class ActiveStorage::Service::AzureStorageService

def blob_for(key)
  client.get_blob_properties(container, key)
rescue Azure::Core::Http::HTTPError
  false
end

def compose(source_keys, destination_key, filename: nil, content_type: nil, disposition: nil, custom_metadata: {})
  content_disposition = content_disposition_with(type: disposition, filename: filename) if disposition && filename
  client.create_append_blob(
    container,
    destination_key,
    content_type: content_type,
    content_disposition: content_disposition,
    metadata: custom_metadata,
  ).tap do |blob|
    source_keys.each do |source_key|
      stream(source_key) do |chunk|
        client.append_blob_block(container, blob.name, chunk)
      end
    end
  end
end

def custom_metadata_headers(metadata)
  metadata.transform_keys { |key| "x-ms-meta-#{key}" }
end

def delete(key)
  instrument :delete, key: key do
    client.delete_blob(container, key)
  rescue Azure::Core::Http::HTTPError => e
    raise unless e.type == "BlobNotFound"
    # Ignore files already deleted
  end
end

def delete_prefixed(prefix)
  instrument :delete_prefixed, prefix: prefix do
    marker = nil
    loop do
      results = client.list_blobs(container, prefix: prefix, marker: marker)
      results.each do |blob|
        client.delete_blob(container, blob.name)
      end
      break unless marker = results.continuation_token.presence
    end
  end
end

def download(key, &block)
  if block_given?
    instrument :streaming_download, key: key do
      stream(key, &block)
    end
  else
    instrument :download, key: key do
      handle_errors do
        _, io = client.get_blob(container, key)
        io.force_encoding(Encoding::BINARY)
      end
    end
  end
end

def download_chunk(key, range)
  instrument :download_chunk, key: key, range: range do
    handle_errors do
      _, io = client.get_blob(container, key, start_range: range.begin, end_range: range.exclude_end? ? range.end - 1 : range.end)
      io.force_encoding(Encoding::BINARY)
    end
  end
end

def exist?(key)
  instrument :exist, key: key do |payload|
    answer = blob_for(key).present?
    payload[:exist] = answer
    answer
  end
end

def format_expiry(expires_in)
  expires_in ? Time.now.utc.advance(seconds: expires_in).iso8601 : nil
end

def handle_errors
  yield
rescue Azure::Core::Http::HTTPError => e
  case e.type
  when "BlobNotFound"
    raise ActiveStorage::FileNotFoundError
  when "Md5Mismatch"
    raise ActiveStorage::IntegrityError
  else
    raise
  end
end

def headers_for_direct_upload(key, content_type:, checksum:, filename: nil, disposition: nil, custom_metadata: {}, **)
  content_disposition = content_disposition_with(type: disposition, filename: filename) if filename
  { "Content-Type" => content_type, "Content-MD5" => checksum, "x-ms-blob-content-disposition" => content_disposition, "x-ms-blob-type" => "BlockBlob", **custom_metadata_headers(custom_metadata) }
end

def initialize(storage_account_name:, storage_access_key:, container:, public: false, **options)
  @client = Azure::Storage::Blob::BlobService.create(storage_account_name: storage_account_name, storage_access_key: storage_access_key, **options)
  @signer = Azure::Storage::Common::Core::Auth::SharedAccessSignature.new(storage_account_name, storage_access_key)
  @container = container
  @public = public
end

def private_url(key, expires_in:, filename:, disposition:, content_type:, **)
  signer.signed_uri(
    uri_for(key), false,
    service: "b",
    permissions: "r",
    expiry: format_expiry(expires_in),
    content_disposition: content_disposition_with(type: disposition, filename: filename),
    content_type: content_type
  ).to_s
end

def public_url(key, **)
  uri_for(key).to_s
end

def stream(key)
  blob = blob_for(key)
  chunk_size = 5.megabytes
  offset = 0
  raise ActiveStorage::FileNotFoundError unless blob.present?
  while offset < blob.properties[:content_length]
    _, chunk = client.get_blob(container, key, start_range: offset, end_range: offset + chunk_size - 1)
    yield chunk.force_encoding(Encoding::BINARY)
    offset += chunk_size
  end
end

def upload(key, io, checksum: nil, filename: nil, content_type: nil, disposition: nil, custom_metadata: {}, **)
  instrument :upload, key: key, checksum: checksum do
    handle_errors do
      content_disposition = content_disposition_with(filename: filename, type: disposition) if disposition && filename
      client.create_block_blob(container, key, IO.try_convert(io) || io, content_md5: checksum, content_type: content_type, content_disposition: content_disposition, metadata: custom_metadata)
    end
  end
end

def uri_for(key)
  client.generate_uri("#{container}/#{key}")
end

def url_for_direct_upload(key, expires_in:, content_type:, content_length:, checksum:, custom_metadata: {})
  instrument :url, key: key do |payload|
    generated_url = signer.signed_uri(
      uri_for(key), false,
      service: "b",
      permissions: "rw",
      expiry: format_expiry(expires_in)
    ).to_s
    payload[:url] = generated_url
    generated_url
  end
end