Gemini 2.5 Flash と Firebase Remote Config で多言語オンボーディング文言を生成し、段階公開で検証する実装ノート

function generateOnboardingCopy(appId, screenId, lang, tone, currentCopy) {
  const apiKey = PropertiesService.getScriptProperties().getProperty('GEMINI_API_KEY');
  const endpoint = `https://generativelanguage.googleapis.com/v1beta/models/gemini-2.5-flash:generateContent?key=${apiKey}`;
 
  const systemInstruction = [
    `あなたは個人開発者の壁紙アプリ「${appId}」のオンボーディング文言を作成します。`,
    `トーン定義: ${tone}`,
    `言語: ${lang}`,
    `画面: ${screenId}`,
    `タイトルは40文字以内、本文は120文字以内に必ず収めてください。`,
    `絵文字は使わないこと。誇張表現（"最強""神""爆速"等）は禁止。`,
    `必ず JSON 形式で {"title": "...", "body": "..."} を返してください。`
  ].join('\n');
 
  const userPrompt = [
    `現在の文言:`,
    `タイトル: ${currentCopy.title}`,
    `本文: ${currentCopy.body}`,
    ``,
    `これを ${lang} 向けに刷新してください。意味は保ちつつ、より自然で温かい言い回しに変えてください。`
  ].join('\n');
 
  const payload = {
    systemInstruction: { parts: [{ text: systemInstruction }] },
    contents: [{ role: 'user', parts: [{ text: userPrompt }] }],
    generationConfig: {
      temperature: 0.7,
      maxOutputTokens: 512,
      responseMimeType: 'application/json',
      responseSchema: {
        type: 'object',
        properties: {
          title: { type: 'string' },
          body: { type: 'string' }
        },
        required: ['title', 'body']
      }
    }
  };
 
  const response = UrlFetchApp.fetch(endpoint, {
    method: 'post',
    contentType: 'application/json',
    payload: JSON.stringify(payload),
    muteHttpExceptions: true
  });
 
  if (response.getResponseCode() !== 200) {
    throw new Error(`Gemini API error ${response.getResponseCode()}: ${response.getContentText()}`);
  }
 
  const data = JSON.parse(response.getContentText());
  const text = data.candidates[0].content.parts[0].text;
  const parsed = JSON.parse(text);
 
  // 長さ制約の事後検証
  if (parsed.title.length > 40 || parsed.body.length > 120) {
    throw new Error(`Length violation: title=${parsed.title.length}, body=${parsed.body.length}`);
  }
 
  return parsed;
}

function updateRemoteConfig(appId, copyMap) {
  const accessToken = getServiceAccountAccessToken_();
  const projectId = PropertiesService.getScriptProperties().getProperty(`FIREBASE_PROJECT_${appId}`);
 
  // 1. ETag 付きで現在の template を取得
  const getResp = UrlFetchApp.fetch(
    `https://firebaseremoteconfig.googleapis.com/v1/projects/${projectId}/remoteConfig`,
    {
      method: 'get',
      headers: { Authorization: `Bearer ${accessToken}` },
      muteHttpExceptions: true
    }
  );
  if (getResp.getResponseCode() !== 200) {
    throw new Error(`Remote Config get failed: ${getResp.getContentText()}`);
  }
  const etag = getResp.getHeaders()['ETag'];
  const template = JSON.parse(getResp.getContentText());
 
  // 2. parameters を multi-locale 形式で更新
  for (const [screenId, langMap] of Object.entries(copyMap)) {
    for (const [lang, copy] of Object.entries(langMap)) {
      const key = `onboarding_${screenId}_${lang}_title`;
      template.parameters[key] = {
        defaultValue: { value: copy.title },
        valueType: 'STRING',
        description: `Auto-generated by Gemini 2.5 Flash on ${new Date().toISOString()}`
      };
      const bodyKey = `onboarding_${screenId}_${lang}_body`;
      template.parameters[bodyKey] = {
        defaultValue: { value: copy.body },
        valueType: 'STRING',
        description: `Auto-generated by Gemini 2.5 Flash on ${new Date().toISOString()}`
      };
    }
  }
 
