Django S3 Pre Signed URLs

# this includes boto3
pip install django-storages[s3]

async function uploadRecording(audioBlob) {
    // Step 1: Get presigned URL from your server
    const response = await fetch('/generate-presigned-url/', {
        method: 'POST',
        headers: {
            'Content-Type': 'application/json',
            'X-CSRFToken': csrfToken
        },
        body: JSON.stringify({
            mime_type: audioBlob.type  // e.g., "audio/webm;codecs=opus"
        })
    });

    const { upload_url, upload_fields, s3_key } = await response.json();

    // Step 2: Upload directly to S3
    const s3FormData = new FormData();
    Object.keys(upload_fields).forEach(key => {
        s3FormData.append(key, upload_fields[key]);
    });
    s3FormData.append('file', audioBlob);

    await fetch(upload_url, {
        method: 'POST',
        body: s3FormData
    });

    // Step 3: Confirm upload with your server
    await fetch('/confirm-upload/', {
        method: 'POST',
        headers: {
            'Content-Type': 'application/json',
            'X-CSRFToken': csrfToken
        },
        body: JSON.stringify({ s3_key })
    });
}

# s3_utils.py
import boto3
import uuid
from django.conf import settings
from django.utils import timezone
from botocore.exceptions import ClientError

def get_s3_client():
    """Get an S3 client configured with Django settings."""
    return boto3.client(
        's3',
        aws_access_key_id=settings.AWS_ACCESS_KEY_ID,
        aws_secret_access_key=settings.AWS_SECRET_ACCESS_KEY,
        region_name=settings.AWS_S3_REGION_NAME
    )
    
def generate_presigned_post_for_recording(mime_type='audio/webm', file_extension='webm'):
    s3_client = get_s3_client()

    # Generate unique filename
    timestamp = timezone.now().strftime('%Y%m%d_%H%M%S')
    unique_id = uuid.uuid4().hex[:8]
    s3_key = f"media/audio_files/recording_{timestamp}_{unique_id}.{file_extension}"

    return s3_client.generate_presigned_post(
        Bucket=settings.AWS_STORAGE_BUCKET_NAME,
        Key=s3_key,
        ExpiresIn=3600,  # 1 hour expiration
        Conditions=[
            {'Content-Type': mime_type},
            ['content-length-range', 0, 100 * 1024 * 1024]  # Max 100MB
        ]
    )

# views.py
import json
from django.contrib.auth.decorators import login_required
from django.http import JsonResponse
from django.utils import timezone

@login_required
def generate_presigned_url(request):
    data = json.loads(request.body)
    mime_type = data.get('mime_type', 'audio/webm')

    # Map MIME type to file extension
    mime_to_ext = {
        'audio/webm': 'webm',
        'audio/ogg': 'ogg',
        'audio/mp4': 'm4a',
    }
    file_extension = mime_to_ext.get(mime_type, 'webm')

    presigned_data = generate_presigned_post_for_recording(mime_type, file_extension)

    return JsonResponse({
        'upload_url': presigned_data['url'],
        'upload_fields': presigned_data['fields'],
        's3_key': presigned_data['s3_key']
    })

def verify_s3_upload(s3_key):
    """Verify that a file was successfully uploaded to S3."""
    s3_client = get_s3_client()  # You'll need this helper too
    try:
        s3_client.head_object(Bucket=settings.AWS_STORAGE_BUCKET_NAME, Key=s3_key)
        return True
    except ClientError:
        return False

@login_required
def confirm_s3_upload(request):
    data = json.loads(request.body)
    s3_key = data.get('s3_key')

    # Verify file exists in S3
    if verify_s3_upload(s3_key):
        # Create Note record pointing to S3 file
        note = Note.objects.create(
            user=request.user,
            title=f"Recording {timezone.now().strftime('%Y-%m-%d')}",
        )
        # Set file path (Django storages handles S3 URLs automatically)
        note.audio_file.name = s3_key.replace('media/', '', 1)
        note.save()

        return JsonResponse({'id': note.id})

    return JsonResponse({'error': 'Upload failed'}, status=400)


# urls.py
path('generate-presigned-url/', views.generate_presigned_url, name='generate_presigned_url'),
path('confirm-upload/', views.confirm_s3_upload, name='confirm_s3_upload'),

  //  S3 CORS Configuration Required

[
    {
        "AllowedHeaders": ["*"],
        "AllowedMethods": ["PUT", "POST"],
        "AllowedOrigins": [
            "https://your-domain.com",
            "http://localhost:8000"
        ],
        "ExposeHeaders": ["ETag"],
        "MaxAgeSeconds": 3000
    }
]

## Required Environment Variables
DJANGO_AWS_ACCESS_KEY_ID=your_key
DJANGO_AWS_SECRET_ACCESS_KEY=your_secret
DJANGO_AWS_STORAGE_BUCKET_NAME=your-bucket
DJANGO_AWS_S3_REGION_NAME=us-east-1