module Maestrano::Connector::Rails::Concerns::Entity
  extend ActiveSupport::Concern

  module ClassMethods
    # Return an array of all the entities that the connector can synchronize
    # If you add new entities, you need to generate
    # a migration to add them to existing organizations
    def entities_list
      raise "Not implemented"
    end

    # ----------------------------------------------
    #                 IdMap methods
    # ----------------------------------------------
    def names_hash
      {
        connec_entity: connec_entity_name.downcase,
        external_entity: external_entity_name.downcase
      }
    end

    def find_or_create_idmap(organization_and_id)
      Maestrano::Connector::Rails::IdMap.find_or_create_by(names_hash.merge(organization_and_id))
    end

    # organization_and_id can be either:
    # * {connec_id: 'id', organization_id: 'id'}
    # * {external_id: 'id', organization_id: 'id'}
    # Needs to include either connec_entity or external_entity for complex entities
    def find_idmap(organization_and_id)
      Maestrano::Connector::Rails::IdMap.find_by(names_hash.merge(organization_and_id))
    end

    def create_idmap_from_external_entity(entity, organization)
      h = names_hash.merge({
        external_id: id_from_external_entity_hash(entity),
        name: object_name_from_external_entity_hash(entity),
        organization_id: organization.id
      })
      Maestrano::Connector::Rails::IdMap.create(h)
    end

    def create_idmap_from_connec_entity(entity, organization)
      h = names_hash.merge({
        connec_id: entity['id'],
        name: object_name_from_connec_entity_hash(entity),
        organization_id: organization.id
      })
      Maestrano::Connector::Rails::IdMap.create(h)
    end

    # ----------------------------------------------
    #              Connec! methods
    # ----------------------------------------------
    def normalized_connec_entity_name
      normalize_connec_entity_name(connec_entity_name)
    end

    def normalize_connec_entity_name(name)
      if singleton?
        name.parameterize('_')
      else
        name.parameterize('_').pluralize
      end
    end

    # ----------------------------------------------
    #             External methods
    # ----------------------------------------------
    def id_from_external_entity_hash(entity)
      raise "Not implemented"
    end

    def last_update_date_from_external_entity_hash(entity)
      raise "Not implemented"
    end

    # ----------------------------------------------
    #             Entity specific methods
    # Those methods need to be define in each entity
    # ----------------------------------------------
    # Is this resource a singleton (in Connec!)?
    def singleton?
      false
    end

    # Entity name in Connec!
    def connec_entity_name
      raise "Not implemented"
    end

    # Entity name in external system
    def external_entity_name
      raise "Not implemented"
    end

    # Entity Mapper Class
    def mapper_class
      raise "Not implemented"
    end

    # Return a string representing the object from a connec! entity hash
    def object_name_from_connec_entity_hash(entity)
      raise "Not implemented"
    end

    # Return a string representing the object from an external entity hash
    def object_name_from_external_entity_hash(entity)
      raise "Not implemented"
    end

    # [{reference_class: Entities::.., connec_field: 'account_id', external_field: 'account/something/id'}]
    # ledger_account_idmap = Entities::Account.find_idmap({connec_id: entity['account_id'], organization_id: organization.id})
    # ledger_account_id = ledger_account_idmap && ledger_account_idmap.external_id
    def references
      []
    end

    def can_read_connec?
      true
    end

    def can_read_external?
      true
    end

    def can_write_connec?
      true
    end

    def can_write_external?
      true
    end

    def can_update_connec?
      true
    end

    def can_update_external?
      true
    end
  end

  # ----------------------------------------------
  #                 Mapper methods
  # ----------------------------------------------
  # Map a Connec! entity to the external format
  def map_to_external(entity, organization)
    ref_hash = {}
    self.class.references.each do |ref|
      ref_hash.merge! ref[:external_field].split('/').reverse.inject(self.class.id_from_ref(entity, ref, false, organization)) { |a, n| { n.to_sym => a } }
    end