  // 3. 段階公開条件を組み立て（20% rollout のための %-based condition）
  template.conditions = template.conditions || [];
  const rolloutCondName = `onboarding_v3_rollout_20`;
  if (!template.conditions.find(c => c.name === rolloutCondName)) {
    template.conditions.unshift({
      name: rolloutCondName,
      expression: `percent <= 20`,
      tagColor: 'BLUE'
    });
  }
 
  // 4. PUT で書き戻し
  const putResp = UrlFetchApp.fetch(
    `https://firebaseremoteconfig.googleapis.com/v1/projects/${projectId}/remoteConfig`,
    {
      method: 'put',
      headers: {
        Authorization: `Bearer ${accessToken}`,
        'Content-Type': 'application/json; UTF-8',
        'If-Match': etag
      },
      payload: JSON.stringify(template),
      muteHttpExceptions: true
    }
  );
  if (putResp.getResponseCode() !== 200) {
    throw new Error(`Remote Config put failed: ${putResp.getContentText()}`);
  }
  return JSON.parse(putResp.getContentText());
}

// Android: Kotlin
val remoteConfig = FirebaseRemoteConfig.getInstance()
remoteConfig.fetchAndActivate().addOnCompleteListener { task ->
    if (task.isSuccessful) {
        val variant = remoteConfig.getString("onboarding_variant")  // "v3" or "v2"
        FirebaseAnalytics.getInstance(this).setUserProperty("onboarding_variant", variant)
 
        FirebaseAnalytics.getInstance(this).logEvent("onboarding_shown") {
            param("variant", variant)
            param("screen", "welcome")
        }
    }
}

// iOS: Swift
RemoteConfig.remoteConfig().fetchAndActivate { status, error in
    guard error == nil else { return }
    let variant = RemoteConfig.remoteConfig()["onboarding_variant"].stringValue ?? "v2"
    Analytics.setUserProperty(variant, forName: "onboarding_variant")
    Analytics.logEvent("onboarding_shown", parameters: [
        "variant": variant,
        "screen": "welcome"
    ])
}

WITH first_open AS (
  SELECT
    user_pseudo_id,
    MIN(event_date) AS first_day,
    ANY_VALUE(user_properties) AS uprops
  FROM `myproject.analytics_123456789.events_*`
  WHERE event_name = 'first_open'
    AND _TABLE_SUFFIX BETWEEN '20260510' AND '20260518'
  GROUP BY user_pseudo_id
),
day1_active AS (
  SELECT DISTINCT user_pseudo_id, event_date
  FROM `myproject.analytics_123456789.events_*`
  WHERE event_name IN ('app_open', 'screen_view')
)
SELECT
  (SELECT value.string_value FROM UNNEST(fo.uprops) WHERE key = 'onboarding_variant') AS variant,
  COUNT(DISTINCT fo.user_pseudo_id) AS new_users,
  COUNT(DISTINCT CASE
    WHEN d1.event_date = FORMAT_DATE('%Y%m%d', DATE_ADD(PARSE_DATE('%Y%m%d', fo.first_day), INTERVAL 1 DAY))
    THEN fo.user_pseudo_id END) AS day1_retained,
  SAFE_DIVIDE(
    COUNT(DISTINCT CASE
      WHEN d1.event_date = FORMAT_DATE('%Y%m%d', DATE_ADD(PARSE_DATE('%Y%m%d', fo.first_day), INTERVAL 1 DAY))
      THEN fo.user_pseudo_id END),
    COUNT(DISTINCT fo.user_pseudo_id)
  ) AS d1_retention
FROM first_open fo
LEFT JOIN day1_active d1 ON fo.user_pseudo_id = d1.user_pseudo_id
GROUP BY variant
ORDER BY variant;