CDN & Object Storage

# Static assets — দীর্ঘ সময় cache করুন
Cache-Control: public, max-age=31536000, immutable
# ১ বছর cache (হ্যাশ-based filename use করুন)

# HTML pages — কম সময়
Cache-Control: public, max-age=3600
# ১ ঘণ্টা cache

# Private (user-specific) — CDN cache করবেন না
Cache-Control: private, no-cache
# Browser cache করতে পারে, CDN পারবেন না

# Never cache করুন না
Cache-Control: no-store
# Real-time data, sensitive information

import boto3
from botocore.exceptions import NoCredentialsError

s3 = boto3.client(
    's3',
    aws_access_key_id='YOUR_KEY',
    aws_secret_access_key='YOUR_SECRET',
    region_name='ap-southeast-1'  # Singapore
)

# ── File Upload ────────────────────────────────
def upload_file(local_path, bucket, s3_key):
    try:
        s3.upload_file(
            local_path, bucket, s3_key,
            ExtraArgs={
                'ContentType': 'image/webp',
                'CacheControl': 'public, max-age=31536000',
                'ACL': 'public-read'
            }
        )
        print(f"✅ Uploaded to s3://{bucket}/{s3_key}")
        return f"https://cdn.myapp.com/{s3_key}"
    except NoCredentialsError:
        raise Exception("AWS credentials not found")

# ── Presigned URL — Direct Browser Upload ──────
def generate_presigned_url(bucket, s3_key, expiry=3600):
    url = s3.generate_presigned_url(
        ClientMethod='put_object',
        Params={
            'Bucket': bucket,
            'Key': s3_key,
            'ContentType': 'image/jpeg'
        },
        ExpiresIn=expiry  # 1 hour
    )
    print(f"⏰ Presigned URL expires in {expiry}s")
    return url

# ── Lifecycle Policy — Auto archive ────────────
s3.put_bucket_lifecycle_configuration(
    Bucket='my-app-uploads',
    LifecycleConfiguration={
        'Rules': [{
            'ID': 'auto-archive',
            'Status': 'Enabled',
            'Transitions': [
                {'Days': 30, 'StorageClass': 'STANDARD_IA'},
                {'Days': 90, 'StorageClass': 'GLACIER'},
            ]
        }]
    }
)

const { S3Client, PutObjectCommand } = require('@aws-sdk/client-s3');
const { getSignedUrl } = require('@aws-sdk/s3-request-presigner');
const { v4: uuidv4 } = require('uuid');

const s3 = new S3Client({ region: 'ap-southeast-1' });

// Generate presigned URL for direct browser upload
app.post('/api/upload-url', async (req, res) => {
  const { fileType, fileName } = req.body;

  // Unique key prevent overwrite
  const key = `uploads/${uuidv4()}-${fileName}`;

  const command = new PutObjectCommand({
    Bucket: 'my-app-bucket',
    Key: key,
    ContentType: fileType,
  });

  // URL expires in 15 minutes
  const uploadUrl = await getSignedUrl(s3, command, { expiresIn: 900 });
  const publicUrl = `https://cdn.myapp.com/${key}`;

  res.json({ uploadUrl, publicUrl, key });
  // Frontend: PUT uploadUrl সরাসরি, তারপর publicUrl save করুন
});