    self.class.mapper_class.normalize(entity).merge(ref_hash)
  end

  # Map an external entity to Connec! format
  def map_to_connec(entity, organization)
    ref_hash = {}
    self.class.references.each do |ref|
      ref_hash.merge! ref[:connec_field].split('/').reverse.inject(self.class.id_from_ref(entity, ref, true, organization)) { |a, n| { n.to_sym => a } }
    end

    self.class.mapper_class.denormalize(entity).merge(ref_hash)
  end

  # ----------------------------------------------
  #                 Connec! methods
  # ----------------------------------------------
  # Supported options:
  # * full_sync
  # * $filter (see Connec! documentation)
  # * $orderby (see Connec! documentation)
  def get_connec_entities(client, last_synchronization, organization, opts={})
    return [] unless self.class.can_read_connec?

    Maestrano::Connector::Rails::ConnectorLogger.log('info', organization, "Fetching Connec! #{self.class.connec_entity_name}")

    entities = []
    query_params = {}
    query_params[:$orderby] = opts[:$orderby] if opts[:$orderby]

    # Fetch first page
    if last_synchronization.blank? || opts[:full_sync]
      Maestrano::Connector::Rails::ConnectorLogger.log('debug', organization, "entity=#{self.class.connec_entity_name}, fetching all data")
      query_params[:$filter] = opts[:$filter] if opts[:$filter]
    else
      Maestrano::Connector::Rails::ConnectorLogger.log('debug', organization, "entity=#{self.class.connec_entity_name}, fetching data since #{last_synchronization.updated_at.iso8601}")
      filter = "updated_at gt '#{last_synchronization.updated_at.iso8601}'"
      filter += " and #{opts[:$filter]}" if opts[:$filter]
      query_params[:$filter] = filter
    end
    response = client.get("/#{self.class.normalized_connec_entity_name}?#{query_params.to_query}")
    raise "No data received from Connec! when trying to fetch #{self.class.connec_entity_name.pluralize}" unless response

    response_hash = JSON.parse(response.body)
    Maestrano::Connector::Rails::ConnectorLogger.log('debug', organization, "received first page entity=#{self.class.connec_entity_name}, response=#{response.body}")
    if response_hash["#{self.class.normalized_connec_entity_name}"]
      entities << response_hash["#{self.class.normalized_connec_entity_name}"]
    else
      raise "Received unrecognized Connec! data when trying to fetch #{self.class.connec_entity_name.pluralize}"
    end

    # Fetch subsequent pages
    while response_hash['pagination'] && response_hash['pagination']['next']
      # ugly way to convert https://api-connec/api/v2/group_id/organizations?next_page_params to /organizations?next_page_params
      next_page = response_hash['pagination']['next'].gsub(/^(.*)\/#{self.class.normalized_connec_entity_name}/, self.class.normalized_connec_entity_name)
      response = client.get(next_page)

      raise "No data received from Connec! when trying to fetch subsequent page of #{self.class.connec_entity_name.pluralize}" unless response
      Maestrano::Connector::Rails::ConnectorLogger.log('debug', organization, "received next page entity=#{self.class.connec_entity_name}, response=#{response.body}")

      response_hash = JSON.parse(response.body)
      if response_hash["#{self.class.normalized_connec_entity_name}"]
        entities << response_hash["#{self.class.normalized_connec_entity_name}"]
      else
        raise "Received unrecognized Connec! data when trying to fetch subsequent page of #{self.class.connec_entity_name.pluralize}"
      end
    end

    entities = entities.flatten
    Maestrano::Connector::Rails::ConnectorLogger.log('info', organization, "Received data: Source=Connec!, Entity=#{self.class.connec_entity_name}, Data=#{entities}")
    entities
  end

  def push_entities_to_connec(connec_client, mapped_external_entities_with_idmaps, organization)
    push_entities_to_connec_to(connec_client, mapped_external_entities_with_idmaps, self.class.connec_entity_name, organization)
  end

  def push_entities_to_connec_to(connec_client, mapped_external_entities_with_idmaps, connec_entity_name, organization)
    return unless self.class.can_write_connec?

