class S3Cache

# File lib/s3cache.rb, line 10
def initialize(**params)

  @logger = Rails.logger ? Rails.logger : Logger.new(STDOUT)

  if not params.to_h[:bucket_name]
    @logger.info{ "requires {:bucket_name => String, (optional) :expires => Integer}" }
  end

  @bucket_name = params.to_h[:bucket_name]
  @expires = params.to_h[:expires] ? params.to_h[:expires] : 32.days
  
  if ENV['AWS_ACCESS_KEY_ID'].nil? || ENV['AWS_SECRET_ACCESS_KEY'].nil?
    puts 'Enviroment variables AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY must be defined. Learn more http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-started.html#config-settings-and-precedence'  
  else
    @s3 = Aws::S3::Client.new
    if not bucket_exist?
      @logger.debug( "creating bucket #{@bucket_name}" )
      bucket_create
    end
  end
end

# File lib/s3cache.rb, line 79
def clear
  cache_keys.each do |key|
    @logger.debug( "deleting key #{key}" )
    @s3.delete_object({:bucket => @bucket_name, :key => key})
  end
end

# File lib/s3cache.rb, line 67
def exist?(key)   
  key_name = cache_key( key )
  begin
    response =  @s3.get_object({:bucket => @bucket_name, :key => key_name})
  rescue 
    response = nil
  end
  
  @logger.debug( "exists? #{!response.nil?} #{key_name}" )
  return !response.nil?
end

# File lib/s3cache.rb, line 53
def fetch(key, **params)
  key_name = cache_key( key )

  if(exist?(key_name) )
    @logger.debug( "fetch->read #{key_name}" )
    read (key_name)
  else
    @logger.debug( "fetch->write #{key_name}" )
    value = yield
    write(key_name, value)  
    read (key_name)    
  end    
end

# File lib/s3cache.rb, line 32
def read(key, **params)
  key_name = cache_key( key )
  @logger.debug( "read #{key_name}" )
  if exist?(key_name)
    Marshal.load(@s3.get_object({ bucket: @bucket_name, key: key_name }).body.read)
  else
    return false
  end    
end

# File lib/s3cache.rb, line 42
def write(key, contents, **params) 
  key_name = cache_key( key )
  @logger.debug( "write #{key_name}" )
  @s3.put_object({ 
    bucket: @bucket_name, 
    key: key_name, 
    expires: Time.now + @expires.days,
    body: Marshal.dump(contents),
  })
end

# File lib/s3cache.rb, line 105
def bucket_create
  @s3.create_bucket({
    acl: "private", # accepts private, public-read, public-read-write, authenticated-read
    bucket: @bucket_name, # required
  })      
end

# File lib/s3cache.rb, line 112
def bucket_exist?
  begin
    response = @s3.head_bucket({ bucket: @bucket_name })
  rescue 
    response = nil
  end
  return !response.nil?
end

# File lib/s3cache.rb, line 97
def cache_key(key)      
  if(key.is_a?(String) && key.downcase.match(/^[a-f0-9]{64}$/) )
    key
  else
    Digest::SHA256.hexdigest(key.to_s).to_s        
  end      
end

# File lib/s3cache.rb, line 89
def cache_keys
  @s3.list_objects({:bucket => @bucket_name}).first[:contents].collect{|e|e.key}
end

# File lib/s3cache.rb, line 93
def cache_valid(key)
  exist?(key)
end