Gmail下書きの添付忘れを送信前に発見｜GASで件数と容量をdry-run監査

function auditGmailDraftAttachmentsFree() {
  const config = {
    dryRun: true,
    maxDrafts: 50,
    maxTotalAttachmentBytes: 8 * 1024 * 1024,
    attachmentWords: /添付|ファイル|attachment/i,
    maxIssueRowsInLog: 20
  };

  validateAttachmentAuditConfig_(config);

  // 安全装置: この無料コードは読み取り専用のdry-runだけを許可します。
  if (config.dryRun !== true) {
    throw new Error('dryRun は true のまま実行してください。');
  }

  const allDrafts = GmailApp.getDrafts();
  const targetDrafts = allDrafts.slice(0, config.maxDrafts);
  const issues = [];
  let attachmentCount = 0;
  let attachmentBytes = 0;
  let keywordWithoutAttachmentCount = 0;
  let overSizeCount = 0;

  targetDrafts.forEach(function(draft, index) {
    const message = draft.getMessage();
    const subject = String(message.getSubject() || '');
    const plainBody = String(message.getPlainBody() || '');
    const attachments = message.getAttachments({
      includeInlineImages: false,
      includeAttachments: true
    });

    const totalBytes = attachments.reduce(function(sum, attachment) {
      const size = Number(attachment.getSize() || 0);
      return sum + (Number.isFinite(size) ? size : 0);
    }, 0);

    const mentionsAttachment =
      config.attachmentWords.test(subject + '\n' + plainBody);
    const flags = [];

    if (mentionsAttachment && attachments.length === 0) {
      flags.push('ATTACHMENT_WORD_WITHOUT_FILE');
      keywordWithoutAttachmentCount += 1;
    }

    if (totalBytes > config.maxTotalAttachmentBytes) {
      flags.push('TOTAL_ATTACHMENT_SIZE_OVER_LIMIT');
      overSizeCount += 1;
    }

    if (attachments.some(function(attachment) {
      return Number(attachment.getSize() || 0) === 0;
    })) {
      flags.push('ZERO_BYTE_ATTACHMENT');
    }

    attachmentCount += attachments.length;
    attachmentBytes += totalBytes;

    if (flags.length > 0) {
      issues.push({
        draftNo: index + 1,
        flags: flags,
        attachmentCount: attachments.length,
        totalMiB: roundMiB_(totalBytes)
      });
    }
  });

  const summary = {
    dryRun: true,
    availableDrafts: allDrafts.length,
    checkedDrafts: targetDrafts.length,
    truncated: allDrafts.length > targetDrafts.length,
    attachmentCount: attachmentCount,
    totalAttachmentMiB: roundMiB_(attachmentBytes),
    keywordWithoutAttachmentCount: keywordWithoutAttachmentCount,
    overSizeCount: overSizeCount,
    issueCount: issues.length,
    issues: issues.slice(0, config.maxIssueRowsInLog)
  };

  // 宛先・件名・本文・ファイル名は出力しません。
  console.log(JSON.stringify(summary));
  return summary;
}

function validateAttachmentAuditConfig_(config) {
  if (!config || typeof config !== 'object') {
    throw new Error('設定が見つかりません。');
  }
  if (config.dryRun !== true) {
    throw new Error('dryRun=false はこの無料コードでは利用できません。');
  }
  if (!Number.isInteger(config.maxDrafts) ||
      config.maxDrafts < 1 ||
      config.maxDrafts > 100) {
    throw new Error('maxDrafts は1〜100の整数にしてください。');
  }
  if (!Number.isFinite(config.maxTotalAttachmentBytes) ||
      config.maxTotalAttachmentBytes < 1024 * 1024 ||
      config.maxTotalAttachmentBytes > 20 * 1024 * 1024) {
    throw new Error('容量上限は1MiB〜20MiBの範囲にしてください。');
  }
  if (!Number.isInteger(config.maxIssueRowsInLog) ||
      config.maxIssueRowsInLog < 1 ||
      config.maxIssueRowsInLog > 50) {
    throw new Error('maxIssueRowsInLog は1〜50の整数にしてください。');
  }
  if (!(config.attachmentWords instanceof RegExp)) {
    throw new Error('attachmentWords は正規表現で指定してください。');
  }
}

function roundMiB_(bytes) {
  return Math.round((bytes / 1024 / 1024) * 100) / 100;
}