Restructure omni services and add Chatwoot research snapshot

research/chatwoot/app/services/imap/base_fetch_email_service.rb

@@ -0,0 +1,130 @@
+require 'net/imap'
+
+class Imap::BaseFetchEmailService
+  pattr_initialize [:channel!, :interval]
+
+  def fetch_emails
+    # Override this method
+  end
+
+  def perform
+    inbound_emails = fetch_emails
+    terminate_imap_connection
+
+    inbound_emails
+  end
+
+  private
+
+  def authentication_type
+    # Override this method
+  end
+
+  def imap_password
+    # Override this method
+  end
+
+  def imap_client
+    @imap_client ||= build_imap_client
+  end
+
+  def mail_info_logger(inbound_mail, seq_no)
+    return if Rails.env.test?
+
+    Rails.logger.info("
+      #{channel.provider} Email id: #{inbound_mail.from} - message_source_id: #{inbound_mail.message_id} - sequence id: #{seq_no}")
+  end
+
+  def email_already_present?(channel, message_id)
+    channel.inbox.messages.find_by(source_id: message_id).present?
+  end
+
+  def fetch_mail_for_channel
+    message_ids_with_seq = fetch_message_ids_with_sequence
+    message_ids_with_seq.filter_map do |message_id_with_seq|
+      process_message_id(message_id_with_seq)
+    end
+  end
+
+  def process_message_id(message_id_with_seq)
+    seq_no, message_id = message_id_with_seq
+
+    if message_id.blank?
+      Rails.logger.info "[IMAP::FETCH_EMAIL_SERVICE] Empty message id for #{channel.email} with seq no. <#{seq_no}>."
+      return
+    end
+
+    return if email_already_present?(channel, message_id)
+
+    # Fetch the original mail content using the sequence no
+    mail_str = imap_client.fetch(seq_no, 'RFC822')[0].attr['RFC822']
+
+    if mail_str.blank?
+      Rails.logger.info "[IMAP::FETCH_EMAIL_SERVICE] Fetch failed for #{channel.email} with message-id <#{message_id}>."
+      return
+    end
+
+    inbound_mail = build_mail_from_string(mail_str)
+    mail_info_logger(inbound_mail, seq_no)
+    inbound_mail
+  end
+
+  # Sends a FETCH command to retrieve data associated with a message in the mailbox.
+  # You can send batches of message sequence number in `.fetch` method.
+  def fetch_message_ids_with_sequence
+    seq_nums = fetch_available_mail_sequence_numbers
+
+    Rails.logger.info "[IMAP::FETCH_EMAIL_SERVICE] Fetching mails from #{channel.email}, found #{seq_nums.length}."
+
+    message_ids_with_seq = []
+    seq_nums.each_slice(10).each do |batch|
+      # Fetch only message-id only without mail body or contents.
+      batch_message_ids = imap_client.fetch(batch, 'BODY.PEEK[HEADER]')
+
+      # .fetch returns an array of Net::IMAP::FetchData or nil
+      # (instead of an empty array) if there is no matching message.
+      # Check
+      if batch_message_ids.blank?
+        Rails.logger.info "[IMAP::FETCH_EMAIL_SERVICE] Fetching the batch failed for #{channel.email}."
+        next
+      end
+
+      batch_message_ids.each do |data|
+        message_id = build_mail_from_string(data.attr['BODY[HEADER]']).message_id
+        message_ids_with_seq.push([data.seqno, message_id])
+      end
+    end
+
+    message_ids_with_seq
+  end
+
+  # Sends a SEARCH command to search the mailbox for messages that were
+  # created between yesterday (or given date) and today and returns message sequence numbers.
+  # Return <message set>
+  def fetch_available_mail_sequence_numbers
+    imap_client.search(['SINCE', since])
+  end
+
+  def build_imap_client
+    imap = Net::IMAP.new(channel.imap_address, port: channel.imap_port, ssl: true)
+    imap.authenticate(authentication_type, channel.imap_login, imap_password)
+    imap.select('INBOX')
+    imap
+  end
+
+  def terminate_imap_connection
+    imap_client.logout
+  rescue Net::IMAP::Error => e
+    Rails.logger.info "Logout failed for #{channel.email} - #{e.message}."
+    imap_client.disconnect
+  end
+
+  def build_mail_from_string(raw_email_content)
+    Mail.read_from_string(raw_email_content)
+  end
+
+  def since
+    previous_day = Time.zone.today - (interval || 1).to_i
+    previous_day.strftime('%d-%b-%Y')
+  end
+end