommitInfo> commits) {
    SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
    Map<String, List<CommitInfo>> commitsByDate = new LinkedHashMap<>();

    for (CommitInfo commit : commits) {
        String dateStr = dateFormat.format(commit.date);
        commitsByDate.computeIfAbsent(dateStr, k -> new ArrayList<>()).add(commit);
    }

    StringBuilder sb = new StringBuilder();
    for (Map.Entry<String, List<CommitInfo>> entry : commitsByDate.entrySet()) {
        sb.append("### ").append(entry.getKey()).append("\n\n");
        for (CommitInfo commit : entry.getValue()) {
            sb.append("- ").append(commit.shortMessage).append("\n");
        }
        sb.append("\n");
    }
    return sb.toString().trim();
}

// 文件: UserService.java
// 新增 15 行，删除 8 行
+ public UserDTO getUser(String userId) {
+     return userMapper.findById(userId);
+ }

@Override
protected void actionPerformed(@NotNull AnActionEvent e,
                               @NotNull List<String> commitHashes) {
    Project project = e.getProject();
    if (project == null) return;

    ProgressManager.getInstance().run(new Task.Backgroundable(project, "生成 Changelog") {
        @Override
        public void run(@NotNull ProgressIndicator indicator) {
            try {
                indicator.setText("正在读取提交记录...");
                ChangelogService service = ChangelogService.getInstance(project);
                String changelog = service.generateChangelog(commitHashes);

                ApplicationManager.getApplication().invokeLater(() -> {
                    showResultDialog(project, changelog);
                });
            } catch (Exception ex) {
                ApplicationManager.getApplication().invokeLater(() -> {
                    showErrorDialog(project, ex.getMessage());
                });
            }
        }
    });
}

private final Map<String, String> commitCache = new ConcurrentHashMap<>();

@NotNull
private List<CommitInfo> readCommits(@NotNull List<String> commitHashes) {
    // ...
    for (String hash : commitHashes) {
        String cached = commitCache.get(hash);
        if (cached != null) {
            commits.add(deserializeCommitInfo(cached));
            continue;
        }
        // 读取并缓存
    }
}