class ShopifyAPI::Webhooks::Registry

def add_registration(topic:, delivery_method:, path:, handler: nil, fields: nil, metafield_namespaces: nil)
  @registry[topic] = case delivery_method
  when :pub_sub
    Registrations::PubSub.new(topic: topic, path: path, fields: fields,
      metafield_namespaces: metafield_namespaces)
  when :event_bridge
    Registrations::EventBridge.new(topic: topic, path: path, fields: fields,
      metafield_namespaces: metafield_namespaces)
  when :http
    unless handler
      raise Errors::InvalidWebhookRegistrationError, "Cannot create an Http registration without a handler."
    end
    Registrations::Http.new(topic: topic, path: path, handler: handler,
      fields: fields, metafield_namespaces: metafield_namespaces)
  else
    raise Errors::InvalidWebhookRegistrationError,
      "Unsupported delivery method #{delivery_method}. Allowed values: {:http, :pub_sub, :event_bridge}."
  end
end

def clear
  @registry.clear
end

def get_webhook_id(topic:, client:)
  fetch_id_query = <<~QUERY
    {
      webhookSubscriptions(first: 1, topics: #{topic.gsub(%r{/|\.}, "_").upcase}) {
        edges {
          node {
            id
          }
        }
      }
    }
  QUERY
  fetch_id_response = client.query(query: fetch_id_query)
  raise Errors::WebhookRegistrationError,
    "Failed to fetch webhook from Shopify" unless fetch_id_response.ok?
  body = T.cast(fetch_id_response.body, T::Hash[String, T.untyped])
  errors = body["errors"] || {}
  raise Errors::WebhookRegistrationError,
    "Failed to fetch webhook from Shopify: #{errors[0]["message"]}" unless errors.empty?
  edges = body.dig("data", "webhookSubscriptions", "edges") || {}
  return nil if edges.empty?
  edges[0]["node"]["id"].to_s
end

def process(request)
  raise Errors::InvalidWebhookError, "Invalid webhook HMAC." unless Utils::HmacValidator.validate(request)
  handler = @registry[request.topic]&.handler
  unless handler
    raise Errors::NoWebhookHandler, "No webhook handler found for topic: #{request.topic}."
  end
  handler.handle(topic: request.topic, shop: request.shop, body: request.parsed_body)
end

def register(topic:, session:)
  registration = @registry[topic]
  unless registration
    raise Errors::InvalidWebhookRegistrationError, "Webhook topic #{topic} has not been added to the registry."
  end
  client = Clients::Graphql::Admin.new(session: session)
  register_check_result = webhook_registration_needed?(client, registration)
  registered = true
  register_body = nil
  if register_check_result[:must_register]
    register_body = send_register_request(
      client,
      registration,
      register_check_result[:webhook_id],
    )
    registered = registration_sucessful?(
      register_body,
      registration.mutation_name(register_check_result[:webhook_id]),
    )
  end
  RegisterResult.new(topic: topic, success: registered, body: register_body)
end

def register_all(session:)
  topics = @registry.keys
  result = T.let([], T::Array[RegisterResult])
  topics.each do |topic|
    register_response = register(
      topic: topic,
      session: session,
    )
    result.push(register_response)
  end
  result
end

def registration_sucessful?(body, mutation_name)
  !body.dig("data", mutation_name, "webhookSubscription").nil?
end

def send_register_request(client, registration, webhook_id)
  register_response = client.query(query: registration.build_register_query(webhook_id: webhook_id))
  raise Errors::WebhookRegistrationError, "Failed to register webhook with Shopify" unless register_response.ok?
  T.cast(register_response.body, T::Hash[String, T.untyped])
end

def unregister(topic:, session:)
  client = Clients::Graphql::Admin.new(session: session)
  webhook_id = get_webhook_id(topic: topic, client: client)
  return {} if webhook_id.nil?
  delete_mutation = <<~MUTATION
    mutation webhookSubscription {
      webhookSubscriptionDelete(id: "#{webhook_id}") {
        userErrors {
          field
          message
        }
        deletedWebhookSubscriptionId
      }
    }
  MUTATION
  delete_response = client.query(query: delete_mutation)
  raise Errors::WebhookRegistrationError,
    "Failed to delete webhook from Shopify" unless delete_response.ok?
  result = T.cast(delete_response.body, T::Hash[String, T.untyped])
  errors = result["errors"] || {}
  raise Errors::WebhookRegistrationError,
    "Failed to delete webhook from Shopify: #{errors[0]["message"]}" unless errors.empty?
  user_errors = result.dig("data", "webhookSubscriptionDelete", "userErrors") || {}
  raise Errors::WebhookRegistrationError,
    "Failed to delete webhook from Shopify: #{user_errors[0]["message"]}" unless user_errors.empty?
  result
end

def webhook_registration_needed?(client, registration)
  check_response = client.query(query: registration.build_check_query)
  raise Errors::WebhookRegistrationError,
    "Failed to check if webhook was already registered" unless check_response.ok?
  parsed_check_result = registration.parse_check_result(T.cast(check_response.body, T::Hash[String, T.untyped]))
  must_register = parsed_check_result[:current_address] != registration.callback_address
  { webhook_id: parsed_check_result[:webhook_id], must_register: must_register }
end