module S3Policy

# File lib/s3_policy.rb, line 42
def encode_document(policy_document)
  Base64.strict_encode64(policy_document.to_json)
end

# File lib/s3_policy.rb, line 12
def generate_policy_document(options={})
  # Required
  bucket = options[:bucket]

  # Optional
  acl = options[:acl] || "public-read"
  content_type = options[:content_type] || ""
  expiration = options[:expiration] || one_week_from_now
  max_size = options[:max_size] || 1024 * 1024 * 10
  namespace = options[:namespace] || ""

  # TODO: ACL Option

  policy_document = {
    expiration: expiration,
    conditions: [
      { bucket: bucket},
      ["starts-with", "$key", namespace],
      { acl: acl},
      ["starts-with", "$Cache-Control", ""],
      ["starts-with", "$Content-Type", content_type],
      ["content-length-range", 0, max_size]
    ]
  }
end

# File lib/s3_policy.rb, line 38
def one_week_from_now
  (DateTime.now + 7).to_time.utc.iso8601
end

# File lib/s3_policy.rb, line 46
def sign_document(policy_document, secret_key)
  sign_encoded_document(encode_document(policy_document), secret_key)
end

# File lib/s3_policy.rb, line 50
def sign_encoded_document(encoded_policy_document, secret_key)
  Base64.strict_encode64(
    OpenSSL::HMAC.digest(
      OpenSSL::Digest::Digest.new('sha1'),
      secret_key,
      encoded_policy_document
    )
  )
end