    Maestrano::Connector::Rails::ConnectorLogger.log('info', organization, "Sending #{Maestrano::Connector::Rails::External.external_name} #{self.class.external_entity_name.pluralize} to Connec! #{connec_entity_name.pluralize}")
    mapped_external_entities_with_idmaps.each do |mapped_external_entity_with_idmap|
      external_entity = mapped_external_entity_with_idmap[:entity]
      idmap = mapped_external_entity_with_idmap[:idmap]

      begin
        if idmap.connec_id.blank?
          connec_entity = create_connec_entity(connec_client, external_entity, self.class.normalize_connec_entity_name(connec_entity_name), organization)
          idmap.update_attributes(connec_id: connec_entity['id'], last_push_to_connec: Time.now, message: nil)
        else
          next unless self.class.can_update_connec?
          connec_entity = update_connec_entity(connec_client, external_entity, idmap.connec_id, self.class.normalize_connec_entity_name(connec_entity_name), organization)
          idmap.update_attributes(last_push_to_connec: Time.now, message: nil)
        end
      rescue => e
        # Store Connec! error if any
        Maestrano::Connector::Rails::ConnectorLogger.log('error', organization, "Error while pushing to Connec!: #{e}")
        idmap.update_attributes(message: e.message)
      end
    end
  end

  def create_connec_entity(connec_client, mapped_external_entity, connec_entity_name, organization)
    Maestrano::Connector::Rails::ConnectorLogger.log('info', organization, "Sending create #{connec_entity_name}: #{mapped_external_entity} to Connec!")
    response = connec_client.post("/#{connec_entity_name}", { "#{connec_entity_name}".to_sym => mapped_external_entity })
    response = JSON.parse(response.body)
    raise "Connec!: #{response['errors']['title']}" if response['errors'] && response['errors']['title']
    response["#{connec_entity_name}"]
  end

  def update_connec_entity(connec_client, mapped_external_entity, connec_id, connec_entity_name, organization)

    Maestrano::Connector::Rails::ConnectorLogger.log('info', organization, "Sending update #{connec_entity_name}: #{mapped_external_entity} to Connec!")
    response = connec_client.put("/#{connec_entity_name}/#{connec_id}", { "#{connec_entity_name}".to_sym => mapped_external_entity })
    response = JSON.parse(response.body)
    raise "Connec!: #{response['errors']['title']}" if response['errors'] && response['errors']['title']
    response["#{connec_entity_name}"]
  end

  def map_to_external_with_idmap(entity, organization)
    idmap = self.class.find_idmap({connec_id: entity['id'], organization_id: organization.id})

    if idmap
      idmap.update(name: self.class.object_name_from_connec_entity_hash(entity))
      if (!idmap.to_external) || (idmap.last_push_to_external && idmap.last_push_to_external > entity['updated_at'])
        Maestrano::Connector::Rails::ConnectorLogger.log('info', organization, "Discard Connec! #{self.class.connec_entity_name} : #{entity}")
        nil
      else
        {entity: map_to_external(entity, organization), idmap: idmap}
      end
    else
      {entity: map_to_external(entity, organization), idmap: self.class.create_idmap_from_connec_entity(entity, organization)}
    end
  end

  # ----------------------------------------------
  #                 External methods
  # ----------------------------------------------
  def get_external_entities(client, last_synchronization, organization, opts={})
    return [] unless self.class.can_read_external?
    Maestrano::Connector::Rails::ConnectorLogger.log('info', organization, "Fetching #{Maestrano::Connector::Rails::External.external_name} #{self.class.external_entity_name.pluralize}")
    raise "Not implemented"
  end

  def push_entities_to_external(external_client, mapped_connec_entities_with_idmaps, organization)
    push_entities_to_external_to(external_client, mapped_connec_entities_with_idmaps, self.class.external_entity_name, organization)
  end

