Done? Needs tests.

app/controllers/api/logs_controller.rb

@@ -13,9 +13,13 @@ module Api
           .select { |i| i.meta["type"] != "fun"} # Don't save jokes
           .map    { |i| i.as_json }
           .tap    { |i| Log.create(i) }
+          .tap    { |i| maybe_deliver(i) }
       when Hash
         outcome = new_log(raw_json)
-        outcome.result.save if outcome.success?
+        if outcome.success?
+          outcome.result.save!
+          maybe_deliver(outcome.result)
+        end
         return mutate outcome
       else
         sorry "Post a JSON array or object.", 422
@@ -36,5 +40,9 @@ private
     def new_log(input)
       Logs::Create.run(input, device: current_device)
     end
+
+    def maybe_deliver(log_or_logs)
+      LogDispatch.deliver(current_device, log_or_logs)
+    end
   end
 end

app/mailers/log_delivery_mailer.rb

@@ -0,0 +1,14 @@
+class LogDeliveryMailer < ApplicationMailer
+
+  def log_digest(device)
+    if LogDispatch.where(sent_at: 1.hours.ago..Time.now).count > 20
+      raise "Device #{device.id} is sending too many emails!!! (> 20 / hr)"
+    end
+    ld        = LogDispatch.where(sent_at: nil, device: device)
+    logs      = Log.find(ld.pluck(:log_id))
+    @emails   = device.users.pluck(:email)
+    @messages = logs.map(&:message)
+    mail(to: @emails, subject: '🌱 New message from FarmBot!')
+    ld.update_all(sent_at: Time.now)
+  end
+end

app/models/log_dispatch.rb

@@ -1,4 +1,16 @@
 class LogDispatch < ApplicationRecord
   belongs_to :device
   belongs_to :log
+
+  # If this method grows, create a mutation.
+  def self.deliver(device, log_or_logs)
+    Array
+      .wrap(log_or_logs)
+      .select { |log | (log["channels"] || []).include?("email") }
+      .map    { |log | { device: device, log: log }}
+      .tap    { |logs| self.create!(logs) }
+    LogDeliveryMailer
+      .log_digest(device)
+      .deliver_later
+  end
 end

app/views/layouts/mailer.text.erb

@@ -0,0 +1 @@
+<%= yield %>

app/views/log_delivery_mailer/log_digest.text.erb

@@ -0,0 +1,7 @@
+Farmbot sent you an email.
+
+Here's what your device had to say:
+
+<% @messages.each do |msg| %>
+ * <%= msg %>
+<% end %>

db/migrate/20170525111655_create_log_dispatches.rb

@@ -8,7 +8,6 @@ class CreateLogDispatches < ActiveRecord::Migration[5.1]
       t.timestamps
     end
 
-    add_index :log_dispatches, :device_id
     add_index :log_dispatches, :sent_at
   end
 end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20170518182029) do
+ActiveRecord::Schema.define(version: 20170525111655) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -66,6 +66,17 @@ ActiveRecord::Schema.define(version: 20170518182029) do
     t.index ["device_id"], name: "index_images_on_device_id"
   end
 
+  create_table "log_dispatches", force: :cascade do |t|
+    t.bigint "device_id"
+    t.bigint "log_id"
+    t.datetime "sent_at"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["device_id"], name: "index_log_dispatches_on_device_id"
+    t.index ["log_id"], name: "index_log_dispatches_on_log_id"
+    t.index ["sent_at"], name: "index_log_dispatches_on_sent_at"
+  end
+
   create_table "logs", id: :serial, force: :cascade do |t|
     t.text "message"
     t.text "meta"
@@ -189,6 +200,8 @@ ActiveRecord::Schema.define(version: 20170518182029) do
     t.index ["email"], name: "index_users_on_email", unique: true
   end
 
+  add_foreign_key "log_dispatches", "devices"
+  add_foreign_key "log_dispatches", "logs"
   add_foreign_key "peripherals", "devices"
   add_foreign_key "points", "devices"
   add_foreign_key "sequence_dependencies", "sequences"

spec/controllers/api/logs/logs_spec.rb

@@ -106,5 +106,24 @@ describe Api::LogsController do
       expect(user.device.reload.logs.count).to be < before
       expect(user.device.logs.count).to eq(0)
     end
+
+    it 'delivers emails for logs marked as `email`' do
+      sign_in user
+      empty_mail_bag
+      before = LogDispatch.count
+      body         = { meta: { x: 1, y: 2, z: 3, type: "info" },
+                       channels: ["email"],
+                       message: "one" }.to_json
+      before_count = Log.count
+      post :create, body: body, params: {format: :json}
+      after = LogDispatch.count
+      expect(response.status).to eq(200)
+      expect(last_email).to be
+      sleep 1
+      binding.pry
+    end
+
+    it "batches multiple messages"
+    it "throttles excess requests"
   end
 end

spec/controllers/api/password_resets/password_resets_spec.rb

@@ -12,7 +12,7 @@ describe Api::PasswordResetsController do
       post :create, params: params
       expect(response.status).to eq(200)
       expect(ActionMailer::Base.deliveries.length).to be > old_email_count
-      message = last_mail_delivery.to_s
+      message = last_email.to_s
       expect(message).to include("password reset")
     end
 

spec/mailers/log_delivery_spec.rb

@@ -0,0 +1,5 @@
+require "spec_helper"
+
+RSpec.describe LogDeliveryMailer, type: :mailer do
+  pending "add some examples to (or delete) #{__FILE__}"
+end

spec/mailers/previews/log_delivery_preview.rb

@@ -0,0 +1,4 @@
+# Preview all emails at http://localhost:3000/rails/mailers/log_delivery
+class LogDeliveryPreview < ActionMailer::Preview
+
+end

spec/stuff.rb

@@ -11,7 +11,7 @@ module Helpers
   MAGIC_NUMBER_TOOL_ID = "8888"
   AST_FIXTURE          = File.read("./spec/lib/celery_script/ast_fixture3.json")
 
-  def last_mail_delivery
+  def last_email
     ActionMailer::Base.deliveries.last
   end