feat: Add sidekiq jobs to monitor applied SLAs (#8828)

Fixes: https://linear.app/chatwoot/issue/CW-2983/sidekiq-jobservice-to-monitor-sla-breach

Co-authored-by: Sojan <sojan@pepalo.com>

enterprise/app/services/sla/evaluate_applied_sla_service.rb

@@ -0,0 +1,78 @@
+class Sla::EvaluateAppliedSlaService
+  pattr_initialize [:applied_sla!]
+
+  def perform
+    check_sla_thresholds
+
+    # We will calculate again in the next iteration
+    return unless applied_sla.conversation.resolved?
+
+    # No SLA missed, so marking as hit as conversation is resolved
+    handle_hit_sla(applied_sla) if applied_sla.active?
+  end
+
+  private
+
+  def check_sla_thresholds
+    [:first_response_time_threshold, :next_response_time_threshold, :resolution_time_threshold].each do |threshold|
+      next if applied_sla.sla_policy.send(threshold).blank?
+
+      send("check_#{threshold}", applied_sla, applied_sla.conversation, applied_sla.sla_policy)
+    end
+  end
+
+  def still_within_threshold?(threshold)
+    Time.zone.now.to_i < threshold
+  end
+
+  def check_first_response_time_threshold(applied_sla, conversation, sla_policy)
+    threshold = conversation.created_at.to_i + sla_policy.first_response_time_threshold.to_i
+    return if first_reply_was_within_threshold?(conversation, threshold)
+    return if still_within_threshold?(threshold)
+
+    handle_missed_sla(applied_sla)
+  end
+
+  def first_reply_was_within_threshold?(conversation, threshold)
+    conversation.first_reply_created_at.present? && conversation.first_reply_created_at.to_i <= threshold
+  end
+
+  def check_next_response_time_threshold(applied_sla, conversation, sla_policy)
+    # still waiting for first reply, so covered under first response time threshold
+    return if conversation.first_reply_created_at.blank?
+    # Waiting on customer response, no need to check next response time threshold
+    return if conversation.waiting_since.blank?
+
+    threshold = conversation.waiting_since.to_i + sla_policy.next_response_time_threshold.to_i
+    return if still_within_threshold?(threshold)
+
+    handle_missed_sla(applied_sla)
+  end
+
+  def check_resolution_time_threshold(applied_sla, conversation, sla_policy)
+    return if conversation.resolved?
+
+    threshold = conversation.created_at.to_i + sla_policy.resolution_time_threshold.to_i
+    return if still_within_threshold?(threshold)
+
+    handle_missed_sla(applied_sla)
+  end
+
+  def handle_missed_sla(applied_sla)
+    return unless applied_sla.active?
+
+    applied_sla.update!(sla_status: 'missed')
+    Rails.logger.warn "SLA missed for conversation #{applied_sla.conversation.id} " \
+                      "in account #{applied_sla.account_id} " \
+                      "for sla_policy #{applied_sla.sla_policy.id}"
+  end
+
+  def handle_hit_sla(applied_sla)
+    return unless applied_sla.active?
+
+    applied_sla.update!(sla_status: 'hit')
+    Rails.logger.info "SLA hit for conversation #{applied_sla.conversation.id} " \
+                      "in account #{applied_sla.account_id} " \
+                      "for sla_policy #{applied_sla.sla_policy.id}"
+  end
+end