Gmail添付ファイルの重複保存を実行前に発見｜GASでDrive保存計画をdry-run監査

function auditGmailAttachmentSavePlanFree() {
  const config = {
    gmailQuery: 'has:attachment newer_than:7d',
    folderId: 'ここを保存先フォルダIDに置き換える',
    maxThreads: 50,
    maxAttachments: 200,
    dryRun: true,
    writeSummary: false,
    summarySheetName: 'AuditSummary'
  };

  validateAttachmentAuditConfig_(config);

  const destination = DriveApp.getFolderById(config.folderId);
  const existingNames = collectDirectChildNames_(destination, config.maxAttachments * 5);
  const threads = GmailApp.search(config.gmailQuery, 0, config.maxThreads + 1);

  if (threads.length > config.maxThreads) {
    throw new Error(
      '検索結果が上限の' + config.maxThreads + 'スレッドを超えています。' +
      'Gmail検索条件を狭めてください。'
    );
  }

  const issues = [];
  let attachmentCount = 0;
  let totalBytes = 0;
  let duplicateNameCount = 0;
  let emptyNameCount = 0;

  threads.forEach(function(thread, threadIndex) {
    const messages = thread.getMessages();

    messages.forEach(function(message, messageIndex) {
      const attachments = message.getAttachments({
        includeInlineImages: false,
        includeAttachments: true
      });

      attachments.forEach(function(attachment, attachmentIndex) {
        attachmentCount += 1;
        if (attachmentCount > config.maxAttachments) {
          throw new Error(
            '添付ファイルが上限の' + config.maxAttachments + '件を超えています。' +
            'Gmail検索条件を狭めてください。'
          );
        }

        const name = String(attachment.getName() || '').trim();
        const bytes = attachment.getBytes().length;
        totalBytes += bytes;

        if (!name) {
          emptyNameCount += 1;
          issues.push({
            thread: threadIndex + 1,
            message: messageIndex + 1,
            attachment: attachmentIndex + 1,
            code: 'ATTACHMENT_NAME_EMPTY'
          });
          return;
        }

        const normalizedName = normalizeAttachmentName_(name);
        if (existingNames[normalizedName]) {
          duplicateNameCount += 1;
          issues.push({
            thread: threadIndex + 1,
            message: messageIndex + 1,
            attachment: attachmentIndex + 1,
            code: 'SAME_NAME_EXISTS_IN_FOLDER'
          });
        }
      });
    });
  });

  const summary = {
    dryRun: config.dryRun,
    checkedThreads: threads.length,
    attachmentCount: attachmentCount,
    totalBytes: totalBytes,
    duplicateNameCount: duplicateNameCount,
    emptyNameCount: emptyNameCount,
    issueCount: issues.length
  };

  Logger.log('dry-run: ' + summary.dryRun);
  Logger.log('確認スレッド数: ' + summary.checkedThreads);
  Logger.log('添付ファイル数: ' + summary.attachmentCount);
  Logger.log('合計容量: ' + formatBytesForAttachmentAudit_(summary.totalBytes));
  Logger.log('保存先直下の同名候補: ' + summary.duplicateNameCount);
  Logger.log('名前なし添付: ' + summary.emptyNameCount);
  issues.forEach(function(issue) {
    Logger.log(
      'スレッド位置' + issue.thread +
      ' / メッセージ位置' + issue.message +
      ' / 添付位置' + issue.attachment +
      ': ' + issue.code
    );
  });
  Logger.log('件名・送信者・本文・添付ファイル名・メッセージIDはログへ出していません。');

  if (config.writeSummary === true) {
    writeAttachmentAuditSummary_(config, summary);
  }

  return summary;
}

function validateAttachmentAuditConfig_(config) {
  if (config.dryRun !== true) {
    throw new Error('安全のためdryRunはtrue固定です。');
  }
  if (!config.gmailQuery || !String(config.gmailQuery).trim()) {
    throw new Error('gmailQueryを入力してください。');
  }
  if (!config.folderId || config.folderId.indexOf('ここを') !== -1) {
    throw new Error('folderIdを保存先フォルダIDへ置き換えてください。');
  }
  if (!Number.isInteger(config.maxThreads) || config.maxThreads < 1 || config.maxThreads > 100) {
    throw new Error('maxThreadsは1〜100の整数にしてください。');
  }
  if (!Number.isInteger(config.maxAttachments) || config.maxAttachments < 1 || config.maxAttachments > 500) {
    throw new Error('maxAttachmentsは1〜500の整数にしてください。');
  }
}

function collectDirectChildNames_(folder, maxFiles) {
  const names = {};
  const files = folder.getFiles();
  let checked = 0;

  while (files.hasNext()) {
    checked += 1;
    if (checked > maxFiles) {
      throw new Error(
        '保存先直下のファイル数が確認上限の' + maxFiles + '件を超えています。' +
        'テスト用フォルダか、より小さい保存先で確認してください。'
      );
    }
    const name = String(files.next().getName() || '').trim();
    if (name) {
      names[normalizeAttachmentName_(name)] = true;
    }
  }
  return names;
}

function normalizeAttachmentName_(name) {
  return String(name)
    .normalize('NFKC')
    .trim()
    .replace(/\s+/g, ' ')
    .toLowerCase();
}

function formatBytesForAttachmentAudit_(bytes) {
  if (bytes < 1024) {
    return bytes + ' B';
  }
  if (bytes < 1024 * 1024) {
    return (bytes / 1024).toFixed(1) + ' KB';
  }
  return (bytes / 1024 / 1024).toFixed(1) + ' MB';
}

function writeAttachmentAuditSummary_(config, summary) {
  const spreadsheet = SpreadsheetApp.getActiveSpreadsheet();
  let sheet = spreadsheet.getSheetByName(config.summarySheetName);
  if (!sheet) {
    sheet = spreadsheet.insertSheet(config.summarySheetName);
  }
  sheet.clearContents();
  sheet.getRange(1, 1, 7, 2).setValues([
    ['確認日時', new Date()],
    ['dry-run', summary.dryRun],
    ['確認スレッド数', summary.checkedThreads],
    ['添付ファイル数', summary.attachmentCount],
    ['合計容量bytes', summary.totalBytes],
    ['保存先直下の同名候補', summary.duplicateNameCount],
    ['名前なし添付', summary.emptyNameCount]
  ]);
}