  def push_entities_to_external_to(external_client, mapped_connec_entities_with_idmaps, external_entity_name, organization)
    return unless self.class.can_write_external?
    Maestrano::Connector::Rails::ConnectorLogger.log('info', organization, "Sending Connec! #{self.class.connec_entity_name.pluralize} to #{Maestrano::Connector::Rails::External.external_name} #{external_entity_name.pluralize}")
    mapped_connec_entities_with_idmaps.each do |mapped_connec_entity_with_idmap|
      push_entity_to_external(external_client, mapped_connec_entity_with_idmap, external_entity_name, organization)
    end
  end

  def push_entity_to_external(external_client, mapped_connec_entity_with_idmap, external_entity_name, organization)
    idmap = mapped_connec_entity_with_idmap[:idmap]
    connec_entity = mapped_connec_entity_with_idmap[:entity]

    begin
      if idmap.external_id.blank?
        external_id = create_external_entity(external_client, connec_entity, external_entity_name, organization)
        idmap.update_attributes(external_id: external_id, last_push_to_external: Time.now, message: nil)
      else
        return unless self.class.can_update_external?
        update_external_entity(external_client, connec_entity, idmap.external_id, external_entity_name, organization)
        idmap.update_attributes(last_push_to_external: Time.now, message: nil)
      end
    rescue => e
      # Store External error
      Maestrano::Connector::Rails::ConnectorLogger.log('error', organization, "Error while pushing to #{Maestrano::Connector::Rails::External.external_name}: #{e}")
      idmap.update_attributes(message: e.message)
    end
  end

  def create_external_entity(client, mapped_connec_entity, external_entity_name, organization)
    Maestrano::Connector::Rails::ConnectorLogger.log('info', organization, "Sending create #{external_entity_name}: #{mapped_connec_entity} to #{Maestrano::Connector::Rails::External.external_name}")
    raise "Not implemented"
  end

  def update_external_entity(client, mapped_connec_entity, external_id, external_entity_name, organization)
    Maestrano::Connector::Rails::ConnectorLogger.log('info', organization, "Sending update #{external_entity_name} (id=#{external_id}): #{mapped_connec_entity} to #{Maestrano::Connector::Rails::External.external_name}")
    raise "Not implemented"
  end
  # ----------------------------------------------
  #                 General methods
  # ----------------------------------------------
  # * Discards entities that do not need to be pushed because they have not been updated since their last push
  # * Discards entities from one of the two source in case of conflict
  # * Maps not discarded entities and associates them with their idmap, or create one if there isn't any
  # * Return a hash {connec_entities: [], external_entities: []}
  def consolidate_and_map_data(connec_entities, external_entities, organization, opts={})
    return consolidate_and_map_singleton(connec_entities, external_entities, organization, opts) if self.class.singleton?

    mapped_external_entities = external_entities.map{|entity|
      idmap = self.class.find_idmap({external_id: self.class.id_from_external_entity_hash(entity), organization_id: organization.id})
      # No idmap: creating one, nothing else to do
      if idmap
        idmap.update(name: self.class.object_name_from_external_entity_hash(entity))
      else
        next {entity: map_to_connec(entity, organization), idmap: self.class.create_idmap_from_external_entity(entity, organization)}
      end

      # Not pushing entity to Connec!
      next nil unless idmap.to_connec

      # Entity has not been modified since its last push to connec!
      next nil if self.class.not_modified_since_last_push_to_connec?(idmap, entity, self, organization)

      # Check for conflict with entities from connec!
      self.class.solve_conflict(entity, self, connec_entities, self.class.connec_entity_name, idmap, organization, opts)
    }
    mapped_external_entities.compact!

    mapped_connec_entities = connec_entities.map{|entity|
      map_to_external_with_idmap(entity, organization)
    }
    mapped_connec_entities.compact!

    return {connec_entities: mapped_connec_entities, external_entities: mapped_external_entities}
  end

  def consolidate_and_map_singleton(connec_entities, external_entities, organization, opts={})
    return {connec_entities: [], external_entities: []} if external_entities.empty? && connec_entities.empty?

