import boto3
from botocore.exceptions import ClientError
from django.conf import settings


def _is_s3_storage():
    return "S3Boto3Storage" in settings.DEFAULT_FILE_STORAGE


def _get_client():
    return boto3.client(
        "s3",
        endpoint_url=settings.AWS_S3_ENDPOINT_URL,
        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_put_url(key, content_type="video/mp4", expires_in=3600):
    """
    Return a presigned PUT URL the client can use to upload directly to Wasabi.
    In development (local filesystem storage) returns None — callers should handle this.
    """
    if not _is_s3_storage():
        return None
    client = _get_client()
    return client.generate_presigned_url(
        "put_object",
        Params={
            "Bucket": settings.AWS_STORAGE_BUCKET_NAME,
            "Key": key,
            "ContentType": content_type,
        },
        ExpiresIn=expires_in,
    )


def generate_presigned_get_url(key, expires_in=3600):
    """Return a presigned GET URL for downloading a private Wasabi object."""
    if not _is_s3_storage():
        return None
    client = _get_client()
    return client.generate_presigned_url(
        "get_object",
        Params={
            "Bucket": settings.AWS_STORAGE_BUCKET_NAME,
            "Key": key,
        },
        ExpiresIn=expires_in,
    )


def object_exists(key):
    """Return True if the object exists in the Wasabi bucket."""
    if not _is_s3_storage():
        # In dev, assume upload happened (no real Wasabi)
        return True
    client = _get_client()
    try:
        client.head_object(Bucket=settings.AWS_STORAGE_BUCKET_NAME, Key=key)
        return True
    except ClientError:
        return False


def preview_url(key):
    """
    Return the public URL for a preview image.
    Uses Cloudflare CDN in production; falls back to a presigned URL.
    """
    if not key:
        return None
    cdn = settings.CDN_BASE_URL
    if cdn:
        return f"{cdn.rstrip('/')}/{key}"
    return generate_presigned_get_url(key, expires_in=86400)