require 'faraday'
require 'base64'
require 'openssl'
require 'digest'

class AzureBlobService
    
    CONNECTION_STRING = Rails.application.credentials.azure_storage_connection_string
    STORAGE_ACCOUNT = CONNECTION_STRING.match(/AccountName=(.*?);/)[1]
    ACCESS_KEY = CONNECTION_STRING.match(/AccountKey=(.*?);/)[1]

    def initialize(container)
        @container = container
    end

    def list_blobs

        date = Time.now.httpdate

        resource = "/#{STORAGE_ACCOUNT}/#{@container}\ncomp:list\nrestype:container"
        url = "https://#{STORAGE_ACCOUNT}.blob.core.windows.net/#{@container}?restype=container&comp=list"

        headers = {
            'x-ms-date' => date,
            'x-ms-version' => '2018-03-28',
            'Authorization' => generate_auth_header('GET', date, resource)
        }

        connection = Faraday.new(url: url)
        response = connection.get do |req|
            headers.each do |key, value|
                req.headers[key] = value
            end
        end

        response.body
    end

    def get_blob(path)

        date = Time.now.httpdate

        resource = "/#{STORAGE_ACCOUNT}/#{@container}/#{path}"

        url = "https://#{STORAGE_ACCOUNT}.blob.core.windows.net/#{@container}/#{path}"

        headers = {
            'x-ms-date' => date,
            'x-ms-version' => '2018-03-28',
            'Authorization' => generate_auth_header('GET', date, resource)
        }

        connection = Faraday.new(url: url)
        response = connection.get do |req|
            headers.each do |key, value|
                req.headers[key] = value
            end
        end

        response.body

    end

private

    def generate_auth_header(http_method, date, resource)

        signature_string = "#{http_method}\n\n\n\n\n\n\n\n\n\n\n\nx-ms-date:#{date}\nx-ms-version:2018-03-28\n#{resource}"

        hash = OpenSSL::HMAC.digest('sha256', Base64.decode64(ACCESS_KEY), signature_string)

        signature = Base64.encode64(hash)

        auth_header = "SharedKey #{STORAGE_ACCOUNT}:#{signature}".strip

        return auth_header
    end

end