    idmap = self.class.find_or_create_idmap({organization_id: organization.id})

    if external_entities.empty?
      keep_external = false
    elsif connec_entities.empty?
      keep_external = true
    elsif !opts[:connec_preemption].nil?
      keep_external = !opts[:connec_preemption]
    else
      keep_external = self.class.is_external_more_recent?(connec_entities.first, external_entities.first, self)
    end
    if keep_external
      idmap.update(external_id: self.class.id_from_external_entity_hash(external_entities.first), name: self.class.object_name_from_external_entity_hash(external_entities.first))
      return {connec_entities: [], external_entities: [{entity: map_to_connec(external_entities.first, organization), idmap: idmap}]}
    else
      idmap.update(connec_id: connec_entities.first['id'], name: self.class.object_name_from_connec_entity_hash(connec_entities.first))
      return {connec_entities: [{entity: map_to_external(connec_entities.first, organization), idmap: idmap}], external_entities: []}
    end
  end

  # ----------------------------------------------
  #             After and before sync
  # ----------------------------------------------
  def before_sync(connec_client, external_client, last_synchronization, organization, opts)
    # Does nothing by default
  end

  def after_sync(connec_client, external_client, last_synchronization, organization, opts)
    # Does nothing by default
  end

  # ----------------------------------------------
  #             Internal helper methods
  # ----------------------------------------------
  module ClassMethods
    def not_modified_since_last_push_to_connec?(idmap, entity, entity_instance, organization)
      result = idmap.last_push_to_connec && idmap.last_push_to_connec > entity_instance.class.last_update_date_from_external_entity_hash(entity)
      Maestrano::Connector::Rails::ConnectorLogger.log('info', organization, "Discard #{Maestrano::Connector::Rails::External::external_name} #{entity_instance.class.external_entity_name} : #{entity}") if result
      result
    end

    def is_external_more_recent?(connec_entity, external_entity, entity_instance)
      connec_entity['updated_at'] < entity_instance.class.last_update_date_from_external_entity_hash(external_entity)
    end

    def solve_conflict(external_entity, entity_instance, connec_entities, connec_entity_name, idmap, organization, opts)
      if idmap.connec_id && connec_entity = connec_entities.detect{|connec_entity| connec_entity['id'] == idmap.connec_id}
        # We keep the most recently updated entity
        if !opts[:connec_preemption].nil?
          keep_external = !opts[:connec_preemption]
        else
          keep_external = is_external_more_recent?(connec_entity, external_entity, entity_instance)
        end

        if keep_external
          Maestrano::Connector::Rails::ConnectorLogger.log('info', organization, "Conflict between #{Maestrano::Connector::Rails::External::external_name} #{entity_instance.class.external_entity_name} #{external_entity} and Connec! #{connec_entity_name} #{connec_entity}. Entity from external kept")
          connec_entities.delete(connec_entity)
          entity_instance.map_external_entity_with_idmap(external_entity, connec_entity_name, idmap, organization)
        else
          Maestrano::Connector::Rails::ConnectorLogger.log('info', organization, "Conflict between #{Maestrano::Connector::Rails::External::external_name} #{entity_instance.class.external_entity_name} #{external_entity} and Connec! #{connec_entity_name} #{connec_entity}. Entity from Connec! kept")
          nil
        end

      else
        entity_instance.map_external_entity_with_idmap(external_entity, connec_entity_name, idmap, organization)
      end
    end

    def id_from_ref(entity, ref, is_external, organization)
      # field can be address/billing/country_id
      field = is_external ? ref[:external_field] : ref[:connec_field]
      field = field.split('/')
      id = entity
      field.each do |f|
        id &&= id[f]
      end

      if is_external
        idmap = ref[:reference_class].find_idmap({external_id: id, organization_id: organization.id})
        idmap && idmap.connec_id
      else
        idmap = ref[:reference_class].find_idmap({connec_id: id, organization_id: organization.id})
        idmap && idmap.external_id
      end
    end
  end

  def map_external_entity_with_idmap(external_entity, connec_entity_name, idmap, organization)
    {entity: map_to_connec(external_entity, organization), idmap: idmap}
  end
end